3D Genius

By February 14, 2013 2 Comments

Full support or partial support: why it matters

Download this thingWe were very taken with Humberto‘s spool holder for Ultimaker printers, above, mainly due to its ability to hold spools with a small central spindle diameter – and also because of the cleverness of the design (the recess to hold small spools securely, the lock pin to stop it rattling out of place). Because of the way the lugs hang down at the back, though, it was clear it would have to be printed with support.

Exterior-only support

supportB5The trouble was: what kind of support do you choose? Using Cura to do the slicing, we started off using its Exterior Only support option, since the alternative – Everywhere – sounded too, well, universal.

And here’s the result after the first lugs have been printed (right). You can see how the support elements have been printed as a thin-walled zigzag, extending out beyond the lugs so that they provide a firm base on which the lugs could rest during printing.

supportB7As the print progressed, however, we soon discovered our mistake. There was support beneath the bottom lugs, sure, which we managed to snap off easily. But the upper lugs were attempting to print on thin air, which clearly didn’t work at all – a significant quantity of filament had tangled its way over the model by the time we noticed what was going on (left).

According to the Cura forums, it seems that Exterior Only support creates support only for those model elements which are actually in contact with the print bed. For many purposes this is ideal – but, clearly, not when there are overhanging elements higher up in the design.

Everywhere support

supportB2

Changing the support mode to Everywhere created far more support structure (right). Rather than just printing small bands under the lugs, it now created vertical columns either side of the lugs which held a horizontal structure between the two lug sets, running all the way up to fill the gap.

This time, the upper set of lugs had something to rest on while they were being printed, which means no more drooping filament and, instead, a solid base which allowed the print to complete.

supportB1

Although it appeared as if the support was a solid part of the structure, it turned out to be loosely held in place and was easy enough to break away using a pair of small, long-nosed pliers – handy for getting into those small gaps. A scalpel was also used for final trimming.

The way support is built is determined entirely by your slicing software, and each program uses a slightly different method for providing this essential feature. The latest version of Cura has a greatly improved engine that now provides support just where it’s needed.

The finished print

Here’s the final result – a clean, smooth print with perfect lugs that, thanks to Humberto’s precise measuring, fits exactly into the slots on the back of the Ultimaker. In general we’d prefer to be able to print without using support at all – after all, it is very pleasing to be able to snap a finished print off the bed without having to perform any clean-up operation – there are cases where there’s really no choice.

supportB4

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2 Comments on "Full support or partial support: why it matters"

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  1. Humberto says:

    Hi,

    One important thing I might add to this is that most of the model was designed not to need support. It is only required on the crucial parts. If you look under the beam itself the interior walls are at an angle larger than 45 degrees from the printing plane, which is very easy to print without support, increasing the speed and reducing the amount of plastic and finishing touches needed. You can see this nicely illustrated in the first partial print photo above where the beam is only halfway done and no support is present underneath it.

    Cheers,
    Humberto

  2. Steve Caplin says:

    Yes, indeed – that does show this very clearly. Incidentally, I’ve been using this as my full-time support arm since I printed it. A truly useful object, and the lock pin is truly inspired (I always used to get the old support lifting out).

    Thanks again!

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