Slop in the Bearings

Okay, so we know how a belt sander works.  Let's find out where the skew originates in the Phlatprinter \\\.

When you examine one of the conveyor rollers used in the Phlatprinter \\\, the first thing you will notice is that if you stand it on end and spin the roller with your hand, you feel all sorts of wobble.

When you look closely at the pulley that is attached to one end, you may or may not see that it was not centered precisely on the end of the roller.

These two elements make up 90 percent of the skew.  The actual tube in which the bearings are encased may also be out of round, making for three distinct places in which skew can form.

If you have access to a dial indicator, a digital caliper, and a set of V Blocks, you can accurately measure all of these elements.

The most offensive of the three is the area in which the hex support rod is mounted in the roller.  Hold the roller in one hand and move the hex shaft with your other.  You can feel the play which in my rollers amounted to .015" each.  

Now couple that with a pulley that is not centered on the end of the tube and you have just added an additional skew point.

When these two rollers are mounted in the Phlatprinter \\\ and a belt is attached to them and as stepper motor pulley, you get a situation in which as the belt tightens up when driven due to the eccentric pulley, the two rollers are squeezed together forcing the rollers out of parallel and acting like an adjustment on a belt sander which does what?  Moves the material sideways.

Granted, it is not a lot, but with .015 in one roller end is multiplied by 4 roller ends, you have .060" of play not counting the pulley being off center which varies per machine.

In the next post I will explain how to get rid of the slop if you have a just one basic measuring tool, the digital caliper and a way to remove the old pulley such as a thin blade saw or better yet, a Dremel tool with a diamond cutter.


I will also recommend a better set of pulleys and why.


Later, I will cover beefing up your Phlatprinter \\\ to include a more powerful stepper motor on the X axis, adding a Bosch Pony Laminate Router, replacing the Easy-CNC controller with a Gecko G540, covering your pressure rollers with a material that does not destroy the material you are trying to cut as the grip tape does and much much more.  Be sure to follow along.  I have much more in store.