Possible problem with travel between multiple parts

[ChrisGill 0]

Hi

I hope someone can help me figure out what I'm doing wrong or misunderstanding ...

I have a Creality Ender 5 (not pro) and I use Ultimaker Cura latest version for slicing. I'm new to this world of 3D printing so I'm still exploring the machine and trying to get it tuned, if that's the right word.

I was tinkering with the problems of elephant's foot and with bulging corners on calibration cubes and then, as a final print for the day, I set up several objects to print. Most were 7mm high and one was about 20mm high. They were laid out by default with Cura and fairly close together. When I took them off the build plate, the taller one, a cylinder with a flat side, showed a distinct change at 7mm up from the bottom, corresponding to the top of the other parts. I've attached a picture of the part and a drawing (sorry about the background colour - a limitation in QCAD). Dimensions in the drawing are as measured with a micrometer. Ideally it should have been 10mm diameter.

The main problem is that below 7mm, when the head is travelling between parts, there is noticeable bulging at the corners although as far as I can measure, the flat is correct. Also, the quality of the surface is relatively poor. Above 7mm, everything is fine. There is even a small circumferential bulge at 7mm up.

I'd stopped playing with settings so the print speed was 80mm/s, but within that the travel speed was 200mm/s. Jerk control was on with all settings at 8mm/s. Retraction was on with it set to 5mm at 50mm/s (to reduce stringing). Acceleration control was off but the Ender 5 defaults to 500mm/s^2 for print and retract, 1000mm/s^2 for travel. First layer expansion was at -0.5mm - still fighting the elephants. I'm not sure what else to look at but most things would be at default values.

I'm hoping to build a model with multiple parts on the build plate at the same time so this problem could be quite serious. Any clues would be great.

Many thanks, Chris