Last leg of the old hot end

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Last leg of the old hot end

One of the first things printed to an immediate end turned out to be a z axis mount for a prusa i1 – not that I meant to make one of them, but it seemed apparent at the time the quickest way to improve print quality could be the z axis, which was (and still is) cobbled together from an old printer and not designed for vertical motion. As the print progressed though it became apparent there were larger issues at stake – the hot end leaked, bridging was unreliable, and accuracy was questionable even considering the thick 0.8mm nozzle I used. This would be the last print in which I’d work with this hot end.

First print

Video

Apologies for the video quality – I was trying a lot of different things before I got the printer to work and rushed into shooting after I finally got it down.

Shown here is the very first print I was able to run from the printer. The printer was able to deposit plastic for every layer it ran on, though by the end of the print the infill settings made the piece of rather poor quality.

Shown prominently is the new hotend – I started with an old bakelite pan handle I’d bought for a quarter at the thrift store. There was a preexisting hole in the handle that was too large for filament, and there wasn’t much room to drill my own hole. Bakelite is also a tricky substance to drill after its already been molded, as it’s prone to crack. As a solution, I filled the existing hole with high temperature sealant to constrict the diameter to the approximate size of the filament would pass through it. At the bottom, I affixed a pipe fitting and acorn nut with a 1/32″ hole drilled through, which was the smallest hole I could drill under my setup at the time.

It turned out after a week or two of calibration that this hot end suffered significant leakage. It did not help things when the bakelite isolator cracked after a failed attempt to reinsert the hot end. This would call for a new hot end, which will become apparent in subsequent posts.

Calibration

Video

Here is the printer in its first iteration. Notable things I would change include the the soldering iron based hot end and the sheet metal arm that holds it.

The soldering iron was mostly just the first thing I had on hand that served as a stand in. My soldering iron broke half way through working on the electronics and I found further use for it. Conceptually, it made sense – the bakelite used within handle would have a thermal operating range very similar to teflon. If anything, bakelite would work better as a thermal isolator as it inherently cannot melt and burns at temperatures comparable to the melting point of PEEK. The nichrome wire from the soldering iron also worked as a nice first order heating element. The 1/8 pipe fitting attached to the soldering iron was a failure to read existing documentation, on my part 🙂 The sheet metal arm I found was far too flexible, causing the position of the hot end to vary. It was soon replaced with plywood alternative.

X-axis calibration

Video

One of the biggest uncertainties going into this project concerned torque. Inkjet printer motors only need to drive a lightweight plastic header and maybe an ink cartridge. Depending on its purpose, the motor of a 3d printer would have to drive a 1kg filament spool of plastic, a bed with a printed object on top, or even an entire axis assembly. It did not help that I was borrowing skeletons from inkjet printers – because an inkjet printer is only intended for horizontal motion, I decided the best way to go was a static x axis driving a mobile z axis mounted on top of it. Doing otherwise with a mobile x axis, such as seen in a standard reprap, would put more weight on the z axis than could be born by a gear/pulley system. This was also very similar to the wolfstrap setup I’d been working with for the base.

Before continuing any further, tests would have to be done. Here, I test the motor driving the x-axis. A 1.5 pound exercise weight I had lying around simulates the approximate weight of the z axis I was working with. The endstop was also tested, which was scavenged from a printer and tacked on to be interrupted by some random ridge on the printer’s structure. An arduino was simply programmed to drive the motor until it reached the endstop, then backup.

The x-axis would turn out to be the only axis which absolutely, positively needed a stronger motor. This is without surprise the only axis which would drive the weight of another axis. The y-axis was perfectly able to drive its weight however the particular motor I’d found used a smaller step size and appeared jittery. Opening another printer could have potentially fixed that issue. The extruder I’d purchased came with its own motor and I figured I would save some effort just sticking with that.

And combining them into instruments yet stranger…

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And combining them into instruments yet stranger...

The electronics for the printer are not extraordinary – a set of 4 pololu stepper drivers wired to an arduino microcontroller. Originally, both the endstops and the arduino shields were wired by veroboard, however I found the standard veroboard configurations offered by the reprap wiki to be rather physically weak and ill fit for experimentation. After a while I switched over to breadboard, but that’s not to say I won’t return to pcb after getting the printer to print some circuitry.

Always buying strange instruments of glass and metal…

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Always buying strange instruments of glass and metal...

Despite all the talk of scavenging for parts, there were a few components I decided to get anyways. A lot of this was ordered before figuring out just what sort of theme I wanted from this project. All but one motor wound up not being used (the purpose of the one used motor will soon become clear). An extruder, while entirely possible to carve from scratch, would have been far too much effort put in just to make a point. The arduino and stepper drivers were very much still required.