3D-Printed Chassis - Oven?

[cgingras]

I use the oven method on a regular basis to straighten a chassis.
http://www.slot.it/Download/FAQ_PDF_en/ ... sis.en.pdf

Do I need to do the same with a 3D-printed chassis? Will it damage the chassis, get it straight or not change a thing?

[Audi1]

I've had the same question; will be interesting to see what the answer is.....

Allan

[Changing-Gearz]

Yea - somebody around here must know something about 3D printing.....

This one has got to be in my wheelhouse! :teasing-blah:
I'll be the first person to admit I don't know it all.... But I'll take a stab at a little explanation... :liar:
I think it's important to understand what happens first of all.....

Shapeways creates our chassis with what's called an SLS printer (Selective Laser Sintering). If you look at a chassis from the side - then imagine that chassis sliced into pieces of paper - that's how the machine builds. The machine shoots a laser into a bed of fine powdered nylon for one sheet - then the part drops down - is covered with powder and shoots the next sheet. until it builds up the shape in layers over a couple hours.


To break it down a little more - when the laser hits the powder - it melts. It makes a small ball of goo - and then the laser moves over and melts another ball of goo - and the two puddles of goo bond. When a chassis is done - that's why it has a grainy feel to it - its a bunch of nylon goo pellets that all melted together.
This is a close up of an sls part - not soccer balls (though they do look very similar for some reason - trust me - not soccer balls)


The curl will occur during cooling - when the stresses start to even out.... Since its Christmas and I know we all wrap our own gifts neatly- Imagine you have ribbon and a pair of scissors. If the scissors are cool air and the ribbon is the part - and you run the scissors over the ribbon - it curls. because the ribbon doesn't all cool at once - it moves from one area to another.... Inducing different stress and viola - warped part. Now - size and shape influence what happens - and you can't control all the conditions (humidity plays a huge part with nylon - but I digress).

So - to flatten an SLS part - is not easy. It has incredible memory and to dump the stress forces out of it - you have to take it close to melting the balls of goo. The nylon melts around 350F. What that softening curve looks like I'm not sure - it may be solid at 300 and melt at 350..... It may be solid at 349 and melt at 350....I probably have enough spare parts around to test certain conditions - so maybe over Christmas I'll devise a way to surmise a guestimate on the temp/time. I've had it in boiling water for 5 minutes and nothing moved.... In the end (as I've found out....) you have to design the material thicker or design in thicker supporting structure..... Also when you start to move the soccer balls around - you may actually pull it apart and degrade the strength. It may be flat - but may fail someday. To SLS a chassis based on traditional injection molding sizes won't work - it's too thin and will tend to warp in the <1mm areas - I think more than a few people making 3D chassis have found this out.

Sloting Plus and 1-2 others make 3D printed chassis as well - this is done through filament printing. I always explain this as a hot glue gun going crazy.... There's 100 yards of solid material and they run it through a super hot nozzle that squirts out with a little more control than a hot glue gun. It's builds up the same way with layering except its a liquid (sort of).. Getting the warp out of a filament print is somewhat tricky as there are so many materials available (different melt points) but since the chassis is a solid - the stress leaves fairly easy - but you have to know the material that was used....... Filament drawback is usually brittleness and I don't think repeated heated cooling will be good... I've avoided filaments for the most part - but I'm switching over to one in 2017 for certain chassis as the material is getting much better. Our line of guide adapters are made from a filament printer - but the material has chopped carbon fiber to help with strength etc.

I think the best answer is not easily - but I'll test it after Christmas with some old chassis I have. It will be like an episode of Myth Busters with explosions and test dummies I'm sure....

[Cincyslots]

The 3D stuff I have is routinely put in the oven at 200 degrees for 50 minutes at a time. No issues yet.

Bruce

[Cincyslots]

hmm, double post.

[TuscoTodd]

[Radarek]

I had a few 3d chassis from sloting plus. They were always perfect flat. Not need for oven. But that maybe only my luck.

[Audi1]

Great explanation of the 3DP process; Matt; thanks.

I have a chassis from Shapeways that is in an "altered shape" form; not straight. I'll run the "Slot.It How to Straighten a Chassis" process on it and report back the results; although I suspect that it will be fruitless if it needs to be up around 350 degrees F to fluidize the nylon goo balls..............

Allan

[ccobra]

I'm probably way out of line here but I thought I could through a nickel in on this even though it pertains to the chassis' from the crazy hot melt glue gun type (FDM). I have always used the ABS plastic filament so here is what I found that causes the warp and I have a five gallon bucket of warped parts to prove it. Anyway three things have cause my chassis' to warp, 1. the angle of the chassis during the print, 2. the extrusion temperature, and 3. the design. First I try to get the chassis flat on the printer bed or no more than thirty degrees. then on the design I try to keep the tubular parts to a diameter of at least 3/32", anything smaller and the circular parts need a plate designed between them that is 0.045 - 0.055" thick. The the plates need to be that same 0.045 - 0.055" and keep as close to horizontal or vertical as possible. When printing, always use the support and brim functions for printing out the parts. Then for the temperature I use an extrusion temperature of 240 C degrees. Which means if you have a ceiling fan in the room you print in, turn it off prior to the print. These prints don't like any kind of airflow during the print process.
Thanks for the explanation of the SLS printing process Changing Gears, I been tempted to get one of those Laser printers but have stopped short due to the print size and the possible mess I could make with the materials.

[JBriggsK9]

I have straighten out a number of the 3d chassis. I just use boiling hot water and put that over the chassis and just let it cool and have had no problems with straightening out the chassis.

Chris

[SlotCarCorner]

Thanks Matt for the informative post - appreciated!

:text-thankyouyellow:

[cgingras]

Thank you very much Matt, I learned a lot. Now, I'm not sure if I need to boil my 3d-printed chassis but at least I know that at 200°, I probably won't damage anything.