Tuesday, April 15, 2014

Broken CNC

Take a good look at the photo below. These are the brass Stand offs used to support the Z stepper motor. When I first put the CNC together I thought of how poor of a design using the stand offs to support a stepping motor. This story starts out with hearing what sounded like loose parts rattling on the CNC while fast traveling to a work position. Using the most sienctiffic analysis method possiable, I took my hand and held verious parts of the CNC to determine what was making the noise. Turns out the Z stepper was the source.  I did what every good technician would do, grabbed my  tools and started tightening bolts and of course the brass stand offs. One of the stand offs appeared to be loose so I tightened and I tightened until,"SNAP". Yes, I broke the threaded portion off in the Z stepper.... Unfortunately I have a reputation of over I tightening just about everything, so in my case it's either TIGHT or  it's BROKEN!   After taking the Z axis apart, I measured the length of the stand offs and found there to be a .010 difference in length.  I ordered new stand offs (they come 20 in a pack) and decided to measure them.  They are all different, close in many cases but different lengths by a few thousands here and there.  With this new information I decided to make my own version of stand offs for the Z axis (see second photo). The results were fantastic! With all three Stan's offs now having identical lengths the CNC runs much quieter when fast traveling to verious locations on the CNC. Once again SUCCESS at the cost of breaking something.  

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