Author Topic: Probing and touch plates - your MSM experience?  (Read 29751 times)

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Offline DaveCVI

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Re: Probing and touch plates - your MSM experience?
« Reply #40 on: January 10, 2014, 01:16:12 PM »
Hi,
I'll try to address your comments here. Please see the information below.

By the way, the main MSM support forums are here:
http://www/CalypsoVentures.com/forums

For future questions you will get a faster response by posting questions there.

 
i experience some problem with your screen.
i use a canadian french computer. So, the default marker for digit is "," instead of ".".
When i edit the tool table, the numeric value in the pop up window use ",". To be able to save my entry, i have to change them all to "."
and i have to do it each time.

I think you have to modify your code to take care of this isue.


I would love to be able to make MSM follow the various regional settings for numbers and currency. Unfortunately, this problem is not in MSM, it is in Mach.  Much of MSM is written in the cypress basic language that mach uses for scripts. Unfortunately neither Cypress basic or Mach itself support internationalization settings. I asked about this for mach 3 and was told by Artsoft that mach3 was never going to be updated to support anything other than US English settings. 

The best I could do was to document this in the MSM release notes. The only regional settings MSM supprots are those that Mach 3 supports and that is only US English settings. Please see teh MSM release notes, section 4 (Known Errata in Mach3), item # 53.

Other thing.
When i probe a pocket or a edge, is not alway to zero it. Often it's because i want to mesure it in reference with another feature. So i propose to add a button to tell mach that i want to zero or not.
This one I can help you with. There is a button called "probe only". It is in the lower left corner of the panels that have the green arrow probing operation buttons. Whenever this button is on, MSM will not tell mach to reset zero to the probe point.
I think this is exactly you are asking for. See section 8.6.3.1 of the MSM user manual.


Other thing,
My probe dont have any possible adjustment. Si the probe is alway off center. To take care of this, i mill a round pocket on my mill table. This pocket is at a know location in the machine reference system. So when i put the prob in, i mesure the center of this pocket. The mesured position of the pocket minus the theorical mesurement of the pocket give me the actual offset of the probe. This way, when i probe a part, i just have to remove the value calculated to know the real position of the part.

To take care of this, i propose to:
-add two value in the screen to enter the real position of the pocket.
-Add a new button in the probing page to mesure the center of this pocket for probe refference purpose.
-Then, each time i probe a part in a specific direction, take care of the compensation for the probe offset.

This type of problem is why I recommend that people use probes that can be adjusted. 

However, I am also thinking about what you have described.
It seems to me that the process you have described is maybe not sufficient to resolve the errors from a probe that does not have a centered tip.  It also seems to only address probes along the X and Y axis.

It seems that the results you are getting are dependent on the diameter of the cylinder that you are boring and using for compensation. I'm thinking of two circles, on inside the other, with their circumferences tangent at one point only. This is what we have for the probe you described. The "compensation amount" is not only a function of the direction of the probe movement relative to the (offset from center)  probe tip, it is also dependent on the relative diameters of the cylinder and the probe tip.
At least Part of this error can not be removed (without using having a physically impossible zero diameter probe tip).

This gets complex quickly and is one reason that the probing routines in MSM are oriented toward increasing productivity of job setups. Most job setup operations only require probes along a single axis, and in those cases it is good enough to assume that the surface that touches the probe tip is perpendicular to the direction of the probe movement.
A probe whose tip is not concentric will create additional error.

Since probes that have concentric adjustments start at about $120. It seems that the most economic way to remove this error is to get a better probe tool. (the reality is that the effort to implement what you describe is much more than $120 of man power time).

Dave
 

Over all, this screen is amasing.
Thanks.
I'll take that as a compliment. :-)

Dave


Author of the MachStdMill Extensions for Mach3
www.CalypsoVentures.com

Offline vinythewheel

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Re: Probing and touch plates - your MSM experience?
« Reply #41 on: January 11, 2014, 10:48:46 PM »
In the tab "Probe only" it will be greate if you add a button for hole center. It's hapen often that i want to know the distance betwen two hole center. It's very hard to mesure it with conventional mesuring tool. Probing is the way to do it, i think...


Another thing,
my probe tip is a perfect sphere so i dont anderstand your argumentation about " It also seems to only address probes along the X and Y axis." if the position of the sphere is know in the machine coordinate system, there is no possible problem. Knowing the z position is easy and dont move that much if the probe get fiew mill ofset in the XY plane. If you probe in the referenced circular pocket (with a know position), you find the position of the probe tip (sphere) in the machine cordinate system. Then any probing operation can be corected easily with the know ofset. eaven if the probing operation is in diagonal.

Please excuse my poor englich.

A probe can be aligned but one secon is needed to bend the stylus without knowing. this cause problem for finding a edge on a part and cause mill operation error. I still think it will be e very good idea to add up those functionality to the interface. For me and for a bunch of user.

I have good programing skill, maybe i can help on that.

Thank for your fast reply




Offline DaveCVI

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Re: Probing and touch plates - your MSM experience?
« Reply #42 on: January 12, 2014, 12:25:46 AM »
Hi,
Here is a little document with some diagrams for you to think about. These illustrate some sources of "Cosine error".
When a probe tip is centered on the Z axis, the error is as least a constant with respect to the XY direction of a probe motion.
When a probe tip is off the Z axis center, the error becomes more complex - and that is just in the XY plane.
Now consider a probe direction that is along an arbitrary vector in X,Y,Z....  I think you'll quickly decide that it's much more cost effective to invest in a probe tool that has centering adjustments.

Dave
Author of the MachStdMill Extensions for Mach3
www.CalypsoVentures.com

Offline derek

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Re: Probing and touch plates - your MSM experience?
« Reply #43 on: January 12, 2014, 08:14:07 AM »
The cheap probes can be a bit of a challenge to get set properly. I was wondering if putting a tiny 4 jaw lathe chuck between the probe and the tool holder would improve this. You could then just center the probe in the holder.
The problem with adjusting my probe is you're moving the contact balls up and down and this causes contact issues.

Derek


Offline vinythewheel

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Re: Probing and touch plates - your MSM experience?
« Reply #44 on: January 12, 2014, 11:00:01 AM »
When i look to your 4 first page of you document (Probe trigger point cosin error pictures.pdf) it's clear that if you probe a inclined surface you can't know the position of the surface. You have to probe two points and calculate the surface slope, find the perpendicular verctor direction then you can calculate the real position of the surface in reference to the probe tip center. This calculation look like the one used when you want to make 5axis tengential machining and need a bunch of man time to implement.

In the case of a the folowing mesurement :
-rectangular pocket aligned in the XY plane
-Edge aligned in the XY plane
 The first two page of your document dont aply

In the case of a circular pocket, the fist 4 page dont aply also cause you recenter the probe in the center to mesure the other axe. thea way, the probe movement is alway perpendicular to the touched surface.

Eaven if you want to digitalise a point cloud of a complex 3D surface, i think the algorithme present on the mach3 webpage take care of cosine error (not shure, never try them). If your probe is off-center, you only have to take the point cloud and translate it the amout of probe ofset in the X and Y direction. and the result will be correct.



The last page of your document represent the problem that can be solved by the routine i propose. (post #39 to #41). With this kind of routine, you can increase the acuracy of the probe positioning operation for a edge probing and pocket center finding.

When i want to zero of my part on the center of a hole i do this operation.
-Install the probe
-mesure my reference hole wich are at a know position (360, 270)
-take the mesured result (360.05, 269,93)
-calculate the position of the ball (360.05-360=0.05  and 269.93-270=-0.07)
-mesure the hole on my part where i want to zero mach3
-after mesurement, the probe go to the center of the hole a zero the XY axis
-edit the X axis DRO and put the value of 0.05
-Edit the Y axis DRO and put the value of -0.07
-hit a G0 X0 Y0
-place a edge finder in the spindle and verify the position of the spindle in reference to the hole.
-Good place all the time

This routine can be automated easily within the MSM app. I can implement it if you can add couple of DRO in your setting page tha i can use.

Thank a lot for your interest

Offline DaveCVI

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Re: Probing and touch plates - your MSM experience?
« Reply #45 on: January 12, 2014, 12:30:57 PM »
Hi,
<ship>
This routine can be automated easily within the MSM app. I can implement it if you can add couple of DRO in your setting page tha i can use.

Thank a lot for your interest
Please feel free to customize MSM to suit your needs. In case you were unaware of it, you can add DROs to MSM screens (there's no need for CVI to do it for you).  I recommend using Machscreen for mach set file editing (that's what was used to create MSM's pages). You're free to add some DROs and script code to support this technique for handling your probe's tip offset errors.  Section 15 of the MSM user manual covers the techniques for customizing MSM.

Dave
Author of the MachStdMill Extensions for Mach3
www.CalypsoVentures.com

Offline Fastest1

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Re: Probing and touch plates - your MSM experience?
« Reply #46 on: April 29, 2014, 09:28:12 AM »
I know this was a bit ago. If the probe was not aligned in Z and you tried to compensate for the error by your calculations. Dont you think spindle orientation would be critical?
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline vinythewheel

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Re: Probing and touch plates - your MSM experience?
« Reply #47 on: May 03, 2014, 09:50:12 AM »
of course, but i have the spindle position with a 4000 count encoder.