Print bed base.
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@Garfield Probably a bit late now but to prove the point with ECOCAST, I dug out this old video from 3 years ago. Admittedly there is 6mm of float glass on top of the aluminium but you'll need some sort of print surface in any case. https://www.youtube.com/watch?v=U733PMTou7M
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Never too late, I've ordered the plate, I will have a Wham Bam setup on top of it so any inaccuracy will get magnified. I'm going to check the surface before anything gets drilled or stuck down.
Might need to relook at my extruder - like your lighting ....
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@Garfield said in Print bed base.:
........................ - like your lighting ....
It's just a circular COB light - Ebay's finest. I think they are also known as "Angle Eyes". That's one of the few things that hasn't changed since I made that video about 3 years ago (that, and the Ecocast plate
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Probably a bit late, but the Australian supplier told me that they start guaranteeing real tolerances in flatness in the thicker sheets, 10mm up.
I bought from Calm Aluminium in Melbourne, and used the 1/4" plate, and it certainly isn't as flat as I'd like.
For a real factory fit I drew it all up in CAD and sent it to the water jet cutters. Cost more but with a Keenovo silicone heat mat under it and Printbite on top I've been very happy with it.
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I got some 6mm and I'll need to go at it a bit I think - put an engineers straight edge across the surface and looked for daylight under it - to the naked eye it is flat but the light tells a different tale.
Anything you put on top of an innacurate surface will magnify the error but this isn't a precision CNC machine so there's no point going mad. That said I want my surface deviation to be less than .1, preferrably much less.
Just need to figure the best way to do this, I've considered scraping or grinding but I've been busy with other aspects of the printer so I'm not really ready for the bed yet.
I'll be putting a wham bam system on mine but a Keenovo underneath, all supported on a Kinematic 3 point mount - constrained but not overconstrained.
Years gone by we would flat a cylinder head on a pane of glass with grinding paste.
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The problem with trying to make aluminum flat is that there is tension in the part causing it to be not flat. Removing material doesn't necessarily remove the tension evenly, IE you'll end up with a part warped in a slightly different manner.
I've been down that road before. I tried to lap a piece of aluminum flat -- it had a bow along the long axis. So I lapped and lapped and lapped until there was no more bow in the long axis, but a definite curve now on the short axis.
Cast aluminum is much better, but there is a reason it's not flat in the first place, and a reason they have a flatness spec of 0.15 mm. It's the truth.
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@Garfield In the past, I've thought about doing the final tramming and flatness by fitting some sort of abrasive to the print head carriage so that the printer laps it's own bed flat. Obviously, you'd need to start with the bed as level as possible and a nice rigid frame and rails. Thought about it but never tried it.......
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Yup - and then you add heat and aren't patient enough to let it equalise - hotter one side than the other = guaranteed bow.
The expansion in my bed at 90 Deg C will be 0.46mm in X and Y and .01 in the Z dimensions - that's why I'm using a Kinematic mount.
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@Garfield said in Print bed base.:
Yup - and then you add heat and aren't patient enough to let it equalise - hotter one side than the other = guaranteed bow.
One property of aluminium is that the hotter it gets, the better it becomes at conducting heat. Which means that it's very unlikely to get hotter one side than the other. Which is another reason why it is such a good material to use for a print bed. But of course if you use a very thin plate, and/or apply a lot of heat, and/or constrain the plate against thermal expansion, then anything can happen. Personally, I don't have any problems with my bed. The only time I check the level is when I transport the printer to a show, and I never use mesh or any other form of flatness compensation. Which is why my idea of using the printer itself to lap the bed flat never got any further than being an idea.
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I can recommend the website www.aluminyumburada.com for aluminium tooling plates / print bed base. Their unit price is cheaper than clickmetal, but their shipping prices higher since they are based in Turkey. So depending on where you are, this could be an interesting option. This is essentially the same product as Ecocast.
