Strange ancillary shape using nylon and slicing with Cura 4.4

[sjstein 0]

Hello community,

 

  I am a routine user of our Ultimaker S5. Up until now, I have only used PLA and PVA for supports. However today I switched to nylon for strength reasons (all consumables are Ultimaker branded). After changing materials, I ran Cura (v4.4) and it updated the settings within the software. I sliced my model and dutifully sent it to the printer, then went on with my day.

 

After a few hours, I went to check and saw something really odd -  not only was my shape printing (along with PVA supports), but there was a "phantom" shape in the corner. A cylinder of (apparently) the same diameter of my model. 

 

Going back to Cura and viewing the preview, I now see that it (Cura) did indeed make a shape off in the corner. 

 

Is this a feature specifically for nylon? If so, where do I find that defined or documented in Cura? 

 

If this is not supposed to happen, can anyone explain what is going on?

 

I've enclosed images of the cura windows - both the model alone and the preview pane.

 

[IRobertI 520]

That's a "prime tower", it makes sure the nozzle is full of material before starting on the actual print (it can also help wipe residue off the nozzle so that it isn't dragged into the print). Some materials are more "runny" than others and loose a bit of material from the nozzle which means you might get a little bit of underextrusion when swapping between the materials. For PLA they've managed to tweak the temps and timings so that the PLA is printed just barely hot enough to extrude properly but still be basically ooze free when swapping nozzles, that's why it can be printed without the tower.

[sjstein 0]

I did let the print finish and it was somewhat of a disaster. The travel between the tower and my part was rife with strings which created quite a mess.

 

I've abandoned the use of the PVA support material - which removed the "prime tower". I'm using the nylon itself now as its own support material. It prints much better, but removing that nylon is a chore.

[geert_2 557]

15 hours ago, sjstein said:

...

I'm using the nylon itself now as its own support material. It prints much better, but removing that nylon is a chore.

 

I haven't printed with nylon yet, so I can't comment on material-specific things.

 

But if you are not happy with the default supports, you could design custom supports in CAD, and switch off support in Cura. In this way you can provide features to make removal easier: holes and gaps where you can insert knifes, hooks, pliers; or tree-like structures to save material and provide additional gaps for access; sideways support for higher models to prevent wobbling; extended supports with extra brim for or tiny features; free-hanging supports to not damage the plate below it; etc...

 

Below a couple of methods I used during the past years.

 

The pink and orange supports (center left) are extended, so I can grab them with pliers and wiggle them out. This model is way too small to insert a knife between support and model. Ribs on top allow tigher gaps, without the model and support fusing too much.

 

Free hanging supports prevent the area below from damage, and can be cut away easily.

 

Idem. They also reduce material-use. The bridge plates are 1mm thick. The tiny support-connection strands are 0.5mm wide, 0.2mm high, and 1mm long if I remember well, and can easily be cut.

 

This is a small keychain, where the blue fork has to slide into the yellow slider. The orange and pink supports got an extra brim, due to their tiny ground-area (only a few mm^2). Without brim they might get knocked off, since the overhangs tend to curl up, and then the nozzle bangs into them brutally (the pink and orange supports do not rest on the yellow slider, they float). For reference: watermark text capitals height is 3.5mm.

 

 

[sjstein 0]

Designing the supports is certainly an option, but increases the workload quite a bit for me as I am not an experienced CAD designer. However I may give this a go because I can't seem to find a decent group of settings in Cura to get this to print properly.

 

Your designs look beautiful btw!