Understanding Bed Flatness for Mandala Rose Works Ultraflat Printer beds

This article is probably quite overdue, but the intent of the article is to help with the understanding of bed flatness, and also explain what we at Mandala Rose Works do to provide our Ultraflat beds.

The first thing to understand is that when raw bed material (Cast Tooling Plate) comes from metal suppliers, there is a flatness rating depending on the thickness of the material.  Most of the manufacturers follow these rough guidelines.

Thickness of 0.25" (6.35mm) to 0.75" (19.05mm) has a manufacturer flatness of -.015" to +0.015" (-0.38mm to +0.38mm) for a total possible variance of 0.030" (0.74mm).
Thickness of 0.75" (19.05mm) and greater has a manufacturer flatness of -0.005 to +0.005 (-0.127mm to +0.127mm) for a total possible variance of 0.010" (0.254mm).

Quite a bit, right?   Let me explain further.

When we started manufacturing our beds, we bought 10 plates from 10 different "brands" of cast tooling plate (ie. Alca 5, Mic6, ATP-5, Kaiser, etc...) I think you get the idea.  There are a LOT of manufacturers.  We tested each blank plate that we received.  The best flatness we EVER got from any 1/4" or 3/8" plates direct from a supplier were about 0.005" (0.127mm) and that was by far the minority of the plates.

Most were in the range of 0.008" (0.2mm)  to 0.020" (0.51mm).  We really wanted to produce some of the flattest plates on the market, so we set our goal to be a maximum variance of 0.1mm for beds up to 400mm, and 0.15mm for our larger beds.  We achieve this by a proprietary process.

That being said, this does come at extra cost.  Both shipping of the material to the facility that does the flattening, the actual cost of the flattening, and then return shipping to us.  Basically, when we get more blanks, we have to buy a minimum of 50 pcs of each size that we use to make our beds.  This process typically takes 6-8 weeks from when we order the material to when we can start manufacturing beds out of the material.

The best part about our flattening process is that it keeps the material from loosing its stress relief, even under the extremes of a 3d printer with the high temps that the bed undergoes.  Part of maintaining that flatness is also why we don't do "blind holes" in beds.  Those blind holes can almost immediately taco a bed if the hole happens to be near a stress point.  Think of it this way, if the spot where you have a blind hole gets heated and expands, the top where there's a hole will have more space to move than the part of the hole that didn't get drilled thru (the blind part).  If you have an opening on the top, and no opening in the same spot on the bottom of the material, you are going to see some weird expansion.

When we finish machining a bed from the raw flattened stock, we actually perform another flatness check on it with a granite surface plate and a dial indicator.

It's a rather long process, with a number of different steps to complete a bed and make sure it's flat.

Hopefully this answers some of the questions about why our beds are a considered more of a higher tier purchase than most.

Thanks for reading!