Layer Misalignment Conundrum

[TheSpider03]

Hi Guys,
I've been struggling with trying to solve a layer misalignment issue that I have been having with one particular print.
the part is a tray with some pockets in it, about 192x107x16. At around the 40th layer or so the whole print offsets about a millimeter (or more) in both the x and y directions.
First attempt warped so much it pulled the tape off of the bed, that was the first appearance of the misalignment (for obvious reasons.) However, once I added a brim, the warping was eliminated but the layer jog reoccurred. After the first 2 failures I also boosted the retraction vertical lift to a full 5 mm to really clear the part (might have been overkill...) still get the misalignment in about the same place of the print (give or take 15 layers). I literally stared at the printer for two hours (on a 6 hour print) waiting for the problem to occur but I still haven't witnessed the actual event.

I'm using the metal motor mount, aluminum carriage plate and the MG v4 hot end (so I'm pretty sure that it isn't flexing or wobbling)
PLA on blue tape, Simplify3D direct USB print (computer standby disabled)

Any thoughts on other culprits? (mechanical or otherwise)

Edit: Here's a pair of pictures of the part; for those that are curious its a tray for lug nuts and their matching socket
(also, the close-up is of the first failure, I had thicker walls and no solid bottom layer which no doubt contributed to the massive warp; they have since been corrected

[insta]

Are you using Z lift in simplify? It's called "retraction vertical lift". Set it to 0.2mm if not.

[ednisley]

a tray with some pockets in it
First attempt warped so much it pulled the tape off of the bed
At around the 40th layer or so
offsets about a millimeter (or more) in both the x and y directions

The shape seems wide & flat with plenty of perimeter threads around the pockets: ideal for edge curling and warping. Figuring 0.20 mm layers, you're seeing a problem around Z=8 mm, entirely enough for curling with PLA. A well-focused picture would be helpful.

Because the extruder's Z lift happens only on retractions, the nozzle can still snag on a curled-up edge while moving within the model's perimeter and stall either or both motors.

The universal solution for PLA curling seems to be Apply More Cooling around the nozzle and, perhaps, using a lower extrusion temperature. You can also increase the platform temperature to keep the PLA sheet a bit softer and reduce overall warping, but that won't affect the upper layers very much.

Normally, I'd suspect too much acceleration, but that wouldn't account for an error along both X and Y axes.

[Jules]

Chuckle! 2 hours? (pobrecito bicho)

Retraction vertical lift is a way to compensate for what your real problem is, which is that the plastic is pulling away from the blue painter's tape. Or pulling the tape off of the plate. (Or warping on overhangs - you didn't mention the shape of the tray. Does it have overhangs?) But it's better to not have the problem happen in the first place, so re-set your retraction on vertical lift back down to about 0.5 mm or less. (If it's warping through 5 mm, you've got a ruined print anyway.)

Without having seen it - I tend to agree with the guys - you need two things - better adhesion on the plate and more cooling. Put some hairspray or gluestick on the tape to hold the print down, and print with a bed temp of 50C. (I know everyone hates hairspray, but we suffer through using it because it works). The lower bed temp will harden up the bottom layers, giving them a firm base to provide support for the layers on top.

I read somewhere that PLA needs to be hot only as it comes out of the nozzle and then cooled off as quickly as humanly possible so that it sets and prevents warping and curling. That applies to the bed and all the layers in between. Setting a lower bed temp helps the bottom layers to cool faster. To keep it from popping off, use adhesive. (It's dicey to try to get PLA to stick just using temperature. Some of the guys can do it, I never could.) Lower the nozzle temp as well - same reason. You want to print PLA at from 190-195C (or less) if you have not removed the fan guard.

If you have a small desk fan, point it at the print through the whole print, particularly at the back side where the air from the front bed fan might be blocked by the print itself.

And it's obvious, but make sure the bed and print head aren't bumping into anything.

Oh, and one last thing....let it cool completely (as in several hours) before trying to remove it from the plate. Shapes like that will warp after you remove it from the plate, and leaving it stuck to the plate keeps it constrained until it settles into shape. (Might want to increase your infill to give it additional strength. I had a tough time with
after-warping on large area thin prints.)

[TheSpider03]

Thanks for the responses,
I will upload a photo after work.
After reading some more yesterday I am going to try dropping the x/y speed as has been suggested elswhere on the forum. The layers where the failure is occuring has lots of isolated infill islands, so its possible the rapid zipping around is part of the problem.

[TheSpider03]

Success! The print completed last night,
I turned down the travel speed to 9000, increased infill to 25%, and set the lift to 0.5mm. For some reason it doesn't seem to be doing the lift all the time, I still have drag marks in the top layers (and as far as I can tell it's not ooze).

I also discovered that somewhere along the line my filament roll decided to increase it's diameter from the calibrated 1.72 to 1.75 so you can see some spots on the top layer were the nozzle did a little plowing.

Pictures:

on a side note, does anyone know how to get simplify to remember the temp setpoint for the bed? even when I save a custom profile it seems to reset to 70 every time I restart the software.

[sthone]

For some reason it doesn't seem to be doing the lift all the time, I still have drag marks in the top layers (and as far as I can tell it's not ooze)

This might help (blue text)... from the Simplify3d Print Quality Troubleshooting Guide

"If you know you are extruding the correct amount of plastic, but are still having trouble with the nozzle dragging across your top surface, then it might be worth looking at the vertical lift settings in Simplify3D. Enabling this option will cause the nozzle to lift up a set distance above the previously printed layer before moving to a new location. When it arrives at its final location, the nozzle will lower back down to prepare for printing. By moving at an elevated height, this can avoid the nozzle scratch on the top surface of your print. To enable this open, click “Edit Process Settings” and select the Extruder tab. Make sure that retraction is enabled, and then set the “Retraction Vertical Lift” to the distance that you would like the nozzle to raise. For example, if you enter 0.5mm, the nozzle will always raise up 0.5mm before moving to a new location. Please note that this vertical lift will only occur when the nozzle is performing a retraction. If you want to ensure that a retraction is taking place for every single move that the printer does, click on the Advanced tab and make sure that “Only retract when crossing open spaces” and “Minimum travel for retraction” are disabled."

on a side note, does anyone know how to get simplify to remember the temp setpoint for the bed? even when I save a custom profile it seems to reset to 70 every time I restart the software.

If you change the set point for the temperatures (or any setting for that matter) and want them to save I think you have to Update the profile if you aren't doing that and change profiles it will revert back to what ever you had the settings at when you first saved it.

[willnewton]

You might want to check that S3D is leaving the values you enter alone. There are times in the FFF settings when you change a setting, click to another settings window and go back to the original window and your setting does not show the change.

S3D sometimes won't save your changes until you deselect the new value by clicking into a new box.

I found that changing the setting, then just clicking into any other box in that window before switching to another window will solve the issue. It does it most often in the temperature window.

You don't have to use Update Profile to save your settings every time, they will persist until you change to a new profile or crash the software. In my case, the "click on another box fix" has to be done before updating the profile or it just saves the original value.

S3D does this on both my Mac computers, not sure if the PC version does it too.