3D Printer

Mar 2014 3

3d Printer - part 9

You might think I've completely forgotten about my 3d printer, but rest assured it is still receiving attention.

My main complain so far with the machine is that some of its prints were not very square. Often successive layers that should be on top of each other, ended up on a diagonal, getting more and more off axis. I didn't have much luck tracking down why this was happening, but I suspect it is a quirk of either the microcontroller not being powerful enough, or the firmware (Teacup) having a subtle bug.

So I decided to redo the electronics. I ordered a parallel port breakout board off ebay for a few dollars, same as I'd used on my CNC machine. This arrived and was duly installed:

These aren't designed to drive 3d printers so a little fiddling was required to make it work. X, Y, and Z on the machine matched up with the respective outputs on the board. The extruder was hooked up to the A axis, and the limit switches plugged straight in.<...

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Aug 2013 11

3d Printer - part 8

Progress continues on my 3d printer.

A lot of research and learning has been done, the learning curve with 3d printers is very steep! However my fifth print came out very well, with only a few minor flaws:

It seems that Printrun sometimes pauses on OS X, unless it is always in the foreground. In other words, you can't really do anything else on the computer at the same time. For a modern powerful computer and multitasking operating system this seems odd.

Extruder improvements

I quickly discovered that even my improved grippy roller for the extruder wasn't up to snuff. The sandpaper gripped the filament quite well, but then just sanded it smooth, clogging up the sandpaper and leaving it smooth! So I went back to the drawing board and dug out the Dremel.

I made up a jig out of spare wood, cable ties and masking tape which holes the steel rod in position, and allows me to position a spinning cutting disk at righ...

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Aug 2013 6

3d Printer - part 7

Progress continues on my 3d printer...

Power Supply

Meters for my power supply arrived a few weeks back, but I only just got around to installing them. I had to drill out a 38mm hole for the mechanism to fit inside of, but I only have 45mm+ hole saws and 32mm spade bits, which made things a bit complicated. If only I had a CNC machine, this would be a piece of cake! For some reason that did not occur to me and instead I used a 32mm spade bit followed by a few minutes on the Dremel with a sanding disk. Did the job pretty well, even if it did cover the garage in MDF dust.

A couple of hastily drilled mounting M3 holes and a whole lot of epoxy leaves this:

I wired the voltmeter in parallel, and the ammeter in series with the output. Nice and simple, works a treat. Completed power supply was reassembled and tested on an RCD protected output, just in case. All tests passed and the meters were even wired up correctly.


Testing showed that t...

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Jul 2013 17

3d Printer - part 6

Progress continues slowly on my 3d printer. While waiting for the increasingly erratic Chinese postal system, I set about getting the extruder and hot-end working.

The hot-end is responsible for turning the plastic filament into a model, by melting it and squeezing it out of a tiny hole. The filament looks a bit like white spaghetti, or like the cutting cord used in line-trimmers in the garden.

The extruder grabs the filament and pushes it down a tube to the hot-end. The hot-end has a large block of metal with a heater and temperature sensor built into it; these work in concert to keep the metal block at a constant temperature, about 180°C for melting the PLA plastic that I have.

So I sent about making sure it was all going to work. First test was to ensure that the temperature sensor worked correctly. The hot-end I'd purchased had a thermistor built into it, which is a type of resister that changes its value as its temperature rises and falls. I did some tests ...

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Jul 2013 7

3d Printer - part 5

Continued from part 4.

My linear bearings finally arrived, just under a month in transit. I wasted no time at all in putting them to use. First I added some supports to mount them by; these are just my usual 1mm thick sheet of styrene, epoxied to the bearing with a couple of supports on each side.

Y axis limit switches were then added:

And then the Y axis was joined to the Z axis. I used some MDF spaces to ensure the Y axis was level with the rest of the machine and glued the whole lot in place.

I then clamped it with whatever heavy objects I could find. It may be a mess, but it worked!

While that was setting up, I started building the electronics. I used a similar approach to my CNC machine, using female mating sockets and some self adhesive copper strip to form bus bars. The various components then get soldered up into sub-assemblies that plug into the female headers.<...

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