Cutting PCBs on Carve King?

[rcferguson]

Is anyone here creating PCBs on a Carve King or Power Router?

I'd like to whip out a couple boards without sending everything out to DirtyPCBs.com or OSHPark, but I don't know where to start.

I use KiCAD for PCB design, and am familiar with Gerber files, but don't know where to start converting this stuff to GCode.

[tgattis]

I just checked Fusion360 and there is a "Create PCB" plugin within the Create tab at the very bottom...I would assume you could design it, then go over to the CAM section and create tool path and then create the G code.

[rcferguson]

Jul 23, 2019 19:04:08 GMT tgattis said:

I just checked Fusion360 and there is a "Create PCB" plugin within the Create tab at the very bottom...I would assume you could design it, then go over to the CAM section and create tool path and then create the G code.

I wasn't aware Fusion 360 had PCB design tools built in... I'll see if I can find them.

***EDIT***

Oh, I see what you are referring to. Eagle PCB has an option to output its files to Fusion 360 for PCB creation, and there is a plugin for that. Unfortunately I don't use Eagle PCB. Thanks.

[rcferguson]

I found a link to Carbide Copper which looks like it might work. I quickly went through one of my old PCB designs and ran it through their online GCode generator, and it look promising. I'm going to run the file on my Carve King and see how it looks.

***EDIT***

MMM not so sure its going to work. It generates just one GCode file, I guess it assumes automatic tool changes. Also it doesn't appear to read my Excellon drill file correctly, as it has all holes the same size. I'll keep looking into it.

[rcferguson]

OK, now we're talking.

Here is FlatCAM.

This looks like it might work great.

[Derek the Admin]

I'm interested to see your results.

[rcferguson]

So I need to test some toggle switches for some USB switch panels I'll sell as part of my simulator controls collection. These will basically be a panel of 18 SPDT switches to make use of the 36 joystick inputs available on my controller. I've been using full-size switches in my cockpit controls, because they have a good feel to them. They are certainly overkill for the application, but I feel it heightens the immersion to have big switches, much like you would really have in a cockpit. The problem with these big switches is that they typically come with screw terminals, which means hand-wiring, which means a LOT of time wiring terminals, increasing the price of the end product. I need to be able to make a PCB that they can be soldered to, to make it easier to assemble. There are some made with spade terminals, which make soldering a little easier, but they are still time-consuming to solder, and getting PCBs made with large slots instead of holes for through-hole switches is immensely more expensive. I found a Miniature switch on AliBaba that they will make with a large (12mm) mounting barrel, and extra long switch lever, so i ordered 100 pieces to try out. After receiving them I'm not sure they will work, because even though they look from the top like a full size switch, the lever doesn't feel as good, mainly because the throw is so short, and it doesn't have a really satisfying travel. I've whipped up a circuit board that I'm going to mill on my Carve King so I can give these switches a real test. Because the traces can't be as fine as if I got PCBs professionally done I've made a quick one-sided design that I'll have to add some jumper wires to the other side. I stick it in my flight sim and use it for a bit to see how it works out. Who knows, maybe these switches will feel OK in action, and if so, I'll tweak the PCB and have a bunch made. After some searching, I found a full-size toggle switch that the company WILL make with solder terminals. I've ordered a hundred of these for testing too, and I'll design another PCB for the Carve King to test them.

Anyway, here are some results from the design:

  

Here are the FlatCAM results:

 

Looks like that's all the pictures I can include in this post.

I need to make a vacuum fixture to hold the raw PCB material down on the Carve King... it needs to be really flat so the V-bit can cut the copper layer on the PC board. Once I've done that I'll post my results.

[rcferguson]

Thought I'd post a few more pictures pre-PCB.

I'm 3D printing the switch panel here for testing purposes. Ultimately they'll be made of cast resin.

[Derek the Admin]

Looks good. I really enjoy updates on your project.

[Bruce]

Thanks for all the updates on your process, Rob. This is a much larger project than I originally thought. Really interesting.

[rcferguson]

OK, designed vacuum fixture. 2 pieces of 1/2" MDF cut 15"x15". Plastic hose adapter for my shop vac will be 3D printed in 3 pieces.

I'll start printing the adapter tonight so it can run overnight, and I'll start milling the MDF in the morning.

With any luck I'll be cutting PCBs by tomorrow afternoon!

[rcferguson]

Didn't get everything done because I went to the beach this morning, but the fixture is mostly done. Hope to cut PCB tomorrow.

This was my first experience working with MDF, and I suspect it will be my last! Easy to cut, yes, but incredibly dusty (I knew that going in) and very fragile stuff. As per the photo below, you can see a number of the supports I built into the base have been broken off... when the end mill makes the last cut the vibration just jars the pieces loose, because the MDF is so weak. I got the end of my shop vac nozzle in there and applied pressure to the supports one by one to try and minimize the damage as they were being cut, and I suspect I put in a lot more than necessary, so I don't think the missing ones will really hurt anything. I forgot to reset my Z when I laid the top piece of MDF on the bottom, so the shoulder I meant to cut in the front right corner goes all the way through the piece. No problem, I glued the pieces together, so when the glue dries I'll replace the long bolt with a shorter one.

The vacuum hose adapter came out almost perfect... the round flange piece that connects to the hose was supposed to be a friction fit, both in the bottom of the adapter, and also on the shop vac hose, but it was a little loose on both counts. No matter, a quick adjustment in Fusion 360 and an hour and a half on the printer and the next iteration came out perfect. I was originally going to glue the top and bottom together, but I think just a piece of masking tape will work fine, and will allow me to easily disassemble it if I need to make any adjustments.

 

I tested it out with my little shop vac by covering the holes with paper and holding the hose adapter in place, and it generated a very strong suction on the pieces of paper, so I think it will work great with PC board.

Tomorrow after the glue is dry I'll flatten the top surface with a 3/4" bit and attach the hose adapter. Then it's off to the races!

[rcferguson]

So I am going to rate this experiment a resounding success!

Since this was the first time I had ever tried this, I was just kind of experimenting. I had no idea what feeds and speeds to use, or what tools.

On the first attempt I used a "60 degree" V bit as was suggested and recommended. I didn't care for how the pads came out, and some of the traces (which I had designed as 1mm) were almost non-existent. Depth is really critical when using a V bit, just a couple thousandths of an inch makes a big difference. I backed off on the depth and tried again, but i was getting a lot of variation in the pad and trace sizes, and a lot of copper was being left between the milled areas where it should have been removed. This led me to look a little closer at my V bits, and I realized they were actually nowhere close to 60 degrees. I guess you can't really depend on the description of cheap bits from China on Amazon. I compared them here with an actual 60 degree V bit, and it is pretty obvious they are probably more like 12-15 degrees. You can see in the 2nd picture below that it left a lot of copper in between traces that I didn't want there, because they come to such a sharp point. I tried a third PCB using the actual 60 degree bit, and they were a lot better, but still not optimal.

Anyway, I watched a couple Youtube videos of other folks milling PCBs and saw they were having the best success using flat end mills, where the depth isn't as critical. The smallest bit I had was a 1/64 inch (.4mm) ball end mill, so I tried that. Really came out nice! I've ordered some .5mm flat end mills for future use.

I'm really happy with the results. I made the holes for the switches a little too big, so it took a lot of solder to fill them, but no big deal, this is just a test anyway. If I end up using these switches it is just a 5 minute operation to redesign the pads in KiCAD.

The vacuum fixture worked perfectly! PC board was rock solid in the fixture with no chance of moving when the vacuum was switched on, and I used a couple pieces of masking tape to ensure it didn't move when I had the vacuum off.

[rcferguson]

A few pictures of the finished product.

I'll be testing over the next few days, and the next batch of switches will arrive this week from China. They will be full size and I expect I will like them better than these, but we'll see.

[Derek the Admin]

Great work man! I'll share this on some social media accounts and give you a mention.

Thanks again for letting us check out your project.