Pneumatic probe.

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Pneumatic probe.

Postby Gridlok » 06 Jul 2015, 05:36

Hi Everyone,

I have just ordered a MK3/2 to replace my ever problematic TinyG on my self built CNC.

I have a few questions so I can plan for when it arrives.

I am looking to construct a probe for my z-axis that retracts when I am not using it. I was thinking a small linear rail with a microswitch so I can centre my spindle and measure the height of my stock. The head will be driven by a pneumatic air ram that forces it down to the same height each time.

Is it possible to script this so that it works like the following. I press a button, the mk3 turns on a relay that turns on a solenoid valve that extends the probe. Then after waiting for a second it homes the z axis using the microswitch, turns off the relay which retracts the probe and then moves the spindle to the tool height microswitch and measures the tool height, sets the offset and then moves it back to the location where it probed.

Are these sorts of scripts possible? I'm trying to eliminate these repeated activities and speed up my cutting times.

Thanks

LJ
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Re: Pneumatic probe.

Postby Support » 06 Jul 2015, 14:01

Do you have any illustration of your idea? What would this probe be used for?
The automated procedures of tool length measurement or surface height are already supported in our sw.

Could you elaborate little more in detail what do you want to do?
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Re: Pneumatic probe.

Postby Gridlok » 07 Jul 2015, 00:40

All I really want is a probe that extends and retracts to measure the height of what I am cutting. It extends to the same length each time which is beyond the length of the end mill. And has a microswitch on the end. The z-axis then extends down until that button is pressed and zeros based on the offset of the tool height. I will design it tonight and put it up so you get a better idea. I suck at explaining things.
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Re: Pneumatic probe.

Postby Support » 07 Jul 2015, 07:39

Great, please do.
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Re: Pneumatic probe.

Postby NXTwoThou » 27 Sep 2016, 14:58

I was looking for the same thing for a project a long time ago. The best I found at the time was the Solatron Metrology probes. http://www.solartronmetrology.com/products/orbit3/digital-automatic-pneumatic-probes.aspx You can basically command them to extend and then get readings from them. They are very high end products unfortunately with mating high end prices(I paid $751 back in 2008 for a DT30 and an additional $420 for the USB interface module so I could read it).

The concept is pretty simple, you've got a spring retract, air extend cylinder mated to a linear encoder. You can adjust your air pressure to decide how rough you are with what you are touching. One of Solatron's great features was a "feather touch" option that would glide if you were doing motion at the same time.

I've always hoped someone would come out with an ultra-affordable version with a long reach as I could see some potential uses for it. For example, one of my old machines had a spindle and a touch probe on the Z axis, they had to be separated by about 60 mm along the Y plane so when I was cutting the probe didn't collide with the part being worked on. If I had an air extend type probe, I could have literally slapped that probe right next to my spindle. Extend it when I needed to take a reading, then retract it and start cutting.

It could also auto-calibrate itself too. You extend the probe, take a reading, retract probe, turn on spindle, move over to where the probe is, try and make a cut, turn off spindle, go back to where probe is over that spot, extend probe, take a reading. If the reading changes, you know you've touched the material and based on the difference between the readings, you know how much was taken off. That means you can now easily calculate your offset of "tip of probe versus tip of tool". You can then probe anywhere and know exactly where you could start cutting.
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Re: Pneumatic probe.

Postby Support » 28 Sep 2016, 12:05

interesting but pricey...
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