Hackerbot Project

Earlier this year I decided that I’d like to have a 3D printer. I’d considered getting one for a while but I’d felt that they were too much hassle for not enough quality. This year I reconsidered and finally took the plunge. After considering my options I decided on a set of design features I wanted: an enclosed build area for better temperature control, independently-controlled axes, and modular construction to make it easy to change things in the future. I found the Hackerbot Project and decided it was just what I was looking for. I made a few minor changes to the design (made it taller and replaced the one big door with two smaller ones) and I ordered my parts and got started.

Well, before I could order the parts, first I had to list them. The Hackerbot instructions suggested ordering the beams for the frame from Bosch-Rexroth but my initial experiences trying to deal with them and their website were not good, so I chose to order from Misumi instead.

The first step was to get their catalog. It’s a beast at around 3700 pages. But the benefit of a paper catalog is that it’s easy to browse even when you don’t know exactly what to search for. The process of building my bill of materials was a slow one: since I was ordering from a different manufacturer (and changing bits of the printer’s design here and there to suit my tastes) it was a challenge sometimes to find everything I needed. The whole process took a couple months.

Unfortunately, at this point I made a few critical mistakes: First, that catalog is three years old, and prices have changed. I had expected my Misumi order to cost around $1000, instead it was closer to $1500. (Adding the cost of electronics, the total cost for the project is probably $2200 or more… Really was hoping I’d manage to make the project cheaper than that.) Second, not wanting to enter my lengthy bill of materials twice, I entered it on Misumi’s website as an order rather than a price check. So I not only was spending more than I’d expected, I committed to that higher cost almost immediately. And because many of the parts were special orders, pre-cut to particular sizes, there was no practical option for cancelling or returning the items once ordered.

Really I ordered more from Misumi than I should have anyway. It’s more convenient to order a 5mm plate cut to specific dimensions rather than to get some metal stock and cut it myself. But with all the other challenges of this project, I needed some convenience. It’s unfortunate that the cost of the machine wound up much higher than I’d expected, but there’s no point in dwelling on those mistakes.

Once the parts had arrived, I was ready to begin assembly. I don’t have all the tools at home I needed for this project so I joined Makeit Labs, a local hackerspace, to get access to some of the tools and help I needed. My membership also allows me to store the project at the labs when I’m not working on it, which is very helpful.

One thing I wanted from Makeit Labs was access to their powder coating system. Powder coating is a method of painting metal – you spray electrically-charged pigmented powder at the part. The electrical charge helps the powder adhere to the metal, then you bake the metal, melting the powder and forming a smooth and durable coating. I coated the frame yellow. During application the powder would sometimes get on my hands or clothes and it reminded me of the powdered cheese that comes with macaroni – so I’ve taken to calling the project “Cheezbot”.

One of the really tough things about powder-coating these frame parts is that some of them are pretty large: the longest beams, the uprights, are 70cm long. Those beams just barely fit in the oven, when placed diagonally between the top-rear-right corner and the bottom-front-left. To keep them from bumping into the oven or other beams (and losing some powder in the process) I pretty much had to bake the long beams one at a time. This contributed to the time-consuming nature of the process.

While assembling the frame for the door, I made another unfortunate mistake: The door frame screws together, but you have to tap the holes for the screws first. Due either to the poor condition of the tap I was using, or the fact that I wasn’t oiling it, I was having awful luck with the process. Instead of tapping out a threaded hole I’d wind up just stripping it out entirely and having to use a longer screw. I switched to using the screws themselves to tap the holes, which was very difficult and time-consuming, and in one case I broke the screw off and had to improvise a solution.

One of the weirdly popular jokes about 3D printers is everybody says “Oh, you should use the 3D printer to print another 3D printer!” That’s not really possible of course, but to a certain extent, it is done all the time. All of the current wave of personal 3D printers trace their lineage back to the RepRap project, which was begun in 2007 on the occasion of some relevant patents expiring. Reprap was designed to be partially “self-replicating” – meaning that whatever parts of the machine could be 3D printer, were 3D printed, so once you had one machine you could build more without having a lot of fabrication skills. (This is why patents are bullshit. Somebody develops a process and patents it, then for the lifetime of the patent they have a monopoly on the process. Then the patents expire after 20 years, and then you get innovation and competition. Rubbish. We could have had Reprap in 1990 if not for patents. We could have been salvaging stepper motors from old printers, controlling them via the parallel ports on our DOS PCs – but thanks to patents that didn’t happen.)

These days you see fewer and fewer 3D printed parts in new 3D printers, because 3D printing is a slow process that’s not well-suited to large-run manufacturing. But many 3D printer designs (especially do-it-yourself designs and some of the kits) still incorporate a few 3D printer parts. In the case of the Hackerbot, this includes the print head, some bearing supports for the X/Y carriage, the filament driver mechanisms, and about 70 panel supports used to mount the enclosing panels on the frame. For these 3D-printed parts I used the Makerbot 2 at Makeit Labs. 3D printing is a slow process, and even now I haven’t printed everything I need for the printer. The Makerbot is also designed for use with PLA, a popular biodegradable printing material. Some of my printer parts needed greater temperature resistance than PLA offers, so I needed to print them in ABS. But ABS tends to shrink and warp during printing, so to keep the print from failing due to this warpage you usually need a heated print bed. Many of my early attempts to print ABS parts on the Makerbot failed: We put these failed prints in a jar, to be drowned in acetone and turned into a slurry which, when applied to the print bed, will make prints adhere to the print bed better.

I also suspect the green filament I was using for early print attempts may have been of rather poor quality… Buying the cheapest filament you can find is not necessarily the way to go.

It took a while to powder-coat everything, and I wasn’t really happy about the fact that I was delaying other parts of the project with this time-consuming process… But I’m glad I did it all the same. While I look forward to having the completed machine, I also enjoy the challenge of building it, and I like to take pride in what I’ve built. Decorating the machine isn’t important for any practical reason, but putting that kind of effort into it results in a machine that I’ll enjoy even more when it’s finished.

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