PCB Milling

[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.