Homebrew PCBs

When applying toner resist to a double sided board, do you transfer the
images for borh sides at the same time, or do you do one side at a time?
If the latter, does applying heat to the second side have any adverse
effect on the preciously applied resist on the first side?

Thanks,

Steve Bartlett

Stephen Bartlett wrote:

>When applying toner resist to a double sided board, do you transfer the
>images for borh sides at the same time, or do you do one side at a time?
>If the latter, does applying heat to the second side have any adverse
>effect on the preciously applied resist on the first side?
>  
>
I do both at the same time. I print both sheets, with top side mirrored, 
line them up together by eye using a bright light to see through, and 
staple a few times along one edge. Then I slide the cleaned copper board 
in between them and use a clothes iron to bring it up to temp, followed 
by a laminator several times. Biggest board so far is 4 inches by 8 
inches. Same process works for single side with component outline.

mickey

On Thu, 23 Dec 2004 15:35:42 -0500, Stephen Bartlett  
<tower.op@...> wrote:

>
> When applying toner resist to a double sided board, do you transfer the
> images for borh sides at the same time, or do you do one side at a time?
> If the latter, does applying heat to the second side have any adverse
> effect on the preciously applied resist on the first side?
> Thanks,
> Steve Bartlett


Both simultaneusly.
use a folded sheet of thin cardboard to put the sandwich in.

ST

--- In Homebrew_PCBs@yahoogroups.com, Stephen Bartlett 
<tower.op@v...> wrote:
> When applying toner resist to a double sided board, do you 
transfer the
> images for borh sides at the same time, or do you do one side at a 
time?
> If the latter, does applying heat to the second side have any 
adverse
> effect on the preciously applied resist on the first side?
> 
> Thanks,
> 
> Steve Bartlett

I did a couple boards doing one side at a time. After ironing the 
one side I then re-wiped the second side with Acetone and then 
ironed the second side. It did not harm the first side at all. To 
line it all up in the first place, I placed them together and held 
it up the light to line it all up. I then taped all 4 sides together 
and then layed it on the piece of copper. I used a very sharp razor 
blade and cut along 3 sides of the paper using the copper as a 
guide. Then lining them up was easy enough, I just made sure the 3 
sides were exactly on the edges of the copper. The biggest board I 
did so far this way was 5" x 6" and it had plenty of vias which came 
out right on the money. I guess your gonna get a couple different 
ways to do it on here and they all seem to work good, so its gonna 
be a personal preference thing. Good luck!

Hi

I promised a description of the PCB shear i made.
First, imagine the standard pivoting-sword paper cutter, this is the basic  
idea.

Then get some angle iron, we are going to make one.

depending on the size you need (i suggest A3) you will need:
A) one length of angle iron ~~50 cm long for the stationary blade
B) one length approx. 15 to 20 cm longer than A) (the extra is the handle)  
for the pivoting blade
c) a short piece of angle iron, 5cm or so, for the hinge/pivot.

You also need one big screw for the hinge, and 2 other screws to mount C)  
to A).
You will want a wood board or something to mount this unit too (it also  
can be screwed to the
edge of the workbench).

Now, we need to make cutting edges on the pieces of angle iron. The  
stationary blade A) will be mounted like
A upside down L when looking from the front of the cutter. (cutting  
mechanism on the right hand side).
In other words, lit looks like a F without the short middle line.
(you can see a quick sketch at <st.such.info/pub/cutter.gif>. Yes, I drew  
that, not a kindergarden child.)

For now stop laughing and look a the top sketch. this is the cutting  
mechanism, sharpen the indicated edges with a angle grinder of file. make  
sure the stationary blade is 100% straight.
You needn't make such a sharp angle, just over 90 degree.
The stationary blade is ground the whole length, but with the pivoting  
blade don't grind the handle.

To get the whole thing together you make a short bracket. use 2 screws to  
mount it to A) and a big screw to make the pivot. I expect you are aware  
you need to drill holes ;-).
You can see a illustration in the bottom sketch (view from back).
The pivot bracket must have one side cut shorter to fit under A).

Really simple, wasn't it?

A few notes: having a low pivot point helps to keep a not too flat cutting  
angle all the way of the blade.
Good paper cutters have a curved blade. That is not to make them look more  
menacing, this keeps the cutting angle constant. (otherwise it will be  
harder to cut at the front, much harder than the shorter lever alone).
You will not be able to cut PCBs the whole length, so make it double the  
size as your PCBs.

It cuts both paper and PCB very well, but it might need another bar to  
press the PCBs down. Simpe to add.

Only a few hours work, and no money involved, so a really good thing to  
buy i think.
IMO the blades will be worn not too fast, and the way i arranged the  
pieces makes sure you have plenty
of material to re-sharpen.

I hope the instructions are clear, feel free to ask.

ST

Hi everyone,

remember some time back we talked about PCB drill viewing mechanisms.

I want to make one for a pivoting drill stand, with the drill from the top.

I think, please correct me, it could work by illuminating the PCB with  
bright light from below, then taking that reflected light and sending it  
through a convex lens which sends it to the projection screen. a mirror  
will be required too.

i'm not too good with optics, but i took a lens, illuinated a piece of  
newspaper and tried to project the image, which worked to the extent you  
can expect from a flashlight.

Now i wonder where to put the screen, it could be under the atual drill  
table, on the front of the machine.
Not ergonomically ideal but if the machine is positioned relatively high  
it might be acceptable (the screen could be angled to get a better view).

Another option would be to have a slightly tilted-down screen on the top,  
back of the srilling machine.
the image would be projected diagonally up through the work surface of the  
machine (cutout).

Each setup requires a lens and a mirror, but the screen-on-top version has  
a much longer optical path.

How can i work out which lens size and focal length i need?

ST

What's your objective?
If it's aligning the drill, you might find it easier to project
crosshairs onto the board.
mike

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" <stefan_trethan@g...> wrote:

> 
> Hi everyone,
> 
> remember some time back we talked about PCB drill viewing mechanisms.
> 
> I want to make one for a pivoting drill stand, with the drill from the top.
> 
> I think, please correct me, it could work by illuminating the PCB with  
> bright light from below, then taking that reflected light and sending it  
> through a convex lens which sends it to the projection screen. a mirror  
> will be required too.
> 
> i'm not too good with optics, but i took a lens, illuinated a piece of  
> newspaper and tried to project the image, which worked to the extent you  
> can expect from a flashlight.
> 
> Now i wonder where to put the screen, it could be under the atual drill  
> table, on the front of the machine.
> Not ergonomically ideal but if the machine is positioned relatively high  
> it might be acceptable (the screen could be angled to get a better view).
> 
> Another option would be to have a slightly tilted-down screen on the top,  
> back of the srilling machine.
> the image would be projected diagonally up through the work surface of the  
> machine (cutout).
> 
> Each setup requires a lens and a mirror, but the screen-on-top version has  
> a much longer optical path.
> 
> How can i work out which lens size and focal length i need?
> 
> ST

On Sat, 08 Jan 2005 18:24:37 -0000, gettingalongwouldbenice  
<gettingalongwouldbenice@...> wrote:

>
> What's your objective?
> If it's aligning the drill, you might find it easier to project
> crosshairs onto the board.
> mike


project crosshairs... hmmm... how?

my thinking was if i project the picture on the other side of the drill  
onto a screen i can draw concentric rings on the projection surface to aid  
in aligning. also, it would have magnification, crosshairs projected on  
the PCB would need another means of magnification to see better.

ST

i got out my box of lenses and built a "optical bench".
Ok, ok, it is only a board, a white shoebox as screen, and a flashlight,  
but... better than guesswork.


The results seem very promising. i could reach the required magnification  
in a semi-dark room easily with the flashlight brightness through a piece  
of paper.

Best seem to be lenses with very short focal lengths (~~~5cm).
I also tried using a mirror to deflect the projection, and it too worked  
surprisingly well.

I'm still unsure whether i should make the projection screen above or  
below the drilling table. above the table requires big cutouts, but below  
would need a semi-transparent projection screen. I guess paper would  
work...


One BAD, BAD thing is because of the lens, if you move the board right the  
image moves left, and vice versa. same for up/down. But i don't want to  
make a more complicated setup with multiple lenses and mirrors and  
whatnot. I think one will get used to the reversed movement.

The whole thing will be made from MDF or plywood, not sure if i should try  
to seal the dust out or just keep everything open so i can easily remove  
the dust.. also, the lens should be mounted in a way that allows to adjust  
it, not sure what i will do there..


Well, i'll let you know what i come up with.

ST

> The whole thing will be made from MDF or plywood,
> not sure if i should try  
> to seal the dust out or just keep everything open so
> i can easily remove  
> the dust.. also, the lens should be mounted in a way
> that allows to adjust  
> it, not sure what i will do there..
> 
> 
> Well, i'll let you know what i come up with.
> 
> ST
> 
Another possibility is to put a slightly higher
pressure within the optical train. Just make sure its
clean air. You can put vent holes near the exposed
surface of the lens as well. However, getting the
hole's correct can be tricky...  We built a optical
system for a saw mill blade years ago, and it stayed
pretty cleaned compared to everything else in the
vicinity.

For what you are doing, the thin lens equations should
work fine, as you don't need to be too concerned with
off axis distortions, or even chromatic distortion of
the image.

Ron


		
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On Sat, 8 Jan 2005 12:24:58 -0800 (PST), ron amundson  
<mnphysicist@...> wrote:

>
> Another possibility is to put a slightly higher
> pressure within the optical train. Just make sure its
> clean air. You can put vent holes near the exposed
> surface of the lens as well. However, getting the
> hole's correct can be tricky...  We built a optical
> system for a saw mill blade years ago, and it stayed
> pretty cleaned compared to everything else in the
> vicinity.
> For what you are doing, the thin lens equations should
> work fine, as you don't need to be too concerned with
> off axis distortions, or even chromatic distortion of
> the image.
> Ron

I guess a small fan with a good filter could be used for that, my shop air  
isn't oil free.
blowing dust away from the lens sounds good.
But then, i have a better idea, why not use a vacuum cleaner to collect  
all the dust away from the
lens. Better dispose of it than have it in the air. The new vacs are a lot  
less noisy than what i'm used to, must look out for one in the junk i can  
repair.

ST

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:
> 
> On Sat, 08 Jan 2005 18:24:37 -0000, gettingalongwouldbenice  
> <gettingalongwouldbenice@y...> wrote:
> 
> >
> > What's your objective?
> > If it's aligning the drill, you might find it easier to project
> > crosshairs onto the board.
> > mike
> 
> 
> project crosshairs... hmmm... how?

My system was computerized, so I put the crosshairs a known
difference from the drill center.  Align it, then drill the hole
relative to the alignment position.

My first choice would be a laser pointer.  But I was too cheap
and mounted an incandescent at the end of a foot-long brass tube.
Soldered wires over the other end for the crosshairs.  What I got
was a "shadow" not a projection.  But if the light is far enough
away to look like a point source, it works out the same.
If you don't want to do the offset thing you can project at an angle
IFF you have fixed height off the board.  Or project two, one from
each side and make sure they align at the reaquired height.

You might consider an annular light source that converges at the
desired height.

I think projection of the alignment marks is always gonna be easier
than trying to project an image of the work.
mike


> 
> my thinking was if i project the picture on the other side of the
drill  
> onto a screen i can draw concentric rings on the projection surface
to aid  
> in aligning. also, it would have magnification, crosshairs projected
on  

> the PCB would need another means of magnification to see better.
> 
> ST

On Sun, 09 Jan 2005 14:01:00 -0000, gettingalongwouldbenice  
<gettingalongwouldbenice@...> wrote:

>
> I think projection of the alignment marks is always gonna be easier
> than trying to project an image of the work.
> mike


Yes, it will be easier, but IMO much less useful for what i want to do.
It doesn't magnify the image, so you need a magnifier or something anyway.

The commercial units do what i plan to do, so i will try that first.


ST

Hello Stefan...and all. My first thought to your question, like one 
other member...was to suggest using a LASER Pointer to "project" the 
contact point of your Drill. 

Simply put...Drill a hole and without moving the PCB align the Laser 
pointer to AIM at the Hole. Then do a few test drills to confirm your 
alingment. 

I have a pointer I grabbed at a local Dollar Store that came with 5 
different heads. None (other than the basic Dot pattern) would be 
useable, but I've seen pointers sold on E-Bay that come with 42 
different heads !!! Who knows...maybe one will be an 
appropriate "PATTERN"...like a Bull-eye for example. 

All due respect but incandecent light bulb, brass tube, "Wires" as 
crosshairs and such seems like a lot of EXTRA effort to save a couple 
of dollars (Pounds, Euro,Francs,etc) on what a pointer will cost. In 
either case you'll have to jury rig an adjustable mounting method to 
hold the "light" source.

Lenses, light sources, screen, dust collectors etc seem like again a 
lot of work unless you've spent weeks (months) on building a fancy 
CNC machine (in which "going all the way" would be justified).

My two cents worth....take it with a grain of salt (Unless high blood 
pressure keeps you on a salt reduced diet...in which case...don't 
mind me!  ;)

Cheers...Dean.

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
<stefan_trethan@g...> wrote:
> 
> Hi everyone,
> 
> remember some time back we talked about PCB drill viewing 
mechanisms.
> 
> I want to make one for a pivoting drill stand, with the drill from 
the top.
> 
> I think, please correct me, it could work by illuminating the PCB 
with  
> bright light from below, then taking that reflected light and 
sending it  
> through a convex lens which sends it to the projection screen. a 
mirror  
> will be required too.
> 
> i'm not too good with optics, but i took a lens, illuinated a piece 
of  
> newspaper and tried to project the image, which worked to the 
extent you  
> can expect from a flashlight.
> 
> Now i wonder where to put the screen, it could be under the atual 
drill  
> table, on the front of the machine.
> Not ergonomically ideal but if the machine is positioned relatively 
high  
> it might be acceptable (the screen could be angled to get a better 
view).
> 
> Another option would be to have a slightly tilted-down screen on 
the top,  
> back of the srilling machine.
> the image would be projected diagonally up through the work surface 
of the  
> machine (cutout).
> 
> Each setup requires a lens and a mirror, but the screen-on-top 
version has  

> a much longer optical path.
> 
> How can i work out which lens size and focal length i need?
> 
> ST

---------------

> Date: Sat, 08 Jan 2005 19:29:49 +0100
>   From: "Stefan Trethan" <stefan_trethan@...>
> Subject: Re: Re: PCB drill viewing mechanism... reviewed

<snipped>

> project crosshairs... hmmm... how?

> ST

Stefan,

Just a thought:   A small motor spinning a small mirror could be used to sweep the beam of a small laser through most of a plane. Using two of those setups, you could illuminate two planes that intersect along the axis of your drill bit.

Off-topic: They used to use rotating mirror systems to get satellite imagery: A rotating mirror system was used to scan perpendicular to the flight path, getting one line of the image at a time.  The light was then sent through a prism. On the other side of the prism were sensors that measured the amount of energy at several spectral locations in the prism's output. Those numbers were digitized, many times along each scan line, and radioed down.

Tom Gootee

http://www.fullnet.com/u/tomg

-----------------------------------



[Non-text portions of this message have been removed]

I have built a pivoting type drill press , but haven't done anything 
about improving the visibility of the drill location. I admit , that 
having a magnified image would make it a lot easier get accurate holes. 
Another big improvement would be to have a foot switch that operated a 
solenoid to feed the drill. That way both your hands hands can hold and 
position the PCB. Both these features are not so straight forward to 
implement. The mechanism of the pivot is superb, smooth and virtually 
zero side to side play.
I think the best approach is like the commercial units. Have the drill 
under the table. Mine is above the table, but will convert it sometime 
down the track. The advantage of having the drill come up from the 
bottom is you have a flat table top to work on, with no drill motor in 
the way. Of course this means you now must have a means to view the hole 
location from above.

A method once talked about on this group was to use a cheapy CCD camera 
module and a TV with a composite video input as the viewing device. 
Cross hairs are drawn on the CRT screen.
If you can get hold of cheap TV and CCD camera than I'd think this is 
the best way to go.

The idea you have of projecting an image to a translucent screen might 
be more effort, but I haven't seen the results so I can't comment if its 
worth going down this route. Not to spend too much money, try one of 
those 12V 20W halogen roof lights that are fashionable these days. The 
screen could be tracing paper behind some 3 mm plexigalss. In my opinion 
the major amount of work would be fabricating the framing to mounting 
everything, since the optics must be stable and also adjustable.
How about a section of  50mm diameter PVC drain pipe with the lenses and 
screen mounted at each end. Some frame made out of MDF to could be used 
to position this pipe. what is the distance between the screen and lenses?
If there is no distance between them than just cut the appropriate size 
hole in some MDF to mount them both in this hole. Adjacent to this hole 
you cut another to mount the halogen lamp.

Adam.







Stefan Trethan wrote:

> 
> i got out my box of lenses and built a "optical bench".
> Ok, ok, it is only a board, a white shoebox as screen, and a flashlight,  
> but... better than guesswork.
> 
> 
> The results seem very promising. i could reach the required magnification  
> in a semi-dark room easily with the flashlight brightness through a piece  
> of paper.
> 
> Best seem to be lenses with very short focal lengths (~~~5cm).
> I also tried using a mirror to deflect the projection, and it too worked  
> surprisingly well.
> 
> I'm still unsure whether i should make the projection screen above or  
> below the drilling table. above the table requires big cutouts, but below  
> would need a semi-transparent projection screen. I guess paper would  
> work...
> 
> 
> One BAD, BAD thing is because of the lens, if you move the board right the  
> image moves left, and vice versa. same for up/down. But i don't want to  
> make a more complicated setup with multiple lenses and mirrors and  
> whatnot. I think one will get used to the reversed movement.
> 
> The whole thing will be made from MDF or plywood, not sure if i should try  
> to seal the dust out or just keep everything open so i can easily remove  
> the dust.. also, the lens should be mounted in a way that allows to adjust  
> it, not sure what i will do there..
> 
> 
> Well, i'll let you know what i come up with.
> 
> ST
> 
> 
> 
> 
> 
> 
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs 
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 
>

> I think the best approach is like the commercial units. Have the drill
> under the table. Mine is above the table, but will convert it sometime
> down the track. The advantage of having the drill come up from the
> bottom is you have a flat table top to work on, with no drill motor in
> the way. Of course this means you now must have a means to view the hole
> location from above.

I think that has the big disadvantage of the drill lifting the PCB,  
requiring a hold down foot or firm pressure by hand. I do not see big  
disadvantages of the upside-down version.


>
> A method once talked about on this group was to use a cheapy CCD camera
> module and a TV with a composite video input as the viewing device.
> Cross hairs are drawn on the CRT screen.
> If you can get hold of cheap TV and CCD camera than I'd think this is
> the best way to go.

I know, and i even put aside a old camera for that. But it doesn't focus  
up close and combining it
with lens seems just as complicated as simply using a screen instead of  
the cam.

> ..

I had the plastic piping idea too. ideally it would have some thread to  
adjust, or screws on the side.


ST

Hi Adam & all
Under the table is the way to go and to make a simple projection box 
out what ever is also good. If you want to put your money on CCD 
camera and TV screen you can work in good daylight as the other 
solution is good when dark around you. Have been working with a pro 
driller with projection box, PITA to change tooling but if you are 
smart and have a big part of the table removable and indexed it will 
work nicely.

Why are you putting all this effort and money on things like this? It 
is far more easier to fix a small CNC driller to do the job.

My 2 eurocents
Bengt

> Another big improvement would be to have a foot switch that 
operated a  solenoid to feed the drill. That way both your hands 
hands can hold and position the PCB. 
> I think the best approach is like the commercial units. Have the 
drill under the table.

----- Original Message ----- 

From: "Stefan Trethan" <stefan_trethan@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Monday, January 10, 2005 7:38 AM
Subject: Re: [Homebrew_PCBs] Re: PCB drill viewing mechanism... reviewed


>
>
>
> > I think the best approach is like the commercial units. Have the drill
> > under the table. Mine is above the table, but will convert it sometime
> > down the track. The advantage of having the drill come up from the
> > bottom is you have a flat table top to work on, with no drill motor in
> > the way. Of course this means you now must have a means to view the hole
> > location from above.
>
> I think that has the big disadvantage of the drill lifting the PCB,
> requiring a hold down foot or firm pressure by hand. I do not see big
> disadvantages of the upside-down version.

The old Excellon drilling machines drilled from underneath, with a clamp to
hold the PCB that locked it when the drill was actuated by a foot pedal.

Leon

On Mon, 10 Jan 2005 14:46:10 -0000, Leon Heller  
<leon.heller@...> wrote:

>
> The old Excellon drilling machines drilled from underneath, with a clamp  
> to
> hold the PCB that locked it when the drill was actuated by a foot pedal.
> Leon
>


I am aware of that, and that's why i see the use of a foot as disadvantage.
Keeping all the other things "like the conventional drill press" would  
allow quick and easy coarse adjustment of the PCB, to find the holes etc.

By the way, does anyone of you use Toner Transfer and a CNC drill?
I fear the distortions might make cnc drilling difficult?


ST

Hi,

I've thought maybe i might reconsider building a CNC just for drilling,  
but i worry that the laser printer and toner transfer distortions will  
make it useless.
So i have printed two 150mm x 150mm square boxes on two separate sheets  
with my HP IIID and compared the two. there is about 1mm distortion.
Of course this is not acceptable for cnc drilling.

Now, i have the new printer already but still no toner so i don't know how  
bad the distortion will be with that one.

You see, i definitely will not build a CNC drill only to find it useless  
because of printer distortion.
I will not change to inkjet because it does not produce toner transfer,  
and toner transfer saves me much more time and money than a CNC drill ever  
will.

So, does anyone here use CNC drilling and laser printouts? Or has anybody  
done more experimenting with laser printer distortion and which models are  
good? The lexmark M412 did only cost 17eur and the toner will cost 50+ so  
i might still choose another printer.

thanks

ST

Bengt wrote:
> 
> Hi Adam & all
> Under the table is the way to go and to make a simple projection box 
> out what ever is also good. If you want to put your money on CCD 
> camera and TV screen you can work in good daylight as the other 
> solution is good when dark around you. Have been working with a pro 
> driller with projection box, PITA to change tooling but if you are 
> smart and have a big part of the table removable and indexed it will 
> work nicely.
> 
> Why are you putting all this effort and money on things like this? It 
> is far more easier to fix a small CNC driller to do the job.


Maybe but its a matter of pure luck that any given person comes across 
one of these small drill machines your talking about. And spending 
$1000's on a brand new drill machine is just not an option. Building a 
CNC machine from scratch is a mammoth task compared, to building a 
manual drill press. I knew of a small PCB fabrication shop that 
primarily produces prototype quantities and they manual drill ALL their 
boards, while the CNC machine sits in the corner gathering dust. When I 
asked why don't they use this machine, the owner said its too slow.


 From what I understand the only attractiveness towards CNC for hobby 
use is drill accuracy. With some clever thinking, a manual drill press 
should be able to be improved and reduce mental fatigue of trying to get 
each hole close as possible on target.

Stefan sounds like he is on a good idea using projection.

Stefan Trethan wrote:

> 
> 
>>I think the best approach is like the commercial units. Have the drill
>>under the table. Mine is above the table, but will convert it sometime
>>down the track. The advantage of having the drill come up from the
>>bottom is you have a flat table top to work on, with no drill motor in
>>the way. Of course this means you now must have a means to view the hole
>>location from above.
> 
> 
> I think that has the big disadvantage of the drill lifting the PCB,  
> requiring a hold down foot or firm pressure by hand. I do not see big  
> disadvantages of the upside-down version.
> 

You could be right, I haven't tried it so I don't know. Also the 
comments about the commercial units having a clamp above thats operated 
by the foot pedal also complicates construction for us hobbyists.
Ok, So lets stick to conventional top side drilling. The problem I see 
now is the lens system cannot be perpendicular to the plane of the PCB. 
Did your lens experiment work ok when viewing the PCB at a angle ?
What diameter was your lens ?
How about just a large diameter lens without worrying about a screen ?

I think its important to be able to look at large areas of the PCB for 
course placement and seeing areas that remain undrilled. So this means 
the projection assembly cannot get in too much in view of the whole PCB.

>  Maybe but its a matter of pure luck that any given person comes across
>  one of these small drill machines your talking about. And spending
>  $1000's on a brand new drill machine is just not an option. Building a
>  CNC machine from scratch is a mammoth task compared, to building a
>  manual drill press.

That is simply not true.  I built a CNC mill/drill based on the Brute
design at www.crankorgan.com and it only took about a week to make it. 
Granted it is not a professional unit, but it is accurate down to
0.00025", plenty good enough for hobby PCB drilling!  It cost virtually
nothing to build, mostly scrap aluminum channel and scrap plastic blocks.

Ed Okerson

>
> Maybe but its a matter of pure luck that any given person comes across
> one of these small drill machines your talking about. And spending
> $1000's on a brand new drill machine is just not an option. Building a
> CNC machine from scratch is a mammoth task compared, to building a
> manual drill press. I knew of a small PCB fabrication shop that
> primarily produces prototype quantities and they manual drill ALL their
> boards, while the CNC machine sits in the corner gathering dust. When I
> asked why don't they use this machine, the owner said its too slow.
>
>
>  From what I understand the only attractiveness towards CNC for hobby
> use is drill accuracy. With some clever thinking, a manual drill press
> should be able to be improved and reduce mental fatigue of trying to get
> each hole close as possible on target.
>
> Stefan sounds like he is on a good idea using projection.
>

What i fear is that in many cases setting up a CNC drill would be more  
effort than drilling the entire board by hand (i have many boards with  
well under 50 holes).
Also if i damage 1 board by faulty setup i can drill two or more by hand  
in the time it takes to etch a replacement.

The only advantage of a CNC i can see right now, for me, is when i need to  
make 10 boards or so to sell it could potentially be less work.
I do not believe it is possible to work with only a CNC and no manual  
drilling at all.

Also, i still doubt CNC goes well with toner transfer.


ST

Woodworking equipment (sliding compound miter saws, for example) use a
laser to project a cut line on the material.  It seems to work pretty
well in light or dark conditions.  I've seen low cost laser levels
(<$40, iirc) that could be adapted to this.  Two of them aimed at the
drill bit would create a crosshair target.  They wouldn't need to be
at right angles and height of the material shouldn't be an issue. 

Phil

On Mon, 10 Jan 2005 14:10:52 -0800 (PST), Ed Okerson <ed@...>  
wrote:

>
> That is simply not true.  I built a CNC mill/drill based on the Brute
> design at www.crankorgan.com and it only took about a week to make it.
> Granted it is not a professional unit, but it is accurate down to
> 0.00025", plenty good enough for hobby PCB drilling!  It cost virtually
> nothing to build, mostly scrap aluminum channel and scrap plastic blocks.
> Ed Okerson


Ed,

How long does it take you to get a single board drilled, say 30 holes, 3  
sizes?

I mean you start out with the layout files. generating drill files, making  
them ready for the machine, setting up the machine (if you need),  
positioning, aligning the board, putting in a drill, starting the  
software, changing drills, until you have the drilled board in hand.
How long does that take you approximately?

Do you use free software, if not, what cost?

Do you drill before etch, if not, how do you align the drill with the PCB?

thanks

ST

0,00025 WOW !!!
did you get the zeros right?? that is 0.00635mm.
Even if you get down to 1/10mm repetability its far better than hand 
drilling your PCB:s and that is more realistic values! To keep 
0.00025 is a real challenge and will change as soon as you sneeze or 
touch your machine. 

If you can get Excellon files from your PCB software you can use 
SheetCam to convert to G-code and also to line up your drillfile to 
your etched PCB using 2 holes as reference on your router. Will let 
you know soon my results when I get my machine ready within 2-3 weeks.

Bengt


--- In Homebrew_PCBs@yahoogroups.com, "Ed Okerson" <ed@o...> wrote:
> >  Maybe but its a matter of pure luck that any given person comes 
across
> >  one of these small drill machines your talking about. And 
spending
> >  $1000's on a brand new drill machine is just not an option. 
Building a
> >  CNC machine from scratch is a mammoth task compared, to building 
a
> >  manual drill press.
> 
> That is simply not true.  I built a CNC mill/drill based on the 
Brute
> design at www.crankorgan.com and it only took about a week to make 
it. 
> Granted it is not a professional unit, but it is accurate down to
> 0.00025", plenty good enough for hobby PCB drilling!  It cost 
virtually
> nothing to build, mostly scrap aluminum channel and scrap plastic 
blocks.
> 
> Ed Okerson

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
wrote:
...
> Ok, So lets stick to conventional top side drilling. The problem I see 
> now is the lens system cannot be perpendicular to the plane of the PCB. 
> Did your lens experiment work ok when viewing the PCB at a angle ?
> What diameter was your lens ?
> How about just a large diameter lens without worrying about a screen ?
...

Two laser pointers with some kind of vibrating mirrors (or surplus
barcode scanners) aimed to make a crosshair on the board? With each
properlly aligned, board thickness won't matter as where the lines
cross will still be in the center. If you don't find a laser pointer
with a head that makes a single line, a mirror attached to a small
speaker, one end in the center, other end on the rim of the speaker
will turn a beam into a line. Surplus small front surface mirrors are
inexpensive. Last I checked, Goldmine Electric and Hosfelt had some.

Otherwise, a camera off of perpendicular means the center of the
screen is only the drill point of the board is the same thickness as
when it was calibrated and there is no curve to the board. This is not
a killer, though, as there are only a few different thicknesses of
boards and it can be "calibrated" for each thickness you use.

Steve Greenfield

Doh! OK, I should have just kept reading before posting...

Steve Greenfield

--- In Homebrew_PCBs@yahoogroups.com, "Phil" <phil1960us@y...> wrote:

> 
> Woodworking equipment (sliding compound miter saws, for example) use a
> laser to project a cut line on the material.  It seems to work pretty
> well in light or dark conditions.  I've seen low cost laser levels
> (<$40, iirc) that could be adapted to this.  Two of them aimed at the
> drill bit would create a crosshair target.  They wouldn't need to be
> at right angles and height of the material shouldn't be an issue.

Hi Stefan,
If TT is that bad why do you use it? If I read this right, you say 
that TT is so distorted that it cannot be used, or?

I agree that if you have simple boards with just a few holes they can 
be done by hand, faster that CNC setup but not that much faster. The 
best thing with CNC is repetability.

Bengt

> 
> Also, i still doubt CNC goes well with toner transfer.
> 
> 
> ST

On Mon, 10 Jan 2005 22:38:45 -0000, Bengt <tecnoconsult@...> wrote:

>
> Hi Stefan,
> If TT is that bad why do you use it? If I read this right, you say
> that TT is so distorted that it cannot be used, or?


..Or CNC is so accurate it can not cope with the distortion of TT that are  
no problem at all otherwise.

Actually TT isn't the problem, the laser printer itself has 1mm distortion  
on 150mm squares.

ST

On Mon, 10 Jan 2005 22:35:57 -0000, Steve <alienrelics@...> wrote:

>
> --- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
> wrote:
> ...
>> Ok, So lets stick to conventional top side drilling. The problem I see
>> now is the lens system cannot be perpendicular to the plane of the PCB.
>> Did your lens experiment work ok when viewing the PCB at a angle ?
>> What diameter was your lens ?
>> How about just a large diameter lens without worrying about a screen ?
> ...

didn't get that before so i'm answering it now.
The trick is to view from the _OTHER_ side of the drill.
the screen has a target painted on it where the drill will come through.
A lens alone will not work because if you move your head the picture  
moves, making it impossibe to draw a target on the lens that doesn't move  
relative to the drill.
Projection solves that problem.
The goal is to have a magnified picture of the pad, underlying a bullseye.  
Align the two and you have the perfect hole.


> Otherwise, a camera off of perpendicular means the center of the
> screen is only the drill point of the board is the same thickness as
> when it was calibrated and there is no curve to the board. This is not
> a killer, though, as there are only a few different thicknesses of
> boards and it can be "calibrated" for each thickness you use.
> Steve Greenfield


Steve, see above. I do not consider looking off-axis an option, it has  
many drawbacks and almost no advantages. Looking from the other side is  
not prevented in any way, so why not do it that way?
Also, commercial machines all have the viewing apparatus opposite the  
drill, but that doesn't force you not to turn the principle upside down  
and have a normal drill from top viewing from bottom.


The reson i'm doing that now is that carbide drills are just working way  
too good. In the past i used HSS and freehand drilling, which is think is  
as fast and easy as it gets. Of course the drills dull quite fast.
If you etch a small hole in the copper pad the drill will catch easily.  
Now, in a drillstand, with carbide drills, the drill will not self-center  
and it is a tedious process to lign up every hole. My boards are actually  
worse since i have carbide drills and i do not like it, at all.

ST

Ed Okerson wrote:
>> Maybe but its a matter of pure luck that any given person comes across
>> one of these small drill machines your talking about. And spending
>> $1000's on a brand new drill machine is just not an option. Building a
>> CNC machine from scratch is a mammoth task compared, to building a
>> manual drill press.
> 
> 
> That is simply not true.  I built a CNC mill/drill based on the Brute
> design at www.crankorgan.com and it only took about a week to make it. 
> Granted it is not a professional unit, but it is accurate down to
> 0.00025", plenty good enough for hobby PCB drilling!  It cost virtually
> nothing to build, mostly scrap aluminum channel and scrap plastic blocks.
> 
> Ed Okerson
> 

They look interesting, but what is used as the linear slides ? How are 
they attached to the U channel ?
Is the lead screw standard zinc steel threaded bar or is it  the true 
thing ?
It looks like X, Y and Z axis are identically built, with only the 
length of the Z axis being smaller.
What CNC software are you using ? Did that take a week to write too ?
And most important, what is the minimum tooling required to build one of 
these ?

>       Ed Okerson wrote:
>  >> Maybe but its a matter of pure luck that any given person comes across
>  >> one of these small drill machines your talking about. And spending
>  >> $1000's on a brand new drill machine is just not an option. Building a
>  >> CNC machine from scratch is a mammoth task compared, to building a
>  >> manual drill press.
>  >
>  >
>  > That is simply not true.  I built a CNC mill/drill based on the Brute
>  > design at www.crankorgan.com and it only took about a week to make it.
>  > Granted it is not a professional unit, but it is accurate down to
>  > 0.00025", plenty good enough for hobby PCB drilling!  It cost
> virtually
>  > nothing to build, mostly scrap aluminum channel and scrap plastic
> blocks.
>  >
>  > Ed Okerson
>  >
>
>  They look interesting, but what is used as the linear slides ? How are
>  they attached to the U channel ?
>  Is the lead screw standard zinc steel threaded bar or is it  the true
>  thing ?
>  It looks like X, Y and Z axis are identically built, with only the
>  length of the Z axis being smaller.
>  What CNC software are you using ? Did that take a week to write too ?
>  And most important, what is the minimum tooling required to build one of
>  these ?

The linear slides are just blocks of high density plastic cut to ride
inside the lip on the aluminum channel.  I used 1/4 20tpi stainless steel
threaded rod for the lead screws on mine.  For software I am using EMC
from www.linuxcnc.org to run the machine, and I do PCB layout with Eagle. 
I am still in the early stages of getting this all working, and my spare
time is very limited, but I built that machine the week of Thanksgiving
when I was off work.

As for minimum tooling, not much.  I used a skil saw to cut the plastic
and aluminum, although a table saw would be better if you have one, but it
could also be done with a hand saw if needed.  Also a drill to make all
the holes for mounting screws.  I did make some custom fittings to center
the threaded rod in the bearings with a lathe, but that is really not
necessary.

If you are not inventive, then I would recommend ordering the plans for
$35, but I built mine just from looking at the pictures on the web site.

Ed Okerson

Ed Okerson wrote:

>>      Ed Okerson wrote:
>> >> Maybe but its a matter of pure luck that any given person comes across
>> >> one of these small drill machines your talking about. And spending
>> >> $1000's on a brand new drill machine is just not an option. Building a
>> >> CNC machine from scratch is a mammoth task compared, to building a
>> >> manual drill press.
>> >
>> >
>> > That is simply not true.  I built a CNC mill/drill based on the Brute
>> > design at www.crankorgan.com and it only took about a week to make it.
>> > Granted it is not a professional unit, but it is accurate down to
>> > 0.00025", plenty good enough for hobby PCB drilling!  It cost
>>virtually
>> > nothing to build, mostly scrap aluminum channel and scrap plastic
>>blocks.
>> >
>> > Ed Okerson
>> >
>>
>> They look interesting, but what is used as the linear slides ? How are
>> they attached to the U channel ?
>> Is the lead screw standard zinc steel threaded bar or is it  the true
>> thing ?
>> It looks like X, Y and Z axis are identically built, with only the
>> length of the Z axis being smaller.
>> What CNC software are you using ? Did that take a week to write too ?
>> And most important, what is the minimum tooling required to build one of
>> these ?
> 
> 
> The linear slides are just blocks of high density plastic cut to ride
> inside the lip on the aluminum channel.  I used 1/4 20tpi stainless steel
> threaded rod for the lead screws on mine.  For software I am using EMC
> from www.linuxcnc.org to run the machine, and I do PCB layout with Eagle. 
> I am still in the early stages of getting this all working, and my spare
> time is very limited, but I built that machine the week of Thanksgiving
> when I was off work.
> 
> As for minimum tooling, not much.  I used a skil saw to cut the plastic
> and aluminum, although a table saw would be better if you have one, but it
> could also be done with a hand saw if needed.  Also a drill to make all
> the holes for mounting screws.  I did make some custom fittings to center
> the threaded rod in the bearings with a lathe, but that is really not
> necessary.
> 
> If you are not inventive, then I would recommend ordering the plans for
> $35, but I built mine just from looking at the pictures on the web site.
> 
> Ed Okerson
> 
> 


Thanks Ed, for your response. I now see there is even easier ways of 
making a "bare bones" CNC drill machine. I'm not interested in building 
one because I still think the effort to get the whole project fully 
functional and usable enough to replace my manual drill press would 
require a lot more work than I'm willing to put it.

Adam

I can't answer specific questions about this unit, but let me do a mini
brain dump from my CNC experience (mill, lathe, much more on to-do list);

 

First, while you can perhaps throw something like this together cheap,
substituting elbow grease, accuracy is what you really need. My minimum
equipment list might look somewhat daunting, but its what I can't live
without.

 

Metal working machinery:

 

Milling machine (mini mill, sold by grizzly, harbor freight or homier in the
US)

7x12 lathe (again, grizzly, harbor freight and northern tools)

4x6 bandsaw (grizzly, harbor freight, clarke)

16" drill press (grizzly, harbor freight, northern tools, clarke, sears,
home depot, lowes)

 

Stepper motors:

 

Minimum ~250oz/in (best prices new from automation direct, used cheaper)

 

Electronics:

 

Some freedom here, as you can probably make boards yourself. Base them on
the Allegro 3977 micro-stepping driver/controller and you are doing great.
DIY or buy the 3 axis Xylotex board. Or go with the Gecko drivers.

 

Software:

 

I use Mach2 from artsoft, but turbocnc from DAK engineering is also popular.

 

Tooling:

 

Here is where things get expensive. A partial list -

 

Set of end mills

Set of lathe cutting tools

Clamping kit

1-2-3 blocks

Kurtz style vice, 3in

Decent selection of drill bits

Center drills

Wiggler set

Parallel set

Dial indicator(s)

Digital calipers (hey, they are so cheap now, why not?)

QCTP (quick change tool post) set for lathe

Transfer punch set

 

Miscellaneous stuff:

 

Machinery's Handbook

 

 

That's all I can think of immediately. If you see it as an investment in
future projects, it's a little easier to stomach. Plus, you have to learn
how to use all this stuff. CNC is not for the faint-of-heart.

 

  _____  

From: Adam Seychell [mailto:a_seychell@...] 
Sent: Monday, January 10, 2005 7:57 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Re: PCB drill viewing mechanism... reviewed

 

They look interesting, but what is used as the linear slides ? How are 
they attached to the U channel ?
Is the lead screw standard zinc steel threaded bar or is it  the true 
thing ?
It looks like X, Y and Z axis are identically built, with only the 
length of the Z axis being smaller.
What CNC software are you using ? Did that take a week to write too ?
And most important, what is the minimum tooling required to build one of 
these ?





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[Non-text portions of this message have been removed]

Ok time to stop lurking and post something. I have built two cnc
drilling machines (so far). The first used drawer slides, a wood frame
and 1/4 20 all thread drive elements. It worked but was slow. I bought
a 24x24 xy table at a swap meet mounted it on a 4x6ft piece of plywood
and built a bridge over the top with aluminum angle. Mounted a air
pencil gringer on a little z axis. This can theoretically allow a 24"
sqaure board. In reality I don't do anything bigger than 6 by 8. Ok
here is the trick. First drill the board. I use dancam which is free.
There are many other ways and programs available to do this. Thats
just the one I started using and it still works for me. The second
trick is POSTSCRIPT!!! (Or ghostscript if you must) Almost all laser
printers are off a little in one direction or another. In postscript
you can scale the printout in both the x and y direction to make it
much more exact.For instance on one HP 4m+ I used to use the scale was
.995 in x and .998 in y. This made everything line up over the entire
6x8 board. So steps are Drill board, Make photomask or tt printout,
align to board , transfer image. This has worked very well for me.

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:
> 
> Hi,
> 
> I've thought maybe i might reconsider building a CNC just for
drilling,  
> but i worry that the laser printer and toner transfer distortions will  
> make it useless.
> So i have printed two 150mm x 150mm square boxes on two separate
sheets  
> with my HP IIID and compared the two. there is about 1mm distortion.
> Of course this is not acceptable for cnc drilling.
> 
> Now, i have the new printer already but still no toner so i don't
know how  
> bad the distortion will be with that one.
> 
> You see, i definitely will not build a CNC drill only to find it
useless  
> because of printer distortion.
> I will not change to inkjet because it does not produce toner
transfer,  
> and toner transfer saves me much more time and money than a CNC
drill ever  
> will.
> 
> So, does anyone here use CNC drilling and laser printouts? Or has
anybody  
> done more experimenting with laser printer distortion and which
models are  
> good? The lexmark M412 did only cost 17eur and the toner will cost
50+ so  

> i might still choose another printer.
> 
> thanks
> 
> ST

The "Brute" is designed to use a Dremel using carbide PCB drill bits.
(or was your tooling question about what's need to buils it?)

You can use TurboCNC to run the machine. Converting an Excellon drill
file to G code is pretty straightforward and I think there are free
utilities already written to do this.

I built one, and with stainless 1/4-20 threaded rod as lead screw it
seems quite amazing. As a test I jogged back and forth repeatedly
along a 4" length, measuring travel with a digital caliper, and it
came up as 4.000" every time. The caliper will resolve .001" so the
repeatability and accuracy of the machine is quite good. If you jog it
.001 that's what the caliper shows.

With your building skills it would be a piece of cake. But it does
take some time.

regards,
Grant

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
wrote:
> Ed Okerson wrote:
> >> Maybe but its a matter of pure luck that any given person comes
across
> >> one of these small drill machines your talking about. And spending
> >> $1000's on a brand new drill machine is just not an option.
Building a
> >> CNC machine from scratch is a mammoth task compared, to building a
> >> manual drill press.
> > 
> > 
> > That is simply not true.  I built a CNC mill/drill based on the Brute
> > design at www.crankorgan.com and it only took about a week to make
it. 
> > Granted it is not a professional unit, but it is accurate down to
> > 0.00025", plenty good enough for hobby PCB drilling!  It cost
virtually
> > nothing to build, mostly scrap aluminum channel and scrap plastic
blocks.
> > 
> > Ed Okerson
> > 
> 
> They look interesting, but what is used as the linear slides ? How are 
> they attached to the U channel ?
> Is the lead screw standard zinc steel threaded bar or is it  the true 
> thing ?
> It looks like X, Y and Z axis are identically built, with only the 
> length of the Z axis being smaller.
> What CNC software are you using ? Did that take a week to write too ?
> And most important, what is the minimum tooling required to build
one of 
> these ?

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
<stefan_trethan@g...> wrote:
> If you etch a small hole in the copper pad the drill will catch 
easily.  
> Now, in a drillstand, with carbide drills, the drill will not self-
center  
> and it is a tedious process to lign up every hole. My boards are 
actually  
> worse since i have carbide drills and i do not like it, at all.
> 
> ST

Why won't the carbide drills self-center? You are still etching the 
guide hole? Are the carbide drills just so stiff that they don't 
follow it? Could you reduce the pressure you use to hold the board 
and let the bit "shake" the PCB into alignment? I have used carbide 
drills in the past (it's been a while) and I don't remember having 
this problem...

On the issue of guiding the drill in from below, can you raise the 
press up so that the bottom of the table is at eye level and then 
use a small magnifying mirror at a 45' angle just under the hole in 
the table where the drill will come through? 

Combined with a very bright spot light from above, there should be 
enough light coming through the PCB to allow you to see the traces. 

A small plastic pointer could be attached to the top of the table, 
pointing to the place where the drill will come through. It would be 
cut as a sharpened triangle from some thin plastic material like the 
flat side of a milk jug. 

If the pointer is adjusted to be just shy of touching the drill when 
it is down through the hole in the table, then when the drill is 
raised, and the PCB slid into place, the pointer will be visable 
against the backlit PCB by looking through the hole in the table 
from below.

In this way, the mirror or other optics do not have to be aligned 
and moving your head will not move the pointer image against the PCB 
since the pointer is rubbing on the PCB.

A convex mirror (like girls use to put on make-up) will give you the 
magnification you want.

On Thu, 13 Jan 2005 01:46:58 -0000, James Newton  
<jamesmichaelnewton@...> wrote:

>
> Why won't the carbide drills self-center? You are still etching the
> guide hole? Are the carbide drills just so stiff that they don't
> follow it? Could you reduce the pressure you use to hold the board
> and let the bit "shake" the PCB into alignment? I have used carbide
> drills in the past (it's been a while) and I don't remember having
> this problem...

They cut so well they will also cut into the side of the pad. i will try  
making the drill table more slippery.


> On the issue of guiding the drill in from below, can you raise the
> press up so that the bottom of the table is at eye level and then
> use a small magnifying mirror at a 45' angle just under the hole in
> the table where the drill will come through?
> Combined with a very bright spot light from above, there should be
> enough light coming through the PCB to allow you to see the traces.
> A small plastic pointer could be attached to the top of the table,
> pointing to the place where the drill will come through. It would be
> cut as a sharpened triangle from some thin plastic material like the
> flat side of a milk jug.
> If the pointer is adjusted to be just shy of touching the drill when
> it is down through the hole in the table, then when the drill is
> raised, and the PCB slid into place, the pointer will be visable
> against the backlit PCB by looking through the hole in the table
> from below.
> In this way, the mirror or other optics do not have to be aligned
> and moving your head will not move the pointer image against the PCB
> since the pointer is rubbing on the PCB.
> A convex mirror (like girls use to put on make-up) will give you the
> magnification you want.


Interesting idea, but i will still try projection first, today i hope.

ST

Stefan Trethan wrote:

> 
> On Sun, 09 Jan 2005 14:01:00 -0000, gettingalongwouldbenice  
> <gettingalongwouldbenice@...> wrote:
> 
> 
>>I think projection of the alignment marks is always gonna be easier
>>than trying to project an image of the work.
>>mike
> 
> 
> 
> Yes, it will be easier, but IMO much less useful for what i want to do.
> It doesn't magnify the image, so you need a magnifier or something anyway.
> 
> The commercial units do what i plan to do, so i will try that first.
> 
> 

Do you what the basic arrangement of the optics should be ? I  did a 
very simple experiment with some odd lenses I have (from microscope eye 
pieces). Trying to get any kind projection seemed futile.
I tried both convex with flat and double convex lenses. The projection 
screen was transparent plastic film with diffuse coating. I could not 
get any close range image projected into the screen any any amount of 
light. The only way I could see reasonable images was looking at objects 
at infinite distance, or greater than few meters distance.

If my thinking is correct, wouldn't a converging lenses need some type 
of very small aperture to get a sharp image projection ?

Adam

On Fri, 14 Jan 2005 11:31:29 +1100, Adam Seychell  
<a_seychell@...> wrote:

>
>>
> Do you what the basic arrangement of the optics should be ? I  did a
> very simple experiment with some odd lenses I have (from microscope eye
> pieces). Trying to get any kind projection seemed futile.

Oh i get very good porjection already, on my test setup.
I used the convex lens, the picture close to focal point (but i don't  
remember if just outside or just inside). then the projected image will be  
sharp at a given distance, what that distance is is determined by how  
close to the focal point you are.

You can draw the optic path. draw a lens, a small arrow on the left. one  
ray goes straight from the tip of the arrow to the lens center, the other  
one goes parallel with the horizon through the lens (which deflects it  
through the focal point on the other side. You see, to make them intersect  
on the other side of the lens (sharp picture) you need to be just outside  
the focal point. By moving the small arrow you can move the size and  
position of the big one. Once you come as close as, or closer than the  
focal point the picture diverges and does no longer project.


ST

> I tried both convex with flat and double convex lenses. The projection
> screen was transparent plastic film with diffuse coating. I could not
> get any close range image projected into the screen any any amount of
> light. The only way I could see reasonable images was looking at objects
> at infinite distance, or greater than few meters distance.
> If my thinking is correct, wouldn't a converging lenses need some type
> of very small aperture to get a sharp image projection ?
> Adam

Here's a link to one mfgr.

http://www.nazdar.com/section.asp?sect_pk=238&subsubsection=Application

It looks like they might have an on-line store.

Norm


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