Ideas to get a cleaner cut? (fiducial)

[TheMotionGuy]

I am in need of some ideas to help my brainstorming. I need to get a cleaner cut than the attached picture. Currently, we are using a laser CNC but unfortunately they polymer we have on the bottom is very soft and it gets kind of torn up when we cut it.

These holes are used for fiducial alignment and must be clean cut or the AOI (automated optical inspection) system will not recognize them.

The only thing i can come up with is a plastic insert of some kind--only problem is that it is really small.

Hole size is 1.52mm and depth of 0.4mm
A picture is attached.

Any ideas on what we can do here?

Thanks--

 

[MintJulep]

Water jet.

 

[TheMotionGuy]

p.s. the polymer is 0.27mm +/-0.02mm and the backing is either acrylic or stiff polyester 0.2mm +/- 0.03mm

 

[Compositepro]

With those dimension, I believe a punch would work well.

 

[TheMotionGuy]

@MintJulep: My boss wants to accomplish this in house, so a water jet is out of the question, unfortunately. But this was a good idea.

@Compositepro: I dabbled with the idea of punches but I am a tad skeptic because these holes need to be incredibly precise--in terms of both diameter and placement.


I am also toying with the idea of laser marking. But I am waiting on a reply from our engineers overseas as to whether or not that is an option--as opposed to a through hole.

 

[Ceramicguy]

Can you shorten the pulse width and raise the peak energy on your existing laser? The edge of the hole looks like it has a pretty significant HAZ.

Bruce

http://www.accuratus.com

 

[TheMotionGuy]

I had kind of peeled it apart and was messing with a few things... Here is a picture of the actual hole.

 

[TheMotionGuy]

In what way do you mean shortening the pulse? Like the PPI (pulses per inch)?

 

[TheMotionGuy]

Oh, i just read that wrong... pulse WIDTH. I can't find an option but from what I can tell just by using it, I think our crappy laser is scales pulse width with intensity/energy.

 

[rb1957]

crappy equipment = crappy results

and it sounds like (through no fault of your own) you haven't had much training on the crappy equipment (to try and get the most out of it).

GL

 

[btrueblood]

And a drill won't work?

 

[TheMotionGuy]

I tried drilling them, but it tore up the polymer on the bottom as well.

 

[EngineerTex]

You might check in the vinyl sign industry. I think your tolerances may be a little too tight for a run-of-the-mill machine, but you could check around. You would be looking for a "vinyl sign cutter."

A quick Google search brought up one with a 0.0005" mechanical resolution:

http://www.uscutter.com/Roland-GX-PRO-Vinyl-Cutter-_p_569.html

Though I don't know if mechanical resolution = smooth hole edge.

Engineering is not the science behind building. It is the science behind not building.

 

[btrueblood]

Did you try drilling with backup boards on both sides of the part? I.e. a piece of smooth wood, or scrap plastic, clamped to front and back surfaces.

 

[Ceramicguy]

Can you mount the polymer sheet on a cold plate? If you can get below the glass transition temp. you can drill a clean hole. You just have to account for thermal expansion on size and position.

Bruce

http://www.accuratus.com