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Temporary Support Structures

Posted by dj_woff 
Temporary Support Structures
February 28, 2015 12:29PM
Hello All

I have a question that I thought someone might be able to answer.

I'm trying to print a design which has a section that's shaped a bit like an upturned J. A.k.a it has a long vertical section (leaving off from the bed) a horizontal and then a drop down that doesn't reach the bed again It doesn't matter how I orientate the design I will always end up with one of these. I've used professional 3D printers at work and they all contain the automatic creation of support structures so I was looking at doing something similar.

My initial though was to create two designs, and effectively print the support structure and then the actual "inside it" using a layer of kapton to prevent adhesion. However this won't work as the width of the head would lead to there being insufficient support under the horizontal and it would need for the head to move up over the structure during horizontal swings and I have no idea how to program this.

Does anyone have any suggestions as to how to go about creating a suitable support structure? Can I set specific pauses in the print that would allow me to print the two together and add the separator?

Many thanks


P.s. I've got a single head Ormrod 2.
Re: Temporary Support Structures
February 28, 2015 01:07PM
Cura and slic3r will both generate support structures automatically.
Re: Temporary Support Structures
February 28, 2015 01:28PM
Well I hadn't realised that.

What does it do about the join?


Re: Temporary Support Structures
February 28, 2015 02:41PM
They are usually only lightly attached (you can tweak parameters for that) so that the support material breaks off easily.
Re: Temporary Support Structures
February 28, 2015 09:26PM
It's better to modify the 3D model than using the support material IMHO.

The right hand arm fell apart from the support pillar.

Small, complex model like this dome, to remove all the support material takes time, leave unwanted pieces inside.

Re: Temporary Support Structures
June 03, 2015 12:57PM
Thanks for the advice all.

I thought I'd re-open this one as I've run into a problem.

I've been using Slic3r as my main application for generating the G code, and I've run into a problem with the support structures that it generates. Basically it's stopping the support structure a long way below the level of the surface that it's supposed to be supporting (typically 0.45mm according to Pronterface). This means that when the head tries to print the supported layer it's 0.75mm above the support. This has two effects, one which I can live with and one which I can't.

The first effect is that the surface is very rough as there material isn't "squeezed" but load down as a 0.5mm wide thread. This is in part essential to create the loose bond to the support so I can live with this.

The second problem is that material is falling from the extruder to sit on the top of the support and thus it's being deposited 0.5mm lower than the surface it's supposed to form. This results in bad adhesion to the layer above which ends up with the gap somewhere around 0.45mm to fill and the object being the wrong size.

I've had a look at cura's output and it doesn't appear to be much better it leaves a 1 layer (0.3mm) gap between the support structure top and the nominal bottom of the supported layer but the support doesn't look as though it will have a flat surface so drop is possible.

Has anyone else experience this? Are there any cures? Logically (in my mind) the slicer should build the support up so that it's top is at or close to the height of the surface to be supported and then miss a layer to create the poor adhesion.


Re: Temporary Support Structures
June 03, 2015 01:07PM
In Cura you can set the z-gap as small as you like. * attached
Also you can define a "pause @z" where you´d have time to put kapton on the support structure.

Happy printing
open | download - cura.JPG (23 KB)
Re: Temporary Support Structures
June 03, 2015 08:28PM
Meshmixer also has a pretty interesting support structure feature. Seems to work ok, but if you make the support diameters too thin, they'll likely break during printing. Takes some experimenting.
Re: Temporary Support Structures
June 04, 2015 01:10PM
Thanks Olaf.

I'd spotted the advanced settings, but not the expert ones. I'll have play and post how I get on.

I'd wondered about the pause at layer feature and doing exactly what you said. but wasn't sure if it would work on the rep rap as it's more of a makerbot feature.

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