Longevity of 3D Printed Models

[Marbelup]

One 3D print bureau suggested not using 3D parts for complete model bodies in scales larger then N due to the risk of warping or cracking over time. He was particularly referring to SLA resin printed parts, due to the fact that there were likely to be internal stresses and temperature cycling could cause problems.

 

I am particularly interested in Modellers experience with i.Materialise Prime Gray, as that is my current preferred material. Prime Gray seems to be more like styrene than most other 3D print materials, but I worry about what will happen long term. What is the oldest Prime Gray model (more than 100 mm long) that people have done, and is it still in good condition?

 

Has anyone had any good or bad experiences with particular materials?

 

I have had a bad experience with a part from Sculpteo printed in Nov 2012 which started to warp almost immediately. The surface which warped was unsupported, and it was flexible enough to bend back to the correct position. However, recently, the same part has developed a crack about 10 mm long in the opposite side. The material is Black Detail Resin.

 

Several other prints of the same part in other materials which were printed in the prior weeks are fine.

 

Thanks

[Rabs]

I'm afraid I don't have an answer but wanted to add my voice to this very good question.  I'd also love to know people's experiences on this issue.

[Delichon]

I have used Prime Grey for coach / loco bodies and underframes in HO - the oldest would be about 9 months. I have experienced problems with sagging when an unused underframe is rested on its truss (so the unsupported ends can droop after a while) and similar problems have occurred with Mk.1 coach bodies - in this case the gangway rubbing plate extends below floor level so the centre of the bodyshell has no support. The solution was to ensure that the items were supported throughout their length while awaiting use. Once incorporated into a model support can be installed - an interior (with flooring) will brace the underframe and the body is in turn supported by the frame. So far I do not seem to have had problems with finished models but only time will tell. When distortion has occurred it has sometimes been possible to correct it by making a saw cut in the centre of the body, bending to shape and gluing in position. Occasionally models have arrived from the printers with slight bending - presumably this occurred during manufacture. If there is a lot of detail then this will all be out of line and may make correction uneconomic.

[Marbelup]

Rabs and Delichon

 

Thanks for the comments.  

 

I just found a blog post at i.materialise indicating that Prime Gray was only introduced in Jun 2011 for a 2-month trial, then discontinued for a while, and reintroduced in Oct 2011.  So there won't be any models more than 18 months old.

 

Prime Gray also has a higher deflection temperature than the other SLA detail resins from i.materialise.  Some materials have deflections temperatures in the range 43-47C, which would be a factor in Australia.  It was 42C in the shade here in Perth on New Years Eve, and 49C today in one of the outback mining towns.  I rejeced the other SLA resins because of limited build size as well.

 

I am planning both the body and chassis for my diesel loco in Prime Gray, and I have allowed for 4 pairs of fixing screws which should help to keep the assembly rigid.  Being a loco, it will be weighted and I don't want it to sag.  The prototype chassis has two large I-beams for structural strength. I found some brass I-beam the correct size, so I plan to slot the I-beams into the printed chassis which will also increase the rigidity.  I may do a second chassis with integral printed I-beams for comparison.

[Etched Pixels]

I've had some bent stuff from Shapeways (which got reprinted) and was apparently caused by removing them from the machine too early.

 

For the resins part of the question is how it responds to UV and also how it ages. Mos of the plastics ought to be pretty stable but resins (as anyone who has handled old castings will know all to well) can get very fragile if exposed to UV light a lot (eg direct sunlight) or left unsealed for a long time. The obvious plastics exception is PLA which is designed to be bio-degradable. However that shouldn't occur unless you cook it or it gets extremely humid for a long period, so most of us are safe except for North Carolina 8)

 

I've been making sure my FUD models are well coated inside and out but I also figure I've got the artwork, so I can reprint it into something cooler and more detailed in a few years anyway !