I’m looking around to buy an aluminium bed plate for my extended @Printrbot Simple.
A local machine shop here tells me that a 1/4" aluminium plate has surface variations of ±0.356mm over it’s surface. Is that enough precise for a printer bed?
The other solution to bet better precision it to machine 5/16" plate. I’m waiting for pricing on both but I’m pretty sure the machined option will be hell expensive…
I’d be interested in the pricing you get on each. I could probably do a 200x200mm bed on my extended Simple.
@Carlton_Dodd I’ll post the prices when I get them. I asked for a 14"x18" plate which is probably more than I need but gives room for fastners,…
If you get it flycut it won’t be that expensive, and will be quite flat. However, a heated bed will make it distort probably more than that 0.3mm because even though aluminum transmits heat well, it doesn’t do so perfectly. For mine, I bought some MIC6 plate, which comes from the factory blanchard-ground flat, because the local surplus yard has a whole rack of it. That’s still only 0.004", as I recall, but that’s about as good as you’re likely to get over a large area with most machining services. You need a surface grinder to get better, and that does get expensive.
@John_Bump No heat bed here so heat expansion should not be an issue. Thanks for the details.
So why not glass? I’ve had good luck with 1/4" generic glass.
@Andre_Courchesne1 14"x18"? That’s a monster! (or a typo)
@Carlton_Dodd Not a typo, the rods I have installed and belts can do it. My current bed is 8"x13" made of MDF…
@Mike_Miller Aluminium is just easier to work with (drill holes,…) than glass.
so aluminum…then clip glass to it. 
All the cool kids are…or appear to be.
You could print corner clamps for the glass plate and attatch the leveling hardware through those. You’d lose some build area but the materials would be way easier/cheaper to get.
@Mike_Miller yeah true. I’ll see when the prices come in.
@Andre_Courchesne1
WOW! That’s some extension!
How do you support the extended Y distance? I know the axis extension will work, but the X rods seem way too far to one side.
0.356mm is not flat enough, unless you print everything on a raft. A typical layer height is 0.27mm, and lots of people go down to 0.1mm for their best quality prints, and you’d want the print bed to be flatter than that or it’ll cause issues.
Instead of aluminum, consider glass. It’s cheap, and is manufactured routinely to surprisingly good tolerances. You don’t need to clip it down, though most do. But if you don’t need to heat the print bed, you can use a square of grippy shelf liner to keep the glass plate from sliding around.
Either that or use one of the ‘bed leveling’ options, so the printer probes the print bed and figures it out, then adapts to the print bed. But that’s slow to start, and adds some complexity to the printer and the print process. And if the print bed isn’t level, the printed stuff won’t be, either.
My interest with a metal bed is also the induction autobed level addon +printrbot made available. It requires a metal bed.
I’m planning on using a layer of thin aluminum under the glass to activate the inductive sensor and help distribute heat more evenly.
@Andre_Courchesne1 you want flatter then that… it will be a struggle to print a raft at that tolerance… you are taking about either have raft thickness of 0 at side points or >.4 at others…the default nozzle is .4 so if you go above .4 the layer will get sloppy…
Is that the measuremet of surface variation or thickness variation… if it is thickness your flatness could be much worse…
Yeah but does the sensor work through glass?
You can get alm tooling plate. It is stiffer and flatter. I regularly straighten plates in my shop. I can get them within .002 in. Send it to me, I will straighten for you.
@Bob_Roth Thanks, I’ll keep that in mind. My friend is the owner of Tourmac (http://www.tourmac.com/), he is the one supposed to get back to me with pricing.