Armageddon421's Hackingblog

RepRap

RepRap upgrades

by on Apr.19, 2012, under Projects, RepRap

Last week I was thinking about improvements for my RepRap Prusa Mendel. I found out that some things didn’t really work as expected. I’ll explain some of my modifications here.

First of all, the print was sometimes slightly irregular. I found out that this was due to the filament screw not having enough grip. I asked my local metal worker if he could help me. He created a filament screw from a raw aluminum cylinder for me, using a mill to make a total of 24 edges to grip on the filament which is way better than the tap and die method.

Additionally I swapped the Wade’s v2 that came with the parts I bought with the Wade’s v3 I printed a while ago. Together this makes a quite powerful extruder that exceeds the 2kg holding force by quite a lot.

After that, I finally replaced the broken linear bearing. Unfortunately, it left really bad grooves in the smooth rod. I worked around this by turning the smooth rod by 45 degrees so the new bearing can have a virgin surface to run on. I also made sure that the screws holding the bearings are not tightened too much because this leads to tensions, affecting ease of movement. While assembling everything, I made sure that the two belts have about the same tension.

Yesterday the filament slipped off the grooved part of the filament screw while printing, effectively ruining the print. To fix this, I printed a modified version of this filament guide for the Wade’s extruder. I used openSCAD to make the part clip-on so I neither have to remove a screw nor unmount the filament. It does its job good enough.

This video shows printing at 36mm/sec, I could only do about 28mm/sec before. I have not found the maximum possible speed yet.

Then I tried the ultimate overhang test again: This bird

This time I decided to do some cooling by putting a small fan next to the build plate. It worked quite well and cooled enough to remakrably reduce the bending that ruined my previous try.

The problem with the fan is, obviously, that it cools down things. But there are parts that shouldn’t be cooled down too much, like, for example, the hot end / nozzle or the build plate. The cooling caused the hot end to only heat up to about 170°C, which is 15°C below the temperature I found out to work best for this filament.

Further problems and possible improvements:

  • Permanently install a fan to do some cooling and to reduce bending, ideally mounted on the carriage.
  • Shield the hot end from the fan to keep the temperature up and reduce power usage.
  • Buy/Build a new hot-end with more heat output and a smaller nozzle (probably 0.4mm)
  • Improve filament spool holder, probably by redoing the whole thing with a different approach.
  • Increase the stability of the printer frame by adding cross-bracings.
  • Replace the temporary mechanical z-endstop with an opto endstop again.
  • Try a different carriage: one with two bearings on the belt-side or one with a total of four bearings.
  • Circles still don’t always turn out perfectly round.
  • Think about a way to automatically take a picture at every layer.
Sorry, there’s no timelapse today!

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It printed! In 3D!

by on Jan.24, 2012, under Projects, RepRap

Yesterday the delivery containing the new PLA-plastic and the spare thermistors arrived. I fixed the printer and after flushing out the remaining ABS I tried printing some stuff. Without any calibration, just drastically lowered the speed. I used Slic3r to convert the .stl file to gcode and pronterface for printing. Of course, there’s a timelapse. Just watch. There’s a realtime-timer at the bottom left.

Finally some pics of the parts. It’s not perfect but still a better first try than some of what I’ve seen on youtube.

Next up: Calibration!

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So I finally built a RepRap 3D-Printer. Or did I?

by on Jan.21, 2012, under Projects, RepRap

Well, I did. Here’s a timelapse of the 24 hour build process. I had some helping hands at the beginning.

24h building – 3h sleep – 1h eating/toilet/etc. = ~20h

However, I encountered some problems.

  • Drilling the holes in the aluminium plates requires a drill press or some other way to precisely drill the holes. I solved the problem by not tightening the screws very much.
  • Because the x-axis motor and idler parts were not standard, the smooth rods had to be the right lenth (or a bit shorter). I’m trimming the rods in the video at about 3AM (time in the bottom left corner). The hardened steel is quite hard to saw manually.
  • The neighbors don’t like the sound of sawing a smooth rod at 3AM, sunday.
  • There were no cables nor the right plugs shipped with the electronics. I used pc-speaker (that beeping thing inside the pc) plugs and cdrom-to-soundcard wire plugs and soldered the cables to them.
Well, does it work? No, not yet :(
I tried using ABS plastic, which normally is best extruded at about 210 to 230 °C. My ABS seemed to require even higher temperatures, about 250°C. The heat dissipation at the hot end led to my x-carriage, which is made of printed PLA plastic, to start bending under the heat. So I tried isolating the hot end. It worked, however after a short time the thermistor in the hot end bursted.
Now I’m waiting for my order, which contains some new thermistors and 2,2kg of PLA plastic filament. I’ll try getting it to work with PLA, which is extruded at about 170°C, before messing with ABS again.
I held a thundertalk at shackspace explaining my progress so far. The recording will be online soon, it’s in german though.

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So I am finally building a RepRap Prusa Mendel

by on Jan.13, 2012, under Projects, RepRap

After I saw those RepRap things at shackspace, I simply could not resist anymore. I had to get one. So I ordered everything needed for a RepRap Prusa Mendel except fot the plastic parts from Cubic Print and the German RepRap Foundation Shop. The delivery from GRRF arrived this morning. As you can see in the picture, it contained the “hot end”, 2.2kg of black ABS filament and the kapton tape.

I was so excited that I wanted to do something with that stuff. So I started assembling the hot end. Pushing the resistor, wich is used as a heater, in the clamp block turned out to be more difficult than expected. Like their (GRRF) manual stated, I had to sand the resistor quite a bit so it could fit in. I was very surprised when I read that you actually don’t need any glue to hold the resistor and the thermistor in place. They wrote that it expands when heated up and then holds perfectly, also making enough contact to transport the heat. I think I can still apply high-temperature-glue at any time later if I really have to.

If you’re new to the RepRap project and want me to explain things more detailed, just leave me a comment and I’ll try to be more verbose on what I did and how.

I am expecting the second delivery to arrive tomorrow, let’s see how far I get with acquiring the plastic parts until then.

Oh and I guess there will be a timelapse of the whole assembly ;)

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