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Siemens post wrong threadpitch in threadmilling operation

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Message 1 of 9
infoGNXXP
301 Views, 8 Replies

Siemens post wrong threadpitch in threadmilling operation

While threadmilling 2 holes in one operation, the default Siemens onCircular section creates two different thread pitch codes. See sample G-code.
Hole one is machined with a delta Z 18mm with 11 turns resulting in a pitch of 1.63 when a pitch of 1.5mm is programmed.
Hole two is also machined with a delta Z 18mm but with 12 turns, resulting in the programmed pitch of 1.5mm.

Debug comment resulted in ;rev=11.999999999999998 and ; rev=12.000000000000002 for the two holes.

Disabeling the build in option "Allow Helical moves" while posting the G-code fixed the problem, but this cant be te correct solution. Is there anyone else having the same issue? How can this be fixed?


Part off postprocessor:

 

function onCircular(clockwise, cx, cy, cz, x, y, z, feed) {
  
  writeBlock(gPlaneModal.format(17));

  var start = getCurrentPosition();
  var revolutions = Math.abs(getCircularSweep()) / (2 * Math.PI);
  writeComment("rev=" + revolutions)
  var turns = useArcTurn ? (revolutions % 1) == 0 ? revolutions - 1 : Math.floor(revolutions) : 0; // full turns
  writeComment("turns=" + turns)

 

 

Sample code:

 

N37 G3 X-17.927 Y0 Z11.749 I0 J4.519
N38 G3 X-17.927 Y0 Z29.749 I-4.938 J0 F310.5 TURN=11
N39 G3 X-22.446 Y4.519 Z30.093 I-4.519 J0
N40 G1 G40 X-22.865 Y0
N41 G0 Z106.904
N42 G0 X-177.865
N43 G0 Z13.406
N44 G1 Z11.406 F150
N45 G1 G41 X-177.446 Y-4.519
N46 G3 X-172.927 Y0 Z11.749 I0 J4.519
N47 G3 X-172.927 Y0 Z29.749 I-4.938 J0 F310.5 TURN=12
N48 G3 X-177.446 Y4.519 Z30.093 I-4.519 J0

 

 

Unfortunately i cant upload any files.

Hope someone can help me out.

 

Kind regards,
Addy

 

Edit: Uploaded files.

8 REPLIES 8
Message 2 of 9
seth.madore
in reply to: infoGNXXP

Could you recreate your toolpath and features in a dummy part and share that here?

Which post processor are you using?


Seth Madore
Customer Advocacy Manager - Manufacturing
Message 3 of 9
DarthBane55
in reply to: infoGNXXP

Check a few things when the helical moves is ON:

-Make sure the 2 holes are perfectly identical, in the selection window as well (depth of hole 100% identical) (just saying that because you are counting the number of turns, and hole depth would of course affect that).

-Don't rely on the number of turns, sometimes it breaks arcs at different locations.  Instead calculate the height difference at the same point of the helix for 1 complete turn, for each hole.  I think you'll find that the pitch is correct in both holes.

 

On your code sample, between hole 11 and 12, the Z are identical, only X is different, and by a lot, so it's in a different hole it seems.  So this is not turn 11 and 12 it looks like...

 

EDIT: Well, I am unsure how your toolpath goes, you are doing 1 turn in 1 hole, then 1 turn in the next hole, and repeat?  In any case, turn 11 and turn 12 move by the same amount, therefore they have the exact same pitch.  I guess you are using a single point threadmill right, otherwise you would never get that many turns for 1 hole.

Message 4 of 9
infoGNXXP
in reply to: DarthBane55

Thanks for your reply.

 

In regard to the hole size, i checked these with the measure function and these are identical within .00mm.

 

Unfortunately the thread pitch really is wrong in one hole since the calliper wont fit. Changing to helical moves is OFF ended up crossthreading the part and accepting the caliper. Ofcourse the part was scraped unfortunately🙄

 

You are right about the single point mill. It`s a single pass cut.

I hope you will look into the part uploaded, finally figured it out.

 

 

Message 5 of 9
infoGNXXP
in reply to: seth.madore

Thanks for your reply.

 

I attached the files to the post. Hopefully you can look in to it.

Message 6 of 9
DarthBane55
in reply to: infoGNXXP

hmmmm, what exactly has a caliper to do with the thread pitch?  you need to check the thread pitch with a thread gauge, caliper will measure the minor diameter, which is not created by your threadmill in the case of a single point tool.

 

EDIT: ok, I opened your file, and posted.  I will leave it to Seth, I am not familiar with the Siemens control and therefore I apologize for answering anything above.  The output is quite different to Fanuc so I should have stayed away.  The 2 holes are identical indeed (in Fusion).  So there is a rounding issue as you pointed out at the beginning.

Message 7 of 9
seth.madore
in reply to: DarthBane55

@DarthBane55 I also have no clue on a Siemens post, I just plan on forwarding this to the Post Team and let them sort it out 🙃

 

(I suspect "caliper" may be a translation issue)


Seth Madore
Customer Advocacy Manager - Manufacturing
Message 8 of 9
seth.madore
in reply to: infoGNXXP

I've got an answer for you:

There is a rounding error in the post (as you suspected), so the answer is going to be to change some code in the "onCircular" section:

Before:

var revolutions = Math.abs(getCircularSweep()) / (2 * Math.PI);

After:

var revolutions = xyzFormat.getResultingValue(Math.abs(getCircularSweep()) / (2 * Math.PI));

 

Result:

N35 G17
N36 G1 G41 X-22.446 Y-4.519
N37 ; rev=0.25
N38 ; turns=0
N39 G3 X-17.927 Y0 Z11.749 I0 J4.519
N40 ; rev=12
N41 ; turns=11
N42 G3 X-17.927 Y0 Z29.749 I-4.938 J0 F310.5 TURN=11
N43 ; rev=0.25
N44 ; turns=0
N45 G3 X-22.446 Y4.519 Z30.093 I-4.519 J0
N46 G1 G40 X-22.865 Y0
N47 G0 Z106.904
N48 G0 X-177.865
N49 G0 Z13.406
N50 G1 Z11.406 F150
N51 G1 G41 X-177.446 Y-4.519
N52 ; rev=0.25
N53 ; turns=0
N54 G3 X-172.927 Y0 Z11.749 I0 J4.519
N55 ; rev=12
N56 ; turns=11
N57 G3 X-172.927 Y0 Z29.749 I-4.938 J0 F310.5 TURN=11
N58 ; rev=0.25
N59 ; turns=0
N60 G3 X-177.446 Y4.519 Z30.093 I-4.519 J0
N61 G1 G40 X-177.865 Y0
N62 G0 Z116.904
N63 M1

Seth Madore
Customer Advocacy Manager - Manufacturing
Message 9 of 9
seth.madore
in reply to: infoGNXXP

Oh, and I should add that I've opened up a ticket to get this fixed in the stock library post; CAMP-2887


Seth Madore
Customer Advocacy Manager - Manufacturing

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