My CNC Router Adventures

[Lane]

Check the price of endmills vs Dremel tool bits. Small Endmills can get a bit expensive and may take a couple weeks to replace, Dremel tool bits OTOH are easy to find.

Do not bother with Carbide endmills for now, you probably do not need it unless you plan on cutting steel, your machine probably could not take the cutting forces that would effectively use a carbide bit.

If you have access to a bench grinder you may also try making your own router/ engraving bits. Even better, mount a Dremel tool to the tool post of your lathe and grind bits there.

[mangozac]

Good tip about the Dremel bits, but after some Googling it seems that they're more expensive than small endmills (in the 2 to 5mm range) from a local supplier! That shouldn't really be surprising - everyone knows Dremel accessories are overpriced.

Even cutting plastic won't the carbide cutters stay sharper longer?

I don't really want to grind my own cutting bits - grinding lathe tools is enough of a pain!

[Lane]

[Bar]

Here are the pics of the bits i have at work. Let me know if you want any of them.
They are on a 1cm graded cutting mat.

[Lane]

Any of those should work though I suspect the cutters with a longer spiral, like #3 and #5-9, will work better.

[mangozac]

[blind pig]

[Lane]

[mangozac]

[Lane]

[mangozac]

OK the milling cutters that Bar sent me rocked up this week. Thanks again Bar! They seem pretty nice so it'll be good to start playing with them. The smaller ones are around 2mm diameter, so I'll eventually have to buy some smaller ones.

I did some playing around on the weekend with a .STL file Paulson sent me of one of his Space Hulk tiles. I soon discovered that there's no way the router will be replicating anything even close to the level of detail from 3D printing, as getting cutter sizes small enough is expensive. Plus the machining times would be painfully slow. For doing 3D stuff in the around 1/35 scale we're used to the only real option is bulk shapes (so the basic shape of the model before detailing).

I've hit a bit of a snag though.

Today at work I had a reason to use my router. I needed to reproduce a bunch of tiny printed circuit boards that serve a primarily mechanical purpose joining a connector to a cable. To get them professionally manufactured would have required us to order way more than we needed and would have been overkill, so I figured it would be a good chance to try out the router.

I then proceeded to waste half of my day and what made things worse was that at the end I was no closer to solving the problem

The software I use to draw PCBs (and circuit diagrams and anything else electronic related) is called Altium Designer. It's an expensive professional software package for doing that kind of stuff. Part of its functionality is to generate the necessary files for manufacture of the PCBs:
- RS274X Gerber files for the actual PCB layout
- Excellon NC drill files for the holes in the PCB.

Both of these formats are similar to the standard kind of G-code that I need for the router, however they are different enough to be completely incompatible. I tried exporting in .DXF format so that I could run the DXF file through a G-code generator but for some stupid reason the DXF export would not use arcs - it just drew a straight line from the start to the end of the arc.

I tried a bunch of different converters and stuffed around in Altium further but in the end gave up. What a frustrating exercise! How can such common operations as Numerical Control have such varied standards? It's so unproductive!

So I gave up for now. I might go and "code" the part by hand in G-code, but I'll have to learn how to do offsets and everything as well, because I want to produce a couple of dozen of these.

The other option that I'm considering is writing some kind of file converter script to convert the Gerber/excellon formats to standard G-code - they are similar enough that it should be possible to do without any number crunching. But I'm doing way to much writing custom applications lately - it takes a lot of time to do and then adds yet another program you have to maintain...

It's so frustrating to have the machine sitting there but struggling to get the machining data for it!

[Lane]

[mangozac]

[blind pig]

Wow, you know?

I didn't understand a single word Zac just said?

[Lane]