Makibox – Oozi

I bought a cheap 3D printer. Once I had bought it, I found out it was from clearance but had probably already been in some way paid for, which is annoying. Someone else didn’t get their machine, and while I know there is no direct connection between me having this and another, particular person not having it, I am still profitting in the cheapness of a clearance machine from the money that someone else put in.

That aside, and it’s not a moral problem for me given the circumstances, I’ve now got a cheap 3D printer. The hot end, where the plastic gets melted, is famously terrible on this machine. It was a new design and tiny tolerances were needed, and it didn’t quite work. And also, I broke mine. So I’ve 3D printed a different big of plastic to hold a different head, and someone who was not using an old heater end and some other bits donated them, meaning I’m still getting a cheap 3D printer rather than an expensive time sink. It’s a cheap time sink instead. Currently bits of the hot end are cable tied together and the whole thing is about as shonky as a unicycle on a rocking chair.

Iterating Wobblebot (and a side project)

I’ve laid the cable track, planned the new screws and bought another identical to the second…

So, as it turns out, not all lead screws are the same, even when they are supposed to be. The first one I bought has a thread that’s at the right pitch, and the right height, but the trapezium shape is too narrow. This was leading to a huge backlash problem, which I thought I would have to deal with by making anti-backlash nuts. However, the other lead screw, which I had bought thinking it was a pair, doesn’t have that. There’s more metal, and it fits snugly in the nut I have. That means there’s hardly any backlash at all.

I’m still interested in making the anti-backlash nuts, and I have other uses for a tap for that shape of screw, so I’ve ordered a length that I’m going to try to tool into a tap, with the lathe and the mill. Clamping it is going to be a right beggar – I might enclose it in a thermoplastic and clamp that instead.

Microswitches and Morality – earning it

I want to buy a couple of packs of microswitches from RS Components on Friday. I don’t have enough in my bank account to cover them right now. So, really, I should not buy them on Friday. I should buy them when I’ve earned cash from painting. So, next in line on the workflow is calling up and checking where my pedlar’s license is. Grrr. This ‘work’ stuff…

Wait, other than the admin I like it. I get to paint stuff. Yep.

ETA: New licence is in the post. Somehow it got lost along the way.

Through-hole soldering tips for the gutter punks

  • When putting headers onto anything flat, do it upside-down with the headers in a breadboard
  • You can use female/male headers above any pins or headers you’re putting on, to make sure they stay aligned and vertical
  • The plastic on headers will melt at soldering temperature, so never rely on a pin staying still
  • Components can be kept in place with blue tack, which does not conduct electricity…
  • …unless it’s got little bits of metal stuck in it
  • Solder diagonal corners of anything with more than two legs, and check how it’s seated before you commit to the rest

Microswitch Fail – in a bad place

I had some cheap microswitches, and one had failed, but we figured that it was just one in the bunch, and put it into the interlocks of a laser cutter, to replace a switch that had started to fail. Then a second one from the batch committed suicide in my hands. This may have had something to do with the fact I was taking wires off and the plastic casing melted a bit, but it was Not Good. And indeed, Demonstrably Not Safe.

So, that’s been swapped out. And I’m off to eBay to find some that look like they were made by the /second/ lowest bidder. Cheap is good! Except in cut-out switches.

Itchy: Improving stuff

The current base of Itchy is a slice of plywood on some 40mm blocks with some nuts used as spacers. I’m calling that ‘non-ideal’. It’s going to have MDF on a raised base of some kind, probably made of lengths of 20×20 extrusion. It might be removable, and probably should be, but ‘removable’ just means having countersunk screws, and maybe some kind of cover for them. ETA:I just remembered I know where there’s some sheet steel. I must remember not to overmake this.

The entire gantry swivels about the lead screw. This is slightly more than non-ideal. It’s a significant error. Mat’s been helpful about that, after he stopped cringing. (He called it an abomination. I’m so proud.) Two lead screws worked from the same stepper would move that squarely. I’ll have to add anti-backlash nuts, but that isn’t a problem – I have two bearing blocks on either side, and I tapped them both. Adding in the second cross-piece hasn’t been a priority yet. When I do it, I’ll have to do it properly and arrange everything nicely. Right now crosspiece #1 is held on with two pairs of corner braces that are bolted to each other. That was only ever temporary, but I’m impressed by how well it’s been working.

The head needs building, rebuilding, or re-re-building, depending on how I’m keeping track. The belts are currently attached to a piece of acrylic, which is not actually terrible given the amount of pressure on it. However, I’ll be wanting to put more pressure on it. This is another non-ideal part. It’s not a critical part of this round of improvements. The motor at the end of the gantry is held on by a single piece of 5mm acrylic and the power of hope. That /is/ a critical part of the current round of improvements. I need to make that out of metal, and have a bottom brace to it as well. I’d have made it out of metal but that all went badly wrong when I put it onto the rotary table on the mill. We don’t have a single bit wide enough to get the raised part of a NEMA motor sit inside a hole. On the head I got around that by not having enough of a hole in the first place, but I knew the head was temporary, and I want to do this properly. The best way is probably to make a threaded rod for the mill that has a cone ending, so I can centre-find. I’m likely to eyeball it all and hope, though.

The biggest features now are the splorted wiring everywhere like someone has disembowelled a pinata full of multi-fruit bootlaces, and the fact that some of those wires are inherently unsafe. The limit switches are currently push-to-make, and should be push-to-break. That was a speed thing, but I can invert them easily enough now I know what the firmware is, and that it’ll support the pin inversion. I have cable track now, so I can run them all safely. The head/motor holder designs both need to take into account limit switches and wiring anchor points. I tried 3D printing track, but the joints were not good enough.

In order of importance, there are the safety items first – limit switches and wiring – and then the thing that’s arguably a safety item, in that I don’t want motors to snap off and should therefore get rid of the acrylic – and then the wobble along the bottom axis, which different people call the X or the Y. I’m thinking of calling it ‘the axis with the motor nearest to me’ which is my kind of naming scheme. (It’s a bit weird, because it’s not like a graph where you plot things. It’s a graph where the axes are used to move the other axes. So a movement in the X, from left to right, can be made by a stepper that is sitting along the Y axis. This has been a source of massive confusion to me, so the milling course at makespace just has ‘long axis’ and ‘short axis’ and then nobody has to think. And, more importantly, there’s less chance of fucking up through people not thinking.)

In terms of what I’m realistically going to do first, it’s got to be the wiring, then it’ll likely be the wobbly bottom, then the motor mounting, and then a big redesign of the head. I can probably deal with the wobble a bit by only having three blocks, which would let me position the rods to minimise the travel available – but that’s the wrong way of doing it, and a double lead screw is the right way.

Itchy: Victory

A block of wood with a distorted silver circle drawn on itLast night I put everything together. The tool chain is now clear. I learned what ‘tool chain’ means from Co-Squidly. It was a word I knew but had never really respected, and now I do. So, here’s the flow:

  • Generate paths in Inkscape
  • Inkscape -> Extensions -> GCodeTool -> Path to GCode
  • Clean Gcode – inkscape uses (comments like this) and gcode needs ;comments like this
  • Import to bCNC (python GUI to send gCode)
  • Send to Arduino
  • Magic happens. Stuff moves!

The silver circle on the wood above was drawn in inkscape and sent to the machine where it was drawn with a Sharpie. I’ve built a machine. I declared tea and victory, and went home.

My friends have nicknamed it wobblebot. This is not unfair. It needs a lot of work, but it’s what I was after.