Printing problem

[DerekRyden 1]

I'm new to 3d printing and enjoying getting to know the Ultimaker2. I'm generating .stl files using the DesignSpark software from RS then converting to gcode using Cura (downloaded late December 2015). However, I'm confused about some of the decisions Cura is making:

1. See attached photo (CAN'T ATTACH THE PHOTO! - TIPS APPRECIATED. In the meantime perhaps you can help anyway). This print is meant to be a matrix of 20mm circles with 0.5mm walls, every layer the same - total height 5mm. The circles toward the centre print well and smoothly, but for some reason, the software decides to print the outer perimeter of the design in short bursts rather that smoothly, leading to the lumpiness which can be seen. The photo shows a "Normal print", if I chose "Fast print" the effect is so bad that the "lumps" don't even join up. I'd like to be able to fix the problem, but I'd also like to understand why the software is choosing to print identical parts of the design in two completely different ways. The material is Polyflex from Polymakr, printing at 227 degrees with the bed at 60.

2. I'm also frustrated with the support structure printing. Sometimes it doesn't print when I ask it to, and when it does print, sometimes it doesn't come up high enough to touch the material it is supposed to support! Any tips?

Thanks for your help,

Derek Ryden (UK)

[JohnFox 25]

Just seen an image of your print, it's in your profile as 'uploads'.

Some of it is due to under extrusion, the skirt around the print is really thin and wobbly, it should be a clearly defined band. What is the temperature?

The bits of filament from circle to circle is stringing, caused when the nozzle moves across the print in a non-print move. Have you got 'Enable retraction' on? In Cura, Layer view, the blue lines show the travel and retractions.

Part of the problem may be the 0.5mm walls when the nozzle size is 0.4mm. It may be trying to print a wider layer than it should.

Edited January 2, 2016 by Guest

[DerekRyden 1]

Thanks, that's really helpful. I'll let you know how I get on.

[DerekRyden 1]

Just seen an image of your print, it's in your profile as 'uploads'.

Some of it is due to under extrusion, the skirt around the print is really thin and wobbly, it should be a clearly defined band. What is the temperature?

The bits of filament from circle to circle is stringing, caused when the nozzle moves across the print in a non-print move. Have you got 'Enable retraction' on? In Cura, Layer view, the blue lines show the travel and retractions.

Part of the problem may be the 0.5mm walls when the nozzle size is 0.4mm. It may be trying to print a wider layer than it should.

 

I've tried a few things - changing material to ABS, and going to High and even Ultra quality. The only way I got a good print was by using different slicing software - Astroprint - this is not really set up for the Ultimaker - there were a few glitches and I wouldn't want to use it on a regular basis. But it produced nice smooth circles in single sweeps straight away - completely unlike the stop/start which Cura did. I can only conclude that the Cura algorithm isn't really suited to this type of print.

I'd really like to discuss this with the software developers - any ideas who to contact.

[JohnFox 25]

Not sure where the software people have got to, they usually reply pretty quickly.

I think it's a conflict between nozzle and wall size. Probably trying to make two 0.4mm walls in a 0.5mm space.

A thought!

In Cura, (Advanced settings), try setting the nozzle size to 0.5mm. It may then just do the one pass over the circles.