CNC Machine

Hopefully you’ve read Little CNC Milling Machine (Part I) in which I completed the mechanical build of a tiny CNC machine. Here’s Part II!

CNC Machine Electronics

The electronics didn’t take much time at all, it was pretty much “plug and play” as far as connecting the three stepper motors and the spindle. No stripping, cutting or crimping wires. The only issue I had was once I tried running it nothing was happening. Turns out the power supply was DOA. I found a 16 volt laptop power supply in my junk bin and tried that, and it still didn’t work (or so I thought.) I ended up cutting the barrel jack off that power supply and putting it on a 24 volt supply I found. It was then I realized that the spindle wasn’t responding because I never set the “spindle speed”. So yeah, steppers worked fine with the 16 volt power supply (but not the original 24 volt supply I got) but the spindle didn’t go, because I’m a fool. All good now! I’ve got functioning 24 volt power supply and a functioning CNC machine.

CNC Machine Electronics

I’ve used Grbl before, usually with an Arduino and a CNC Shield with some steppers. Some of these kits seem to use an Arduino Nano, but this one is its own board with an ATmega328P and a CH340 chip. So yeah, an Arduino with Grbl 0.9 pre-loaded.

There are no endstops, but it looks like there’s room on the board to add them in the future. I can think of a few other improvements as well. I may add an e-stop, or just an “on/off” switch for the power supply. One nice thing about these machines is that if you make a mistake, like jogging the head too far in one direction, you can just cut power to the motors and the software will keep going, assuming the motors are moving, and then once the software is done, you can resupply power and try again.

Oh, you might also notice that next to the spindle connector on the board is a spot to plug in the laser. Yes, there’s also a 500mw laser that can be put in place of the spindle. I’ve not really tried that yet, and have to figure out the software to control it first. (I’ll get into software in a future post.)

CNC Machine Bed

Another area that could use some improvement is the bed. Attaching things with the screws meant to attach things to the Aluminum extrusion is not great. I’ll work on a better clamping system. (Maybe a 3D printed piece, not sure yet.)

You might also notice I left the lead screws hanging in mid-air. I did have a little bit of a binding issue with the x axis, so I just removed both lead screw holders. I think it’ll work fine without them, as the lead screws are not that long.

CNC Machine Collet

The machine came with two tiny collets that allow you to attach bits to the spindle shaft. It also came with super-small set screws. I’m pretty sure I’ll lose the screws, but…

M3 Set Screws

…luckily a few years ago my friends at Evil Mad Scientist Laboratories sent me a lifetime supply of M3 set screws of various sizes. I think I’m good!

CNC Machine Electronics

And yes, I did actually mill something. I’ll cover that in the next post. Overall I have to say I’ve been pleased with this machine (so far, it’s still early, obviously.) It was easy to put together and it works. Once I get things dialed in I’ll look into milling PCBs, and foam, and wax, and chocolate…

Stay Tuned!

Little CNC Mill

I’ve completed the mechanical build of a small CNC mill/engraver. I’ve seen these on eBay from various sellers (like this, this, this, and this) and I’ve even seen one on Amazon from LinkSprite. I didn’t order from any of those sellers…

Somehow I happened across a blog post at TC Maker about a CNC Building Class at The Hack Factory. While I would have loved to have attended the class, I couldn’t make it, but I got in touch with Alex to ask a few questions, and the next thing you know I’m ordering a kit from him.

Alex said he’ll be doing another class, and hopes to sell these to other people as well. (I guess I’m one of the first customers?) I was attracted to the mill because it’s small (my workshop is cramped already) and it runs Grbl. I’m hoping to mill PCBs with it, and other small things. If I get really ambitious I can extend the machine with some longer lead screws and Aluminum extrusion. But first I have to get it working… I still have the wiring and electronics to deal with.

I’ll go through a bit more about building it in this post, and probably follow up with a few more posts once it’s complete.

Little CNC Mill

First, let’s talk about the instructions. Remember, Alex does an entire class on building this, which I did not attend, but I’ve built a few CNC machines in the past, so I wasn’t too worried. I did get a construction manual, and it was helpful, though in the end it sort of reminded me of building my RepRap. At some point the instructions seem to lose their usefulness and you just have to figure things out. Luckily, there’s the Internet.

The page titled DIY CNC 3 Axis Engraver Machine PCB Milling Wood Carving Router Kit Arduino Grbl is helpful, as is the video LinkSprite DIY CNC 3 Axis Engraver Machine installation tutorial. I should mention that these kits come from different sellers, and they all seem just a slight bit different. Minor things here and there, so again, if you can figure things out on your own, it’s not that bad.

There’s some videos from Jingfeng Liu that might be useful, including LinkSprite CNC Kit base Video 1, How to assemble LinkSprite CNC kit front video 1, and How to assemble LinkSprite CNC kit front video 2. Again, use them as loose guides.

Little CNC Mill

The worst problem I had during the mechanical build was dealing with the rod holders. Now, I’ve used rod holders before to hold smooth rods, and didn’t have issues, but these caused me some heartache. The one on the front right was the first I dealt with. I tried to tighten it up on the rod, and I could not get it tight enough to hold the rod. After I sent an hex key flying across the room, I tried one more time to tighten it up enough by putting a Torx bit in a drill (I know, bad idea.) This just stripped out the screw, and now it’s in there, and not coming out. (Oh, before I over-tightened/stripped it, I tried to put a little tape on the rod. Kapton tape seemed thin enough, but was still too thick.)

Little CNC Mill

I still had three rod holders to deal with, so I took a different approach. I put one in the vise and cranked on it to pre-bend the metal just enough to hold the rod tight, but not too tight. Well, I managed to do that with one of the rod holders. The next one I cranked too much, and then had to pry open a bit with a slotted screwdriver. (You can see in the photo above a little bit of the damage from that. In the end I got them all working good enough, except for the first one, but since the back rod holder is good, I may not have to worry about the front one being tight enough. (It doesn’t wobble, but I was able to rotate the rod when it was just in the front holder.)

CNC Machine

There’s a 3D printed part on the front for the lead screw to set in, with a bearing. I have not mounted this yet, as I’m not sure it’s a good idea. Some builds use this, or a metal plate, and some let the lead screw hang free in the air. (The x axis has a similar holder.) As this is not a super-precise machine, constraining the lead screws might not be the best thing…

Little CNC Mill

The shaft coupling is one rigid piece, which means that if not perfectly aligned, constraining it on the other end could cause binding while trying to turn. I’ve used flexible couplings before and they might be a better option. Again, I’ll probably get the machine up and running first to check the performance before I think about upgrades. (I talked to Alex and he suggested that flex couplings might not work as well as I think they would. I’ll do more research on it.)

Little CNC Mill

The mechanical build took an evening, not a late-night evening, but a full evening. I expect the electrical portion to take maybe a few hours at most, including getting it up and running. Hopefully I’ll find some time this week to get that going, and report back.

Stay Tuned!

USB Mount

I designed a small part to hold a panel mount USB cable. I started with the Phoenix Connector Mount I briefly mentioned before, and did some quick modifications to make it work with the USB cable.

USB Mount

I designed this thing in OpenSCAD though I did borrow a few elements from another recent model so that I could use 5/8″ #4 screws. The bottom where the screws go in is set to a height that allows the screws to go in just under 1/4″ which is enough to hold, but not enough to go through the material they’ll be screwed into. This is one of the things I love about making custom mounts and brackets, you can configure them to match the hardware you have available.

USB Mount

With many of the things that need (semi) precise placement of things, it takes two to three revisions to get it right. I actually used the second revision because I was in a hurry, but I’ve modified the file so version 3 will be just right next time. (I had the panel mount screw holes just a little too close together. Things flex enough that it works, but it could be better, and will be… next time.)

USB Mount

The first version actually warped quite a bit in printing. It’s a problem we seem to have occasionally with the old MakerBot. It’s always the front left corner of the print. I find that by shifting the print on the bed to the right just a bit often fixes the problem (at least for small prints.)

USB Mount

You can find this design on YouMagine and Thingiverse.

Ethernet Tester

I should probably just submit this to Hackaday’s Fail of the Week because this is full of fail. I’m going to share it all anyway.

Sometimes at work we make our own Ethernet cables, and we usually test them by connecting them to computers, or whatever weird electronic thing we’ve built, and we hope they work. They usually do, but we don’t have a good way to test them. I know there are network cable testers but they are expensive. (Mistake #1, more on that later.)

I had some RJ45 8-Pin Connectors and some RJ45 Breakout Boards on hand that I never used so I came up with the “brilliant” idea of building a simple Ethernet Cable Tester. (Mistake #2.)

Ethernet Fail

The idea was that you could make an Ethernet cable, plug it in to each end, and then use a multimeter to check continuity by matching up the colored wires on each side. Simple, right? Right…

Ethernet Tester

I decided to use a piece of stripboard, which seemed perfect for this project. For whatever reason, my soldering skills went out the window. I swear I know how to solder, and I’m actually pretty good at it. Maybe it was just one of those nights where everything goes wrong. And when I tried to clean things up my solder sucker kept not working. Just, not working. Why? I don’t know!

Ethernet Tester

Oh, and you see those notches in the board? I had to Dremel those out because it was too difficult to press the little lever that releases the RJ45 connector. It was even worse with cables that had boots on them. (Mistake #3, or #4, I lost count.)

Ethernet Tester

There’s also a lot of hot glue on there. I was using that to hold the wires in place because it seemed like some didn’t take to the stripboard very well and I had to add more solder. Yes… more solder! (Mistake #4 or maybe #5.)

Ethernet Tester

Sure, more hot glue. This time to make the breakout boards stay level and not flex around when plugging in cables. This sort of worked, so it’s not terrible, but yeah… hot glue. Fine.

Ethernet Tester

So the good news is, it does work. I tested some cables. I didn’t have to build an expensive Ethernet Cable Tester. I was so proud of myself I decided to see how much money I saved the company.

Oh hey, look… I can find some cheap network cable testers on Amazon (with Prime!) for under $10. Aw, shit… I give up.

Bitbeam Fan Holder

I have a computer fan on my workbench at home that helps draw the fumes away from me when I solder. I’ve been meaning to get some Carbon filters for it (which I just ordered) but I also want one for my desk at work, so I finally got around to building a little stand to get it up to the same height as the helping hands I use for soldering.

Bitbeam Fan Holder

I ended up using some piece of Bitbeam to build the frame. I love Bitbeam and should probably use it more often. Jason hasn’t really done much with it in the past few years, but you can still find some info on Thingiverse and Github. (I’m sort of tempted to start designing some compatible pieces, plates, and other bit and bobs.)

You might notice I had to angle two of the pieces. Things didn’t quite line up with the fan mounting holes, so I improvised a bit.

Bitbeam Fan Holder

And while I did have a good collection of 6-32 nuts and bolts, most of the bolts I had were either too short or too long. (I ended up using the ones that were too long because the other option didn’t work at all.)

Bitbeam Fan Holder

Here’s the fan stand raised up to the proper height to match the helping hands… all ready for soldering! Well, almost ready…

Bitbeam Fan Holder

I added a barrel jack to the fan wires. These brushless DC fans (from an old Apple Computer) require you to twist three wires together for the positive, and use one wire for negative. (You have to experiment to determine which are which.)

I also used a 5 volt power supply from an old Zip Drive. What else am I gonna do with a Zip Drive power supply? While the fan expects 12 volts, it just runs a bit slower (and quieter) at 5 volts. If it doesn’t draw enough air I’ll change it to 12 volts.

Bitbeam

If your 3D printer is sitting idle, print some Bitbeams to have on hand for a future project. I’ve got a box of various sizes at the ready for the next time I need a simple framing system.

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