# Panic Stop and $212 Z-axis hold

**URL:** <https://forum.sienci.com/t/panic-stop-and-212-z-axis-hold/17403>\
**Category:** 💾Firmware\
**Created:** [May 26, 2025, 3:24pm UTC](https://forum.sienci.com/t/panic-stop-and-212-z-axis-hold/17403 "2025-05-26T15:24:19Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![jpnharris](https://forum.sienci.com/letter_avatar_proxy/v4/letter/j/bbce88/32.png) [@jpnharris](https://forum.sienci.com/u/jpnharris)\
**Post date:** [May 26, 2025, 3:24pm UTC](https://forum.sienci.com/t/panic-stop-and-212-z-axis-hold/17403/1 "2025-05-26T15:24:19Z")

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For those of us using a larger (heavier) spindle (I have a PWN 2.2 80mm) we need to have $212 set so that the spindle doesn’t drop due to the weight. From a safety perspective this voltage to the z-axis should be maintained in the event of a panic button push as the spindle will be spinning for several seconds after activation.

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**Author:** ![chrismakesstuff](https://forum.sienci.com/user_avatar/forum.sienci.com/chrismakesstuff/32/10759_2.png) [@chrismakesstuff](https://forum.sienci.com/u/chrismakesstuff)\
**Post date:** [July 23, 2025, 7:59pm UTC](https://forum.sienci.com/t/panic-stop-and-212-z-axis-hold/17403/2 "2025-07-23T19:59:58Z")

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@jpnharris I believe what you’re asking for here is a change to the SLB firmware, correct?

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**Author:** ![jpnharris](https://forum.sienci.com/letter_avatar_proxy/v4/letter/j/bbce88/32.png) [@jpnharris](https://forum.sienci.com/u/jpnharris)\
**Post date:** [July 23, 2025, 11:46pm UTC](https://forum.sienci.com/t/panic-stop-and-212-z-axis-hold/17403/3 "2025-07-23T23:46:09Z")

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I would guess it is firmware, maybe software but panic stop wouldn’t allow a spinning bit to drop uncontrolled, I don’t like to use the panic stop much but it does happen. On at least two occasions work piece was ruined by falling spindle.

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**Author:** ![terjeio](https://forum.sienci.com/letter_avatar_proxy/v4/letter/t/a4c791/32.png) [@terjeio](https://forum.sienci.com/u/terjeio)\
**Post date:** [July 24, 2025, 6:35pm UTC](https://forum.sienci.com/t/panic-stop-and-212-z-axis-hold/17403/4 "2025-07-24T18:35:42Z")

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For grblHAL set $37=4 to keep the Z driver enabled. However, I am not sure if SLB estop cuts power to the drivers - if it does then it will not work.

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**Author:** ![chrismakesstuff](https://forum.sienci.com/user_avatar/forum.sienci.com/chrismakesstuff/32/10759_2.png) [@chrismakesstuff](https://forum.sienci.com/u/chrismakesstuff)\
**Post date:** [August 11, 2025, 7:56pm UTC](https://forum.sienci.com/t/panic-stop-and-212-z-axis-hold/17403/5 "2025-08-11T19:56:21Z")

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@terjeio on our older branch, it seems hitting the E-stop disables the $37 holding on the motors. If that’s not the current behaviour then completing our update to Main should resolve this issue. Thanks for chiming in!