Monday, October 4, 2010

New z-axis

The part which work the least well currently is the motor drive of the z-axis. The z-axis is constructed using 2 motors, one on each side. Since the construction is not completely straight, the vertical threaded rods wobble a bit. The threaded rods are also made of cheap galvanized iron and small bits of metal are falling off when in use. Forgetting to lubricate the threaded rods regularly causes one side of the z-axis to stop turning causing some damage to the system. This setup was the easiest to construct in the beginning when I did not have a 3D printer available to create parts. Since upgrading the extruder, the z-axis construction creates a bigger problem; the new extruder does not stick out from under the x-axis quite as much as the old one, meaning the z-axis needs to be lowered further. But the lower the x-axis is moved the worse the misalignment for the threaded rods starts to cause friction. To be able to print without lowering the extruder too much, a temporary solution was to increase the height of the print bed using a square piece of foam some 3 cm thick (visible in the picture in this post). This works, I printed all the PLA on it so far, but the print bed is not as stable as it used to be. So time to improve it.

I bought the mendel timing belts a while back and printed z-pulleys for the threaded rods. Since I do not have a mendel frame in the printer I needed to create a base for the z-axis threaded rods and a single motor so they can be mounted on the wooden base of the printer.

On one side only a support for a ball bearing is needed which has space for the z-pulley under it. It looks like this:

On the other side the same construction is needed, but in addition a stepper motor needs to be mounted and an idler wheel which can be moved to adjust the belt tension.  It was printed upside down like this:

This was the biggest object which I printed so far. It took 4 hours to print it and measures 6 by 12.5 cm. Even PLA starts to warp a bit at this size, but the warping is small enough that it the object is fully functional.

Before this setup is going to be integrated with the printer I want to make sure it is reliable, so I first mounted it on a piece of scrap wood to run some tests. The hex bolts temporarily take the place of the vertical threaded rods.


The testing has not been finished. More information about the success (or failure) later.

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