Help with Support Distances

[Tom-yota 0]

Hello All,

 

First, let me give a huge thanks out to the programmers for improving the supports in Cura 3.0. 

I am trying to print the attached part (it's from the universal construction kit, it is a Lincoln Log with a k'nex piece sticking out the side).  

I have oriented it laying on the side so the layers will go down the length of the k'nex part to make it stronger and hopefully prevent breakage along the layers. 

 

The problem is the support structure is sticking to the part.  In previous versions of Cura, I could pull the supports off with my fingers, in 3.0 it is taking an Exacto knife and a jackhammer. 

I'm running a 0.35 nozzle with a 0.2 layer height and I have increased the Z support distance to 0.35 and the XY to 0.7mm and its still sticking.   Today I printed this part multiple times incrementing the Z support height from 0.1 all the way to 0.35 in 0.05mm increments.   All of the supports stuck. 

 

I'm running Cura 3.0.4 if ti matters

 

Thanks for any assistance.

 

 

 

uck-06f03m.stl

Cura 3.0 Circular profile.curaprofile

[gr5 2,333]

I don't have much of an answer sorry because I rarely use supports.

 

However for PLA you should see no difference in stregth if the knex part is sticking straight up versus sticking horizontally.  PLA does a very good job of thoroughly melting the layer below and has excellent bonding.  This *should* be true for other materials but you have to do a few tricks (like lower fan speed).

 

When my ABS parts break they tend to break along layer lines.  When my PLA parts break they don't.

[geert_2 560]

For PLA, printing cooler and slower usually helps for me on our UM2. Also, I use ribs on top of my supports (=0.5mm wide ribs with 1mm horizontal gaps in-between, for a 0.4mm nozzle): these make removal easier, but still give good underside quality. Most of the time I use a vertical gap of 0.2mm to 0.3mm between support and overhanging part.

 

And I provide all sorts of methods to make support removal easier: gaps to wiggle supports loose, holes to insert pliers or hooks to pull out the supports, protruding areas where I can push with my fingers, etc...When designing the support, I calculate all this in from the beginning.

 

For a few examples, see below. Some are parts of real designs, some are test pieces to try what worked best.

 

 

[Tom-yota 0]

Thanks for the information guys.   

Unfortunately, I'm printing these out of ABS.

 

Geert_2, did you model your own supports up? 

 

Edited March 13, 2018 by Tom-yota

[Tom-yota 0]

So playing around with these values again today, I think I have a better understanding of what they are doing.   I was wondering if someone could correct my assumption I am making here. 

 

Does the "Support Z Distance" just affect vertical surfaces?    For the Lincoln log file, I uploaded the issue I was having was the supports was sticking to the sides of the log.   Therefore I kept increasing the "Support Z Distance" what I noticed was the bottom flat, where it transitions from support to part layer, area got worse each time I increased the Z distance.

 

So my new school of thought is to bring the Z distance back down to 0.25mm and increase the "Support X/Y Distance" to keep the side supports from sticking.

 

From https://ultimaker.com/en/resources/20422-cura-support-settings

 

[geert_2 560]

For most models, I disable all automatic supports in Cura. And I design my own custom supports in the CAD-program, as part of the design. This is because of the special features of my models: often the models are quite small, or with difficult to access areas. This is for UM2, with one nozzle.

 

The blue support in the first pic above is ca. 10mm wide. The red/orange support in the second pic, center-left, is even smaller: it is too small to get into it with a knife. So I have to extend the supports so I can grab them with pliers.

 

The first times it takes trial and error, but after a while you know what works and you can design them right from the beginning.