Aluminium beds – some thoughts on levelling

The Wanhao printer bed is made of Aluminium, below this is a flexible heating element.

It’s been widely reported that the D9 doesn’t level very easilly, Here’s why people are having issues….

Aluminium expands when heated!

If you’re having ‘levelling issues’ ensure to do the electronic bed levelling whilst the bed is hot! – (pre-heat to typical printing temperature first)

 

Anyways, some math.

Here’s a datasheet for the Aluminium I purchased for my carriage upgrade

Two things I note here –

Physical Property	Value
Density	2.71 g/cm³
Thermal Expansion	24 x10^-6 /K

Density – Steel (which the carriage is made of) is generally around the 7 – 8 g/cm³ – or Three times that of Aluminium! – win there, I can use a sheet of aluminium Three times thicker than the steel on the carriage and have the same weight (in theory)

Thermal Expansion – Translated this means that Aluminium expands by 24 micrometers per millikelvin. Also known as 0.000024 meters per degree

 

How does this affect the D9 Printbed?

When heated, the 325 x 325 x 2mm thick aluminium bed  becomes a bit larger

………How large?

 

Here follows some very rough calcuations……..

Wanhao D9 Bed upgrade

The Wanhao Y axis ‘bed’ is known to be a little flimsy,

It’s made from pressed, welded steel sheet just under 1mm thick and notably flexes when adjusting the levelling springs

Some closeups below….

My new plan – Create a new Bed / Carriage with some suitably cut Aluminium from this bloke on ebay – 4mm thick and 325 x 325mm for just over £13, bargain!.

Once cut, this should be stiffer and more importantly, lighter than the existing carriage as shown below…….

 

https://www.ebay.co.uk/itm/Aluminium-Sheet-1mm-1-2mm-1-5mm-2mm-3mm-4mm-1050H14-S1BH4-Various-Sizes/271210657802

When tightning, this black part can often bend, it’s only 1mm thick!

Exposed bed – it looks ‘deep’ from the front, but the ‘wings’ on the sides are flimsy and flex with levelling

More Upgrades – X axis Linear Rails

Finally got a few hours over Christmas to knock up the X axis linear rails upgrade for the printer.

Printer seems to run nicely and i’ve printed a few small things….I’ll work on quantifying any improvements next as, right now it only ‘seems’ better, and print quality improvements are really marginal. The biggest difference was on the Y axis bed, and I suspect there are now easy further improvements to be had………

Photos Below

Side view showing the new Carriage (designed by someone else)

The new idler mount – this was needed as existing thingverse ones don’t have space for the rail at the top

Top down view of the new rail carriage

side view of the new idler and it’s tension adjustment screws