Armageddon421's Hackingblog

Archive for April, 2012

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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