A plotter/drawing machine that uses 20x40mm and 20x20mm aluminium extrusion for both structure and linear guides.
I've tested the design up to A1 but it's probably best A3 or A2 size - after testing in A1 size I've now cut it down to a bit bigger than A3 size (old Ikea kitchen cupboard shelf). Also: you can learn from my experience & DON'T USE A PLYWOOD BACKPLATE, it's too uneven and has caused me problems - go with MDF instead.
I use EiBotBoard drive electronics because I have an EggBot, you may use this or any other system to drive 2x NEMA 17 stepper motors and one 9g servo.
I've added the OpenScad file now that it's mostly working, it should be parametric but I really wouldn't trust this. Near the top of the file there are two sections for assembly and printing; uncomment what you want from each as you want it. Each separate part is a separate module. Common variables are right at the top with some comments. It's probably not very easy to read - sorry about that.
These files are not quite the ones I printed for the A1 machine, many are slightly changed (and hopefully improved e.g. hole in the upper part of the carriage to make feeding belts through less of a pain than I had to suffer through). If I change parts I'll update the version(s).
The latest version of the machine has metal pulleys for the steppers, central belt guides and the return pulley at the pen end. The printed pulleys worked OK but I think that these will be more accurate and are quite cheap.
I have recently improved the pen lift and I'll be re-rendering the STL files & publishing the *.scad file to include this once the OpenSCAD is cleaned up
0.2mm (0.3 for large parts if desired)
Strength needed: ~20% & 3+ perimeters for the main parts
Small parts can be printed as you wish, larger parts & especially the ends and carriages need to be strong and stiff. I used rectilinear & 3D honeycomb infill mostly but again, as long as it's strong choose what you want.
PLA works well.
You need to print:
2x endBase & endStepperMount
4x centralPulleys (I think the STL contains 4 already)
...and 1x of everything else (assuming I didn't miss any files)
Socket cap screws needed for construction (M5 and M3), stainless steel is probably best
You will need 8x M5x70mm for the central assembly with nuts (ideally lock nuts but this is not mandatory)
For the rest of the construction you will need an assortment of M3 socket-cap screws in 6mm, 8mm, 12mm, 16mm, 20mm shaft lengths - if you don't have these already it's probably best to buy a pack with these lengths.
You will also need 4x M3x35mm screws, often these will need to be bought separately as I've never seen them in packs with the other lengths needed.
You will need some M3 nuts also. Many parts require holes to be tapped so a 2.5mm drill bit and M3 tap is required.
You can print all pulleys required (made using droftarts pulley library https://www.thingiverse.com/thing:16627) but you can buy 20-tooth GT2 metal drive pulleys also with (normally) 5mm bore to fit your steppers, these are a bit small but work. The printed pulleys are 24-tooth because reasons so you'll get different resolutions if you change between the two.
You will need GT2 timing belt, I bought 10m and had plenty for an A1 machine.
You will need to buy aluminium extrusion - for an A1 machine I bought:
- 100cm of 20x20mm extrusion
- 80cm of 20x40mm extrusion
If you're printing pulleys you need 6x ball bearings for the central pulleys and the return pulley (3mm bore, 10mm OD). You will also need 8x 15mm diameter v slot rollers (like this http://ooznest.co.uk/V-Slot/Wheels/Mini-V-Wheel) with 5mm ID. I've also bought wheels on Amazon (UK link: https://www.amazon.co.uk/V-Slot-V-Wheel-Xtreme-Delrin-Printer/dp/B07KKG4RM7/ref=sr_1_5?ie=UTF8&qid=1547817008&sr=8-5&keywords=mini+delrin+wheel)
If you buy pulleys for the central and return get 5x 3mm ID smooth (not toothed) pulleys. Drive pulleys need to be toothed with lock grubscrews, 20 tooth is good.
The cable management solution I chose was based on some stiff 5mm OD tubing I had lying around, you may choose a different option if you don't have or can't find that. There are holes provided in some parts to mount these cable management fixings, if you use these carefully & slowly drill & tap holes where required (don't go fast and melt things, the bolts won't bite).
Because I used an EiBotBoard (which is excellent, but expensive & somewhat hard to find) with the same kinematics as the AxiDraw I use the AxiDraw Inkscape extension to drive the plotter. If you choose this option you need to make changes to "axidraw_conf.py". I decided to alter the settings for the AxiDraw V3 XLX for my A1 machine (in inches because 'murica):
XTravel_V3XLX = 25.75
YTravel_V3XLX = 34.33
NativeResFactor = 1016.0 # for 20t metal pulleys
NativeResFactor = 850.2 # for 24t printed pulleys
I didn't change anything else (although I think you should change MaxStepDist_LR & MaxStepDist_HR)
If you don't have an EiBotBoard I think that there is an emulator for it that should run on an Arduino but I've never tested it, other solutions are possible & there should be many examples on Thingiverse.
I have found a drop-in EiBotBoard replacement that is quite cheap, I bought one and it does work. I will keep this board on the plotter so that the EiBotBoard can go back on the Eggbot. I bought this: https://www.aliexpress.com/item/EiBotBoard-board-eggbot-drawing-machine-main-control-board/32789757886.html
It arrived in a couple of weeks and I'm ashamed to say the way that the black circuit board coordinates with my white printed parts and black bearings, belts and wheels pleases me quite a lot :)
All parts designed in OpenSCAD, I've uploaded it - good luck understanding it