# What is the purpose of partial (<100%) backlash correction?

Marlin has an option to fade out the amount of backlash correction, given as BACKLASH_CORRECTION. It is also available in GCode as M425 [F<value>], where 0.0 = none and 1.0 = 100%.

Assuming backlash correction is otherwise well tuned at 100%, when is useful to reduce its effect? Why not always keep it at 100%?

• Because tuning 100% correct is unlikely and undercompensating is likely preferable to overcompensating, I guess
– FarO
Nov 12 '20 at 12:45
• That would mean backlash correction is not otherwise well tuned at 100%. In this case, why not reduce the root cause of overcompensation, BACKLASH_DISTANCE_MM? Nov 12 '20 at 22:07
• Wouldn't the same apply to flow rate? The setting is done in the steps/mm, different for each material, but you still have flown rate compensation.
– FarO
Nov 15 '20 at 15:56
• I can think of a use case for a percentage based flow adjustment: it allows hardware independent filament profiles. Different filaments extrude at different rates due to differences in how deep the feeder teeth bite and other factors, but the percentage change per filament may be similar across various machines. Is there a comparable scenario for backlash correction? Nov 17 '20 at 2:21
• Good point. Open a ticket in GitHub marlin repo so that they can let us know, then post here an answer!
– FarO
Nov 19 '20 at 8:12

• It looks like it actually only adjusts existing segments, which is certainly better than a zig zag going through the planner, but even if BACKLASH_SMOOTHING_MM is undefined, it still takes the length of the first segment. Nov 21 '20 at 7:05