Jump to content

Curve and Sharp Corners


---
 Share

Recommended Posts

Does anyone have any tips/tricks they'd like to share regarding measuring Curves with the tactile probe, and scanning over sharp corners?

Typically I would just break the segments up, but I do lose some coverage because of this.

If this was being done optically, it wouldn't be an issue.

Any and all help is greatly appreciated.

Thanks.
Link to comment
Share on other sites

It's not so much the masking of points, it's the fact that an edge is not clearly defined, so a lot of times (especially with small probes) it will cause a crash when trying to transition from one edge to another.
Link to comment
Share on other sites

I do many of those measurement methods, at the moment this is my favorite solution:

Since tactile forces go in vector direction is common to have jumps during scanning, also when the adjacent vector change dramatically you will see that change in probe diameter corrections..

for that reason, I generate separate curves for scanning and evaluation:


Nominal curve : vectors change 90° generating jumps during scanning and probe correction. 1375_ce61b55ae561bbbfec8b7cdab88e1084.png



Scanning curve: allows smooth transition during scanning. 1375_287fb3c87583349f580bf9b8a37fe86d.png



Evaluation Curve: change vectors gradually to avoid peaks in probe corrections. 1375_da325eb1368c704f7670e52a477d9abf.png



Other consideration is to use small probes to reduce the mechanical filter of the edge (in our case we use Ø 0.5 mm ): 1375_fee94321b0ddf8e7ce2c8ec966d33e0f.png



Also, for sensitive parts we give some flexibility to the metrologist:
MES_SCN_OPT = 0         		// Scanning orientation +Z = 1   -Z = 0 
MES_SPEED = 1.5				// Profile Scanning Speed  (mm/sec.)
MES_PRF = 150				// Curve probing Force in mN,  
GRV_SCN_RAD1 = 0.4			// Transition radius  for scanning
Link to comment
Share on other sites

You can divide segment to three where middle one will have slower scanning speed to avoid jumps. Don't forget to select all segments to group them. Then it will scan without interruption.

Adding one point to extact corner with tilted vector is good too.
Link to comment
Share on other sites

Israel,

This is good stuff. I will see if I am able to achieve the same level of success. Thank you.

Chad,

I didn't realize that. I am using a smaller stylus for this inspection - 0.8mm, but I will go smaller if needed. Thanks.
Link to comment
Share on other sites

Please sign in to view this quote.

My intuition says that .8 should be good. My rule of thumb for complex curves is 1.0mm or less. I think it has something to do with less probe radius correction error.
Link to comment
Share on other sites

When dealing with small radius's, corners and small probes, SPEED KILLS.
I'll slow them sections down to 0.100 to 0.300 mmsec and avoid some of probe-bounce/compensation/noise issues.
Link to comment
Share on other sites

Please sign in to view this quote.

Would be an awesome feature to have dynamic scanning to where when it approached a sharp corner or small radius it slowed down.
Link to comment
Share on other sites

Please sign in to view this quote.

That already exists, since like 5.8
In the way that you can scan different part of a curve with different speeds. Without removing the probe from the part.
Link to comment
Share on other sites

Well, its really simple.

Create segments of your curve, edit the speed. Mark all (the ones you wish) segments and right click and choose "Group for the measurement".

.....Now that will be 4 beers + tax.
Link to comment
Share on other sites

Please sign in to view this quote.

I was looking for the easy button. You know how us Americans are.

Tell me what beer you want, and I'll send them your way.
Link to comment
Share on other sites

The speed can be adjusted by group of points (in the curve strategy), unfortunately this is not enough to avoid jumps, mainly if the edge is potentially deviated from the nominals and vectors change dramatically...

The probing force goes in the direction of the vector, if there's no material the probe jumps, same happens if the vector changes and the surface still not achieve the edge, in some cases you could have broken tips..
Link to comment
Share on other sites

Please sign in to view this quote.

That can also be dealt with, to some extent. With point definition. I admit, it's a bit "fiddely". But it do work. 114_83a1091f4779acb06ec58fc18b6074fc.png
But yeah, tactile measurements have some limitations. You can't toutch something that isn't there. One thing that also can help, depending on how the geometry looks, is measuring the curve inverted.
Link to comment
Share on other sites

Please sign in to view this quote.

If say there are clamps in the way of certain areas you would normally put a clearance, does this cause an issue for group for measurement?
Link to comment
Share on other sites

 Share

×
×
  • Create New...