RepRap Prusa Mendel

To mount the sensors on the large outrunner as i wrote about in this post I got a couple of 3D printed plastic parts for holding the hall sensors at exactly 17.14°.

Plastic sensor brackets printed on 3D Printer
Plastic sensor brackets printed on 3D Printer

This raised my interest for 3D printing and I started to do some research on which printers that were available. There are several different projects that sell a kit that only needs assembly for example the MakerBot but I decided to go with the RepRap that is a more DIY kind of printer. The main reason of this is that the RepRap seemed to have the highest  buildvolume/price ratio and the community around the RepRap is very large and helpful.

There are several different versions of the RepRap but when I started this build a couple of months ago most people seemed to be building the upgraded Prusa Mendel with LM8UU linear bearings, upgraded z-axis couplings and slight changes in som other plastic parts. The nice thing with a RepRap is that once you’ve built your machine you can print most of the parts needed to build another one. Therefore there are a lot of people around the world selling the plastic parts on for example ebay.

The RepRap can print two different kinds of plastic:

ABS (Acrylonitrile Butadiene Styrene)
Is made from petroleum and has a quite high melting point. This is the kind of plastic which  LEGO blocks are made of. This plastic is softer than PLA and more flexible.

PLA (PolyLactic Acid)
This plastic is made from corn starch and has a lower melting point than ABS and is a little bit harder but more brittle.

I decided to go with parts in ABS, I’m not sure yet if that was a good choice since I’ve heard that it’s more difficult to produce good quality prints with this plastic. I ordered the plastic parts from a dutch guy on eBay and the first parts I got were pretty bat prints all parts were ugly and the x-axis mounts were so warped the were unusable.

Warped x-axis mounts
The x-axis mounts are to warped to insert the x-axis smooth rods in the corresponding holes.

Luckily enough the guy I bought them from were kind enough to send me a new set of parts which were good enough.

Apart from the plastic parts you need what is caled Vitamins, this is all the parts that you cant print on another RepRap. For the Prusa Mendel this is:

  • About 6 m M8 threaded rod
  • About 3 m 8 mm smooth rod
  • A big pile of nuts, screws and washers M3, M4 and M8
  • A couple of 608zz ball bearings and LM8UU linear bearings
  • Printbed
  • 5 Nema 17 stepper motors
  • Electronics (for example RAMPS or Sanguinololu)
  • ~200-300W 12V power supply

The current status of my build is that I’ve acquired and assembled the first five parts in this list, the rest will be bought when I can spare the money.

RepRap Prusa Mendel
Current build status of the printer. The frame is ready, motors, electronics and hotend is missing

The threaded rod, nuts, screws and washers I bought at a local hardware stores (Bauhaus and  Hornbach) and the bearings are from eBay. The smooth rods are from a Swedish webshop called Maskindelen.

To get good quality prints you need a heated printbed and most of the Prusa Mendel DIY kits you can buy includes a heater built on a pcb but since I had a nice sheet of 5 mm aluminum left from the motor mount on the E-Puch, I decided to build my own. The aluminum will be used to spread the heat from three 100 W power resistors mounted underneath the bed. On top of this I will place a 220 x 220 mm piece of glass to print on.

For the rest of the parts I’m pretty sure I’ll buy a Prusa Mendel electronics kit from ReprapWorld togehter with a 12V 348W MeanWell PSU from Sure Electronics on eBay.

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