G50 programmimg on old Bullard VTL

[Simon1964]

Hi, havent used Master Cam for Lathe programming. We have a lot of old cnc programs for this Bullard VTL using a fanuc control. One thing that has been done over the years is previuos programmers have used G50 to set X and Z positions in the programs. I do understand the concept and used it in the past but always went back to a 'tool change' position first, then picked up new G50 and tool changed. Here, they seem to go up in Z after cutting, then cancel offset, pick up a new G50, index to next tool. Problem?? The positions for X do not match my calculations for where they should be, meaning, i think the X diameter of the next toll should be X22.5", but the program states it is X 32.5", I am not totally stupid, but cannot for the life of me see where these numbers come from!! The programs do work though!

My dilemma is I have 2 new parts to machine, but they have been prevoiuosly semi finished so i do not need existing rough machininh, just the finish bore, finish id groove and back chamfer. When i 'chop up" an existing program to just do this, I get over travel and I am finding that the machine is not where it should be. I have gone through these programs tons of times and cannot see the 'pattern' from where the G50 X position should be. This is hard to explain here like this, but i am hoping that someone sees this and says, 'oh yeah, seen that before, here is how you work out the positions"!!

Is there anyone??? i am in deep doggy doo right now as i need these new programs for Feb 2nd.

I am also not stupid and have over 26 years CNC experience, i just can't get the machine to do what it should do. If i run the existing program without any changes it is perfect!!

See, doesnt make sense!!

Please help ASAP if you can, and if anyone at In House in Cambridge Ontario can help me ( our distributor) please call me at 519 452 5285.

Thanks in advance!!

Simon.

[taperlength]

That's real old school. G50 creates a work coordinate system relative from the current position of the tool. So, if the tool is in the wrong place when G50 is set, the work coordinate system will be wrong. The X value in the G50 line should be the diametric distance from the tool to the X0 point on the workpiece. If the tool is a boring bar and it has a tool offset, the X value would be from the center of bar.

If you deleted some tools from the program, the tool may be indexing at a place which is different from what the existing G50 is set for. Hope this helps. Be sure to dry run away from the part.

[Simon1964]

Thanks for the reply. That is what i thought, but what I am seeing is that the next G50 value, EG, for a back face tool, is G50 X32.55, but, the machine is currently at an X value od X9.345. When i look at the tool set sheet, the X distance from the Centre of the tool to the tool tip is 3.25", so in essence, the G50 value should be closer to G50 x16.5 ??? That would make sense, but the existing program has the G50 X 32.55, whcih is why the machine then goes into over travel!! I am reluctant to enter the x values I think it should be as the existing program works!! So there is my dilemma!!

 

Below is a copied part of the program i am on a bout.

 

O0167( 40144552 REV-A OP1 PR SB WITH 10 DEG LEAD JAN 26 2009 )

G98

N001G50X76.Z24.

N002G00T0110

( TOOL 1 OFFSET 10 )

( CUT HUB FACE. ADJUST X OFFSET TO GET SUITABLE CHAMFER.)

N003X54.1804Z11.91

N004X54.Z11.81

N005M00

( INDICATING POSITION.)

N006G00T0110

N007X40.2Z11.81

N008X40.

N009M00

( Z GAP 6.500" )

N010G00T0110

M05

M42

N011G97S0155M03

N012G00X8.6196Z11.81

N013G01X8.4196F9.9975

N014G04P5000

N015G00Z8.07

N016Z7.18

N017G01Z7.08F9.9975

N018X13.9864F3.1

N019X14.2982Z6.99F2.325

N020G00Z24.

N021M01

( ADJUST X OFFSET TO GET SUITABLE CHAMFER.)

N022G00T0100

N023G50X14.2982Z18.

N024G00T0202

( TOOL 2 OFFSET 2 )

( ROUGH BORE )

N025G97S0160M03

N026G00X8.7752Z8.077

N027G01X8.7196Z7.977F10.

/N028M05

/N029G00X10.8Z7.3411

/N030X11.Z7.28

/N031M00

(************************* Z GAP .200" ***)

/N032G00T0202

/N033G97S0160M03

/N034G00X8.9196Z7.9159

/N035G01X8.7196Z7.977F10.

/N036G04P5000

/N037G00X9.0548Z7.23

/N038G01X9.0996Z7.13F10.

/N039Z6.477F4.48

/N040X8.9796

/N041G00X8.737Z7.877

/N042G01X8.7196Z7.977F10.

/N043M05

/N044G00Z18.

/N045M00

( BORE DIA = 9.100" )

/N046G00T0202

/N047G97S0160M03

/N048G00X8.7196Z8.077

/N049G01Z7.977F10.

/N050G04P3000

N051G00X9.143Z7.23S0160M03

N052G01X9.1996Z7.13F10.

N053G04P3000

N054G01Z0.159F4.48

N055X9.0796

N056G00X8.7242Z7.877

N057G01X8.7196Z7.977F10.

N058G00X9.4748Z7.23

N359G01 Z7.0751 F2.4

N361G02 X9.2705 Z6.9896 K-.1037

N362G01 X9.1434 Z6.6338

N363X9.0434

N062G00X8.7536Z7.877

N063G01X8.7196Z7.977F10.

N064G00Z18.

N065M01

(***************************** 9.200" DIA, .020" UNDERSIZE)

N066G00T0200

N067G50X-5.7804Z18.

N068G00T0207

( TOOL 2 OFFSET 7 )

( FINISH HUB FACE )

N069G97S0267M03

N070G00X14.8Z7.918

N071G01X15.Z7.82F10.0125

/N072M05

/N073G00X9.3996Z7.2986

/N074X9.1996Z7.28

/N075M00

( Z GAP .200", FLUSH WITH BORE.)

/N076G00T0207

/N077G97S0267M03

/N078G00X14.8Z7.8014

/N079G01X15.Z7.82F10.0125

/N080G04P5000

N081G00X8.7996Z7.82S0267M03

N082G01X8.5996F10.0125

N083G00Z7.23

N084G01Z7.13F10.0125

N085Z7.07F2.67

N086X13.25F3.204

N087G00Z18.

N088M01

N089G00T0200

N090G50X31.808Z21.625

N091G00T0303

( TOOL 3 OFFSET 3 )

( M/C BOTTOM HUB FACE )

N092G97S0175M03

N093G00X9.1076Z11.2088

N094G01X8.9076Z11.117F9.9925

N095G00X9.0754Z7.17

N096G01X9.0796Z7.07F9.9925

/N097M00

(*** FLUSH WITH HUB FACE, X GAP .060" ***)

/N098G00T0303

/N099G97S0175M03

/N100G04P5000

N101G00X9.0796Z0.765S0175M03

N102G01Z0.665F9.9925

N103X13.088F2.625

N104Z0.605

N105G00X9.2796

N106G01X9.0796F9.9925

N107G00Z0.7825

N108G01Z0.8625F9.9925

N109X9.3946Z0.705F1.75

N110X13.088F2.625

N111Z0.7569F0.875

N112G04P1000

N113G01Z0.6569F3.5

N114G00X9.2796

N115G01X9.0796F9.9925

N116G00Z9.664

N117Z21.625

N118M01

(************************** HUB THICKNESS = 6.375 +0/-.02 ***)

N119M05

N120G00T0300

 

There is more but this will give you the idea of what is going on. Any ideas please let me know, i need a new program today!!

thanks,

Simon