Aluminum Buildplate flat Solution?
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Hey Guys,
i currently ask my self how i can fix the issue that my Aluminium Buildplate is not as flat as i wanted to be.
Here is how it is positioned:
https://thingiverse-production-new.s3.amazonaws.com/renders/9a/fb/1f/af/1c/2ae19c11927f280227e93c32d91b02d7_preview_featured.JPGI used a Aluminium Plate and drilled 4 Holes on it and attached it with 4 Screws and Springs.
A maybe better way is to attach it instead with Magenets (they should be realy strong) and maybe Aluminium is here not the perfect solution.
Did somebody tryed that already or got a better way? -
Its quite a thin piece of aluminium. I use 5 or 6mm thick tooling plate which has been machined flat on both sides. https://www.clickmetal.co.uk/click-by-category/tooling-plate/aluminium-tooling-plate And since its cast aluminium it doesn't warp when heated. However you have a piece of glass on there, that should not be bending when heated.
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Level in 4 corners doesn't help either 3 point attachment is much better
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As above - i.e. use thicker aluminium tooling plate and 3 point levelling. But also, if the glass has been toughened, that can cause what starts out as flat glass to bow. Use float glass but don't have it toughened.
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Maybe is too heavy for the way you have it?
I mean, the bed seems quite big, and it's only attached to the frame by the back and the motors, which are in the back too, so the bed can bend a bit to the front, if you know what I mean.
I had the same problem in the past with big beds, you can amend it a bit by moving the Z motors to the front so is holded by the back and the front, or you can put the Z motors in the left/right side and 2 more rods in the front for adding more support.
Regards
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That's a nice, clean-looking D-bot build!
I faced the same issue, as well as other Z axis stability issues. I upgraded my Z axis from the standard D-bot 2 leadscrew/2 stepper configuration to one with 3 leadscrews driven using belts by one stepper (with a nice, nearly 4:1 reduction ratio). My build plate is far more stable now.
I still have a fairly flexible build plate, but I'm solving that by going with a really thick and machined aluminum plate, as others have suggested. I probably went massive overkill with mine, which is 1/2" thick. I haven't mounted it yet because I'm waiting for the new 24V heated pad to arrive, but I'm expecting this beast to be flat and to stay flat. I'll be mounting it with a 3-screw leveling arrangment with 2 screws in the corners on one side and one in the center of the opposite edge.
My only concern is to make sure my leadsdcrew assemblies are mounted very rigidly, and in a way that's strong enough to bear the weight of it without flexing.
I'd say if you don't want to upgrade with a thicker, more stable build plate, you could still do wonders for your Z axis by going to three leadscrews/one stepper. It's not as onerous of an upgrade as you might think. You'd have to shift your control box a few inches on the front rail, move the rail that supports your Z axis a little closer to the front of the printer, and install a new leadscrew mount onto the rail at the back of the printer.
If you check out this leadscrew assembly I posted to Thingiverse, I have some photos attached to it that show the whole leadscrew arrangement as installed on my system.
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I still have a fairly flexible build plate, but I'm solving that by going with a really thick and machined aluminum plate, as others have suggested. I probably went massive overkill with mine, which is 1/2" thick. ..........................I too fell into that trap. One thing to be aware of is the time it takes for the heat to find it's way from the bottom of the plate to the top. As well as the time it takes, the temperature sensor positioning will likely give you problems. If you have the sensor in the "normal" place which is in the centre of the bed between the heater and plate, what happens is that the sensor sees the temperature rise, and turns off the heater but the top of the plate is still cold. Then eventually the temperature at the sensor drops, the heater comes on but soon turns off again as the temperature immediately on top of the heater rises but the top of the plate is now only slightly warm. And so it goes on until after a very long time, the top of the plate reaches temperature. To get around this, I drilled a small hole in the edge of the plate as deep as I could go (about 30mm) and put the sensor in there. In hind site, I wish I had bought 8mm plate instead of 10mm (although I'd still put the sensor in the dee in the side) to speed up the warm up time (I use an 800 Watt mains heater BTW). Moral of the story - buy thick tooling plate but not too thick (and fit the sensor as close to the top surface as possible).
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Yeah that's a good idea. I've been thinking about this, and my current plan for the thermistor is the same as you: I'll drill a hole near the top surface of the plate, from the edge, and put it in there.
I think the yo-yo heat problem you talk about will be less of an issue for me because I'll be using a 350 W heater, so it will take longer, which means the heat will have a chance to equalize more throughout the plate as it heats up.
If I were ordering this plate again I'd probably go thinner, like 8mm or maybe 10mm. My plate truly is monstrously thick. It's 1/2", which is around 12.7mm. It's even worse than yours. I'm looking seriously at the rails and fittings that will support this weight to make sure they're as strong as they need to be. It would suck if I went through all that and still had an unstable build platform just because the plastic fittings that support my leadscrews were flexing all over the plate.
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I haven't had any issues with the plastic lead screw mounts on mine. I very rarely have to adjust the level (which I do by slackening the grub screws on the pulleys and rotating the screws). Maybe once every 6 months or so. But as you point out, yours is a bit thicker. The again, mine is 400mm square but I don't know what size yours is. If it's 300mm square then my plate may be heavier than yours. Ref the YoYo heat thing - that only happens with the temperature sensor sandwiched between the heat pad and the plate so putting the sensor in the side, near the top surface will be fine.
