Homebrew PCBs

thank you for the description of the viewing mechanism.
i was thinking about how it is made.

but i have one question:
what advantage has video viewing? i cant find any.
why should a video image - reduced in resolution etc. be superior to a full 
optical system?
is the light source to weak to produce a clear projection?

such a machine would be nice but i have absolutely no idea where to get it 
here in austria.
i didn't see at ebay any here. also it would be too expensive for my few 
boards.

regards
stefan







On Thu, 19 Jun 2003 14:45:37 -0000, twb8899 <twb8899@...> wrote:

> Adam,
>
> The Nawide delt driven machine has a maximum speed of 30,000 rpm. Speed 
> is important but feed rate is more important. Higher speeds allow higher 
> feed rates. Do some research on "chip load" which will give you an idea 
> of what speeds and feed rates to use. I just adjust the scope drills 
> until it "feels right" with highest speeds for small bits and slow speeds 
> for big bits. Feed rates are adjusted for minimum drill wander in a scrap 
> of material as viewed in the scope. That's another benefit of these 
> machines, you can actually watch the bit come through the board and check 
> for drill wander which is minimal to begin with.
>
> The Excellon Uni-Drill uses a Precise #65 spindle that will go to 45,000 
> rpm and the Aetna Acrodrill uses their own Aetna spindle that runs up to 
> 40,000 rpm. The optical scope on the Nawide uses a small prism that 
> projects the image onto a screen that has a bombsite reticle. Aetna uses 
> a small microscope lens in the scope that projects onto two "first 
> surface" mirrors and then to the ground glass screen. These mirrors are 
> at 90 degrees to each other for image correction (left-right movement)and 
> that assembly is at a 45 degree angle between the lens near the drill bit 
> and the screen. Aetna uses a focused lamp and Nawide uses fiber optics 
> for illumination.
>
> Excellon had two scope systems, the small one used a lens at the table 
> and and a small mirror (looks like a dentit's mirror)to reflect the image 
> to a paper screen in the back of the scope housing. It worked but was a 
> cheap looking device. Another optional scope was offered that was much 
> larger and better with mirrors and a big ground glass screen. I have one 
> of these scopes laying around and can provide a photo of it as well.
>
> The best way is to use the right lens with a cheap video camera and 
> monitor. Many of these machines were converted to this setup over the 
> years. The Excellon scope drills are the easiest to convert to video and 
> the Nawide would be most difficult.
>
> BTW, I got one of my Nawide machines for free because no one wanted it. 
> My Aetna Acrodrill was purchased for $200 after it sat in a surplus shop 
> for almost five years. They said no one knew what it was.
> A guy on eBay had a brand new Electro-Mechano scope drill (just out of 
> the crate) and he couldn't get a $500 bid for this $7500 new machine! He 
> asked me to make an offer but I didn't need another one and the shipping 
> would be way too high for me. These machines can be had for next to 
> nothing now days. They can't be beat for prototypes and small volume 
> hobby boards. Just keep looking and you will find one for the right 
> price.
>
> Tom
>