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Author Topic: Why is this not an arc?  (Read 719 times)

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Why is this not an arc?
« on: August 07, 2021, 04:15:31 PM »
See attachment.

WTF?
Re: Why is this not an arc?
« Reply #1 on: August 07, 2021, 05:27:05 PM »
I don't see any error on the history line, so Mach thought it was running an arc.
At first I thought you might have forgotten to set the XZ plane, but status line shows G18.
Did you try running this in air and watch the motion. Could it be a display artifact, but actually cut correctly?
Steve Stallings
www.PMDX.com
Re: Why is this not an arc?
« Reply #2 on: August 07, 2021, 05:30:08 PM »
It cut exactly as displayed.
Re: Why is this not an arc?
« Reply #3 on: August 09, 2021, 07:25:31 AM »
This is the code for the toolpath:

Code: [Select]
%
O0000
(PROGRAM NAME - LATHE_LEAD_SCREW_V3.0_OP3)
(DATE=DD-MM-YY - 05-08-21 TIME=HH:MM - 22:01)
(MCAM FILE - M:\DOCUMENTS\DENNIS\SOLIDWORKS PROJECTS\LATHE_LEAD_SCREW_V3.0.SLDPRT)
(NC FILE - D:\DOCUMENTS\MY MASTERCAM 2022\MASTERCAM FOR SOLIDWORKS\LATHE\NC\LATHE_LEAD_SCREW_V3.0_OP3.NC)
(MATERIAL - STEEL INCH - 1030 - 200 BHN)
G20
G0 G54 G17 G40 G80
(TOOL - 3 OFFSET - 3)
(TOOL 3 INSERT - DCMT32.51)
G0 X1. Z-5.
T0303 M6
G97 S2500 M03
G0 X.4815 Z-5.0751
G99 G1 X.4621 Z-5.0926 F.006
X.3031 Z-5.236
Z-5.4472
G3 X.5081 Z-5.5497 R.1025
G1 X.5281 Z-5.5324
G0 X1. Z-5.
M05
M30
%

@Cbyrdtopper you are a lathe guy; can you pull this up and see if the last cut segment is an arc or not?
Re: Why is this not an arc?
« Reply #4 on: August 09, 2021, 07:33:21 AM »
Actually I think I just caught it.... I have G17 in the safe start block, when it should be G18.....

It looks like I copied the safe start line from somewhere in the lathe manual that was either talking about lathes with a Y axis or was itself copied/pasted from the mill manual and not caught.

Whoops. I'll test this later and fix the Mastercam post tonight.

Isn't testing fun?
Re: Why is this not an arc?
« Reply #5 on: August 10, 2021, 07:23:36 AM »
That fixed it - and revealed that my postprocessor needs to swap G3 and G2.