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Hesine Prusa i3 china copy - uneven Heated bed

Posted by Shinobi 
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Shinobi
Hesine Prusa i3 china copy - uneven Heated bed
March 29, 2016 09:45AM
Hi guys,

I got my new Prusa China printer working, but it still needs some time until i figure everything out. One problem I already came across is that the heated bed seems to be uneven. The material is acryl and when I level all 4 corners and try to move the nozzle to the center then there is no more distance between nozzle and heated bed... thats a problem, right?

I read that most printers use glass to print on. Do you think it would work if I just put a glass plate on top?

I attached a picture to clarify

Thanks a lot!
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Attachments:
open | download - 16.jpg (355.5 KB)
hoxsiew
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 29, 2016 10:15AM
I would remove that acryl plate and put a glass plate there instead. You can use plain window pane glass from the hardware store with good results. Have it cut it to fit just inside of the screw heads and hold it down with those fat binder clips. You'll lose a couple of mm of build size, but it's no big deal. I haven't found any glass cutters that can notch the corners for a full-size plate.

While you're at the hardware store, get some of their fiberglass insulation and cut a piece to fit under your bed. This helps a ton. I use the stuff with a mylar-foil backing. A whole roll was only like $5 at Lowes.
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Shinobi
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 29, 2016 01:26PM
thanks for the advice. i'm not sure if i can remove the acryl plate from the pcb. what kind of clips do you mean? can you show me a picture please? i will ask a glass cutter if he can also drill the holes, so i can still use the screws for mounting maybe...

what thickness would you suggest with or without the acryl plate in between? how does the fiberglass help? redirecting the heat to the top only?
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msaeger
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 29, 2016 10:32PM
Binder clips [ecx.images-amazon.com]

You might need some different screws but you just take the acrylic plate off then attach the glass to the heated build plate pcb using the binder clips. I didn't find the glass to be flat either I just used window glass and it's so thin it just bends like the acrylic plate. I got this aluminum plate and that made it flat. [www.ebay.com] The aluminum plate does make it take a lot longer for the bed to get to temp but I do not have any insulation under it like hoxsiew is saying so that would probably help.

Newbie with Folgertech 2020 i3.
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hoxsiew
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 29, 2016 11:21PM
This is the clip. You can see the fiberglass as well. It helps keep the bed heat even and I find I can use less of a temperature setting and still get good adhesion. I used to set it for 60°C but with the insulation, 45°C gives me good adhesion with PLA.



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Shinobi
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 30, 2016 02:10AM
ah thanks now i get the clips grinning smiley

i am torn between a glass plate and aluminium... i know both have advantages and disadvantages. most printers seem to use glass, so i guess i will go with this one. i could use thicker glass do make sure its even. what would you recommend?

the binder clip seems ok, but does not look nice winking smiley. i would prefer a smoother solution... i'm awaiting the reply from the glass company
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Shinobi
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 30, 2016 02:15AM
i should be able to use clips like this, right?

[www.aliexpress.com]
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wampablo
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 30, 2016 03:18AM
those are the clips I used with my printer not had any issues yet.
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Shinobi
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 30, 2016 04:02AM
i just found out that my plate is not acryl, but aluminium smiling smiley. but that still doesn't solve the problem that it's a little bent...

@wampablo. how big are those clips. the pcb is about 1mm but how thick can the glass plate be?
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Shinobi
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 30, 2016 05:21AM
so right now i'm thinking of machining a new aluminium plate. i do have access to a cnc machine and could make a complete straight surface with it... the other option is still a glass plate
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wampablo
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 30, 2016 05:35AM
what I did was to do away with the aluminium plate I found mine took an age to heat up. so I secured my pcb to the acrylic carrier of the printer the same way as to secure all of it. I then got some 3mm glass that sits on top of the pcb within the screw mounts using the clips you linked to it makes life a lot easier when you want to remove prints and warm up time is dramatically reduced.
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wampablo
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 30, 2016 05:47AM
just like this
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Attachments:
open | download - heatbed.jpg (21.9 KB)
Shinobi
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 30, 2016 08:02AM
yes maybe i will try both solution. the glass one will be easier and faster...

my biggest concern is that the glass might also be uneven :/
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eried
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 30, 2016 09:50AM
I have ordered 4 beds because of this... and I am thinking on machining it down too. It might be the only way to get a fully flat surface however I am unsure of what it is going to happen because the thermal impact when heating after it is flat, it might bend again?

My printers:
-Makerbot TOM (#5215, circa 2011), MK6 extruder, ABS 3 mm
-HICTOP Prusa i3 (modded for auto-level, thread screws), ABS/PLA 1.75 mm

About me:
[www.thingiverse.com]
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Shinobi
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 30, 2016 09:54AM
i talked to a glass company and they said with the regular glass they cannot guarantee that the glass won't make any problems when i heat it up to 70-80°. however there is also a special glass that can take heat up too 300°, but it is 6mm thick. would that still be ok?

in german it's called "VSG glass"
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wampablo
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 30, 2016 04:08PM
what are you planning on heating up to 300 ?
trust me and everyone else when we tell you what you need if your new to this then listen to what you are being advised if your not then you should know better.
sorry if I'm sounding harsh but we are trying to help.
look at the diagram I gave you most people go this way because it works a 3mm borosilicate glass will work just fine.
what plastic are you planning to print ?
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Shinobi
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 30, 2016 04:19PM
i just meant that this glass would be able to be heated up to 300° smiling smiley

yes i just bought a borosilicate glass from amazon. which is made for the MK2/3 heat bed

[www.amazon.de]

that should do fine. i just wanna explore all options and understand why this is better or worse and not just blindly follow some advice... i really do appreciate your help!
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wampablo
Re: Hesine Prusa i3 china copy - uneven Heated bed
March 30, 2016 04:33PM
the glass is stronger than you think it is I was surprised.
does your pcb come away from the aluminium?
what material are you planning on printing?
you may need to get a few bits from a hardware store or online.
I found the counter sunk screws that are holding the aluminum to the pcb arnt really ideal I went fro a more classic head. depending on what you plan to print with also depicts what type of adhesion to use on the glass.
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