Scaffold: A Soluble Support for Total Geometric Freedom
We all know about the age-old overhang problem: The inability to print features that overhang beyond a certain angle.
Same-material breakaway supports are far from a perfect solution - even with some really great algorithms out there you’re still never going to be able to extract support out of an awkward internal cavity, or deep screw hole. Fragile models break during removal, and the surface finish left behind is poor.
But we’re also restricted in other ways, such as parts that don’t have a large area contact with the bed to hold them down while printing. We also cannot print objects within objects or printed in place mechanisms (some incredibly cunning designs notwithstanding). We created HotEnds - like Chimera - which we thought would really stimulate the use of separate material support. But for quite some time the software and the materials were unable to realise the dream of proper support material for open 3D printing.
For years now people have been saying “just use PVA!” or to use HIPS and dissolve it in limonene. But PVA isn’t really up to the task of being a great support material - it really struggles with adhering to build materials. Exceptionally high viscosity results in low flow and the need for high pressures (particularly troublesome with bowden systems). Standard PVA also has another hidden nasty: when heated in the nozzle for an extended period of time the polymer chains begin crosslink and form a new, non-liquid material, with a consistency that resembles sand. Sand cannot be extruded. This kills the nozzle.
HIPS works decently as a support material exclusively for ABS, and exclusively in breakaway situations. There’s also a lot of misinformation about the use of Limonene as a solvent for HIPS out there, so let's clear some things up. Limonene does not exclusively dissolve HIPS and leave the ABS unscathed, it has a significant negative effect on the properties of ABS, making it weaker.
The next and most important thing is safety. We hear a lot of voices saying “oh it’s natural and comes from oranges! Totally harmless!” Sure, limonene isn’t very toxic, and a splash or two of it on your hands is unlikely to damage you. However once you dissolve a polymer in this solvent all bets are off. If you get limonene with HIPS dissolved in it on your skin the limonene soaks in and leaches the polymer into your skin. I have personally made this mistake and the tip of my index finger is now permanently damaged with what I can only describe as a polymer tattoo, with significantly diminished sensation and hardened skin, even two years later. It’s also a flammable solvent that produces flammable vapour.
We had grown complacent, and resigned ourselves to acceptance of not being able to achieve the true and total geometric freedom that 3D printing has the potential to offer.
This does not need to be the case. Scaffold is a leap forward in soluble and breakaway support material. We really think Scaffold opens up great new capabilities in what is possible on open platform 3D printers.
The Story of Scaffold
Scaffold was born due to a need for awesome support material that works. We set about evaluating all the materials we could get our hands on (some materials that were meant for use as support and some other weird combinations too!): PVA/PVOH, BVOH, and even some other more exotic resins.
We knew we wanted a support material that could dissolve, and with PVA being the safest option we started with what we saw as the most critical problem - getting it to stick to the build material. Viscosity and cross-linking were problems, but ones that could be worked around. If the material won’t stick then it’s a deal breaker.
Enter our star intern, Max. Max sat for a very long time, running test print after test print on many many resins and blends for weeks. Eventually, by using a blend of PVA/PVOH resins we were able to get a material that sticks really well to a range of materials.
During the beta period we started working on Edge, and found ways that we could get Edge to stick very effectively to Scaffold. We capitalised on this, and made the two materials such that they would work exceptionally well together as a support and build material combination.
Feedback from beta showed good results, but the already known issues (cross-linking, viscosity) were rearing their head. Finally we hit on an effective way to boost flow without compromising adhesion or solubility. An unexpected bonus here was that it also interrupted the cross-linking process, slowing it down considerably, and once cross-linked the material is less like sand and more of a paste like substance. This means that in most cases you can just purge out the substance and save the nozzle. With this final addition we were happy to remove the Beta caveat and promote Scaffold to a ready to market soluble support material.
PVA problems we've completely solved
- Poor adhesion to materials
- Scaffold adheres well to Edge, PLA, nylon, PET, and co-polyesters
- Poor melt flow of material through the nozzle
- Melt flow vastly improved compared to conventional PVA
PVA problems we've drastically improved (but still to be aware of)
- Cross-linking blocking nozzles
- Resistance to cross-linking considerably increased
- If cross-linked the material forms a not fully solid (more paste-like) material that can usually still be purged
- Very long dwelling in a hot nozzle should still be avoided (it would be great if slicers could help in this regard by cooling down inactive nozzles)
- Moisture absorption
- Less susceptible to moisture absorption, comparable to Nylon
- Supplied in a nice resealable bag with desiccant for storage and use
- In-bag-spool holder available from Thingiverse means that material can be kept dry even during use
- If in doubt, dry it out on a heated bed at 45C
What you can do with Scaffold
The use of Scaffold has transformed the way we design and print parts here at E3D. Having a reliable and easy means of supporting complex overhangs has enabled us to print things that we previously considered out of reach.
For us, the largest use-case has been in mechanical parts with overhanging internal features. Greg has been working on some exceptionally challenging parts for a gearbox housing, which utilises geometry that would have previously been completely unfeasible.
Moving beyond simple mechanical parts with tricky geometry we now have vastly expanded abilities to create printed-in-place mechanisms with moving parts.
Beyond the purely functional applications Scaffold provides fantastic new opportunities in design freedom. Some amazing sculpting work has been done to create supportless models, but now that we can abandon the shackles of overhangs you can be as creative as you wish without worrying about the previous constraints.
How to get the best out of Scaffold
Unfortunately you can’t just pop Scaffold into your machine, enable supports, and instantly get perfect results. Printing optimally with soluble and breakaway support requires specific strategies to get the best results. Perhaps the most important of these is having solid interface layers of support material, where the final top layers of support are printed solid, not sparse. These interface layers are now available in many of the popular slicing packages out there, Slic3r, MatterControl, and Simplify3D. Simplify3D has the additional advantage of being able to manually place and remove supports which can be extremely useful. The latest Cura release for the Ultimaker 3 has very good support material generation strategies too (N.B We’ve tested Scaffold with Edge on an Ultimaker 3, which works fantastically).
The correct strategy for soluble support is quite different to same-material breakaway support. The best way of thinking about this is that you are basically creating a “mould” into which you are printing the build material. The surface finish and shape of that “mould” is what will define the shape and surface of the supported build material. The better you can get that supporting structure to form the shape you want of the underside of the model, the better results you get.
Different materials behave quite differently with Scaffold, and selecting an appropriate build material to go alongside is essential. We obviously recommend Edge as a go-to material as it’s been carefully matched to adhere in the goldilocks zone of effective sticking, while still breaking away easily and cleanly. PLA, other PETs, and co-polyesters - like Colorfabb XT - work decently as well but are not quite as perfectly tuned as Edge, with adhesion being lower, but are still effective enough for use in most cases.
Nylon of almost all varieties sticks like hell to Scaffold. Really really sticks. You aren’t going to be breaking it away easily and cleanly like you would with Edge. This does have its upsides though - it really holds the warp-prone nylon in place, and makes rafts a very effective bed surface for printing nylon. Even though you can’t break it away you can of course still remove it with water.
|PLA||Yes||Yes||Very usable, good for large parts|
|Nylon||Yes||No||Extremely strong adhesion prevents breakaway but resists warp|
|TPU Flexibles||Yes||Yes||Flexibility provides very satisfying peel-away|
|PET/Co-polyester||Yes||Yes||Usable, but with reduced adhesion|
|ABS||No||No||Does not adhere|
We’ve made some headway in making Scaffold more resistant to moisture but it’s a water soluble support material, so you can’t have your cake and eat it too! To mitigate this we provide Scaffold in a nice resealable bag with desiccant as you would expect. To make things even easier, we’ve designed an in-bag spool holder that can be printed and only needs some minimal hardware that you probably already have on hand.
This means that you only ever need to open the bag once, to get the material onto the holder and fed through the outlet, keeping exposure to atmospheric moisture to a bare minimum.
If you’re using a ram-purge oozeless extrusion technique we find that Lite6 can achieve slightly easier stop-start printing, as the longer PTFE lining into the melt zone allows for more aggressive retraction and less material dwelling in the hot zone. Rafts also always come off really easily, and Scaffold always sticks to the bed exceptionally which helps reduce the need for super accurate bed levelling and improves overall print reliability.
- Print Temperature - 215°C
- Bed Temperature - From 20°C to 55C ideally, but will cope with bed temperatures as high as 110°C
- Print Speed - ~50mm/s
- Support Infill - ~15%
- Support Angle - 45° & -45° (create a crosshatch pattern)
- Dense Solid Layers - 3
- Dense Solid Infill - 90%
- Upper & Lower Separation Layers - 0
- Support Angle - 46° and up
- Support Pillar Resolution - 1mm
- Raft - Yes
- Remove the print from the Bed
- Break away as much as is possible
- Leave submerged in water to soak for ~60 minutes
- Flush out the part and clean off as much as you can
- Soak for a further 2 hours or overnight
- Clean off the remaining Scaffold with scourer pads or scrubbing brushes (for easily accessible areas) bottle brushes (for small openings)
- Dry the part - take note that there may be some water incursion into the model from soaking that can leak out over time
Scaffold opens up new possibilities in design freedom. Large overhangs, protruding features and complex models are now all possible thanks to Scaffold. We're incredibly proud of it and hope that you enjoy creating with it as much as we do. Try Scaffold for yourself as part of our spoolWorks range, available directly from E3D-Online