[itsme]

Hi there,

I am going to be making a simple ignition circuit for a model engine, but need a circuit board.

I'm looking for some suggestions/advice on how to go about this. Since it is small and simple, I thought I would mill it on my CNC mill. Should be easy . What's an effective way of creating the toolpath and how deep should I be cutting?

Thanks
Warren

[Jason Marsha]

This circuit was based on perfboard 0.1" hole spacing so I set the CAD program to a 1.27mm (.05") grid with 0.635mm (0.025") snap spacing and drew the traces that way. Major grid lines every two minor lines so that the major lines intersected at points corresponding to the perfboard holes.

I then used VCarve Pro (www.vectric.com) to mill around the out side of the traces. Isolation tracing can be used but I just preferred the look of all the unused copper milled away. I used a 0.8mm solid carbide (avoid HSS) end mill with a depth cut of 0.30mm ( may not need to be that deep).

Jason

[Beaker]

Hey Warren

A software program that I use is called Diptrace http://www.diptrace.com/.
It will export to a DXF file so you can mill and drill your board. The trial version will let you export as well. I don't mill my boards I use the toner transfer method with excellent results.
Milled boards can really look the part.
Go for it and show us the results when your done, good luck.

[itsme]

Hi,

Thanks for the replies. I milled a trial board last night and it turned out OK. It's not perfect, but it will do the job. I used a 2mm HSS endmill, simply because that is the smallest endmill I had. The design was drawn on CAD. This is obviously not the best way to do it, but due to the simplicity of this board, it wasn't a hassle. I'll look into programs like Diptrace for the next attempt at some DIY electronics.

I assembled the board this morning and briefly tested it - it all seems to be working as it should, although I haven't actually tested it on an engine.

Regards
Warren

[nick.gilling]

Looks interesting warren. I know very little about electronics. For something that simple you could have used strip board but it looks better with a dedicated PCB. You can also draw on normal circuit board with an etch resistant pen then etch the board in acid.

What you've done there looks great though.

Nick

[itsme]

Hello again,

I have downloaded the freeware version of Eagle and have pretty much figured out how to use it now (after doing a tutorial and just playing around). From what I have seen of it, I am quite impressed by what it can do.

I'm now looking for information on how I can turn my board design into a board on my CNC mill. Does anyone have any experience turning gerber and excellon files into something usable with a CNC mill? What can be done with a gerber file? Can it be turned into a Gcode file somehow?

Regards
Warren

[fyffe555]

Eagle is a great free program. There's a ULP addon for eagle to produce G-code directly, its downloadable from the Eagle Cadsoft site. It will output top and bottom isolation, drill and outline gcodes. There's two versions on there, Mr Bean here on the Zone had a recent thread showing a board he produced with the PCB-Gcode ulp. His board looks superb..

[itsme]

Hi there,

Thanks for that information. I have now downloaded the PCB-Gcode ulp and briefly tried it. Software like this makes PCBs too easy - I was expecting more of a challenge!

Now I just need to get a board design finished so that I can test the software properly. I managed to find some Dremel high speed cutters that I'm going to try. I'm not sure how long they will last with the board material, but it's worth a try.

Regards
Warren

[MrBean]

Hi. Like fyffe555 said. Make sure you get the correct version of the ULP.
If you get a good cutter and have everthing setup right, you can get some really good results.
This was my second attempt at milling a board using the ULP, and I've not played with the settings that much yet.

Regards Terry.

[itsme]

Hi Terry,

Firstly, your board looks very impressive! I hope I can get similar results.

I could only find one version of the ULP on the Cadsoft site (3.3.2). It seems to have all the extra little features that I have read about in various different places.

If you don't mind, I have a few questions. I have been playing around and I am getting good results (on a gcode simulator anyway...), but I am having a minor problem. I can't get text to work. I am able to write it and place it on the board where I want it and on the layer that i want, but when I run the DRC, it keeps finding problems with it. I'm guessing it has something to do with the lines on the text being too close together. How did you get your 'Rev 2.0 Gizmo' to come out? Also, what net width/s did you use on your board?

Have you had a go at doing any double sided boards yet?

Regards
Warren

[MrBean]

Make sure you have set the text to be a "Vector" rather than just "text".
I'm not too sure where the setting for that is. I'll go see if I can find it.

Regards Terry.

[MrBean]

It looks like in the "board view" editor, under options > user interface. There's a global option to set all fonts to "Vector".

Looks like that should do it.

Hope that helps.

Regards Terry.

[MrBean]

The other option is to...... Select the text icon, type your text.....OK...
Now while the text is still attached to your mouse pointer, you can select "Vector" from the toolbar where it says, "FONT", dropdown=(Proportional, Vector, Fixed).
Easy peasy.....

[MrBean]

Ooops. Almost forgot the other questions....

3.3.2 Sounds like the one. :-)

When you say "net widths", are you referring to the "size" tab in the DRC editor?
If it'll help I can zip up my DRC file and post it here. Also if there are any other settings files you'd like to look at just shout and I'll post them here too.

I can even send the .sch and .brd files if you'd like to look at those.

Regards Terry.

[fyffe555]

Terry,

I'd certainly like to see what settings you used in DRC to get your results, if you wouldn't mind.

Does the PCB-Gcode ulp account for the width of the cutter when doing the gcode for the trace? The old Gcode ULP I've used centered the cutter on the edge of the trace so you actually cut 1/2 the tool diameter into either side of the trace you'd so carefully routed. The trace ended up being the DRC width less the diameter of the cutter.

Andrew

[MrBean]

Terry,

I'd certainly like to see what settings you used in DRC to get your results, if you wouldn't mind.

Does the PCB-Gcode ulp account for the width of the cutter when doing the gcode for the trace? The old Gcode ULP I've used centered the cutter on the edge of the trace so you actually cut 1/2 the tool diameter into either side of the trace you'd so carefully routed. The trace ended up being the DRC width less the diameter of the cutter.

Andrew

I'm pretty sure the script accounts for the cutter size, so the traces end up at the size they're supposed to be. In other words the cutter only mills outside the traces and pads.

I'll zip up some files that people may find useful and post them here in a few mins...

With my cutter being conical, it's hard to guage the actual cutting width so it's a calculated guess as much as anything.

In the meantime, here's a view of the gcode...

[pminmo]

I've been playing with the PCB-Gcode the last week also. The new version on the yahoo group has a machine setup which give you a number of options including tool diameter.

Mr. Bean, where did you get the cutter?

[MrBean]

Mr. Bean, where did you get the cutter?

I'm not sure if it'll be of any help to you, being in the US?
I got my cutters from MegaUK.
A bit pricey, but they're the dogs doo dahs!

Halfway down this page, under "Accessories".

http://www.megauk.com/cnc_production_centre.php

[MrBean]

Okay. I've zipped up my .sch and .brd files. Also included is the .nc gcode files for the bottom layer, milling and drilling. The header contains the PCB-Gcode settings that were used. Sizes are in MM.

Also attached is my DRC file.

Here's a copy of the settings from the .nc (gcode) header....

( Settings from pcb-machine.h )
( tool size = 0.4000 )
( z high = 3.0000 z up = 0.5000 z down = -0.2540 )
( drill depth = -1.8000 )
( spindle on time = 3.0000 )
( milling depth = -1.7000 )
( tool change at X0.0000, Y0.0000, Z45.0000 )
( feed rate = 254.0000 feed rate z = 127.0000 )

( Settings from pcb-defaults.h )
( Default isolate = 0.0025 )
( isolate max = 1.8000 )
( isolate step = 0.2000 )
( Generated: top outlines, top drill, bottom outlines, bottom drill, )
( Unit of measure: mm )

[itsme]

Hi there,

Thanks for those files and the info, Terry. I changed my text to vector. The DRC stopped giving the text error, but then started to give another width error for the text.

I tried running your DRC along with your board design and it gave the exact same error. I'm going to just ignore this error for now though, as when I run the Gcode that the ULP generates in a gcode simulator, the text turns out just fine.

For the net widths, I meant what widths you had set in your net classes. From looking at your board design, it seems that you have used the default net width for all nets? I'm not sure what width that is, because for the default settings it just says '0mil' in the settings and doesn't actually give the width.

What drill did you use to drill the holes? Is it one of those carbide drills from MegaUK?

Regards
Warren