My little CNC shop
By now, you should already know one of my hobbies is flying RC machines, either quadcopters or planes. My quadcopters fly, but due to imperfections they aren’t locked in. I used to cut two plates out of aluminum using wood cutting tools, drill holes with my hand-held drill and screw it all together. Needless to say the arms weren’t always square to each other. I yearned for more precision.
The ShapeOko
Enter the ShapeOko. This little CNC machine, developed by Edward Ford, appeared on Inventables in April 2012. I immediately ordered a mechanical kit. This included just the mechanical parts, no electronics. This thing needed to be imported from the States, so I could avoid some tax duties by chosing to source the electronic parts within the EU.
The kit arrived somewhere at the end of the summer 2012, but I only got around finishing it in January 2013. Proud as I was, I made a short video about the first pen drawing:
Since that video, everything was moved to my garden shed, where I wasn’t bothered by dust created by milling wood.
Waste board holders
I needed a system to hold down the piece of material to be milled. I decided to use captive nuts in a 20 mm waste board. The holders itself are made of 3 mm MDF, which is sufficient for now, but I will make them out of something stronger later on.
Mods
How great the ShapeOko might be, it seems to be designed for light work. And I mean light work, like pen drawings! As soon as you attach a milling tool, the machine shows its weak side: slack on at least two axes, y and z. Luckily a lot of changes, developed by the community, can be made in order to stiffen it. Around this point I started regretting not having waited for the eShapeOko. This machine is based on the ShapeOko, but is made by a guy in the UK and it offers a lot of upgrades when ordering it. The upgrades I will describe below, are available immediately when ordering a eShapeOko… It might seem more expensive than the ShapeOko, but you need to include shipping costs and import taxes! So everyone in the EU who wants a better ShapeOko should really be buying an eShapeOko, sorry Edward.
The first upgrade I did was installing a second Y axis motor. Without it the left side of the Y axis gets dragged along by the right side (with the motor). Perfect circles were impossible, this is just unacceptable! So this upgrade is a must! While I was installing the second motor, I also moved the Y belts to the outside. This required some extra parts, like smooth idler wheels and some belt, which I bought from Makerslide Europe (the eShapeOko shop). This increased the possible part size from about 19×19 cm to 21×21 cm. I’m still struggling with the Y belt tensioners though. Because the belts are further outside, the ShapeOko belt tensioners don’t really fit anymore. I still have to find a good solution for that.
Future upgrades I want to do are installing limit switches, dual X axis (really needed, again an option when ordering the eShapeOko), lengthening the Y axis to 70 cm and drag chains. Basically, I want Timothy Foreman‘s machine 🙂
Software chain
I make my models in AutoCAD. Thus far I’ve only mastered 2D design. Then I import the drawing (exported as dxf file) in CamBam which generates the Gcode. I double check the Gcode in OpenSCAM and send it to the ShapeOko using Universal Gcode Sender.
I have yet to learn 2.5D design (as the ShapeOko can’t do real 3D). This software chain will be updated as soon as I do.
The Arduino that interprets the Gcode and controls the ShapeOko motors, is running Grbl v0.9a Build 2013-03-19. The Z axis can’t have the same speed as the X and Y axes, due to the different way of driving them (screw vs belt). This Grbl build lets you set different acceleration parameters for the different axes, which wasn’t possible with previous builds. I managed to increase the X and Y seek rate significantly, while leaving the Z axis untouched. This spares a lot of time while milling!
Designs
My sister got married in April and I made her a stand to put her vows on:
About two weeks ago I milled my first prototype plates in 3 mm MDF for my next quadcopter, the MR450. Everything turned out great, except for one thing. In my next version, I’d like to slot pieces together. My current plate has 3 mm slots perpendicular to the X and Y axis. I noticed that when I wanted to insert a piece of 3 mm MDF in these slots, this was only possible in the slots perpendicular to the Y axis. The slots perpendicular to the X axis however are only 2.85 mm wide! This is due to slack from the Z axis carriage. This needs to be solved with a dual X axis rail…
Until now I’ve only milled MDF. Next step is milling Lexan (polycarbonate) which will be a challenge to avoid melting the plastic. I’ve also found some 1.5 mm FR4 (PCB material) that I will use for a spider quad.
