Mucking about with a cheap chinese CNC

One of the offshoots of the rise of 3d printer tech is the proliferation of cheap "CNC" machines thet use the same control circuitry as a 3d printer but usually swap out the belts for drive screws and guide rails use a cheap spindle instead of the hot end and are usually constructed out of standard 2020 extrusion and a few machined parts.

I've seen these things knocking around but mostly assumed they were trash but their prices have been dropping a lot in recent years and you can pick one up for under 200 bucks.

I decided to give one a go picked up the genmitsu cnc 3018-pro off of amazon for about 180 bucks. The 3018 is basically the dimensions of the work area
300 x 180 x 45 mm and they are mostly sold as engraving machines.

For that price you get the kit for the machine with a controller board and a power supply (little brick laptop style thing) a set of v engraving bits a separate add on box that allows manual control, two spanners for tightening the collet on the spindle, and a small brush (I assume this is for dust removal) and all the cable sheathing zip ties etc to make it neat.

It's a nicely complete package although it would have been nice if it had a milling bit as well but you can always get that and it's stated function is engraving.

The thing came as a kit with 3 little stepper motors for to drive the axis, a little Dc motor for the spindle with a prefitted 1/8" collet, some precut aluminum extrusion pieces for the frame and the bed, several drive screws and guide rods for the three axis, and some chunky plastic cut parts (not sure what it is but maybe 10mm thick rigid hard plastic cut and drilled with things like bearings preinstalled) for the sides and motor mount.

Assembly is incredibly straightforward (although I forgot to take pictures), it's all basically t-nut assembly you slot the t-nuts into the slots in the extrusion pieces put the screws in to the plastic parts tighten it down it all clamps together. The various axis require a little more work slotting the guide rods into the precut holes and then fitting in the drive screws with their anti backlash nuts attached to the movable parts then just a simple grub screw coupler to attach it to the steppers. The Z axis came basically pre assembled you just slotted it onto the x axis screw and attached the spindle motor. Electronics comes just as a premade board just attach it to the frame and plug in the steppers and spindle motor and you're done. I did have one issue with one of the stepper cables having the wrong type of plug on it but I had some of that type lying around so just popped out the wires and slotted them back in to the right plug.

It took me about an hour or so to assemble with the fiddling about to swap out the plug socket. After I'd bolted the thing together I checked it to see if it was square and it wasn't bad maybe off on the x axis but a serviceable starting point.

Usually you control this sort of machine via usb with some sort of controler program on a pc that fires gcode over a serial link to the control board that then runs the motors. This kit came with a small external box which connects to the control board (which looks like some sort of ramps derivative) and then allows you to move the three axis turn the spindle on and off but it can also send it gcode from a sdcard running the machine without any computer input.

It had three example codes ready on the sdcard included with it so I fitted one of the engraving bits that came with it (they look like 1/8" vcut engraving bits maybe v20 or 15 or so it came with a little pack of 8 of them) connected the little box up put a bit of wood on the bed clamped it down and then used the controller to set the zero point.

It doesn't have any end stops so you have to setup the zero point yourself and getting the z height correct takes some fiddling. I used the paper trick where you take a piece of paper put it under the cutting bit and slide it back and forth lowering the z height by small increments till the paper just starts to catch. I've seen you can add a z probe to the machine fairly easily basically you take a bit of metal of a known height connect it to a pin on controller and then use a crocodile clip to connect a wire from the spindle to another pin then the machine slowly lowers the cutter such that when the it touches the metal it will make a circuit then you just offset your z home point by the height of the metal. I might look at adding that although I'm not sure that will work with the controller box.

I ran the three gcodes one made a engraving of some sort of chinese word the second one engraved "IPhone" the third one did more chinese symbols but this time did more of a mill than an engrave where it did multiple passes to cut out the shape which was pretty time consuming for that little v bit where the contact point is tiny.

Here you can see the results

This is the first one a bit more closeup

Not sure if I got the z height right for that nice clean lines but just barely cutting into the surface

The IPHone thing

Came out pretty well nice sharp lines and cuts

The final one

This one is pretty nice it seemed pretty well cut out nice and sharp lines and some depth to it as I say it's not really what a v bit is suited for but shows what can be done with the machine.

So I'm pretty pleased with the results so far my next step is to try and generate my own tool paths maybe test the accuracy with some tool paths of known dimensions with these test gcodes I have no idea what they are supposed to come out like what dimensions and shape so I can't tell how accurately they were reproduced. I'd also like to get a milling bit for the thing try some more demanding work see if it's rigid enough to do more than engraving. Supposedly with slow speed settings and some cutting fluid you can get this thing to cut soft metals like aluminium.

But all in all not bad for a very cheap little machine really


This is cool. Are you tempted to get something a bit more - grunty? Do you have any projects in mind that might need it?

brainwipe's picture

I've thought about it I've been tempted by things like the Xcarve or a shapepoko or some such but the lack of space is an issue. I was quite interested in the smaller carvey cnc as it was built with an enclosure which meant dust and other shavings wouldn't get out of it while it was operating but it seems to have been discontinued.

In most respects my Shaper Origin (which is a self guiding router where it uses computer vision and fiducial markers to correct the motion of the bit in a small area and relies on the operator for the large scale movements) fixes that problem in that it can do basically any size you can physically fit into your workspace with reasonable accuracy and even work directly on objects although it can't do things like 3d cutting to any great degree it's basically just cutting 2d profiles at set depths and engraving. I used it to make a little end table thing with some fun sine wave joinery I'm not sure if I posted about that here or not. Theoretically that will cut softer metal and wood up to a reasonable depth (I've done 3/4 inch stock mostly but it supposedly can do up to 1.75" which is probably more than enough for most practical purposes).

I have the glowforge laser as well which can cut parts to very precise accuracy and 3d engraving to some degree although only if the stock fits on the bed and it's max depth is 1/2" (theoretically you can do multiple passes or double side cut through thicker stock as it can do alignment with markers or jigs but I've never tried that) it also can't do metals.

This little cnc machine can potentially do 3d carving I can't do with the Shaper Origin and more cleanly and predictably than the laser (3d engraving varies power intensity so the depth of the engrave is not very easy to predict and you are burning material away so you result is going to be charred or melted depending on the material and require some sort of cleanup)

Evilmatt's picture