Bed drops when motors are turned off

Hi guys

I recently completed a vulcanus max 40 and i have run into a smag it seems that when i then off the printer the bed falls. Is there anything i could do to keep the bed up after powering the printer off?

There are many ways to do it, but how much are you willing to spend and how much trouble are you willing to go to?

Cheapest/easiest would be to print some TPU bumpers or put some springs at the bottom of the Z axis and let it drop. You can try counterweights, but be careful not to use too much weight or you'll introduce backlash into the Z axis. There are EM brakes you can add on, or get motors with integral EM brakes. You can use a geared motor to drive the Z axis- if the gear ratio is high enough the bed won't drop, or will only drop slowly.

---

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Im willing to get whatever is the best option. I was looking at the counterweight pulley option as i dont think i meed alot of weight to assist the holding torque. I am also going to decrease the weight of the mounting plate as that imo might help significantly. Another problem is the slop present in chinese lmk12uu bearings so ill be upgrading the z axis to a vslot solution instead od the rods

Counterweights tend to make the machine look like some sort of Rube Goldberg device (which wouldn't hurt the appearance of many machines, anyway), and can't compensate for print mass, so a heavy print may cause the bed to drop even with counterweights. EM brakes are OK, but motors with brakes cost about the same a motors with gears. Motors with gears provide more torque and higher resolution - brakes don't. I started looking into designs for centrifugal brakes that would work like a seat-belt ratchet in a car, but decided I didn't want to spend the time trying to develop it.

Here's what I ended up with after 3 design revs for the Z axis in my coreXY printer.



The motive power is provided by a 160 oz-in NEMA-23 motor on a 30:1 worm gear reducer. It moves the 3.5 kg bed/support/bearing blocks/belts plus 4 kg print mass (that's as high as I have tested it) up and down at 20 mm/sec and does not move when power is removed.



Edited 1 time(s). Last edit at 08/18/2017 11:16AM by the_digital_dentist.

---

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]