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Custom Angles with RDS


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I am measuring a 1.41 wide x 28 deep slot that is tilted 1° with a 1mm x 30L stylus. See attached. I am shanking out about half way down. Is their a simple mathematical formula that allows me to calculate what combination of angles on the RDS will net a 1° tilt. I understand I will need to use mirrored angles to allow me to measure near each end of the slot. Custom angle on RDS.pdf
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I find it easier to setup my parts on a sine plate/angle vise when I have this problem. Clearly not the answer to your question. Just an alternate route.
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I've done this a few times and the process I take is first make a stylus with a 1° tilt to it. You can cheat by driving the stylus to the hole or using a pin to line it up pretty close and tighten the knuckle or joint. Next when qualifying the stylus tip you need to drive in the same vector as the hole or it will correct it for you. So I actually run the base alignment so I can use the "move in part system alignment" fount on the stoplight window under "view". You might have to move things around on the stoplight to see the new drop down option in the traffic light for the "joysticks: move to". In this you can find that cylinder in the drop down and when selected you will now move your stylus vectoring with the cylinder.
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Thanks, but I'm using a standard XXT adapter plate and want to use a stylus in the -Z direction because I am measuring other features at various angles.

I ended up using a CAD system to simulate my application and found if I tilt the B axis of the RDS to 2.5° and rotate the A to 17.5°, I get a net angle that is close to 1°. I did't check the angle but it appeared to be symmetrical to the slot. (My sketch was a view from -X)

I was looking for a quick, simple formula or calculation that I could use without going into CAD.
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  • 1 month later...
Hi Tom!

I'm having the same problem from time to time. Unfortunately, at my current job I'm not working with a Zeiss machine anymore (sigh...), but I registered here just for giving you an Excel-sheet I whipped up. I modified it, so you can use it with a VAST XXT probe head or other on an RDS.

As you might have guessed by now, there is no simple formula for this problem, but it is solvable using matrix transformations.

The sheet is protected (but no password), so you can modify only the two green outlined cells. Enter the angles and see the changing projected angles below. You might want to play around with the entered values until you find a projected angle that suits your needs. Feel free to modify the sheet as you see fit.

By playing around with the values, you'll see that A+22,5 / B+2,5 yields a projected angle that is 1,03°, whereas your A+17,5 / B+2,5 yields only 0,78°.

Good luck!

Daniel

Vector transformation VAST XXT.xlsx

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Hi Daniel,

Great job. I also used excel to calculate various angles, not quite as interesting as yours. I found my original angle s to be off, too. I'll post mine when I am back in my office.
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I don't remember exactly, three years ago I was operating brown and sharp pcdmis. I could rotate this probe head with respect to x axis, this is what I mean..

Just told a comparison ....
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Seems okay. And you've made a nice table, that was going to be my next step.

Did I mix up the A- and B-axis? It's been five years since I worked with an RDS.

Daniel
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I was viewing the angles from the X direction and my values may be off. Unfortunately, I didn't pay attention to the correct A and B orientation, but I was able to figure out the right combination.
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Having trouble with your form. In left graphic, I entered .8 as shaft diameter and 1 as probe diameter. I get .1 shaft clearance. When I click Calculate, the clearance field in right graphic goes to 9999.
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Hi Tom,
I would scan half of the circle with a probe at 0° and the other half at 2.5°. Won't be able to get to the bottom though.
Regards,
Jay Blaine
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Hi Jay, the feature was a plane at a 1° tilt in a 1.4mm wide slot, using a 1mm probe. Through indexing to the angles worked out in my spreadsheet, I was able to get a stylus angle with an effective angle of 1.03°. I had to measure half of the slot in one orientation and then index to a complimentary mirrored angle to measure the other half.

See the attached pages.

rds angles for 1 deg.pdf

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Make sure that the value of the shaft clearance on the right side is smaller than the value
of the shaft clearance on the left side. (because of the tilted probe shaft)
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