What happens when there's a power loss?

General Discussion
1

Just witnessed something when my 4L was inadvertantly powered off after a print (user error).

Cutting power to the z-axis stepper will “unlock” it, allowing the build platform to move down due to gravity. If you have a heavy print on the platform, it will go all the way down to the resin.

Of course, that’s just natural with any stepper when you cut power to it, but isn’t something I’d thought about until now. Not sure if there’s any way to lock the z-axis mechanically after a print. A power failure could ruin a super long, heavy print if it sinks back into th resin and is left there for a day.

Certainly this is an edge case, but something for us to keep in mind. Anyone using UPS?

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2

I see this too. I think this was an oversight from the design team.

All leadscrews and ball screws can be “back driven” depending on the pitch and the force applied (in this case, weight of the BP + parts).

My build plate stays up with no parts on it during a power loss but it drops with gravity if there are lots of parts, or a big heavy part on it during power loss.

I don’t think this really affects most people day to day, but it does mean that these machines will never have a power recovery feature implemented imo.

3

There would have to be a mechanical lock at full travel. But that’s additional things that could break. Ideal solution would be to use a UPS to make sure stuff stays powered up.

4

Yeah, people do this by integrating a brake onto the leadscrew, but that’s probably not a simple “add-on” kit type offering.

I think most people doing any kind of serious work need to have a UPS!

5

If it used a worm gear instead, then this probably wouldn’t be an issue.

6

You definitely need an UPS, compared to other machines LCD, DLP, or Laser based ones consume much less energy so UPS will last longer.

7

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