Bed levelling (and also print surface discussion).
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Just had a look at LokBuild and the stockists that I have checked it seems it is available in only 2 sizes 203x203 or 305x305 not big enough for any of us in this thread
I did Email Clever3d to enquire if they could do me one for my 650 diam bed and got the reply that the max size they could do was 550 IIRC but they do do one that will fit my CoreXY at 450x450x8 at €195 plus carriage or €155 for a 410x410x8 tho not cheap it may be worth a go?
Doug
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That's quite a lot for the Clever3D bed. I guess whether it is worth it or not depends on how durable the PEI coating is, and how flat they guarantee the plate to be.
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yeah I know it isn't cheap but I believe Lykle has one and rates it highly
I think they must disolve the PEI Granules in a solvent ant spray it onto the Alloy bed which they claim is machined flat and has 4mm holes in each corner for mounting?
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If it's machined flat, then in a new printer build it would save the cost of an aluminium tool plate for the bed, which makes it better value.
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Indeed
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If it's machined flat, then in a new printer build it would save the cost of an aluminium tool plate for the bed, which makes it better value.
Good point. I have it on my todo list to replace the 10mm thick plate with something thinner - hmmm…........
Edit. ..........but then it is handy to have a removable surface such as glass, in order to rapidly print multiple parts without having to wait for the bed to cool.
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If it's machined flat, then in a new printer build it would save the cost of an aluminium tool plate for the bed, which makes it better value.
Good point. I have it on my todo list to replace the 10mm thick plate with something thinner - hmmm…........
Edit. ..........but then it is handy to have a removable surface such as glass, in order to rapidly print multiple parts without having to wait for the bed to cool.
I like that facility too. On a printer with a non-removable bed, I would want a fan below the bed to cool it faster when the print is finished.
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I got a good price for 3mm PEI sheet from a Chinese distributor. I haven't ordered it yet because I read that material thickness is hard to keep flat using adhesives. I originally though to mount it to the tool plate with stainless flat head screws but now I'm unsure, I'm afraid that method will produce bulging around the screw heads . Has anyone used a thick sheet of PEI? Thanks…
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I have never tried PEI that thick but I think it will be sub optimal for a number of reasons
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loads more PEI than you need. PEI is useful as an adhesion surface, other than that it is an insulator which does not help your heated bed.
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As you mentioned: difficult to keep flat. I have used thinner ~1mm PEI and an issue is the adhesive coming debonded over time. The 3mm will have the same problem but probably earlier as you will be pumping more heat into to maintain the same surface temp.
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PEI is pricy why pay for what you don't need.
Regarding screwing it down. You will probably get a air gap in the middle which will mess with the effectiveness of the heated bed. It won't be flat around the screw heads either
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I had thought to use a combination of adhesive and fasteners on the thicker sheet. I imagined the extra thickness would improve durability and flatness given the larger surface area of my bed. I had not given proper consideration to the insulator effect, do you think it would act more so than say a 6mm piece of glass? The price quote I got for a 560 x 803 x 3mm sheet of PEI was less than any of the print surface supplier here are charging for their thinner material….given equal size that none of them offer. Thanks...
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I've just renamed the title of his thread to reflect what is now being discussed (which is probably more useful than my initially shameless bragging).
Ian
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hey Simspeed
I found that the adhesive debonding was relatively random (ie it did not debond in the middle or the edges in any sort of constant way). The only exception to that was if I was impatient anf forced a part off a hot bed - that caused debonding in extremis. A thicker sheet of PEI should be better at resisting that sort of (user imparted) force. The other force you need to consider is the thermal expansion/retraction which is part of what the glues have to put up with. If you are going to screw it down then check to see if the difference between the expansion of the PEI vs what its screwed into is significant room temp vs bed operating temperature. As the bed size increases this become more of an issue.
For durability. It will obviously be more durable that kapton tape (really really thin) but after you get over a certain thickness I am not sure what benefit you get.
In general plastics are better thermal insulators than glass (which is not a great thermal insulator or conductor). Using Google I got the following properties:
Glass (ordinary) 0.8
PEI 0.22
both in W/m K so doubling the thickness between the glass than the PEI puts it in the same order of magnitude.But actually all of this is secondary to the flatness. If the PEI sheet is flat, and stays stuck down and flat then it will probably work well.
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Ian… sorry for hijacking your thread!
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I just want to chime in and say that using very thick PEI is, IMO, much superior to the thin stuff.
I use a 3.2 mm sheet on several printers, for almost two years now. Sometimes the thicker pieces do have a bow to them, but they can be held flat easily with a clamp or simply binder clips. The thicker sheet does not at all insulate the bed too much, in terms of heat. I use a 12v 280mm PCB heater, and it can get the bed to 120 no problem (other than being at the max rating of the PCB heater). The surface temp of the PEI is about 5 degrees lower than the reading at the PCB heater, with a 3mm mirror and a 1.27mm aluminium heat spreader sandwiched between it all.
The advantage of the thick sheet is that it does not need to be adhered to whatever makes the bed flat, it only needs to be clamped. Also, it can be sanded over and over again (when needed) to give extra print adhesion and to renew the surface texture on the surface.
The downside is cost – but consider the savings of not having to purchase adhesive to adhere a thin sheet of PEI, as well as never having to replace it (thin sheets become damaged much more easily) I think the thicker sheets are the way to go.
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Bot thanks, that really helpful - good point about the binder clips.
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I posted an earlier reply to you comment Bot….just disappeared?? I said I appreciated hearing from someone like you with a positive experience with the thicker PEI sheet. That's encouraging...I think I'll go ahead and take a chance on a sheet for my build. Thanks....TP.
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I'm wondering what PrintBite actually is. I'd sort of assumed that it was PEI stuck to something. It has a very fine texture to it - like very finely etched parallel lines. so maybe it isn't. Whatever it is, my measurements tell me that there is 13 deg C temperature difference between the top surface and the bed, whereas with plain glass the temperature difference is around 2 deg C so from that I deduced that the PrintBite was insulating by 11 deg C. So in theory, if I run the bed at 70 deg C instead of 50, it should work (for PLA). I wonder if I just got unlucky and it's a bad batch? I got mine on 8th November 2016 and it was the first a new batch. Did anyone buy any at around that time or after, and if so, does it work?
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I got a tiny piece for my micro delta just 100mm diameter, probably around early December which is the best piece I've had so far, abs stays bonded down to 56 deg C. My large sheet on the kossel Xl releases abs at about 85 deg C.
As for what it's made of it has a sort of fibreglass like texture and weave. But I don't know what it's made from.
You do need to be achieving 60 on top of the printbite for pla and 110 for abs which I find is 70 or 120 set temp.
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The stuff I have is an early one that came without any backing adhesive or grid marking's on it?
Mine is attached directly to my Ecocast plate and just works.
@simspeed do you have a link to that Chinese PEI Supplier please?
Doug
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PrintBite seems to be a type of G-10/FR-4 sheet, allegedly with a treatment done to it. I think it is simply an off-the-shelf G-10 sheet with branding applied and price marked up.
