Dynomotion

Group: DynoMotion Message: 8272 From: dotma99 Date: 9/5/2013
Subject: Geo Correction Problem
Hi Tom<p></p><div><br></div><div>I have a gantry type CNC with a 1200mm X axis and 2400mm Y axis.  I have added a tilting head which is quite heavy and is causing the X axis to sag about (1.2mm in the middle).</div><div><br></div><div>I am trying to compensate for this with a Geo Correction file.  I have followed the help page on this, but am struggling.  I have attached the file in question.  </div><div><br></div><div>I am using a 50mm square and just trying to adjust the Z axis.</div><div><br></div><div>When I apply this file the Position indicators (X, Y and Z) all show this "-1.#IND" and no motion is allowed.</div><div><br></div><div>I have obviously made a mistake.  Could you look at my Geo correction file and put me right.</div><div><br></div><div>Many thanks</div><div><br></div><div>Edward</div>
   @@attachment@@
Group: DynoMotion Message: 8276 From: Tom Kerekes Date: 9/6/2013
Subject: Re: Geo Correction Problem [1 Attachment]
Hi Edward,

Your calibration file has 0,0 for all the calibrated XY points.  The calibration file should contain the absolute corrected position not just a correction amount.

Another problem is that the calibration file must be in inches.

I created a file for you on a 2 inch grid (rather than 50mm).  See the attached file.  I might be off on the direction and axis of the "sag"  It seems to me the corrected position should be in the +Z direction.  Sag is a funtion of the Y position?  The values in the file should be the positions where the XYZ motors need to be driven to to put the tool at the exact theoretical XYZ CAD grid point (where Z is zero).

Your file assumed a V shaped sag.  Seems like a parabolic sag might be more realistic.  I've attached one like that as well.  There is an attached plot.

I also attached Excel Files that I used to create the tables.  To use them to make a new file you will need to select the updated values, paste them into a blank Excel File, save the file as a CSV text file, then delete some extra commas Excel puts in on the first few lines.

HTH
Regards
TK





Group: DynoMotion Message: 8295 From: Edward Forwood Date: 9/9/2013
Subject: Re: Geo Correction Problem [5 Attachments]

Perfect, many thanks.  Your parabola formula has made my Z axis accurate to within 0.2mm across the bed (1.5 metres) which is more than adequate for my machine/application.

 

Best

 

Edward

 

From: DynoMotion@yahoogroups.com [mailto:DynoMotion@yahoogroups.com] On Behalf Of Tom Kerekes
Sent: 06 September 2013 18:56
To: DynoMotion@yahoogroups.com
Subject: Re: [DynoMotion] Geo Correction Problem [5 Attachments]

 

 

[Attachment(s) from Tom Kerekes included below]

Hi Edward,

 

Your calibration file has 0,0 for all the calibrated XY points.  The calibration file should contain the absolute corrected position not just a correction amount.

 

Another problem is that the calibration file must be in inches.

 

I created a file for you on a 2 inch grid (rather than 50mm).  See the attached file.  I might be off on the direction and axis of the "sag"  It seems to me the corrected position should be in the +Z direction.  Sag is a funtion of the Y position?  The values in the file should be the positions where the XYZ motors need to be driven to to put the tool at the exact theoretical XYZ CAD grid point (where Z is zero).

 

Your file assumed a V shaped sag.  Seems like a parabolic sag might be more realistic.  I've attached one like that as well.  There is an attached plot.

 

I also attached Excel Files that I used to create the tables.  To use them to make a new file you will need to select the updated values, paste them into a blank Excel File, save the file as a CSV text file, then delete some extra commas Excel puts in on the first few lines.

 

HTH

Regards

TK

 

 

 

 

 

From: "edward@..." <edward@...>
To: DynoMotion@yahoogroups.com
Sent: Thursday, September 5, 2013 11:47 AM
Subject: [DynoMotion] Geo Correction Problem [1 Attachment]

 

 


Hi Tom<p></p><div><br></div><div>I have a gantry type CNC with a 1200mm X axis and 2400mm Y axis.  I have added a tilting head which is quite heavy and is causing the X axis to sag about (1.2mm in the middle).</div><div><br></div><div>I am trying to compensate for this with a Geo Correction file.  I have followed the help page on this, but am struggling.  I have attached the file in question.  </div><div><br></div><div>I am using a 50mm square and just trying to adjust the Z axis.</div><div><br></div><div>When I apply this file the Position indicators (X, Y and Z) all show this "-1.#IND" and no motion is allowed.</div><div><br></div><div>I have obviously made a mistake.  Could you look at my Geo correction file and put me right.</div><div><br></div><div>Many thanks</div><div><br></div><div>Edward</div>