0.17 Path gcode feed rate?

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robinh
Posts: 40
Joined: Wed Apr 30, 2014 10:06 am
Location: Ottawa, Canada

0.17 Path gcode feed rate?

Postby robinh » Thu Feb 08, 2018 4:11 pm

When in Path-Job-Tools, there are 5 columns: Name, #, mm/s, mm/s and Spindle.

I am not sure why two columns have the same header?

Anyway, using the first column, I set my feed rate to 13.33 mm/s corresponding to 800 mm/min. I set the output processor to grbl and expected to see some lines with F800 thinking that the post-processor would convert to mm/min.
When I look in LinuxCNC http://www.linuxcnc.org/docs/2.4/html/c ... :Feed-Rate I see "F is in units per minute in the XYZ cartesian system".

I read that grbl stays pretty close to LinuxCNC. I am using mm.

It looks as though the mm/s I defined is being used directly without conversion from mm/s to mm/min. Or is the column label wrong? Or what?
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sliptonic
Posts: 1559
Joined: Tue Oct 25, 2011 10:46 pm

Re: 0.17 Path gcode feed rate?

Postby sliptonic » Thu Feb 08, 2018 5:43 pm

robinh wrote:
Thu Feb 08, 2018 4:11 pm
When in Path-Job-Tools, there are 5 columns: Name, #, mm/s, mm/s and Spindle.

I am not sure why two columns have the same header?

Anyway, using the first column, I set my feed rate to 13.33 mm/s corresponding to 800 mm/min. I set the output processor to grbl and expected to see some lines with F800 thinking that the post-processor would convert to mm/min.
When I look in LinuxCNC http://www.linuxcnc.org/docs/2.4/html/c ... :Feed-Rate I see "F is in units per minute in the XYZ cartesian system".

I read that grbl stays pretty close to LinuxCNC. I am using mm.

It looks as though the mm/s I defined is being used directly without conversion from mm/s to mm/min. Or is the column label wrong? Or what?
It's vertical and horizontal feed rates. The headers should probably be changed for clarity. Conversion to output units happens during post processing. Check your actual gcode output to verify that it's not being converted
robinh
Posts: 40
Joined: Wed Apr 30, 2014 10:06 am
Location: Ottawa, Canada

Re: 0.17 Path gcode feed rate?

Postby robinh » Thu Feb 08, 2018 8:12 pm

Here is a sample:

G0 Z25.0000
G0 X0.1500 Y0.0000
G0 Z23.0000
G1 Z20.0000 F3.00
G2 X-0.1500 Y0.0000 Z18.5714 I-0.1500 J0.0000 F13.33
G2 X0.1500 Y0.0000 Z17.1429 I0.1500 J0.0000 F13.33
G2 X-0.1500 Y0.0000 Z15.7143 I-0.1500 J0.0000 F13.33
robinh
Posts: 40
Joined: Wed Apr 30, 2014 10:06 am
Location: Ottawa, Canada

Re: 0.17 Path gcode feed rate?

Postby robinh » Thu Feb 08, 2018 8:15 pm

Sorry, I should have included the front showing the post-processor selected:

(Exported by FreeCAD)
(Post Processor: grbl_post)
(Output Time:2018-02-08 10:30:53.985000)
(begin preamble)
G17 G90
G21
(begin operation: T3: 1/8" end mill)
(Path: T3: 1/8" end mill)
(T3: 1/8" end mill)
(begin toolchange)
; M6 T1.0
M3 S9000.0000
(finish operation: T3: 1/8" end mill)
(begin operation: Helix)
(Path: Helix)
(Helix)
(helix cut operation)
G0 Z25.0000
G0 X0.1500 Y0.0000
G0 Z23.0000
G1 Z20.0000 F3.00
G2 X-0.1500 Y0.0000 Z18.5714 I-0.1500 J0.0000 F13.33
User avatar
sliptonic
Posts: 1559
Joined: Tue Oct 25, 2011 10:46 pm

Re: 0.17 Path gcode feed rate?

Postby sliptonic » Thu Feb 08, 2018 11:20 pm

Looks like a bug in the grbl post processor. Please enter a ticket on Mantis (or fix it and and send a pull request if you're up to it).
robinh
Posts: 40
Joined: Wed Apr 30, 2014 10:06 am
Location: Ottawa, Canada

Re: 0.17 Path gcode feed rate?

Postby robinh » Fri Feb 09, 2018 1:33 pm