Issues with Duplicated Objects (Lulzbot Cura 2.6.69)

I’ve only been printing for about a year. In that time, I’ve noticed some issues with the latest version of Cura that have recently given me some trouble.

Non-uniform Slicing

Whenever an imported model is duplicated and Cura re-slices, I often find that the each model is not sliced identically. This results in minor inconsistencies in the appearance of the finished parts. Features of each part may be printed in different sequences. For example, some models may be printed where the outer wall is printed first but for other models, the inner walls are printed first. This is particularly frustrating when printing thin walled objects where sometimes an outer wall is somehow recognized as an inner wall or infill and prints too quickly. I’ve tried using a specified z seam alignment in attempt to have the extruder take the same path for each duplicate part but haven’t had much success. Is it possible to slice a model and ensure that each duplicate is identically sliced?

How does grouping models affect settings like z seam alignment? Is a group of models treated like a single object for the purposes of z seam alignment?

Also, is it possible to see an animation of the path/sequence taken by the extruder? It would be handy to see how the arrangement on the build plate influences the order in which each object is printed.

Alignment Issues for Multiplied Object

In older versions of Cura when a model was multiplied, the duplicates where neatly arranged on the build plate. In the current version, the placement of duplicates appears haphazard and requires manual repositioning. This inconvenience is compounded by the fact that when manually keying position values, models have a tendency to ignore the input values and “snap” to a particular position on the build plate. Even with all models laid flat on the build plate, there are instances where certain duplicates will display different z position values. I’ve tried turning on and off the “ensure models are kept apart” setting, but there’s no noticeable difference.

Print Speed Variance

After completing a print job, I’ll often remove the parts, clean the bed and then re-print the same job without shutting down Cura or restarting my printer. On occasion I’ve noticed that the second print seems to default to a much higher print speed even though no settings have been changed. If I don’t monitor the print and manually adjust the speed I may wind up with some very ugly parts.

Has anyone else experienced these issues? I’m considering rolling back to a previous version of Cura or moving forward and experimenting with the alpha release of Cura Lulzbot Edition v3.

Side note: it appears as though the latest Ultimaker version of Cura has a feature to address issues with thin-walled models. Does anyone know if this feature be incorporated in Lulzbot Edition v3?

The slicing engine is going to attempt to print your object with as little superfluous movements as possible. When printing multiple objects, this will attempt to reduce the travel moves as much as possible between the two. This causes different stop and start points on each model to be different affecting the Z seam.

We have not seen this one before. If you can replicate the issue, can you submit the gcode file along with the settings used on our work board for investigation?

We have seen this one as well, and are looking into a possible re-write of the model positioning algorithm. Unfortunately, for the time being manually placing duplicated objects is required.

We have not seen this one internally. What OS, printer/tool head, material and profile were you running? We would like to try to duplicate this in house.

It sure has!

If you would like to give the Alpha a try, you can find directions on setting it up here: Be sure to clear the cache after installing, as it can prevent some major conflicts!

Thanks for the prompt reply! I’ll give the v3 alpha a go.

With regard to the non-uniform slicing, it sure would be nice if there was an option to keep z-seams consistent on a per-object basis. Does the z-seam alignment option reference the local position of the object or the global position on the print bed? I’d like to be able to print an array of objects and have them all come out identical. Currently the only way I can achieve this is by printing objects one at a time.

I’ll try to submit gcode and settings the next time I notice the outer wall/inner wall issue.

With regard to print speed variance, here’s my setup:
Windows 7
Taz 6 - Single Extruder Tool Head v2.1
Firmware v1.1.5.71
IC3D ABS (black)
Custom Material Profile