Raise the platform during a print pause


#1

when i am trying to trouble-shoot a failed print or simply wish to check the quality and progress of a print, using the  pause print feature seems to be a great way to do so. The only issue is that its terribly difficult to actually see what is going on since the platform remains in the last position.

If the build platform were to raise up to the max height during a pause it would make checking a print much more easy and save time. the only issue i see with this feature is whether or not the machine is capable of accurately returning the platform to the last known position. Now i have to say i was kinda surprised that this wasn’t already a feature of the pause option. that being said, with my luck, its already built into the firmware and i missed something along the way.

thanks for the consideration,

~John


#2

That’s a good thought, John, and I’ll pass it on to our mechanical team. You’ve touched on the challenge yourself, however. As precise as our z-stage is, it’s challenging to return the build platform to precise point needed to avoid any artifacts once the print is restarted. This is also why we wait to complete a full layer before pausing – so we don’t interrupt the laser midstream.


#3

I would second the request to allow it to move to max z… sometimes you really have no idea what is going on unless it goes all they way up…


#4

I would think you’d end up with air bubbles at that layer (and a good chance of the print failing at that point,) if you pulled the bottom of the print out of the resin.


#5

I’d vote for this, too … seems like just raising it about an inch gets the most recent layer clear of the resin.  A little up-and-down dance once it’s back in the resin might do the trick to clear bubbles by generating resin flow around the part.

And then, once this feature is in place, the ability to selectively abort only the failed objects (and thereby stop cooking resin to the silicone) would be super.


#6

I vote for too, even if ther will be quality problems.

Any way I would use it only in the “support build phase”, the first 5 to 7 mm, to verify if my model adhered.

It keep me from waiting till about 10 mm befor knowing if supports really printed.

Would be especailly useful while correcting the z-axis offset.


#7

Another vote for that function here please.


#8

With the Form 3, the only way I have observed to get it to raise up is to trick the machine into thinking it needs to add more resin. It raises the build platform while adding resin in order to allow the wiper to function.

Removing the cartridge during a print will cause the print to pause after the peel step, which can sometimes provide a better glimpse of the progress if it has printed at least 7-10 mm already.


#9

Stepper motors and ball screws have been used in CNC since maybe back in the 1950s (maybe earlier, that’s the oldest machine I’ve ever seen). They are highly repeatable. If they weren’t, they’d be no good for CNC. My bench-top Taig CNC will move back and forth along all 3 axes all day long and always come back to the same spot (plus or minus maybe a half thousandth).

There are two factors that reduce repeatability, lost steps or high backlash. Lost steps happen if the stepper is overloaded, either asked to move too fast or the motion path is obstructed. Backlash can make the positioning system sloppy (it’ll move a little if you push/pull on it), but it also introduces an offset in the absolute position reference as a function of the direction of the current move relative to the previous move. If the next step is in the same direction as the last move, the backlash is “taken out” already and the motion stage moves exactly as far as it’s supposed to. If the move is the opposite direction of the previous move, the distance the stepper moves has to exceed the backlash before the motion stage will move.

The F3 build stage moves up a fair amount during the print to make room for the wiper to sweep. That move is much, much greater than any possible backlash that might be present (because that’s going to be very small or the printer wouldn’t work correctly). So it doesn’t matter if it moves even further, even all the way to the top of the stage. The increased distance contributes nothing to positioning error unless the stepper loses steps along the way. In which case, the machine is busted somehow, since if it’s working as designed that should never happen.