sunderlandjoe

G76 Threading Acceleration Distance and lead in angle problem

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So I've got a weird post issue.

If I post out a G92 threading cycle the Z start point will match my acceleration distance as it should for example as .2.

If I post it out in G76 the start point is .2 with a lead in angle of 0.

but if I post it out with a lead in angle of anything other than zero it changes that Z acceleration distance but does not adjust the taper to suit.

Any one have any insight into what is going on here and how I can fix it? 

Examples:

With lead in angle at 30°

G0 T0303
G97 S380 M03
G0 G54 X4.2333 Z.2608 M8
G76 P010030 Q0030 R0030
G76 X3.7683 Z-3.95 P1325 Q0271 R-.3458 F.25
M9
G28 U0. W0. M05
M30

With lead in angle at 0°

G0 T0303
G97 S380 M03
G0 G54 X4.2333 Z.2 M8
G76 P010000 Q0030 R0030
G76 X3.7683 Z-3.95 P1325 Q0271 R-.3458 F.25
M9
G28 U0. W0. M05
M30

 

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It's been a long time since I've used G76 but isn't the taper I-.3458? I seem to remember R is the chamfer amount.

I used to add .400 for my lead catch up amount but that was in the 90's. I started my taper at the +.400 start point also.

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38 minutes ago, Tim Johnson said:

It's been a long time since I've used G76 but isn't the taper I-.3458? I seem to remember R is the chamfer amount.

I used to add .400 for my lead catch up amount but that was in the 90's. I started my taper at the +.400 start point also.

Yes, but you can see in the above that it added .0608 to the start value but the R value didn't change accordingly.

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2 hours ago, sunderlandjoe said:

So I've got a weird post issue.

I believe it is a post issue.

Many of the canned cycles are incomplete in the post(s) and like the POCO stuff needs to be "dialed in" for a specific machine (and its specific parameter settings) or scenario.

Your reseller should be able to help. Alternately you could get the MP post processer language documentation (again from your reseller) and start learning.

The canned cycles are pretty discreet areas in the post. I am not sure but I think they should be relatively easy to edit.

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Tim Markoski (may he Rest in Peace) brought this up to me back when I used to work at CNC Software. Yes, this is broken. Try Posting the same path, with the latest version of MPLMaster, and the latest version of the Generic Fanuc 4X MT_Lathe Post.

Some Posts will have the old logic, and some use the new logic. I'm not sure if all the Lathe Posts were ever updated or not.

I think Tim had a sample NC Code generator that would calculate the taper values correctly. It's been so long now that I have trouble recalling all the details. 

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10 minutes ago, Colin Gilchrist said:

Tim Markoski (may he Rest in Peace) brought this up to me back when I used to work at CNC Software. Yes, this is broken. Try Posting the same path, with the latest version of MPLMaster, and the latest version of the Generic Fanuc 4X MT_Lathe Post.

Some Posts will have the old logic, and some use the new logic. I'm not sure if all the Lathe Posts were ever updated or not.

I think Tim had a sample NC Code generator that would calculate the taper values correctly. It's been so long now that I have trouble recalling all the details. 

I know how to do the math manually so I can change the value myself, i'm just trying to figure out how to fix my post so I don't have to do that.

I tested the latest MPLMaster post from here and it still does it

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4 hours ago, sunderlandjoe said:

I know how to do the math manually so I can change the value myself, i'm just trying to figure out how to fix my post so I don't have to do that.

I tested the latest MPLMaster post from here and it still does it

Let me see if I can dig up the Post I had that contains the fix. I might still have something, but I can't make any promises yet.

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11 minutes ago, Colin Gilchrist said:

Let me see if I can dig up the Post I had that contains the fix. I might still have something, but I can't make any promises yet.

I would really appreciate that if so. Even just to compare and make the appropriate edits to my post.

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Hello All,

 

I'm facing an oddly an issue when I generate a program in G92 or G78 program. The following image below shows how the machine moves during its end cut and are in a taper angle.

image.png.591e45ed64872e815c6331efb87b9a79.png

 

I have not given any taper angle I just want the tool to first move downward in X direction and retract back rather than having a taper angle. The depth I had specified is 20mm here is the code below

 

G0 T9191
G18
M05
G0 G54 X9. Z10. M8
G99 G78 X4.699 Z-20. F.8
X4.514
X4.369
X4.244
X4.134
X4.134
G0 X9.
M9
G28 U0. V0. W0.
T9100
M30

I wanted to know if there is any changes in the post I need to do or is it in the program I would have to mention some parameters.

 

here's the screenshot of the program

image.png.730744fccd5bf27c012084ccea298611.png

 

Can any one help me with this?

 

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Bump still trying to fix this.

@Colin Gilchrist were you ever able to find the post with a fixed acceleration distance?

I'm trying to figure out how the post logic is working.
What is wrong is it is not using the value entered in the "acceleration clearance" area when a Lead-in angle is present.

Additionally I determined by second line Q value is wrong but I can't find where it does the math (thread depth/(Sqrt(number of passes)).
This appears to be what the *thdfirst$ is but that has no visible logic attached to it that I can find so far.

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On 3/6/2019 at 5:11 PM, sunderlandjoe said:

I know how to do the math manually so I can change the value myself, i'm just trying to figure out how to fix my post so I don't have to do that.

I tested the latest MPLMaster post from here and it still does it

I wasn't able to find those old sample posts unfortunately.

If you can post up a sample file, with several G76 Thread Ops, that you know are good (hand-edit the "good" NC Code), I'll take a look at your Post.

It would help if you could give me both "as posted", and then "hand edited" code, that shows what you are after (and that I can compare back to the original Mastercam Ops), that's what I would need to help you sort this out.

For Ops, if you can do 6 Ops, as follows, that would help:

  • OP1 - G76, Straight, with 0 Degree Lead-In
  • OP2 - G76, Straight, with 30 Degree Lead-In
  • OP3 - G76, Positive Taper 2.0-Degrees, 0 Degree Lead-In
  • OP4 - G76, Positive Taper 2.0-Degrees, 30 Degree Lead-In
  • OP5 - G76, Negative Taper -2.0 Degrees, 0 Degree Lead-In
  • OP6 - G76, Negative Taper -2.0 Degrees, 30 Degree Lead-In

 

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