Beyond PLA: how to avoid long-term warping?

[FalmouthLouis 3]

I do a lot of demonstrations in schools and trade fairs, so I have printed a serious range of models - from toys to engineering products - which I can use to engage people in discussions about the potential of 3D printing.

 

I have primarily printed in PLA, being attracted by its surface finish and wide range of colours. However, in the recent hot spell here in the UK, I've had some quite important prints warp where there are relatively thin elements to the design. Clearly, some PLA prints cannot withstand the heat when left for an afternoon in the interior of a car during a reasonably hot British summer day.

 

What filament should I move on to, since I want to avoid having this happen again? I need something which is as robust as PLA, but which won't suddenly warp on me in this way. Having a good variety of colours available is important - as would be surface finish.

[FalmouthLouis 3]

.....and it would be good to be using a bioplastic.

[geert_2 557]

Yes, I know the experience with PLa demo-models left in the car...

 

Now I use PET and NGEN for parts for my car: dash cam filter mount, clamps,... Up till now these have survived unwarped. These materials are still easy to print.

 

[FalmouthLouis 3]

Geert_2: I started printing in NGEN and got some nice clean results.

 

However, I just tried a 24 hour print of a good test design - the Platform Jack - and printed slowly play safe. It printed without problem until about hour 22 when it slipped on the print bed. On checking, the base of the print had warped badly. Photo is attached. The print is upside down. The warped face was on the print bed.

 

Any thoughts? I set the design up using setting taken from the Colorfabb website. I've only just realised that Eastman's template for Amphora AM3300 could well be more precise.

 

Does NGEN have a reputation fo r warping during printing?

[geert_2 557]

I haven't had NGEN warping and coming off the bed, but I haven't printed big items either: mine took maximum 3 hours and were low flat models.

 

PET sometimes did warp if printing on bare glass, in the beginning when I used 100% cooling. Now when using no cooling, it does not warp anymore. But here too, my models are low and flat, and take maximum 3 hours.

 

So, try to print without cooling if the model allows it (=no overhangs, no bridges), or try a good bonding method. I used gr5's bonding method a couple of times (=white wood glue 10% dilluted in water) on models that needed cooling, which gives excellent bonding. But that bonding is sometimes too strong and might chip the glass, depending on the model...

 

The problem with no cooling for PET is that it tends not to pull nice strings when bridging, contrary to PLA. PLA gives really nice bridges. But PET-bridges tend to snap and fold back onto the nozzle into a blob: it is too rubbery. So the gap or bridge isn't closed. And that blob gets deposited onto the next wall when the nozzle arrives. The accumulation of blobs will finally close the gap, but it is ugly. At least, that is with the PET I have here...

 

So it may take some trial and error to find the right balance.

 

Before doing long prints, make a small test print that will undergo some load, for example a clamp. And try if that survives well in your car, under load. Or try it in a test-environment at the same temperature.