Things are progressing fairly well with the second revision of the Gemini 3D printer’s CoreXY gantry. The new corner pieces assembled well the first time and the resultant frame is quite strong and rigid.
The former corner bracing scheme was fraught with issues of warping and it was a chore to get things completely square – this is not an issue with the new design.
A large part of why this is working is a twofold change with how the parts are designed – I have increased the thickness from 3mm to 5mm and added 1mm thick guide ridges that fit into the slots of the aluminum extrusion frame.
No photos for this post, but I should have an update later today – the motor mounts are being printed off as I write this. These new motor mounts should be much tougher than the previous ones which I anticipate should eliminate the warping issues found in the original prototype.
Getting the object models to be manifold from Sketchup turned out to be a problem, however Netfabb’s mesh repair made short work of correcting the issue. Potentially I could have spent a lot of time trying to fix up the models in Sketchup, but due to the complexity of some of the details on the part it seemed to be a fools-errand. Some things are just out of the STL export plugin’s realm of capabilities and these parts fall into that category.
The new motor mounts will bolt to the frame on two inner faces as well as the lower side of the rear span. This might be a bit of over-designing on my part, but I wanted to ensure that there was little chance for the mounts to come loose from vibrations and heat.
A small revision is necessary for the X axis configuration. I need to re-introduce the previous design’s slotted mounting system for the support beam.
The reason for this is that although the design is very accurate, the reality of mounting the parts to the linear carriages is that there is a small amount of wiggle room required to get things squared away nicely.
Currently the assembly is off by a fraction of a millimetre which prevents it from sitting perfectly even between the two sides of the frame. The result of that is excessive pressure on the Y carriages causing them to come out of alignment. This should be a fairly easy fix by slotting the four-point mounting holes on the aluminum flat bar and slotting the rail mount holes on the X-ends.
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