Saturday, July 10, 2010

Fundementally changing Mini Mendel in HeeksCAD

After installing my Makerbot MK5 worm gear, and a Makergear idler wheel my Plastruder has printed almost 40 hours non stop without a single hiccup, which is unprecedented for me.

In case you didn't know Makergear's version of an idler wheel is almost twice as thick as the Makerbot standard one, I honestly can't imagine anything breaking it. If you need a replacement idler wheel, get their $2 4.5mm idler wheel before you invest in one of the metal ones.

I am in the process of trying to change up the Mini Mendel to make it cheaper, especially for us Americans that can't get Metric Rod Locally.

The changes I am making:
-NEMA 17 motors, because they are easier to find, and cheaper to buy
-All 608 bearings (can be picked up at the local skate shop)
-All 1/4 inch smooth and structural rod
-M8 Z drive rod, so I can use 608 bearings.
-A bed raised on m3 nuts like a Makergear heated build plate, and a ceramic build plate from the start.
-Electronics mounted like the techzone alternate electroncis mount at

I thought I was going to get away with reusing allot of the Mini Mendel parts... no such luck. The bearing and motor changes means almost every parts needs to be redesigned. Luckily some parts have already been moved to Openscad, so I can easily alter them to fit Imperial, such as Erik's standing feet , and Whosawhatsis's y bar clamp .

I looks like the most challenging part will be getting 360 bearing chases around a 6.35mm rod with 8mm bearings. It works, but I am having a hard time getting a printable knuckle that holds the bearings tightly.

Does anyone know an easier way to do this?

I also have a Bearing/Spring idler extruder for the gear motor I have been working on for a few weeks, but unfortunately my Heekscad was recently possessed by a demon. No matter how many times I reinstall, I can't Undo without it crashing, I can't go 15 minutes without it crashing.. Honestly if I look at it wrong it crashes, which really hurts when you get things lined up just right...

Another project I am working on is a printable rip off of the Maker Bot Filament box. It uses 5/16 rod 608 bearings, 2 wing nuts and a length of 1/4 plastic tubeing. Haven't got to print it yet, but It looks like it will work.

I haven't uploaded any of this to Thingiverse yet because they all have either not been printed, or were printed, but could be better if I do just a little more work on them (The extruder works, but the idler is off center a little).

Added after the fact:

I did make a printable Sorobansu Abacus, but my daughter ran off with my printed copy, once I reprint (or find where she hid it) I will upload to Thingiverse.

Anyway if you guys have any advice, want the design files before I upload them, or just want to berate me for my obviously undiagnosed Adult Attention Deficit Disorder, exasperated by access to a RepRap printer and free Cad programs, just comment :).


  1. I'm working on a similar project. Basically, I'm remaking the entire design parametrically in openscad, using the stl of the assembled mini mendel as a reference. I'm learning a lot from assembling my own mini mendel while I work (like that the x-carriage design that I thought was genius actually sucks), but it's also dividing my attention and slowing me down.

    The 608 bearings are an interesting choice. I've been working under the assumption that you have to use bearings with a bore that matches your screw diameter. I'm planning to get the bearings all the same size by attaching the leadscrew bearings to the z-belt pullies, rather than putting the leadscrews through them.

    Also, as with the y-bar clamp you mentioned, I'm trying to redesign all of the smooth rod clamps to use pinch blocks rather than multiple parts.

  2. I am using m8 bolts for all the bearings, m8 bolts can be had for $10 for 100. Even though the bolts are more expensive, the total cost of Mini Mendel is reduces by nearly $30 by going to the M8 bolts and bearings. That's significant.

    The pinch block makes since. Can't wait to see your work!

  3. Ohh I agree the Mini Mendel x carriage is strange, I am redesigning also, but again the fat m8 bearings are challenging, but we only have to solve these issues once!

  4. Do you have an imported stl in your file? There's a known bug in heekscad that if the file has an stl, the undo causes a crash.

  5. I like your blog by the way. It's nice to see other people doing some more sophisticated designing in HeeksCAD.

  6. Hmm your right, the STL is the issue, but here's the funny part. Deleting the STL out of the files does not help, and if I copy components out of the drawing and save it into a non stl document, the behavior follows the pasted parts, even though no STL had been loaded into that document. Really odd stuff, but at least now I know how to aviod the crashing issue.

  7. What prices for the bearings are you using for comparison? I saw variations of more than an order of magnitude when I was sourcing my bearings. Ended up getting them for $1.16 each from ebay: link.

  8. Just found I can get 5/16" threaded (whitworth) rod ZP 36" for ~$5 in Australia easily from Bunnings (local hardware shop). It is 7.9375mm so close enough to 8mm I think for the z axis. Pitty the round bar is not so easy - requires a specialist store which also has the 8mm threaded rod.

    What is the OD of the pulleys for the Z axis???

  9. I am new to the boards and just wanted to say i am very very happy to read this blog.