I recently purchased a little CNC Engraving Machine. They call it a "Wood Carving Milling Engraving Machine", but pretty sure it's not going to do any heavy milling. But that's OK with me. Since I already have a couple of 3D printers and a laser engraver/cutter, I wanted a small CNC "Mill" to play with. This is the model I got:
Before I go to far, let me give credit to CaptainObvious. I did a partial remix of his "Clamp set for 4030 CNC Router" thing. https://www.thingiverse.com/thing:901649
All I basically did to his set was change the hardware from M4 to M3, because that's what I have. I've included the parts I modified here, but if you need M4 or want the whole set, go check out his thing.
OK, now that credit where due is out of the way....
There are a lot of these little CNC machines out there, and other than work area, they're pretty much all the same. The one I got came with everything needed to assemble it, including tools, and had a few spare items left over. This one has a work area of 30 X 18 CM, but you should be able to use most of the parts even if your size is different.
After assembly, I found a few that were irritating or that I wanted to enhance:
- Missing any kind of handwheels
- No endstops included, so no auto-homing (I knew this when I bought it...)
- No cable management
- The workpiece clamps they included are jokes
The first thing I found annoying is that the only way to move X and Y around was to either turn the lead screws by hand, or use the software. So it needed some handwheels. This was actually pretty easy. The lead screws have support bearings on the far ends of them. First I moved the X bearing/mount to the Y screw. The X bearing mount wraps around the extrusion, so to use it you can either do what I did and add some rubber feet to the bottom of the frame, or you can trim off the part the wraps around the extrusion. The 'new' Y bearing goes on the inside of the frame. This gives you a little more lead screw to use when attaching the Y handwheel.
I designed a new bearing mount for the X lead screw. You use the bearing out of the old Y support. Mounting the X bearing support does take a little planning. The bearing gets pressed in after you install the mounting bolt/screw. First, run the X carriage almost all the way to left. Now take the screws out of the X stepper mount so you can slide everything to the right. Mount the the new bearing mount, but leave it loose enough to move a little if needed. Once the mount is in place, press the bearing into the mount. I had to use some pliers, but it didn't take any force at all. Now that the bearing is in place, you can slide the X assembly back to the left, running the lead screw through the bearing. Don't push it all the way through yet. You're using the X rods and lead screw to set the position of the bearing mount. Adjust the mount up and down until things look good, then go ahead and tighten the mounting bolt for the support bearing. Once tight, go ahead and slide everything the rest of the way to the left and reattach the stepper to the frame. It sounds complicated, but you'll see what I mean when you start doing it.
The handwheels come in two sizes. I used a large one on the X and the small one on the Y, but you could use the same size on both if you wanted to (and had clearance on the Y for it). The handwheel handle is the same for both sizes. They are designed around 3mm hardware. Place your screw through the handle and thread on a nut. Don't tighten it down. Place that assembly onto the handwheel. The nut should be in the recessed area. Attach a nut on the back of the handwheel, but don't tighten it too tight yet. Use an allen key to adjust the clearance between the handle and the first nut. The handle should spin freely on the screw. Now tighten the rear nut. You're basically squeezing the handwheel between the nuts. Once tight, the handle should still spin on the screw. If not, loosen the rear nut, adjust the screw and the retighten until you get it where you want it to be. Once you have that the way you want, install the handwheel assembly onto the lead screw. They should "screw" onto the leadscrews without too much force. You can secure the handwheels with a couple of short cap screws if you need to.
I knew endstops were not included before buying the kit, but I also knew the control board supported them.
WARNING: Before I go any further, you should be familiar with the "Right Hand Rule" and the way CNC machines understand that. Quoting from the GRBL wiki.... "By default, Grbl's homing cycle moves the Z-axis positive first to clear the workspace and then moves both the X and Y-axes at the same time in the positive direction." Also, "By default, Grbl assumes your homing limit switches are in the positive direction...". This means with a default GRBL config, the endstops for X and Y would opposite of the way I mounted mine.I had to modify the $23 variable (Homing dir invert mask) to get my machine doing what I wanted it to do.
The X endstop mount mounts to the top extrusion on the frame and the switch is activated by hitting the side of the X carriage. The version I uploaded includes a small channel for wire routing.
The Y endstop mounts to the lower rear extrusion of the frame. It could mount on either the left or right side. I'm using the right side because it's closer to the board. The Y endstop is triggered by a 'flag' hanging down under the work table. The flag slides into the table extrusion and is held in place by a captive nut and cap screw.
The Z endstop mount replaces 2 of the spacers under the Z stepper motor (the other spacers are replaced by X_Nema_Cable_Mnt). The Z endstop switch is activated by the Z carriage. It's tight, but it works.
I used some split loom to clean up the wiring going to the carriage. The split loom clips into the spacers. I've tried to keep the spindle motor power lines mostly away from the stepper lines. Use X_Nema_Cable_Mnt to replace 2 of the Z stepper motor spacers (the other 2 are replaced with Z_Stop_Mount), keep things seperated using Cable_Spacer and secure the board ends of the wiring to the frame using Cable_Spacer_Frame_Mount.
As I said at the top, I remixed https://www.thingiverse.com/thing:901649 to use 3mm hardware. Much better than the clamps supplied with the machine.