Centre of bed/plate measurement

Just a quick ponderance:

When calibrating, both my printers regularly show a 0.1/-0.1 measurement on all 4 corners, but the centre is regularly 0.5-0.6 after it has been in use for a while.

Are these measurements in mm? so 0.6mm?

What is an acceptable tolerance here - is the first layer of the raft that is put down thick enough to account for the differences between the centre and edges of the bed? - If parts are lifting at the edges can this be to Blame?

Why does this happen... is there any way to counter it?

Non-level build plate can cause parts to lift.   I dont know what is officially acceptable, but 0.6mm is high.

It's usually caused by material working between the build plate and the heater bed.

http://support.zortrax.com/platform-maintenance-m200/

On the older style build plates (the thinner ones) they were also more susceptible to warping and Zortrax recommend flexing the PCB to remove the warp. Those instruction seem to be gone now (probably because the build plates are thicker now), but if you find you have a permanent warp causing the center to lift off the heater bed even after cleaning, then you can try to save it by flexing.

Cheers,

I'll check under the plate to see if it's got build up there. It's the v2 plate. 

Marcin - any response here, would you consider 0.5 measurement on the centre of the bed too much?

When cleaning use thin strong bond double sided tape in between the erf. late and hot bed. I did it and it's fine now.

Little nervous to do that as tape uses glue that going very gunky when hot... and the perf board is so solid I cant see how tape could possibly un-bend it?

No need for tape. Did you clean under it yet? Take scraper to backside of plate to remove any plastic sticking through..

No need for tape. Did you clean under it yet? Take scraper to backside of plate to remove any plastic sticking through..

Yea, sorry should have mentioned I did this already, still measures 0.5.

Did you bend the plate by hand. Zortrax has a method documented somewhere 

Did you bend the plate by hand. Zortrax has a method documented somewhere 

I tried, but the plate is really quite solid, it certainly didn't feel like there was any give in it. 

I tried, but the plate is really quite solid, it certainly didn't feel like there was any give in it. 

Make sure when you tighten all the screws down that the holes in the plate line up with the holes. They have a taper on them and may cause the plate to push toward the other side causing it to bow up.Try loosening them a bit and see if it fixes the bow..

Make sure when you tighten all the screws down that the holes in the plate line up with the holes. They have a taper on them and may cause the plate to push toward the other side causing it to bow up.Try loosening them a bit and see if it fixes the bow..

Right you are!

Loosened all the screws on the bed and ran a calibration and got a 0.3 reading from the centre. Gave the whole board and heat plate a good scrub with acetone again and replaced the board. When tightening the screws (now knowing from your tip they have an influence) I tightened the 4 centre screws first, then the 4 corners, then the 8 remaining 'inbetween' ones.

Result is a 0.2 measurement on the centre of the board, which is indeed a result.

Cheers Kyle. 

Right you are!

Loosened all the screws on the bed and ran a calibration and got a 0.3 reading from the centre. Gave the whole board and heat plate a good scrub with acetone again and replaced the board. When tightening the screws (now knowing from your tip they have an influence) I tightened the 4 centre screws first, then the 4 corners, then the 8 remaining 'inbetween' ones.

Result is a 0.2 measurement on the centre of the board, which is indeed a result.

Cheers Kyle. 

Glad that worked!!