3D Printing in Acetal

[nick-foley 5]

Over the past few months, we @ Social Bicycles have been blown away by the quality, speed, and reliability of our Ultimakers. The parts coming off of the machines have changed the way we make products - not only how we develop and test them, but even how we mass produce them. PLA is a great material, too, and with the right settings and a high quality filament (Printbl FTW!) we've been getting beautiful, precision prints with ample strength for both prototyping and real-world requirements.

 

Nonetheless, our application (bike-sharing systems) frequently demands something higher performance than what PLA is capable of delivering. I've experimented with other materials, like ABS (smelly, tough to get good prints from a stock UM) and Taulman Nylon (awesome material, strong, but not as rigid as PLA, and a lot slower to print) but what I knew I really wanted to print, from the beginning, was a material we already make many of our production parts in - Acetal. (As a quick overview, Acetal (or Delrin, or POM) is a strong, rigid thermoplastic with excellent wear resistance and very low friction. It is frequently used for gears, bearings, and moving parts.)

 

After several weeks of testing, I am happy to say that we are 3D printing in acetal. We are getting amazingly strong, slippery, rigid, complex parts with only very minor modifications to our stock machine. It is frequently said that 3D printing is limited in its ability to replace traditional mass-production because of the limited materials it can utilize, but Acetal is one plastic for which there is generally no superior, and the parts we have been able to produce are certainly as strong as their injection-molded counterparts.

 

Here are a few photos of one part I printed. More details about the process below.

 

Print in progress

 

 

A buttery-smooth helical focusing mechanism for a camera lens I have (Printbl Grape PLA, White Acetal) Will post thingiverse model soon.

 

The "filament". ACETRON. Lawl.

 

 

Machine Mods:

After searching around for prior examples of acetal being used in 3D printers - or a source for acetal filament - and finding nothing, I turned to McMaster-Carr to see if they had what I needed. Of course, they did. Mcmaster stocks 4' lengths of 0.125" (~3.2mm) white acetal rods - and while that diameter is too large to fit in a stock Ultimaker without clogging... Mcmaster also has 3.4mm drill bits for opening up that pesky hot-end's ID, and thin-walled teflon tubes for replacing the bowden.

 

Bowden Replacement: 5239K12

3.4mm Drill: 30565A254

Acetal Rod: 8497K11

Bowden Stiffener: 5239K13

( ^ Sleeve this over your new, thinner bowden in order to increase rigidity and improve retraction when printing in floppy filaments like ABS, Nylon, PLA)

 

Print Settings/Process:

 

The hardest part about printing acetal is getting it to stick. A heated bed would probably help here. My best results come from printing on a wooden platform (birch ply) and a large raft with very thick lines. Temp of 258° seems good, although thin sections (<1mm) can get layer adhesion problems, so higher temps might work better. No fan, 30mm/s speed (much higher is probably possible). 0.1mm layers gives amazing detail. Acetal seems to hold heat very very well, which means that thick sections (>4mm) get messy, quickly. Parts that are designed as if they were to be injection molded (ie with uniform wall thicknesses) seem to print great.

 

Apart from first layer adhesion challenges, the only real problem with Acetal is that it (currently) only comes in 4' rods. The problem here isn't running out of filament - it's easy enough to feed them into the machine as necessary. The problem is that unless you fuse the rods together, it is impossible to use retraction once there is more than one filament section inside the machine. This makes prints with fine detail and many jumps more challenging.

 

 

Going forward:

 

My next goal is to try to find a source for proper acetal filament - there are probably manufacturers that will do custom lengths. There are also many different Acetal copolymer mixtures with very different melting points, so it is entirely possible that a different blend of Acetal could be even more 3D printing-friendly. I'm also excited about setting up a dual-extrusion machine so that first-layer adhesion can be solved by printing a few layers of PLA first. A heated build environment is something I would also like to try. Would love to hear about the results from other people who try printing in Acetal and have a heated build environment.

 

[codemaven 0]

Great work! I'd really like to see a printable Acetal filament. It's one of the materials that I'm interested in using. It would be great to be able to print my own MakerSlide and V-Slot wheels.

Cheers,

Troy.

 

[stratum3d-ltd 0]

Stratum3d Ltd is a brand new start-up bringing 20 years experience from Injection Moulding production and materials to 3d Printing.

Just last week produced 1st batch of materials. 1.75mm POM (Acetal), 1.75mm HIPS (High Impact Polystyrene), 1.75mm TPV (Vulcanised Thermoplastic Rubber).

These materials will now go through extensive testing.

Will be producing many more as we progress.

If you think we can help get in touch.

 

[nick-foley 5]

As an update, I've started fusing filament rods together using a flame and a file - the results are extremely clean and easy to achieve. This should solve the retraction problems for now.

I'm also mid-print with Black 1/8" acetal rod from Amazon.com, and the print seems to be going well. It is definitely a different polymer mixture, as the filament has a different feel, stiffness, weight. Will post results when the print is done.

 

[gr5 2,177]

3/4 of purpose of retraction is to just stop *pushing*. This is still achieved with unfused ends of filament in the bowden. You can't *pull* but at least you can stop pushing with retraction.

 

[nick-foley 5]

True. The acetal filament is so rigid and strong, though, that I think the possibility exists for some great retraction qualities, and I'd like to test them. My prints today with the fused filament came out very clean, but they weren't prints that benefited much from retraction. I'll try some stuff tomorrow with more jumps to see how things come out.

 

[codemaven 0]

 

Just last week produced 1st batch of materials. 1.75mm POM (Acetal), 1.75mm HIPS (High Impact Polystyrene), 1.75mm TPV (Vulcanised Thermoplastic Rubber).

 

Any chance of producing 3mm filaments in the future?

 

[stratum3d-ltd 0]

Yes if 3mm is required I will produce some for you. Look me up on Twitter. Stratum3d Ltd.

We will be producing a full range of engineering materials as we progress. Already have TPV, POM, PA66. Will soon have PBT, GFN and others.

We are a brand new start-up with many years of experience in Injection Moulding. Will have website available shortly. let me know what you would like.

 

[gr5 2,177]

Awesome! Just be aware that if the filament goes much over 3mm it is considered "junk" by most ultimaker people because it gets stuck in the bowden tube and won't print. Unfortunately everyone's UM is slightly different and some can handle up to 3.2mm and most up to 3.1mm but ideally you want to be between 2.8 and 3.0mm and you want as little variation as possible (because if it has a bigger cross section then you get some over extrusion and if it is smaller you get underextrusion).

So really 2.9mm should be the nominal diameter even if it is advertised or quoted as "3mm".

 

[stratum3d-ltd 0]

Good advice. I will set our process with that in mind.

More materials to follow!

 

[martin-van-wezel 0]

Does anyone have any experience with these fillaments?

Both vendors provide POM in standard 1,75 and 3mm size

http://www.suntec3d.com/e_productshow/?20-POM-Filament-20.html

http://www.stratum3d.com/collections/acetal-613

 

[gr5 2,177]

The first link mentiones 3.0 +/- .05mm which is too large for the Ulitmaker. If you hit 3.05mm I'm pretty sure it will get stuck in the bowden. I've heard from enough people on this forum who had to throw away a whole roll because of this - so I would avoid it.

 

[antiklesys 3]

Hi,

what about the POM/ Delrin filament sold by E3D? http://e3d-online.com/Filament/Engineering-Plastics/POM-Natural-300 would this be a better option?

 

[am001 0]

I bought a roll of POM from a Chinese suplier (ebay vendor bilalzafar82), and whilst it seems good quality, I have never been able to get it to stick long enough to get a full print. Everything else works fine, feeds well, detail is excellent etc. etc..

I have a heated bed and chamber, and have tried ABS slurry, cardboard sheets, various types of tape and various temperatures, and nothing works! POM has around 2% shrink rate compared to ABS at 0.7% and PLA at 0.4%, this gives an idea of the issue.

I'm very surprised (and jealous) you have had so much success. I'll try and get some birch ply and have another go.

Andrew

 

[liesmuller 0]

I bought some POM-like material at

https://www.3dprintersonlinestore.com/consumables/filament-pom

It seems very flexible though. Anyone knows how to be sure about the material?

And sticking?? I'll soon try the birch plywood...

[hazyj 0]

All. I'm printing POM successfully at 177C on PEI coated hot bed @ 140C. Not great prints so far, but at least the stuff is sticking and not warping. I have my extrusion and movements set to VERY SLOW however. Makes this less than ideal, but hey it finally works.

I've had a heck of a time with Gizmo Dorks POM. Warping is the main issue. I'm able to get it to stick to a LARGE bed of PLA at 50C and below (so the PLA bed remains flat), but laying down the PLA takes awhile and there's still the issue of warping. The only way I can stop the warping is extrude at 177C.

If I could I'd heat up the entire chamber @ 150C and try 195C to see of that warps. Can't do it with my gear though.

Feel free to email me at jahearn@sbcglobal.net

[luisito 12]

Acetal has to be used with caution, specially when heated.

Please, read this:

http://www.cityplastics.com.au/site_files/687/pdf_files/acetal%20msds.pdf