Monday, October 4, 2010

New z-axis, part 2

The new z-axis is going through some tests before the 3D printer will be upgraded. See pictures of the testbed in previous post. When letting the stepper motor run, it seemed that the belt tried to escape from the pulley which is on the stepper motor when turning in one direction. This was not foreseen and would be disastrous if it would happen during a print. To make sure that the belt can not run off the pulley, an additional idler with large washers is mounted so that the belt will be forced back to the middle of the pulley should it try to escape. Fortunately there was some space right next to the motor where an extra hole could be drilled for the idler. It seems to work fine now as can be seen in this short video:

One reason why the belt was trying to move down the pulley is that the motor was not mounted 100% straight. It seems the PLA was warped a bit more than I thought initially. The motor is now mounted straight by adding 2 very thin washers between the PLA plaform and the stepper motor on one side. The additional idler will be a useful saveguard anyway; it also changes the path of the belt slightly so that the belt has more contact with the pulley, reducing the chance the belt would skip.

I still want to do some more tests with the threaded rods in place before I upgrade the printer. More on that later. Also, the y-axis needs to be lifted a bit to allow the z-belt to move under it.

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