I’ve blogged a few times about my Sinton i3 Prusa 3d printer. I think this is a great first 3d printer and found that it creates high quality 3d prints. A few of its features are:

  • Heated bed;
  • One of the lowest cost printers in the market;
  • Prints PLA and ABS filament;

Of course this printer isn’t going to be the right one for everyone – it arrives a kit, and that’s a difficulty for some people. For me, this turned out to actually be an advantage. There are a couple of the parts of this printer that I think haven’t been designed that well. And fortunately as this is a RepRap printer – it’s a self replicating machine – I can build a better part.

I’ll describe a couple of the parts on my printer that I decided to replace, and how I replaced them.

Extruder motor mount

When I was using the printer first and only printing with PLA filament, I didn’t have a lot of problems with this part. However, when I started printing with ABS and raised the temperature of the hot-end to 230C, I found that the factory supplied extruder mount started to sag. In the photo below, it’s possible to see how the plastic was starting to curve (allowing the motor to start slipping out).

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This turns out to be a bit of a common problem. Fortunately there’s a solution on Thingverse – http://www.thingiverse.com/thing:723656.

This Thingiverse object has 3d STL files – one of these is a replacement for the original part, but the one that I used was the heavy duty modification – called MK8_Heavy_Modded.stl.

This was a bit nerve-wracking to print – this was probably the biggest ABS piece I had printed to that date, and the extruder mount was already starting to sag with the hot-end at 230C. The consequence was that the heavy duty part wasn’t a very fine quality ABS print, but it was strong enough to replace the existing part that was deteriorating. Later ABS prints have been much better.

X-axis limit switch mount

The mount for the X-axis limit switch…it kind of sucks.

  • It’s meant to be attached to just one of the X-axis steel rods, but there’s not a good way to clamp it in place so it moves around quite a bit.
  • Also, if you want the limit switch to actually be triggered when the extruder reaches the switch, it can only be attached by one M3 nut and bolt, which means it can rotate.
  • As the limit switch mount moves too easily, I’ve found a few times that the extruder doesn’t actually trigger the limit switch – leading to the extruder trying to push itself off the end of the axis and some pretty disturbing noises.
  • Finally, I found the mount also interferes with the X-axis toothed belt.

So it’s all pretty bad.

Fortunately, there’s a solution. I found this – http://www.thingiverse.com/thing:784801 – on Thingiverse. This nearly works straight away for me, but for this configuration of a Prusa printer, I needed to make a slight modification. The problem was that if I mounted the limit switch straight onto this part, the switch would actually sit too far behind the extruder.

This is pretty easy to fix.

  • I opened up the STL in Autodesk 123D Design, and converted the mesh to a solid;
  • I split the solid just beyond the second hole using a polyline and the splitting tool;
  • Finally, I extruded the face containing holes for the limit switch by 10mm.x-axis-mount

I converted this to an STL, and then printed this using my usual toolchain (i.e. open the STL in Cura, saved the G-code, open this G-code in PrintRun, and send to the printer). I printed this part using 1.75mm ABS.

The photo below shows both of the replacement parts, printed in black ABS.  The heavy duty modified extruder mount surrounds the stepper motor in the left hand side of the picture. The replacement X-axis end-stop is on the right of the motor, and has a limit switch screwed into it.

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Since replacing these parts, I’ve been able to print using ABS without problems of the extruder mount warping – or the extruder missing the x-axis limit switch.