Reverse Run

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mwinterm
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Senior Member

09 Mar 2021 19:46 #201591 by mwinterm

Reverse Run was created by mwinterm

Hello,

I'm using LinuxCNC 2.8.1. The release notes of 2.8.0 state that there is a new feature for reverse run:

Reverse-Run: Negative feed-override will now run the G-code path in reverse.

I'm using the following set-up for the feed-override:

Component Pins:
Owner   Type  Dir         Value  Name
    10  bit   IN           TRUE  halui.feed-override.count-enable
    10  s32   IN            100  halui.feed-override.counts <== _feed_override_int
    10  bit   IN          FALSE  halui.feed-override.decrease
    10  bit   IN           TRUE  halui.feed-override.direct-value
    10  bit   IN          FALSE  halui.feed-override.increase
    10  float IN           0.01  halui.feed-override.scale
    10  float OUT             1  halui.feed-override.value

However when I now input negative values for halui.feed-override.counts the resulting halui.feed-override.value is just 0 and no reverse movement (see below):

Component Pins:
Owner   Type  Dir         Value  Name
    10  bit   IN           TRUE  halui.feed-override.count-enable
    10  s32   IN            -62  halui.feed-override.counts <== _feed_override_int
    10  bit   IN          FALSE  halui.feed-override.decrease
    10  bit   IN           TRUE  halui.feed-override.direct-value
    10  bit   IN          FALSE  halui.feed-override.increase
    10  float IN           0.01  halui.feed-override.scale
    10  float OUT             0  halui.feed-override.value

Not sure if I'm missing out here something... Any help appreciated...

Best regards,

Marc

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andypugh
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09 Mar 2021 21:12 #201595 by andypugh

Replied by andypugh on topic Reverse Run

I think that there is an error in the release note. (I will correct it)

It isn't feed-override which enables reverse-run, it is negative adaptive-feed.

You need to set motion.adaptive feed to a negative value. (typically this would be done with some form of sensor, rather than with a jogwheel)

From the motion manpage:

motion.adaptive-feed IN FLOAT
When adaptive feed is enabled with M52 P1, the commanded velocity is multiplied by this value. This effect is multiplicative with the NML-level feed override value and motion.feed-hold. Negative values are valid and will run the G-code path in reverse.

The following user(s) said Thank You: Mike_Eitel

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mwinterm
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Senior Member

10 Mar 2021 22:34 #201737 by mwinterm

Replied by mwinterm on topic Reverse Run

Thanks, works like a charm :-)

PS: ...why this needs to be enabled by M52 P1 and is not active by default? Would not hurt as long as adaptive-feed is not modified....

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andypugh
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10 Mar 2021 22:43 #201739 by andypugh

Replied by andypugh on topic Reverse Run

I think it has a G-code switch because it was originally intended to be driven by a spindle load meter, and you might not want that all the time.

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