This is a continuation of the improvement in the Z-axis for the movable gantry cnc machine. The previous post was about making a more accurate vertical z movement by changing the Z housing from one made of MDF to another made of plywood. By cutting the housing and installing the parallel linear rods more accurately, the milling spindle could then travel more squarely.

However, after having a good spindle housing, it was found that because the Y-axis parallel rods were cut not exactly vertically in line, the spindle was found to be tilting at a slight angle from vertical. In order to rectify this, I would have to fabricate the two sides of the gantry, and its connecting structures.

This would be quite a major modification.

It would be helpful if I could get the machine to cut. It would then be more accurate than if I were to cut them by hand like before.

Aiming to use the machine to cut, a quick fix to improve the machine would be the best option now. The modified machine would then be able to cut accurately the gantry sides, which could then be replaced later.

So that would be my plan.

In order to do a quick fix, I would need to attach a correcting tapered board between the Y parallel linear bearings, so that even though the parallel rods were not exactly vertically in line, the Z-axis housing could be installed exactly vertical.

After some investigations and measurements, the correcting angle of taper was established. So I set off to machine pieces of plywood with the required taper and glued them together to form a board. I did the machining with another cnc machine that I had made previously, the movable bed cnc machine. After some sandpapering, the board took on a smoother appearance and this became the backing plate for the Z housing.

Since the taper plate would be a transition piece, pockets were machine away to allow for the bolts to pass through. As I mentioned before, this would be a quick fix measure. Later, when the machine axes had been corrected, I would then want to use the machine to cut proper gantry sides and other supporting parts, so that I could further improve on the machine. Therefore, the taper plate was designed so that it could be removed easily in the future.

After the taper plate had been installed, the movable gantry cnc machine was re-calibrated and re-trammed. The results of cuts were found to be more accurate.