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Pushing the edge of print volume

Discussion in 'General Questions' started by OutsourcedGuru, Jun 12, 2017.

  1. OutsourcedGuru

    OutsourcedGuru Active Member

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    Having thought about this a lot... the strategy shouldn't be to push down on the raft. This just results in pushing down on the bed and pushing down on the bed screws up the z-offset, resulting in layer separation at some point.

    New strategy... prevent the raft from rising by restricting its upward movement with a closely-measured clip. So my new clip design is basically an adjustable pair of arms with clips on both left/right side of the bed and bed plate. Three of these clip assemblies will be added at the beginning of the print job, initially adjusted so that the raft won't get in their way.

    After the raft has been completely printed and the 1st layer of the part is being laid down, I'll then adjust one cam per clip assembly to adjust the clips inward, while applying a little upward pressure to get them to sit on top of the raft on left/right sides. Everything will be created with such tight tolerances that it should just fit in the vertical direction.

    This should arrest any upward curl of the raft and therefore that of the bottom of the part itself. Since it doesn't push down on the bed, it shouldn't affect the z-offset for any of the layers.

    Here's the STL of the key/cam assembly that I've done so far. It's printing now.
     

    Attached Files:

    #21 OutsourcedGuru, Jun 27, 2017
    Last edited: Jun 28, 2017
  2. daniel871

    daniel871 Well-Known Member

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    This seems like an awful lot of work for something that should be solved by a simple brim that gets deburred off later.
     
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  3. OutsourcedGuru

    OutsourcedGuru Active Member

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    The brim won't prevent curling in a 3mm-thick, tall-wall part like this to the edges without a heating bed, will it? Given the print volume maximum versus the print size, there's not a lot of surround on this that could hold it down by itself.
     
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    PLA? Probably. Other materials that want to curl? Probably not. You learn to be clever with how you create and orient the models to minimize that with materials that tend to curl a bit.

    Sent from my SAMSUNG-SM-G930A using Tapatalk
     
  5. OutsourcedGuru

    OutsourcedGuru Active Member

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    What sucks is that the enclosure inside is really tight in one direction already. I can't implode the design to fit the printer's volume. I'll get it, eventually. (Because I'm bull-headed that way.) :laugh:

    If I had some aluminum, I'd just bend some to make this in a jiffy but it would be so cool to have printed the solution. meh...
     
  6. daniel871

    daniel871 Well-Known Member

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    Why not just cut the design into quarters, add some bevels at the intersecting edges, then friction-weld the pieces together after printing the individual sections?
     
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  7. daniel871

    daniel871 Well-Known Member

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    Also, just because you can 3d print something doesn't necessarily mean that you should. You've probably spent more in time and effort at this point than you would have finding/buying that sheet of aluminum and making the part the traditional way.
     
  8. OutsourcedGuru

    OutsourcedGuru Active Member

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    Not a terrible suggestion, tbh. The Raspberry Pi supercomputer is an open-source project so I was hoping for something that others could (easily) recreate and this is the chassis for that.
     
    #28 OutsourcedGuru, Jul 3, 2017
    Last edited: Jul 3, 2017
  9. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Like I said... to maximize your printability you get clever with the modeling ☺that is a great example.

    Sent from my SAMSUNG-SM-G930A using Tapatalk
     
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  10. daniel871

    daniel871 Well-Known Member

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    You could probably just use an already-existing computer tower chassis with simple adapter plates.

    EDIT:

    There are scattered projects where people used server racks they already had to mount the multiple Pi units with fans added to said racks to maintain cooling, but few actual details or 3d models of anything because they stuck with traditional methods.
     
    #30 daniel871, Jul 3, 2017
    Last edited: Jul 3, 2017
  11. Kilrah

    Kilrah Well-Known Member

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    The mess required in this case is however likely beyond what most want to bother with.

    If you want something reused it involves making it easy to reuse :)
     
  12. daniel871

    daniel871 Well-Known Member

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  13. daniel871

    daniel871 Well-Known Member

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  14. OutsourcedGuru

    OutsourcedGuru Active Member

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  15. OutsourcedGuru

    OutsourcedGuru Active Member

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    Just adding to this (@KRGraphicsCG), I later knocked all four of those Cura profile settings on the right-hand side of that screen to 5mm: X/Y min & X/Y max. This will allow the raft some breathing room.
     
  16. Frank van Gilluwe

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    I have similar curling problem printing a box that is at the limit of the printer (114mm x 114mm) a little smaller than I really want, but I'll need to upgrade to a R2 to do exactly what I want. Good for testing and proving out the design. The back was ok, but the front corners were curling, and I killed the job after about 2mm of height over the raft.

    I'm working on two fixes. One I'm making a door to keep the heat more consistent. My thought is the open front is causing the front curling (not yet confirmed). I'll put out instructions for the door and parts I made in a few days (still printing the last parts for that project).

    The second is the use of clips as OutsourcedGuru suggested. I bought some 1" metal clips at Home Depot. I took off the gray plastic coating on the clips, and then flattened the metal with channel locks. It clamps between the raft and the plastic bed (not the aluminum) and should hold down the front edges. The clip after the modification has about 1/2" of range. They will not work for the rear edges as they are too big. These are super thin, so should be usable after about 1mm of the box is printed without hitting the extruder. They also don't have a problem when the bed moves to the the bottom.

    I should know in a few days if either of these solutions works.
     
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  17. OutsourcedGuru

    OutsourcedGuru Active Member

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    @Frank van Gilluwe I'd be interested to see if you can stop the curl. I'm trying to find some local thin aluminum to create a pair of expanding clips, having just purchased the springs.

    There would be a pair of these which would clip under the bed, reaching around the edges and just have enough height to hold the raft from curling up.

    Code:
    __                                                __
    |____________________ spring ______________________|
     
  18. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yea, raft issues :)
    A good reason to avoid it where ever possible. I only use it for tall, narrow prints (like a pole) or for supports that will look like poles (give them something to stick to)
     
  19. Frank van Gilluwe

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    @OutsourcedGuru - Funny - I thought of a similar idea. I think the aluminum may be too thick and/or difficult to bend without breaking. I think you'll need thin steel, which also has a bit of spring to it.

    The clips I got would actually work on the sides, but would not clear the sides when the Z axis goes down below about 2.5" or so. For me, the box is about 2.3" high, so it may work if I pull the clips before the end of the print. They might even just snap off or pull the bed off when lowered - I don't think it would harm the C2 or the print.

    Also might be easy to shorten the length of these clips - the are only $0.49 each.

    @mark tomlinson - I tried a couple of prints without a raft, but the PLA didn't stick on the first layer so I stopped it. Any tricks you can suggest to print without a raft?
     
  20. Frank van Gilluwe

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    Another note - I think the clips will work better if they attached to the bottom of the plastic bed rather than the aluminum plate. This should reduce leveling changes and deformation of the plastic bed.
     

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