Pin registration system preferences

[Pere Casals]

So, once again the truth emerges: you've never had glass cut with a water jet.

Interneg, in post 17 I explained it to you, I have cut glass with waterjet: https://www.largeformatphotography.i...=1#post1521034

So, once again the truth emerges: you've never had glass cut with a water jet. I've just spoken with a local specialist glass supplier who water cut all sorts of glass for engineering & technical purposes & their comment was that they were unwilling to cut a smaller than 6mm hole. Which is not much use for either a 3.5mm hole for the pin body or clearing the 1.5mm pin itself in the top glass.

LOL, what an specialist !!!

Look, to cut a hole (or to start cutting in the middle of the sheet) first the machine makes a perforation operation (nozzle distance to material is changed), this hole has some 1mm, once perforation is made the nozzle adjusts to the cutting height and starts movement.

A (say) 10mm hole is made by the nozzle making the perforation in the "circunference" of the hole, and then it describes a circle...

...but to make a (say) 2mm hole the procedure is different, once the perforation is made the nozzle starts describing circles of growing diámeter, say each circle being 0.5mm larger than the previous one until reaching the desired size.

I cannot believe that your "technical engineering expert" was not aware...

Which is not much use for either a 3.5mm hole for the pin body or clearing the 1.5mm pin itself in the top glass.

See the design:

The position of the register pins are determined by the precision holes drilled in the metal plating, that metal plating is fixed to the glass with larger bolts, the small holes in the glass are to let pass the pins through the glass not to keep the pins in position.

Is it that difficult to understand?

[Drew Wiley]

Pere is describing an optional pin positioning method on the perimeter frame rather than the glass. This works, but crops away more edge of the negative itself unless a punched register strip is taped to the film to give extra width. It becomes more a liability in a registration contact frame than carrier application, but if necessary can be done in that case too if drilling the glass itself is unrealistic.

[Pere Casals]

Pere is describing an optional pin positioning method on the perimeter frame rather than the glass. This works, but crops away more edge of the negative itself unless a punched register strip is taped

Not necessary... see this:



The pin is 1.5mm

[Drew Wiley]

I've been there, done that, Pere. It's relatively tricky not to have a bit of meat around the pin itself, but if you can pull it off, congratulations. For certain precisely composed originals with nominally sized glass, that kind of spacing is just too much of the image edge to sacrifice. But it might simplify design. With smaller format originals using LF punches and pin glasses, you need a taped register strip anyway, so there's no penalty in that case. The Durst system only worked with a secondary register strip, but was oversized to begin with.

[Pere Casals]

Drew, see it, it does not take more than any register system, the register strip it's always a possibility anyway... When I finish a ATL 2500 rebuild I've in course then I'll make that register, I'll show it to you...

[Drew Wiley]

Thank you, and good luck. Unfortunately, I'm not likely to experiment in this manner anymore myself, because I already have the personal equipment I need.

[interneg]

Pere - as usual, it was none of your assumptions. The people I spoke with can deliver higher accuracy than you have quoted for water jet, but said that the big problem with fine holes is cracking at the point that the jet contacts the surface of the glass. Only at about 6mm can you cut away enough to safely be rid of the initial cracks - that said, they supply to industries where cracks that propagate could result in life or death situations, so I can see their caution. Perhaps you'd like to show us the fine holes you had cut in glass and tell us who did the work rather than flinging around CAD drawings?

I think the last avenue I'll explore before resorting to something along the lines of Durst or Inglis's use of pins in the metalwork of the carrier & accepting a small image area loss is the latest generation double sided glass drills - apparently they can reliably cut 3mm holes.

[Pere Casals]

apparently they can reliably cut 3mm holes.

From 6mm to 3mm you have moved a bit.

Let me explain you that in a Waterjet several parameters can be adjusted for a job, beyond cutting speed.

You may vary:

>> nozzle aperture
>> water pressure
>> abrasive type
>> abrasive granularity


With lower water pressure, an smaller aperture and a low granularity abrasive you make a perfect 1.5mm hole, it takes a bit more time but if only two holes are to be made... what you end paying is machine preparation for a lower speed work.


Look, your "engineering & technical expert" does not want to exchange the nozzle and the abrasive for you... , and you ended saying that only 6mm holes can be made...

show us the fine holes you had cut in glass

In post 17 I told that I only have cut linear, but in the workshop I order my regular WJ cuts I asked, and I've been shown samples of 1.5mm holes well made on glass, this is the reason why I made my register design with 1.5mm pins.

[Drew Wiley]

You'll still need a bit of wiggle room to adjust the pin spacing as the epoxy sets up, or you'll never achieve perfect register. That was the convenience of off-center pins on a larger barrel.

[Pere Casals]

You'll still need a bit of wiggle room to adjust the pin spacing as the epoxy sets up, or you'll never achieve perfect register. That was the convenience of off-center pins on a larger barrel.

Yes... I was considering allowing one the pins to shift, to tension just a bit the sheet... This would make less critical the distance between pins...

Also I was considering the film sides touching some top-left edges to make the register... I don't know if that was ever succesfully used...