I'm interested in converting my CNC Mill to use a laser to cut Solder Paste Stencils for PCBs, but I'm wondering if it's possible to accurately laser cut things down to 8mil?  Can someone suggest (preferrably a reasonably priced) laser that is capable of that kind of resolution, or at least give me an idea of what characteristics I should be looking for?  I'd prefer to cut the stencils in aluminum, but if this isn't possible I could settle for thin plastic transparencies as well.

I've seen some lasers on ebay, but I'm not sure what kind of resolution they offer?

As I understand it lasers do not cut Al well due to Al is to reflective. It reflects to much of the light back into the laser.

Don't know how it is on transparent stuff either. If the laser light goes straight through it probably don't cut that well either.

Bit late for a reply perhaps but the material Kapton is often used for solder paste stencils and this laser cuts quite well. It is sometimes for sale on ebay.

Tweakie.

I am using a cheap DC-K40III modified to Mach3 to cut paste stencils out of OHP TRANSPARENCY sheets.
The precision is good enough for all of my SMD boards so far. I have used this for the last few months for all of my SMD production, so my machine has already paid for itself.
There is an IMPORTANT TRICK to getting things cutting well. You MUST allow cooling time between each CUT to prevent problems.
I have achieved this by writing software to order the cuts so no consecutive cuts are within 10mm of each other.

I will make the TAP FILE software tool I created for stencil cutting available for download on my software page.

Another important trick is to apply around minus 4 thou offset to the paste mask layer BEFORE exporting it from PCB CAD to DXF to allow for beam width offset.

http://www.dockerty.co.nz/lasercutter.html

Hi Brian,

Seems you have overcome the problem with the Mylar Film melting and are producing usable masks with this material - congratulations on achieving this.

Tweakie.



btw. the software download links on your website don't work.

Try the link again now. I think I may have fixed the issue.

Can u please tell me how to modify my machine to do stencils.

I am electronically inclined and able to locate wiring and to soldering just need to know what i need to modify my laser cutter.

thanks in advanced and best reguards

Exodus,

I don't think there is any modification necessary. Just draw your required stencil and send it to the machine to cut. If I am missing something here perhaps you could elaborate.

Tweakie.

It wont do it with the default software that comes with the ebay units; so i was asking how to do the modification so i can do it from mach3

Had second thoughts about this one and deleted my earlier post.

One of the cheap, Chinese, stepper control boards would work and if you were careful in the way it was fitted then either the original or the new options could be used, as required. Something like this  http://cgi.ebay.co.uk/3-Axis-12-36V-3A-CNC-Stepper-Motor-Driver-TB6560-NEW-/250703238018?pt=UK_BOI_Industrial_Automation_Control_ET&hash=item3a5f13d382

Tweakie.