Runout Testing

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Runout Testing

Postby bdring » Sun Mar 18, 2012 3:33 pm

I attempted to do some runout testing on the ORD Bot. It was quite difficult to find a flat and smooth reference surface. The best I could find was a marble tile with a piece of glass on top. This is a 100mm move. A single wheel rotation is about 75mm. I ran the test about 10 times. It was not super consistent where the changes occurred, but the levels were pretty consistent.

This is a super sensitive "test dial indicator". Each major, labeled index on the dial is 0.001 inch. This test shows about +/- 0.001 inch in runout. The dial was mounted flat to remove all cosine error.

Some rapid changes seemed more of a function of the flatness or cleanliness of the glass. This was tested on the prototype Hadron which was built about 2 weeks ago and has many hours on it.

Bottom Line: I do not think runout will be a problem. Expect about 0.001 to 0.002 runout. I am using the term runout, but in reality I am looking at smoothness of the extrusion and glass too.

Bart
"If you didn't build it, you will never own it."
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Re: Runout Testing

Postby JeremyBP » Sun Mar 18, 2012 3:53 pm

That's nothing. Fantastic.
Also, if you ever need a good reference, you can use my surface plate.
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Re: Runout Testing

Postby macona » Tue Mar 20, 2012 7:06 am

You should pick up a small surface plat from enco when they have free shipping going on. A small plate is surprisingly cheap. They also show up on CL now and then. I picked up a 12x18x4 Do-All for $50.
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Re: Runout Testing

Postby r691175002 » Tue Mar 20, 2012 8:41 am

To measure the performance of a mill you are generally looking for repeatability and accuracy.

There is no real standard, but a reasonable test of repeatability is to indicate off a fixed object and then make a series of movements in all three axes and see if you can return to the exact same spot. It is a similar process to what you have in the video, except more movement between measurements.

Accuracy is measuring the exact difference between the programmed move and the actual movement. It can be done over short distances with a dial indicator but it is expensive to do properly and doesn't really matter for a 3d printer anyway.
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