Graber i3: Base/Bearings Adaptador

The Graber i3 is a 3D Printer Prusa i3 clone, but with a laser cut MDF structure. There are lots of Graber i3 kits, a little bit different from each other, but the majority is based on the same MDF structure, provided on this GitHub project. It’s a good project, to be honest, it’s ver stiff and easy to assemble.

A problem that had not occurred to me though – in fact, I didn’t notice it for months – is that MDF wood expands/shrinks depending on the heat difference. For the most part of the MDF structure, this is not a big deal. But the printing bed, for ABS printing is heated up to 100C and it is bolted to the MDF base, thin and almost fragile. After some time, I noticed that the heat from the printbed made the MDF base to curve down. The consequence is that the base was colliding against the zipties that hold the Y axis rods and endstops. This collision was enough to make a difference on the printber height (relative to the nozzle) and propagate as object imperfections.

When I first detected the situation, I just inverted the base, sure that it would fix the problem for good. However, after some more prints, the MDF based curved down and again began colliding against the zipties. Off course, keep inverting the base every few prints would not gonna work: Unbolt the printbed (4 screws, 4 nuts, 4 springs e 12 washers); Cut te zipties that hold the bearings to the base; Invert the base; Strap new zipties to the bearings/base; Screw everything again; And, the worst: to calibrate the bed (I don’t have auto-leveling system. No way!

After some measuring, I determined tha the base curve something between 3-4mm. So, I figured out that I just needed to raise the base about 5 mm, enough to clear the zipties. So, I designed the pair of parts below:

  

 

With these 2 parts, would be possible to attach the bearings to the base using M3 screws instead of zipties, what makes the base more stiff besides being reusable (in case they needed to be removed for some reason).

  

  

 

The parts are printed and OK, now it’s time to disassemble the printbed and install the adapters.

  

 

Before:

 

 

Assembling the parts:

  

 

After:

  

 

Parts

This project requires on a few parts:

I included, on Thingiverse project, the OpenSCAD file, containing the original project in case it’s necessary to change something.

 

Printing

Nozzle 0.4mm is enough
Material ABS: Scale in 1.01
Infill No difference, not used due to the small size of the pieces
Other After printing, the base/bearing adaptor may need some filing / sanding

 

Author

Fábio Lutz

Bachelor degree in Computer Science by UFRGS / Brazil; 18 years of professional experience on software development (Delphi/Pascal, Java, PHP, Javascript, ...
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