CNC milling a PCB starting from DIYLC

[Hemmel]

Hi all,

I've made this using DIYLC

First: I'd appreciate your feedback on the "quality" of this layout
Second: I want to mill this PCB with my CNC. Does anyone have any experience doing this? How do I transform this layout to a workable one for the CNC? What bit did you use?

Thanks,
Hemmel

[Kevin Mitchell]

There's no simple way to create a file for your CNC from an image created in DIYLC. I've seen some folks create software just for this but isn't public. Perhaps there's an open-source alternative floating around the internet.
However, I believe gerbers can easily be converted to the appropriate file for your CNC. So it may be worth your while to learn how to use something like Kicad - which is free and there's also plenty of export options.

Without being too critical, your layout is pretty bulky. And the ground plane is unnecessary here.
It's good practice to adjust the components to real-size with correct lead spacing.
But nothing wrong with it for experimental purposes! It's a hard line to follow when shooting for a pretty & functional single layer layout. If you're shooting for a conservative/short & clean signal path, you pretty much nailed the concept.

[Hemmel]

I appreciate your feedback, Kevin, thanks!

I was thinking of having this build fit into a Hammond 1590B enclosure... Hence why it's tiny and yes, bulky. But perhaps I could go ahead and "free it up" a little and eventually put it in a BB enclosure instead.

Why is the ground plane unnecessary? I thought the more ground plane, the better. Especially for milling, that way the bit doesn't have to scrape off all that copper...

[vigilante397]

So if you want to get this milled out, you really have two options:

#1 The most common, do the layout in actual CAD/CAE software like Eagle, Diptrace, KiCAD, etc. and export as gerbers. You will still need a CAM program to convert your gerbers to g-code to send to the machine, but there are plenty of free CAM software specifically for gerbers. My favorite was always Flatcam, easy enough to use, free, and capable of even doing 2-layer boards.

#2 If you're dead-set on sticking with DIYLC you can get the layout shown without the components on it, i.e. like what you would use when etching, and export it as an image file. You then need to pull that into come sort of CAD program that can handle images. I use CorelDraw for things like that but I think a free program like Inkscape may work as well. In that program you need to verify that the measurements are all what you expect them to be, then export it as a .dxf/.dwg or other drawing file to make sure you retain the scale of the drawing. From that point you will take it into your CAM program and treat it like an image and you will just do shallow pocket engravings around the traces. You'll probably have to place points for peck drilling as well. I'm not sure what CAM program you typically use, but I can tell you PCB-oriented CAM software like Flatcam will not be able to handle this. I use Aspire for most of my milling and I know Aspire has enough options that it would be able to process it, but Aspire is not free.

Either option should give you results, but the first one is the most common because it is by far the simplest and least time-consuming. You can get a free license for Eagle, KiCAD, or Diptrace (I always recommend Diptrace), and you can get Flatcam for free, so zero cost in software there. Doing it the workaround way you can make it work, but it won't be anywhere near as intuitive as method #1.

So if you're comfortable with PCB layout software I would ABSOLUTELY recommend option #1, and if you're completely not comfortable with PCB layout software but are VERY comfortable with CAM software and CNC machining then sure, go for option #2.

EDIT: just saw your question about what bit to use. Personally I like using LPKF 0.2mm tip engraving bits, that's literally what they're designed for. Most hobbyists use cheap V-bits because they're cheap and they get the job done. For drills I always used a 1mm drill, also from LPKF. For cutting out the board when it's finished I always used a cheap chinese 3mm flat end mill.

Depending on which method you go with, your tools may change. If you're doing a full rub-out, i.e. removing all copper that isn't being used for signals, you'll want a bigger flat end mill as it would take a million years to clear out all the empty space on that board with a v-bit.

[Kevin Mitchell]

Why is the ground plane unnecessary? I thought the more ground plane, the better. Especially for milling, that way the bit doesn't have to scrape off all that copper...

You have a good point for CNC efficiency - just doesn't look right to me (I'm picky!)

Here's what I do for a ground plane in DIYLC.
-Right click the though-hole pad icon - this should select all pads on the layout
-Copy it
-Increase the size appropriately, around a .6mm or so (just guessing)
-Also change the color to white
-Do the same for the traces
-Now change the PCB background color to black.
-Line everything up with the black traces & pads in the foreground.
Voila!

-Side note, thermal relief on ground pads would be ideal - takes less heat to solder.


Here's a layout for a fulltone fuzz clone I did a while back. It illustrates my points.

Let us know how the CNC run goes after you're done!

[mark2]

For milling I've used Carbide Copper. It's from the shapeoko company, but should work for any mill.

[ElectricDruid]

Especially for milling, that way the bit doesn't have to scrape off all that copper...

This is a good point, but on that basis, you need to improve the density of the components. You've got *nothing* in the bottom-right corner, and *very little* in the top-left. You'Ve got acres of unused space, and yet there's one resistor that's actually mounted vertically like it was jammed in there! If you can shrink this layout to something where the used area is much more rectangular, you'll make life much easier.

You're also using resistors at very variable lengths, hence using up more space than they really need. Typical 1/4W or even modern 1/2W resistors will fit in 0.4" comfortably. 1/8W will fit in 0.3". Your capacitors are probably 0.2" or 0.3" spacing. You've got a pair of 0.3" diodes taking up 0.6". That's wasted space that will just be bare wires on the top of the board!

HTH

[mozz]

I've milled a few boards on my Chinese CNC. Hardest part was getting a perfectly flat surface, second was the dust, it can kill you.

[mark2]

I've milled a few boards on my Chinese CNC. Hardest part was getting a perfectly flat surface, second was the dust, it can kill you.

This was my experience too.  Even doing a fresh surfacing pass right before engraving the board wasn't enough. I did quite a few trials and they were never very good; Always too deep in some areas, or too shallow in others. Usually both.

Granted this is on a 2x4 ft machine. If I could convince both myself and the wife, it would be a little tempting to try the Nomad machine, which is very small and uses a lead screw. Looks practically made for PCBs

[soggybag]

You should only mill FR1 material! The FR4 boards contain fiberglass which is hazardous!

I have a desktop CNC. I have made a few PCBs and mostly use it for milling enclosures now.   

The software specific to my machine will take an Eagle .brd file and mill from that. It's a one step process.

I could also mill something manually if I created an SVG file or gerber file. I think I can also mill from a bitmap file but I haven't tried this, should work in theory.

If DIYLC can export an SVG of the traces of your design you should be able to import that and start milling.  If the image is positive there should be an option to mill the negative areas. You could get more efficient by editing the SVG to draw an outline around your shapes. That would leave your traces without removing all the copper in between.

Be sure to check the scale and make sure it's 100%. My software always wants to scale art to the size of the material.

You'll need to set the bit and depth and feed rate based on the bit and material. When I set up a job on my machine I need to measure the material and enter that into the software. I stick the PCB to the bed with double stick tape. Add the thickness of the tape to the thickness of the PCB material.

You can repeat the process to drill. Set the depth to the thickness of your material. The tape should leave you enough room to avoid drilling the bed!

Repeat to cut out the board outline.

Check the file before you begin and imagine the traces from the underside of the board, you may have to mirror everything.

If you're any good with illustrator, Inkscape or other vector drawing program it might be faster to trace your PCB design or just draw it from scratch there! Set the grid to 0.1".

[Hemmel]

I appreciate all your answers, thank you to all.

I have a ShapeOko 2 CNC, I already have made a "PCB holder" which has been levelled and accounts for the double-sided tape - meaning that if I zero the bit right outside the PCB on the holder, it's on level with the PCB even with the double-sided tape under it. The CNC is only 500mm x 500mm and the actual footprint is even smaller.

I have a collection VBits, I've tested one but I wasn't too satisfied with the results, it seems there was too much residue after milling that was still stuck to the PCB's copper. I have used Easel online and it's quite easy to use.

I have FR1 boards, not FR4. I had already checked into that, but thanks for the warning!

Now as for the design of the board itself, this is where I'm a bit puzzled. I used DIYLC to make the PCB shown in the original post of this thread, and I know how to export it to either PDF or PNG. I have InkScape, where I know I can mirror the design, invert the colors, etc.
I had found at one time, a way to fill the design with black apart from right around the traces. That way the milling would only be done around the traces and not mill out an entire square of copper off the board. Unfortunately, I can't find that software anymore. I will have to scan my old laptop to see if it's still there.

Another thing is the fact of having traces too close to one another. DIYLC showed me that there were many traces that were too close but I felt like I couldn't do much about it (they were mostly around the IC). I'll have to re-work the layout to have it more "open".

Anyway, I'll do more tests in the coming days. I'll keep you all posted.

Thanks again for your replies!

[soggybag]

You may have to swap bits to mill the narrow gaps. The software suggests this to me. For example it will use the 1/32" flat end mill to do most of the work, then it will ask me to switch to the 1/64" end mill and clean up the details.

I tried milling with the engraving bit. This works and the engraving bit has pretty fine detail, but it leaves the edges of the copper rough, it's not as clean as the flat end mill.

I try to use the 1/32" as much as possible because the 1/64" bits break pretty easily. The 1/32" bit limits spacing and trace size.

Truth be told I bought the mill with the intent to make PCBs. Now I'm protyping my boards through a service. My last order through PCBWay.com was $60 for 60 boards, I made 6 different designs. I got 6 different boards 10 of each (they always send 11) for $1 per board.

The advantage of this has been that I get better quality boards. I like to mount the pots to the board. With the FR1 boards the copper tends to peel off if there's too much stress. The boards are all plate through and pre-tinned, so they are super professional to work with. And the biggest advantage, I can use much smaller traces.

This last point is important if you want manufacture the boards later. If I design a prototype type on the mill, with larger traces, I might not be able fit all the parts I want, and when I go to production I need to redesign again.

[vigilante397]

I have a collection VBits, I've tested one but I wasn't too satisfied with the results, it seems there was too much residue after milling that was still stuck to the PCB's copper.

I tried milling with the engraving bit. This works and the engraving bit has pretty fine detail, but it leaves the edges of the copper rough, it's not as clean as the flat end mill.

That's a common complaint with V-bits. The LPKF engraving bits are pricey, but they give excellent results and last forever. https://www.lpkfusa.com/store/pages/ProductDetail.aspx?cat=11%2F43&cid=43&pid=211

@soggybag sounds like you're using a Bantam machine?

[soggybag]

@vigalante397 yes, I have a Bantam tools Othermill pro. I'm worried the software may lose support, since they don't sell the Othermill anymore.

[PRR]

Why milled? I'd have it done already, with a Sharpie. Or just a drill and scrap wire links. Unless you are making a LOT.

[Hemmel]

Why milled?

Just because I have a mill 

[vigilante397]

Why milled? I'd have it done already, with a Sharpie. Or just a drill and scrap wire links. Unless you are making a LOT.

I went to mill first and foremost because I'm awful at etching. I had trouble getting consistent results. And as the saying goes "If at first you don't succeed, give up and try a more expensive method."

[soggybag]

I've done plenty of etched PCBs. The method has a lot to recommend. For me the down side was drilling all the holes! Super dust work after all the trouble of doing the etch.

The milling machine was nice. But I didn't find it worlds better. Just a step up.

Mass production on the mill is not what you'd think because it can 30mins mill a board. There's setup time.

For me the way to go now is having boards professionally fabbed. The quality is better I'm get is way better than anything I puked make by hand. I can pack more stuff into the same space, the boards are more reliable.

The downside to having stuff fabbed is waiting for delivery. It typically takes two weeks. But that time isn't wasted. I use that time to work on the last batch of boards and design the enclosures etc.

My work flow is design the boards in Eagle. Double check everything. When I get a few designs finished. I send them to The service, I have been using PCBWay.com, they typically finish the boards in a couple days, the rest of the time is shipping. Cost to effort it's a great deal. Like I said earlier the last order cost me $60 for 60 boards. The hourly cost to hand make all those boards would have a lot higher!

I don't want to sound discouraging. I like my mill, I'm just offering the evolution of my process.

Take a look at my: http://www.super-freq.com/

[Hemmel]

Thanks soggybag,

By the way, I sent you a PM, if you haven't noticed... 

[soggybag]

Here's a picture of the bit use for engraving enclosures. It's metal engraving bit it's pretty sturdy and has lasted a while.

https://store.bantamtools.com/products/engraving-bit?pr_prod_strat=copurchase&pr_rec_id=11123425b&pr_rec_pid=191529913&pr_ref_pid=162235861&pr_seq=uniform

The edge is getting pretty rough but it hasn't broken yet! I got some cheap bits on Amazon but the tips snap off. I'm not super familiar with tools so I'm probably not buying the right thing.