Hotbed warped

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Niho3D
Posts: 13
Joined: Tue Dec 16, 2014 3:20 pm

Hotbed warped

Post by Niho3D » Thu Feb 25, 2016 1:51 pm

Hi,
my hotbed is warped.
It has been so from the start but i never gave it too much thought printing small parts at suitable point on the bed.
Now i need some big prints and i can get the bed leveled, took a comparator gauge and measured and wow ;up to 0,89mm diffeerence in X axis and 0,33mm in Y axis bulged in the center.

Took off the kapton tape and tried to sand the high point a bit but it gave no good result.

I even thought to take teh bed down and put it on a flat grinder to even it out but if i take 0,89 from center the plate will open up as the aluminium sheet on top is around 0,9mm thick!!

An suggestions?
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Hugues
Posts: 270
Joined: Thu Apr 04, 2013 5:36 pm

Post by Hugues » Thu Feb 25, 2016 9:05 pm

could a "thick enough" glass sheet help correct the issue a bit ?

I do have a glass sheet on mine, 2-3 mm thick i would say.

If the alu sheet bends more than the glass sheet, it would then help.

Worth a try, glass is cheap.
Hugues
Regards from Switzerland

Niho3D
Posts: 13
Joined: Tue Dec 16, 2014 3:20 pm

Post by Niho3D » Fri Feb 26, 2016 10:38 am

i had the same idea but i tried with 4mm glass but you need to tighten it somehow to the bed to fix it and it bends to the shape of the bed.
I was thinking of applying some specialty glue in drops and place the glas on top,this way it should stay flat and also be glued to the bed.
I am a bit worried about the increase in wetght of the bed and it effect on speed.

JTa
Posts: 36
Joined: Sat Feb 02, 2013 6:02 pm
Location: Finland

Post by JTa » Mon Apr 18, 2016 10:52 am

Use picture frame glass sheet, about A4 size. Thick glass takes longer to heat and makes the bed heavy. These picture frame glasses are easy to get, cheap and light.

Heat the bed to working temp, check with the glass where the bump(s) is/are and put some mark on those spots. Apply something like thermal paste on those spots and place the glass on that, clamps on and check the flatness with metal ruler (or something else that is supposed to be flat. If the glass bends, apply small paper pieces in the spots where glass is highest from the aluminium bed. Has worked fine for me, YMMV.

Another option to keep glass flat on the bed I've used in combination with above method: zero the bed on the highest point (bed on working temp of course!) and print it level.

I made this STL for just that:
Bed Flatness pads.stl
For A4 sized glass on Felix bed.
(95.39 KiB) Downloaded 77 times
Only problem I had with this was getting PLA to stick on the bed since I did not have any kapton on my bed so I had to add small patches of it on those places where the pads are printed. When printing the pads I manually adjusted z-height for the first layer since the bed is really warped and it varied from spot to spot.

I recently got this new type of bed myself and it's not that flat either (and inherently these cheap ones will never be) but it is much better (and lighter) than the old 2.0 version was.

My wish list item for FelixPrinters: Bed made from MIC-6 (or similar) tooling plate aluminium milled to proper dimensions together with milled Y-carriage attached to 2 points on the Y-rail instead of 1. Like that Pro1 seems to have and I hope they'll start selling those separately too. :)

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