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Need some help with adhesion and configuration of supports.

I'm printing a large piece (300mm plus) that is tapered (ie: base is wider than the top). It has multple protrusions (like horizontal antennae and spikes) over the surface. These spikes will need supports. I've tried using Simplify 3D, and due to the tapered nature, some of the supports need to be placed on the objects surface, not just run from the bed. Additionally, some of the supports for the topmost spikes, need to be from the print bed all the way up to 300-350mm height. To avoid too much damage to the print surface when removing supports, I have them horizontally separated from the surface and I upped both the top and bottom vertical separation of the supports as well (not a huge amount, but enough to make them easier to detach). The entire print job is going to be around 120-150 hours I think. Printing PLA, heated bed with PEI surface, .12 layer height.
The problem - I kicked off the print yesterday and this morning I checked on it. The object itself has great adhesion to the bed and the surface quality and layer lines look great, but some of the really tall supports are already failing to stick to the bed, resulting in spaghetti. And this is only maybe 40-50mm in to the print.
My thoughts are:
Option 1 - reduce the vertical seperation from the base of the supports to improve attachment (at risk of damage to the objects surface - is there a way in S3D to dictate different seperation for bed supports and those which will touch the print?)
Option 2 - Implement a raft, to give the supports something better to stick to
Option 3 - Explore something like Meshmixer for a different kind of support? (I've only ever used those kinds of solid "vine-like" supports with DLP printing so I'm unsure how well they work with FDM)
Any advice or suggestions? (apologies for lack of pics, I'm at work and my Onedrive isnt syncing properly so all my pics are out of reach)

What machine you are using CR-10, build volume: 300 x 300 x 400
What plastic are you printing with: PLA (3D Fillies PLASteel)
What is your printing temps bed/hotend: bed 70, hot end 195
What firmware are you running stock/custom: stock fimrware
What slicer are you using: Simplify3D

Comments

  • First off, welcome to the site. Sometimes supports on part of the object are inevitable however they are generally easier to remove than normal.

    To be completely honest, PEI isn't the best option for PLA, granted you are using high bed temps to make PEI more acceptable. What I used for years when I printed PLA was clean glass with a few coats of aquanet hairspray. Nothing beat it, and it's still widely used as the best bed adhesive. I would print a several day print and not even worry about anything pulling up. Very clean glass/mirror and PLA is great as well.

    With that said, you could try getting your nozzle just a bit closer to the PEI or try making the support layout a bit more dense (spacing between lines). Another trick is to model some thin squares/rectangles under 1mm. Think of them as rafts but you get to place them and not have the entire print on one. Place these around where support from the bed is going to be and you will have a solid foundation for the supports.
  • Thanks for that. Funny, no-ones ever suggested to me that PEI wasn't good for PLA. I've tried bare glass, tape, glass with hairspray, glass with tape and hairspray, glass with glue, mirror with all of the above. None of them work even remotely as well as PEI. The print itself adheres to the build plate far better than on a bare substrate - won't budge till it cools below 35 degress. It's the supports that seem to be having an issue.
    I think i have the nozzle height and bed level really nice on this one and it was turning out to be one of the smoothest prints I've done, it's just the supports playing up. I had to play with flow, temperature, speed settings to dial in this filament (hence the lower 195 degree nozzle temp) and I think they're pretty good now.
    I think the supports do need to be a bit more dense or a a bit less bottom separation. Just a shame that it will probably effect the surface of the print where they attach. Much prefer doing supports from the bed only, but S3D can't do that in this case as they only do straight up and don supports.
    Do you have any experience with MeshMixer? The supports seem really flexible and operate in a kind of "vine-like" fashion, meaning you can run them from the bed and have them branching out to reach higher parts. I just worry that they don't seem to have a lot of support connections with the part (ie: two or three supports for 40-50 mm of print) so it looks like it needs to do a lot more bridging over the unsupported areas.
  • cyris69cyris69 Posts: 33
    edited November 2017
    Interesting with PEI, never bothered with it for PLA only when I did other materials which still performed worse than hairspray. However, that's the frustrating part of printing in which many people have completely different experiences.

    If you don't want to densen the supports up then I recommend doing the under 1mm squares or rectangle objects and place them under where the supports are needed so they print on top of it and no more issues with peeling up and also not needing full raft everywhere.

    As for meshmixer supports or 'trees' those are specifically designed for SLA type printers. Can you use them for our FFF printers, sure, but you run the risk of ruining a full print if a stalk or section fails/pulls up. I've personally tried them without success, others have had varying success. Make the vertical top separation 1 layer for supports and give 1-3 layers of dense supports a try. The dense adds like it's own raft where it meets the part.

    These also work great and a price you can't beat. It's the same stuff as buildtak etc https://www.amazon.com/gp/product/B073TW738G/
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