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MakrBBot III

My third 3D Printer Build. Let's do a CoreXY Model.

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In 2015 I built my first 3-D Printer:
https://c-scope.blogspot.com/2015/05/the-makr-b-bot-part-1-getting-started.html
and named it MakrBBot. Because it was inspired by the then popular 'Printrbot' and built from MakerBeam profiles. It worked, but was cumbersome to use. So I created the MakrBBot II, inspired this time by the Prusa i3. This still works fine, but I kept reading lately about 'CoreXY' printers and found this concept inspiring enough to start my third build.
And, surprise, just a few weeks after I started, Prusa printers introduced the 'Prusa XL'. Their first CoreXY based printer. So it looks I'm indeed on to the latest technology.

The CoreXY mechanism is not new, but 3D printer that use it are suddenly popping up everywhere. A popular one is the completely open source Voron Printer.  A great design, but if you want to build it exactly like the description, it is still quite expensive to source all the specific parts. My goal was to build it as cheap as possible, and to make maximum use of all the parts I already had lying around. Which includes 4 NEMA17 Stepper motors, an old power supply from a server, a RAMPS 1.3 controller board with LCD display, some 8mm steel rods with LM8UU linear bearings and a handful of 5x10 mm radial ball bearings.

The 15x15 OpenBeam worked fine in my previous printer, so that will be the base of the frame. And since the set of 9 pieces 240 mm beam was still on sale I ordered two of these.And 2 linear sliders, as everybody is using these for this type of printer. Added some T2 timing belt (I'll need more than a meter) and a bag of 15mm corner brackets. And so the total cost already adds up to about €80,- It looks like this build is again not going to be cheaper than a ready-made printer from China...

There seem to be quite some variants in how to build them and specifically in how to route the belts. As I first did not completely understand the kinematics behind this I chose the belt layout that made the most sense to me.

This image shows how to place two belts at different heights, so they do not cross or touch. The arrrows show where you can tension the belts without changing the printing results. There is an excellent explanation of this subject on the blog of Mark Rehorst. And even if you don't read or understand it all, the essence it that certain belts must be exactly parallel to the moving axis for it to work at all. So I decided to make all my belts as parallel as possible. Something like this:

Here there are two belts in different layers and it's all 90 degrees angles.

  • Handmade Rollers

    Cees Meijer6 hours ago 0 comments

    The CoreXY mechanism requires at least 8 rollers for guiding the belts. And so the set of 10 ball-bearings (set of 10 for MakerBeam) that I had seemed a good candidate for making the rollers. These bearings are 5 mm thick, have an outer diameter of 13 mm and 3 mm hole.

    And it worked out fine. Had to fine tune the model a few times for a tight fit, but in the end rollers looked great and rolled very smooth.

  • Belt routing, as I see it

    Cees Meijer3 days ago 0 comments

    After drawing the frame, and adding the pulleys in the correct position, I decided I had to draw the belts as well, just to see if my assumptions were right. And they were. It looks like this is going to fit exactly as expected.

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