Appendix A & B of ALLIN1DC Installation Manual

[AMDlloydsp]

I probably evoked a negative response like that by using the word 'trivial'.

I did not mean it is not useful -- only that it's useful only once when setting up the machine. Then, after that, it's just a vestigial appendage that clutters things up. My use of the word just meant, "of limited usefulness", given that the screw ratios/steps-per-inch are never changed, once set.

Now, true, I haven't seen it; I'm going from your description of what it does, and why you wrote it. If those issues have changed, then I'll retract my opinions until I see it.

You never stated that you had changed its purpose from the first time you mentioned it.

I never meant to say it wasn't a good program or that you are somehow incapable.

OK?
Lloyd

[rderkis]

After such a eligent reply, I will elaborate more,
I know vary little about mpu11 and the mill. My experience comes from setting up and using a 14" research grade telescope. A lot of the calibration is the same principles, but must be extremely precise.
Let's think about setting the revs/inch up. Like you said one division and two multiplication problems per axis. You need to do this a minimum of 2 times per axis. For a total of 6 calculations per axis.
to do 6 calculations X 3 Axis = 18 calculations.
I would guess there are a maximum 6 key strokes for each calculations. Fror a total of 6 key presses X 18 caluclations = 108 keystrokes. That number is probably max. Not real world.

To get this really set up precise you should do it till the new revs/inch value starts to bounce up and down. At that point you have reached the limits of your machine or the limits of your measuring device.

As far as only doing this only when you first set up mpu11, I question that. A belt change or a radical change in tempreture might change it. Heck just wear and tear might change it. These changes would be vary small but if you aim for perfection you might want to check them once in a while.
If I can access the DRO and current revs/inch from my program all you would enter is actual measursement moved. The program could do everything else.
It would sure make it easier with fewer chance of mistakes. And that is exactly what computers are for.
I am a geek and can not communicate my ideas very well, buy I try.
BTE My programs are FREE and I believe like the doctors creed "Do no harm"

[AMDlloydsp]

As far as only doing this only when you first set up mpu11, I question that. A belt change or a radical change in tempreture might change it. Heck just wear and tear might change it. These changes would be vary small but if you aim for perfection you might want to check them once in a while.
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No, the ratios are fixed, and need be calculated only once -- only one time, period. The pitch of the screw and the 'steps' of the motor (regardless of stepper or servo), and the pulley ratio between motor and screw are all you need to know to get it right in one calculation. (unless you have such bad ball screws that they vary from spec by an amount that is _scary_bad_.)

Belt wear does not affect the ratios, unless you're using Vee belts! Cogged belts may change absolute position or generate backlash if they are loose, but they keep their step ratio with the cogged pulleys -- always. The only thing wear will affect is backlash; never the motor-to-inch relationship.

Temperature always will change things, and cannot be compensated for except by keeping the machine at the 'stable' temperature for the screws, as documented by the manufacturer of them. Just like a telescope mirror's focal length will change with temperature (I have a 12" Newtonian on a Dobbs mount), there's still a "sweet spot"; that's the temp the mirror was at when it was figured. (BTW... I made my first 8" mirror from scratch... three weeks of walking around a barrel! <G>)

Lloyd

[rderkis]

It's a shame you didn't have a cnc mill when grinding that mirror. Coming up with the programing and apparatus would have been fun.

[AMDlloydsp]

Yep! And the hogging of all that Pyrex out of the meniscus would have been LOTS easier!

Hmmm... If I could figure out how to keep the abrasives out of the guts of my machine, that might be a worthy experiment! I've been wanting to build a Mak-Cass for a many years, but the glass for those is mondo-expensive!

Denton Vacuum is still in business, and not much more expensive for aluminizing and over-coating than they were in the 1980's.

Darn! Now you have me thinking! <G>

Lloyd