Difference between "Rapid Approach" vs "Approach" points in a Post Processor

In my post processor I see:

*RAPID*
N"lnbr" G00 "x" "y" "z"
*END_SECTION*

*RAPID_APPROACH*
N"lnbr" "x" "y" "z"
*END_SECTION*


*APPROACH*
N"lnbr" G01 "x" "y" "z" F"feedz"
N"lnbr" z0.100
N"lnbr" M08
*END_SECTION*

Am I correct that the workpiece is first approached at full rapid speed to some point and then approached at a feed rate to a much closer point (prior to the first cut)?

How close are these approach points in relation to the workpiece?

Can these points be configured via the post processor ... say to make the rapid approach point one inch and the second approach point 0.100"?

In preliminary testing of a new post, it would be very reassuring to be able to closely watch the approach with the rapid & feeds manually reduced to visually judge that there are no major errors in offsets/zero settings.

I appreciate any help with understanding how this actually works!!!

Best regards!

Bruce

RAPID is the traversal to a new toolpath where a RAPID_APPROACH is used until an APPROACH is activated which is the final descent. But beware, the RAPID_APPROACH is not always used, you can get a program that goes from RAPID directly to APPROACH.

Svenakela,

I appreciate the reply. Let me see if I have this straight by a practical example from a code snippet:

(M17Vgroove)
N100 G40 G56 G80 G90 G94
(Bullnose 60radius)
N101 G111 T1
N102 M01
N103 S9000 F80 M03
N104 G00 X-1.53442 Y-3.96625
N105 Z1
N106 Z0.00331
N107 G01 Z-0.09669 F40
N108 M08

Lines 104 is a "Rapid" move and Line 107 is an "Approach" ... and lines 105 and 106 are "Rapid Approaches" since they are not directly connecting to the beginning of the next toolpath.

That seem right?

Am I correct that Rapid Approaches are internal to madCAM program and the machinist can't modify them?

Thanks!
B

I think you are correct.
And yes, the RAPID_APPROACH is somewhat internal, the G code processor decides if it can use a RAPID_APPROACH or not when the G-code is generated. So lets say you want to automatically open an air valve (or start a plasma torch) you should put that in the APPROACH part of the post processing config.

/S

The underlying reason behind the question was that on the MC post processing page there was a Home Position that I was trying to figure out its functionality. My system defaulted to 0.25", but I don't see anything in the output code to that effect. The same situation appears when z38 is set in the help example:

https://www.cnczone.com/forums/attac...d=393388&stc=1
https://www.cnczone.com/forums/attac...d=393390&stc=1

The Z=38 in the window doesn't seem to post in the code ... but the help says some parameter has to go in the Post Processor too. Just curious how to use this.

It would really be nice to be able to turn Single Block 'on' to step through the first few lines of an untested programs and be able to see the machine come to say 1.0" of the work before actually initiating the cut.

I always enter a Z1 to sniff for offset errors or something else grossly wrong, before turning a new program loose. This little precaution has saved me more times than I care to admit.

I was thinking the "Home" position here might allow me to set a starting point to test automatically in the code ...

Tnx!

B