Accuracy Problem

[richie00boy]

I bought a 3020 mill primarily for making PCBs and small panels and I think I might have an accuracy problem creeping in somewhere in my operation or setup. Here is my routine:

1. Export tracks HPGL milling file from CAD program.
2. Export outline HPGL milling file from CAD program.
3. Export Excellon drilling file from CAD program.
4. Import tracks milling file to SheetCAM, set outside contour routing operation and save job then save TAP file from post processor.
5. Import outline milling file to SheetCAM, set outside contour routing operation and save job then save TAP file from post processor.
6. Import drilling file to SheetCAM, save job then save TAP file from post processor.
7. Load tracks milling TAP file into Mach3 and do.
8. Load drilling TAP file into Mach3 and do.
9. Load outline milling TAP file into Mach3 and do.



Is this something that a Smoothstepper would sort? Or some other problem?

[ptjw7uk]

Not sure what's going on but the drilled holes all look offset to the right!
Maybe a zero positional error when you loaded the drill!
Just a thought!

peter

[phill05]

Try exporting all as one file out of Cad then make your individual tool-paths in sheet cam move tap files to Mach3 keeps everything in same 0 position.


Errors can creep in if you split up the cad file.

Phill

[richie00boy]

I've done two boards, first had holes offset mainly too low, this board I added 0.25mm offset but it also had a right offset it seems too.

When changing tools or loading TAP files, the same instance of Mach3 is running so should still be in the same place?

[phill05]

Why use an offset? if you create your tracks in cad with the given clearance between and place holes where needed then export or import into sheetcam, select all holes make toolpath, select all tracks make toolpath, export individual taps files into mach job done they all reside on the same Zero centre.

Phill

[phill05]

Just done a google on Excellon Ref: Excellon format - Wikipedia, the free encyclopedia

(Furthermore, the implementation of Excellon output in CAD is often poor, resulting in problems such as poor registration between the drill and the image.)


Could be your problem.

Phill

[richie00boy]

Thanks for that. The ref point seems to be the same across all 3 files. I didn't know that about Excellon files not being that accurate, and with the drills moving seemingly randomly it could be the answer.

I'm not sure if I can export a Gerber file showing drill data though. It's only a basic CAD package.

[richie00boy]

OK, after a quick check my software will export Gerber RS-274X which can includes hole data if I tick the box on exporting. Now my problem is how to I convert this into a drill file for my mill?