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Tips for printing large parts

I'm sure there are going to be plenty of tips for printing large parts, so I figured this warrants a topic of its own.

Comments

  • My experiences come from printing this set of parts to date.
    In this case I printed in PLA

  • The machine; In my case, a Type A Machine Series 1 Pro, several in a print pod (6). The print volume of this particular machine is 300mm x 300mm x 300mm, so it can handle all of the parts without any splitting.

    I didn't do the following, but wish I had before I started.
    Check the lubrication of all linear sliding things.

    The large prints, such as the base, and shoulder pieces, can take up to a day. That's a lot of time on your machine, and if you're not used to doing such long prints, there may be defects or wear on your machine that doesn't show up until you've started a 21 hour print. This is particularly true if you're printing in a range on an axis that rarely sees movement. For example, the shoulder is very tall, my machine is typically printing things no taller than 100mm, so the bottom half of the linear slides may not be lubricated, or the lubrication may be sticky. Check your whole system, and apply lubricant where necessary.

    Bed leveling.
    This is a must for sure. A small error at the bottom means at least a small error at the top, and in worst case a big error at the top, resulting in parts that don't fit.

    Filament guide
    Make sure your filament guide does not cause binding on its own. Particularly when you're nearing the end of a spool. One snag on the filament may be enough to cause a layer shift, and ruin your nice 21 hour print. If it's an option for you, invest in a filament spool holder which has some ball bearings, or something similar, which helps make the ride very smooth.

    Heated bed
    These days lots of filaments say "no heated bed required". When you're doing these long prints, it's probably better to go with a heated bed. It will help adhesion at the very least. There's a lot of plastic with a lot of built up tension in these large parts. Heated bed helps reduce warping, even with relatively low warping PLA.

    Use a camera
    If it's an option, there's nothing like catching the disasterous print culprit in the act. If you have a webcam option, use it. This will help sooth your frustration if you can catch the failure in the act, and take corrective measures for the next attempt.

    Uninterruptable Power Supply
    This is an awfully good idea. One well timed brown out or black out can ruin your print, and your day. If you can, put your printer on a UPS, so at least you can be alerted that something's about to go wrong, and possibly pause, or otherwise prepare to resume your print. If you there is a computer attached to your printer, make sure it's got a fully charged battery if it's a laptop.

    Basically, these large prints are taking on any machine. Spend some time up front for less headaches later.

  • Filament

    The design as it stands today was optimized for printing with ABS. The shrinkage characteristics for ABS are different than those for PLA or PET, or anything else. There's no easy formula here, but if you do print in PLA, you're likely in for some sanding here and there.

    Slicing
    Use a slicer that allows you to adjust the laying down of support material. You'll want to eliminate support material from all the tiny nooks and crannies, like in small screw holes. Printers these days can handle fair small bridges, particularly if not printing in ABS, and you won't be able to get that small stuff out.

    Use as thin support material lines as possible
    use the simplest support material patter possible. It's too hard to pull out in some places
    If you're doing custom support material, set the overlap to 0%. It's typically defaulted to 15%, which has the support material sticking to the side walls. This is harder to remove, and will leave you with a lot of sanding in spaces you can't reach.

    Layout
    Better to print big pieces on their own. This goes for the shoulder gears, the individual forearms, and of course anything larger. If one fails, that's alright. If two fail on the same plate, that's a real bummer.

    Plate up the smaller pieces. That's the gripper, the shoulder small bits, and the wrist small bits. These are small enough and quick enough that it pays off to do them together.

    Layer Height and other parameters
    Larger layer height is actually better on large parts. 0.2mm and above is great for everything up through the shoulder gears (green, orange). 15% infill is probably good enough. Higher probably won't provide that much more strength, but will add a lot more weight. If you've got a slicer that does 3D infill patterns, then you can probably reduce this even further. Avoid using a honeycome though as this will add dramatically to your print times. Simple triangles will suffice.

    On the smaller parts (small wrist parts, gripper, and shoulder small bits), using a lower layer height, and possibly increasing the infill might be ok.

    perimeters
    Using 4 or more 'perimeters' ensures that you get some nice solid holes for the screws to sink into. If you go too thin, you'll end up with screws trying to thread through the wall, and into the sparse support material. Makes for very weak connections.

    Closely related is the top and bottom layers. Using 7 top, and at least 5 bottom will ensure that you get solid feeling parts, and you won't have sagging on the top sides due to not enough plastic to fill in the gaps between the internal infill lattice structure. In the pictures, the round orange cover plates suffer from not having enough top layers, so they look ugly, and saggy.

    surface pattern
    Using concentric on the round parts might work out well. Using straight linear surface pattern on the others is perfectly fine. This is a matter of aesthetics, more than anything structural.

  • filament
    Designed for ABS, but printable in anything, choose your favorite filament, and do the following.

    Print a temperature calibration thing. Basically, anything that lets you figure out what's the best temperature to be printing at for the given material. I use several varieties of PLA, and 210 celcius seemed to be the sweet spot between them all. You'll want to check this with your filament, printing a temperature thing at the speed at which you intend to print.

    Use fresh filament
    Nothing worse than popping in that role that's been sitting in the garage for a year collecting moisture.

    Use PLA+, or other variants which have extra goodness mixed into them to help with their strength and flexibility. PLA from two years ago is probably a lot more brittle than the PLAs of 2016.

    Try out PET(G) if your printer is capable of the higher temperatures. PETG and variants, has great printability, although moving much slower than PLA. Has good mechanical properties (gears will stay strong and not break), and it looks good and shiny (even translucent if you want that).

    Bottom line is, you're going to spend a ton of time, energy, and emotion on building these parts, you should start with the best filament you can afford.

  • Thanks for the guide Will! Ill include this in the next update. Im sure a lot of people are going to run into some problems with the shoulder and this is going to help them out a lot.

    I agree with your points on the heated bed. We have been testing out some of the bigger parts with PLA+ and we are still getting better results with a heated bed. There is also a new ABS from EasyFil which I want to try out. Its more expensive but if I can reduce the print density it will be worth it.

  • I'm curious about the benefits of ABS vs PETG, for this application, but I don't think you've done a PETG version as yet. I really dislike working with ABS (did it for a couple of years early on). I've never really needed the supposed benefits of ABS, so I finally just gave up on it, besides the fact that most of the printers I use these days are open frame, so not so great for satisfying the build environment requirements of ABS.

    I also found that ABS didn't do well for the gears that I printed in other applications. In this robot arm, it's a bit different because you have timing belts rather than meshing gears, so it should be fine.

    But, for every criteria I can think of where ABS might be beneficial, PETG is probably just as good.

    We'll see.

  • With ABS I have had all kinds of cracking issues. The reason I usually print with it is because if it can be printed with ABS it can generally be printed with other materials without a lot of modofication. If I print test parts with PLA its harder to notice flaws in the design that will hinder an ABS print.

    I have been working on another robot as well, mabye I will migrate that prototyping to PETG :)

  • I'll do a PETG set and put some electronics in it, then we'll have something to debate about.

  • Excited to see how the PETG comes out!

  • Here is the base motor mount done in Form Futura HD Glass, which is essentially a PETG

    I'm having challenges with PETG in general on my print hub because it's located in a place (my garage), which is really cold right now, throwing off the various fan and bed slicer settings.

    But, this was done, with painters tape over the glass bed, low fan, 240/80

    It curled up at the corners, but not so much that the part is unusable.

    I'm currently printing a wrist body in eSun PETG. I used a brim of 8 lines on that one, and there was curling at the bottom as well, mostly of the brim. Using a larger (10 lines, two layers) brim is probably warranted in that case.

    Sitting on painter's tape atop the glass in both situations.

    The feel is nice, the look is more interesting than opaque PLA, the strength is solid. If I can manage to do a whole set in PETG, this might be a good material to use. We'll see how it goes. Perhaps a clear PETG to give it that "I can see the gears turning" look.

  • This is very cool. I wonder if I could manage to print PETG. It's quite glossy and I love the idea of transparency to see gear movement.


  • This is the wrist body done with eSun PETG

    In this case, I put blue painter's tape down on top of the glass build plate. Then I threw some extra elmer's glue on top of that.

    I used a brim of 8 perimeters, for one layer.

    80% bed, 240% filament.

    It did manage to curl up around the edges a bit, but not to an extent that would make the print unusable.

    I'm imagining turning down the build plate temp a bit, and running the fan full blast (currently 50%), might actually help with the slight curling. It's something I can plat with to fine tune over time.

    I'll try the base, and base gear thing next to see how that goes.

    These PETG parts are quite nice. They are semi-transparent, so you can see a bit of the infill structure. The part itself is strong, and slightly flexible, which is probably good for this application. They'll flex a bit instead of snapping when under stress. They are dimensionally sound, with the holes being firm, with 4 perimeters.

    I've been trying to print with clear PETG, and that seems to be extra curly. If I get that one sorted, I'll do the gear pieces in clear PETG, which looks pretty interesting.

    So, there you go. PETG is certainly possible. Once I have a full set, plus some hardware, I'll be able to compare it against a PLA set for actual usage.

    I'm also going to try PLA/PHA because I've heard that's good for strength. I don't know about heat though.

  • I believe we are missing this part:

  • I was wondering the same thing, and waiting to see the instructions come out, but there it is. I guess it should be part of the forearm set right?

  • Yeah, I would expect it to be part of the forearm as well. I'm eager to print it. I'm glad I'm not alone lol

  • This is a picture of a shoulder after it was done printing

    Ambient: my garage at 45 degrees F
    machine: Type A Series 1 Pro
    material: ColorFabb PLA/PHA
    temp: 210
    bed temp: 50
    bed prep: glass, Elmer's glue (couple of layers)
    slicer: simplify 3D
    speed: 50mm/s
    fan: layer 1 - 0 percent, layer 3 (onward) - 75 percent
    support: custom, only in the larger overhangs

    I was running out of filament in the last few hours, so had to swap in a new roll half way through the top, but with the exception of a slightly under extruded few centimeters, you can't really notice.

    In this case, it came out absolutely flat on the bottom

    I want to try this PLA/PHA combo because it has some good strength properties compared to other PLAs, and seems to be easier to print than PETG.

    I was having problems with their yellow version, mainly tangled spool, but did manage to get a couple of good prints on that as well.

    In general, for large parts, bed adhesion is the name of the game. A little heat, some glue, hair spray, or whatever it is you normally use, and relatively slow speeds while going light on the parts fan, and these seem to come out pretty good, in my environment at least.

    With each new material I try, I first print a temperature calibration tower that Type A machines supplies, and find the sweet spot for the strength and finish I'm after (210 degrees seems to work best across multiple materials and my ambient at the moment). The model is such that it will show where stringiness will occur as well, which I definitely want to reduce. Saves much headaches later on as I want to do minimal post processing.

  • @ethicaldesign
    I was actually confused about the groupings of things in the .zip file. I get the shoulder thing, but the 'wrist' set has a one of those giant body pieces as well, but I think it's the one that's supposed to attach to the shoulder, before what is called the 'forearm'.

    The actual 'wrist' body piece is the one that's missing, the one indicated in the picture, and should either be in the forearm set, or should replace the big body piece that's currently in the wrist set.

    Either way, I'm imagining the current 'wrist body' was mistakenly put in there and the actual wrist piece was left out.

  • That shoulder print is absolutely exceptional! I love the matte finish on it and the fact that it is going to be stronger than PLA is an awesome bonus. I'm glad you were able to get it to print without much aggravation. I know without a heated bed, I'd probably have a tough time with this. I'm hoping I don't run into a strength issue with the PLA and this robot or I'll have to find an alternative print. Great print and awesome attention to detail of your machine!


  • Here's the first attempt at the wrist. There's extreme layer shifting at the top end. I don't know if that was caused by a snag on an upturned portion or something, but it's fairly significant both out and back on the y-axis of my machine.

    Also, even though I did custom supports, I need to be more judicious.

    While I was removing supports, I used some force to hammer through the hole in the upright, which caused the upright to break.

    So, for the next one,

    Use a slower speed. The topend probably curled and caused a snag of the print head. Slowing down, and possibly adjusting the cooling fan at that layer might help.

    Increase the infill at the layers where the uprights connect to the lower to improve lateral strength.

    go in meticulously with custom support for easier removal.

    certainly a challenging part to print. 70% of the way it was fine, then it kind of fell apart. I'm sure with some fine tuning I can get it dialed in.

  • Here are the twins. The broken up layer shifted first print on the right, and the much better successful print on the left.

    And here it is on its own.

    This is the new wrist piece. I pretty much did what I mentioned above. I also discovered the printer I was using had a stuck parts fan. that probably contributed to excessive curling around the holes near the top, which eventually caught the print head and caused the shifting.

    The support structures were hand tuned, and I erred on the side of not using support if possible, and relying on the fairly good bridging the printer can do.

  • A couple of things to point out. I printed with 4 perimeter (shells) and 30% infill. The 30% is a bit excessive, but I was trying to fill in the space where the uprights take off from the base. This space is hollow, no infill, so I was trying to get it to go in there.

    What I should do instead, but didn't quite make time for, is do custom layers. For a few layers before the upright goes up, and for at least a centimeter into it, the perimeter layers should be increased, as well as the infill, but more the perimeter because that's where the strength is.

    Easy enough to do in Simplify3D and slic3r, and probably others.

    I might also try slic3r because it does 3D infill, which requires even less density, and makes for an overall stronger part.

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