Z-axis creeping

I have a 3030 mk2. I have a 800w water cooled spindle mounted. This spindle is about 2-1/2 lbs heavier than the recommended trim router. I have only had this set-up for a couple of months and have done 6 or 8 projects. I really like the machine and only the user has been the responsible for any issues except one. I like to do detailed 3-d carves. Some of them can take 8-10 hours on the finish pass. I have found that as the carve progresses my z-axis is very slowly creeping down. Over the course of an 8 hour carve it could be as much as 2 mm. The surface of the carve is very smooth, you can not see any steps where it suddenly jumps down. I believe the cause is the weight of the spindle gradually dragging the axis down over extended time.
How can I stop this? Would setting my grbl $1 setting to 255 help? Is it ok to do that? Do I need a higher torque stepper motor on the z axis? Maybe tweak the potentiometer on the driver? Any suggestions would be appreciated

Thanks

I think if that’s what the problem is, axis creeping because of weight, then setting $1 to 255 could help. The only problem is the motors will get hotter because they are never off. This could maybe shorten their lifetime. I would look into some active cooling for them if I was forced to set $1 to 255. Just my opinion.

My two cents…

I would start by ensuring your assembly still agrees with these instructions with respect to the locking nut and coupler. They need to sandwich the bearing plate firmly. Then take a look at the lead screw anti back lash assembly.

After that …

In case you missed it here are some procedures for adjusting $1

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