The two hole alignment system is a good way to align the PCB in X and Y
to the carrier ... the carrier X location is known with the added sensor
... carrier Y is not yet known or controlled.
I think this is two separate problems 1)locating the PCB relative to the
carrier and 2)locating the carrier relative to the printer.
I don't have the printer modification finished yet. Still scratching my
head on the cutting of the paper platform. I'm leaning toward your way
with the dremel tool. When finished, I will be able to observe the
operation of the carrier/printer. ... I'm sure you will have the problem
solved by then. ... I will cut tomorrow and then re-assemble. (I don't
have a day job to get in my way!)
Jim KI6JMZ
mlerman@... wrote:
> Hi Jim,
>
> I have a cnc pcb router that registers by 2 holes. What I thought for this was a hole near the top and a slot on the bottom of the blank pcb. I would then print a line down the exact middle of the carrier and drill a hole to mate with the one on the board. The hole wold fix the top and the slot would align the bottom. Put a pin through the holes, align the slot with the line, tape the top and bottom of the pcb to the carrier, remove the pin. Then print the top, remove the pcb and put it in the oven to fix, then flip it over and pin and tape as above to do the bottom as a mirror.
>
> That would work fine if I could be sure the carrier hit the print point at the exact same time each run. However, due to slippage, I can't. The best way I can think of is to get the carrier rolling and have a sensor that triggers the print well after the carrier gets under the drum. This can be done, but I'm not entirely sure it is worth the effort.
>
> Mark
> -----Original Message-----
>
>> From: Jim <jhutch17@...>
>> Sent: May 23, 2010 3:06 PM
>> To: Homebrew_PCBs@yahoogroups.com
>> Subject: Re: [Homebrew_PCBs] DLP Double Sided Update
>>
>> Put the carrier on a rail so it cannot move side to side but still (be
>> adjusted?) move up n down.
>> Then have a raised area (maybe a square) to butt the PCB (corner) up
>> against ... there may be other details that
>> that need attention ... but this may be a start.
>> When the PCB/carrier is staged (prior to print) maybe the x and y could
>> be trimmed.
>> There would have to be a fiducial mark on each side of the blank PCB.
>> Jim KI6MZ
>>
>> Mark Lerman wrote:
>>
>>> Well, I've done some tests trying it the easy way, and while it
>>> SHOULD work, it doesn't, at least not consistently. The problem is
>>> that both the carrier and the board are (obviously) much thicker than
>>> paper, and when they hit the drum/transfer roller interface there is
>>> a slight (and variable) delay as first the carrier and then the board
>>> go through. There are also problems in the X axis because the carrier
>>> "grabs" slightly when it hits the drum and has a tendency to get a
>>> little out of parallel to the motion axis. In theory we could wait
>>> till the pcb (or a "header" of equal thickness) is under the drum
>>> before telling it to print. However, this may create problems in the
>>> charging timing since the printer does not expect there to be a board
>>> present at that time. The X axis problem could be handled with a
>>> better and longer carrier guide, but too much friction would create
>>> its own problems.
>>>
>>> There is no reason that DLP can't do ds boards, but I'm far from sure
>>> that the mechanics of your typical laser printer can be "bulked up"
>>> enough mechanically to produce consistent results. Probably the best
>>> way to do ds DLP would be to make a flatbed laser system, much as has
>>> been done for inkjets. Print one side, put it in an oven to fix the
>>> toner, flip it and print the other side.
>>>
>>> This would also be the way to go for a commercial product - anyone
>>> interested in collaborating?
>>>
>>> Mark
>>>
>>>
>>>
>>>
>>>
>>> ------------------------------------
>>>
>>> Be sure to visit the group home and check for new Links, Files, and Photos:
>>> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>> ------------------------------------
>>
>> Be sure to visit the group home and check for new Links, Files, and Photos:
>> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>>
>>
>>
>>
>
>
>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
>
>
>