# \[Proposal\] Forbidden velocities for printer steppers

**URL:** <https://klipper.discourse.group/t/proposal-forbidden-velocities-for-printer-steppers/3995>\
**Category:** Developers\
**Created:** [August 29, 2022, 8:39pm UTC](https://klipper.discourse.group/t/proposal-forbidden-velocities-for-printer-steppers/3995 "2022-08-29T20:39:47Z")\
**Posts on this page:** 1\
**Showing post:** 5

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**Author:** ![LifeOfBrian](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/lifeofbrian/32/2380_2.png) [@LifeOfBrian](https://klipper.discourse.group/u/LifeOfBrian)\
**Post date:** [October 7, 2022, 4:21pm UTC](https://klipper.discourse.group/t/proposal-forbidden-velocities-for-printer-steppers/3995/5 "2022-10-07T16:21:05Z")

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Is there still any attentionon this topic here?  
I’m fighting against VFAs/marks as well and have a range from about 70 to 110 mm/s where you can see the following ripples/marks:

 ![20220916_150422](https://global.discourse-cdn.com/free1/uploads/klipper/original/2X/c/c1f0dd00bec30f9428f1ad0d38374a2a16143787.jpeg)

Same with TMC2209 and now with TMC5160.  
I read in other forums that some users want to exclude the bad speed ranges to get rid of the ripples but it does not seem to be that easy.  
Others seemed to have edited the MSLUT in the stepper drivers to avoid sine wave artefacts causing the VFAs.  
And I’m currently struggling in getting the fast decay settings for the Constant off time mode set up:

> [@TMC5160 - Classic Constant Off Time Chopper with fast decay time](https://klipper.discourse.group/t/tmc5160-classic-constant-off-time-chopper-with-fast-decay-time/4359):
>
> Hi folks, I’m working on my CoreXY with a SKR 2 and TMC5160 stepper drivers. Due to visible VFA (I think those are VFAs) I try to set up the TMC5160 into Classic Constant Off Time Chopper by setting chm=1. As the motors are now horribly loud I want to change the fast decay time. When I check the datasheet of the Trinamic driver (page 52 on [https://www.trinamic.com/fileadmin/assets/Products/ICs\_Documents/TMC5160A\_Datasheet\_Rev1.14.pdf](https://www.trinamic.com/fileadmin/assets/Products/ICs_Documents/TMC5160A_Datasheet_Rev1.14.pdf)) it says: “Fast decay time setting (MSB: fd3):” But I fe…

This solved the issue for a friend but he is using RRF where this is possible easily.

Either with the measurements from @dmbutyugin or with such a vase mode tower you can determine the speed range quite easy but then we need the option to exclude those speeds from being used.  
But in my opinion this would be the easiest way to get rid of those marks.

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_[View the full topic](https://klipper.discourse.group/t/proposal-forbidden-velocities-for-printer-steppers/3995)._