Rafts Y/N? (Supports not sticking to bed)

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RonniCox1
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Joined: Tue Sep 04, 2018 8:14 pm

Rafts Y/N? (Supports not sticking to bed)

Postby RonniCox1 » Fri Oct 05, 2018 9:46 pm

Hey, I'm wondering if the consensus here is to use rafts or not. I've been having an issue printing small complicated models where supports don't stick to the buildtek, so my boss suggested always printing with rafts and that's been doing the trick. The supports stick to the raft fairly well, and don't fall over before the printer can get to what they're supporting. However, I see a lot of 3D enthusiast communities whining that rafts aren't a good idea, or are a band-aid for a different problem.

So, should I be looking more at my temperature settings, or perhaps bed leveling, and not use rafts? (I'm using the standard settings for Raise3D premium PLA)

Alex M.
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Re: Rafts Y/N? (Supports not sticking to bed)

Postby Alex M. » Sat Oct 06, 2018 12:14 am

I have never had much luck with rafts as they always seem to be very hard to detach from my models and leave a less than desirable surface. I also try to minimize supports were at all possible when printing parts. The N2 Plus can handle overhangs quite well if your print speed, filament temperature and cooling are set well.

As for PLA sticking to Buildtak, the keys for me are a clean bed (always wipe down with alcohol before printing), proper bed leveling, and proper 1st layer "squish". I've seen night and day differences with a simple alcohol wipe before a print. My coworker often forgets and his supports almost always detach while printing. A simple wipe with alcohol and reprint without any other changes has solved it for him.

I also find that it's important to have the bed level in the area in use and the z offset to be correct for the desired layer height to get that perfect 1st layer "squish". Too low / close and it sticks a bit too good. To high / far away and it will likely detach during printing.

zemlin
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Joined: Sat Oct 21, 2017 2:02 pm

Re: Rafts Y/N? (Supports not sticking to bed)

Postby zemlin » Sat Oct 06, 2018 10:57 am

If your raft is hard to remove, increase the separation distance between the raft and your first layer. In IdeaMaker it is "Raft Gap from Model". Adjust the value and print a small test part to check the setting - keep at it until you get the results you want before running a big print. You don't want the raft to peel off too easily, as it won't hold the model well enough to prevent warping/curling. It is a very material-dependent setting.

I was anti-raft for a long time, but have started to use them more. Raft removal and surface finish is a matter of getting the optimal separation distance. Lately I've been printing eSun ABS+ with rafts and I can print any size part with no curl or separation, and the raft just peels right off leaving a very clean bottom layer. Just a few bits around the edges that need to be cleaned up.

The thing with the N2 printers is the gantry is supported by the pair of 8mm rods. With the weight of the gantry they sag a tiny bit. It's just the nature of beams and I haven't seen a work-around for that. A lot of the larger parts I've printed have been hollow tubes, so those work well without rafts since the sag is not a factor when printing a circle. I can level the bed and set the height where it matters. For printing large, flat parts I find a raft can eliminate the variability on the first layer and result in a cleaner part with less fiddling with the bed to get started.

I have been doing some printing with a 0.2m nozzle - and my first attempts to use a raft did not turn out well, but since the parts are normally very small it hasn't been an issue to print without a raft.

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Julia Truchsess
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Re: Rafts Y/N? (Supports not sticking to bed)

Postby Julia Truchsess » Sat Oct 06, 2018 2:03 pm

I print PLA, PETG, and PolyMide on PEI. If the print has a large amount of surface area in contact with the bed, I will often go raftless. With parts that have only edges, or a lot of support, in contact with the bed I use a raft to ensure adhesion. Never had a problem with raft removal, they peel right off, using the standard PLA profiles. With PolyMide a whack with a scraper might be needed to get it started. Can't comment on ABS as I've never printed that on the N2.


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