Heated bed

I have 3 mm glass on top of my Prusa heated bed that's as long as the Mendel build platform so I have just enough room to clamp it down with bulldog clips. The nuts under the carriage does hit the clips when I get too close to the corners so I'm still trying to come up with a better way.

I'm sorry. I have glass on top of the Prusa PCB that's the same length as the build platform on the Mendel so I can clamp it down with a bulldog clip. I didn't think that the PCB will stay flat enough without something on top of it. If your bed is aluminum, why not just heat it directly with resistors or nichrome wire as a lot of people have done?

brupje: If you connect those 2.2Ohm resistors(4x) in series you should have 8.8~9Ohms, if you run that off ~18V (pretty common laptop PSU) you should be at/about the right temp for PLA.

to:brnrd

thanks for glass idea
what glass you use ordinary one or forged?
how your prints stick to glass? do you coat it with some type of film or sand blasted it?

You're welcome. I got it from the wiki.

It's just window glass. I went to a stain glass place and they cut it 6 pieces and ground the edges and corners for me. For PLA you don't need to put anything on it. Just make sure that it's clean. I clean mine really well with detergent and water and then wiped it down with acetone. I heat the surface to around 55-60C.

I haven't gotten to ABS yet but I expect that I would need to put kapton or PET tape on it and heat it up to 70-100. Some seems to be using hotter beds but I don't know if it's safe to go beyond 100 with window glass.

so you fix glass with buldog clips?
Have you tried to attach with silicon heat paste?

What good would silicon heat paste be?
The idea is too remove the glass to let it cool.
If you have a second piece of glass then you clip it on, wait one minute (or two) to let it get up to temperature and start printing.
The other piece of glass will have cooled down after 5 or 10 minutes and then you should be able to easily remove the plastic pieces with no effort. Then clean the glass with aceton (or nail polish remover) and you are ready for the next print.

See Adrians video on printing PLA on glass.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Quote
rhmorrison
What good would silicon heat paste be?
The idea is too remove the glass to let it cool.

Exactly. Not to mention the fact the glass breaks easily and it would be a pain to replace it if it was glued down. This actually happened already when I knocked the z endstop flag off alignment and the extruder tip ran into the bed during a homing step at the start of a print. I got too confident and I didn't pay close attention at the beginning of a print.

silicone is supposed to transfer heat and fix glass to Prusa heatbed which bends on heating and is way smaller than built bed of BFB3000
so I have no option to use buildog clips
double sided adhesive tape is no option too - it will deteriorate on heating

I'm not familiar enough with the BFB3000 but why not do the same thing that I did and get a glass cut to the same length as the bed and put it over the Prusa Bed? Then you might be able to clamp them together.

I finally got around to printing ABS. This stuff behaves so much better than PLA. Print quality seems to be improved. I didn't really change my skeinforge 40 settings (speed, flow, retract, feed size, etc) aside from the extruder and bed temperature that much. I've tried printing up to 85 C on kapton tape over glass being heated by the Prusa PCB heat bed. It sticks but it seems to lift off easily. I'm printing a part (about 70 mm x 35 mm) with support right now and the support is lifting on one side. I read in nophead's blog that I need to go to at least 100C. Unfortunately, I can't seem to get it to go much higher. It's puzzling since I can see the LED indicator for the bed blinking on and off and it's not even running at more than 50% duty cycle.

I think I'm safe up to 100C with glass. But beyond that, I would have to switch to aluminum. Correct?

Is anyone running their Prusa PCB heat bed above 80C?

Edited 1 time(s). Last edit at 03/10/2011 11:42PM by brnrd.

I have run toughened 6mm glass at 140C and plain 4mm glass at 120C without any problems, but I haven't done it repeatedly, so I don't know if there is a chance it will shatter.

It needs to be heated evenly and must be allowed to expand sideways or else it will crack, even it low temperatures. I have always done it on top of aluminium, so it is all the same temperature and stuck the edges with Kapton tape.

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[www.hydraraptor.blogspot.com]

Why would you want glass on top of aluminum? Is it just for PLA? I am thinking of going the other way due to the poor thermal conductivity of glass. I find that the cool areas on the edges allow a lot of warp when using ABS. It seems like kapton on aluminum would work better for ABS.

bryanandaimee Wrote:
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> Why would you want glass on top of aluminum? Is it
> just for PLA? I am thinking of going the other way
> due to the poor thermal conductivity of glass. I
> find that the cool areas on the edges allow a lot
> of warp when using ABS. It seems like kapton on
> aluminum would work better for ABS.

Yes, the glass is for PLA. It sticks well to hot glass and removes easily once the glass is cooled.

I'm using kapton on glass because I have plenty of glass plates to fit on top of the heated bed and no aluminum plates. Besides, it's easier to get flat glass than it is to get flat aluminum.

hey got a heated bed for my mendel this week
google cassidys heated bed

brilliant idea one side ABS the other side PLA

no need to use electronics it plugs straight in to my power socket
you need 100 - 240 volts it has tempreture regulator
takes about 5 mins to heat

the guy is selling them and the parts
says he is doing a instuction manual for wiki soon

why didnt some one else think of this idea

$80 for a heated build plate you could build yourself with a sheet of aluminum and some $1 reistors is not the greatest deal in the world

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repraplogphase.blogspot.com

Also you tend to need the first layer hotter than the rest so it needs to be under control of the micro.

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[www.hydraraptor.blogspot.com]

Hmm... I am afraid I am not particularly trusting of posts where the poster is not a registered user on this forum...

Can anyone recommend a supplier of an aluminum bed around 5 mm or 3/16" thick for the Mendel without a notch? I think the notch takes away useful build area on the bed. I'm thinking of drilling a hole in one of the corners to use as dump location if needed. So far, I've found that I don't need it with SF 040-041 skirt feature. Also, I don't want to have holes drilled for heating resistors.

I suppose I can just buy the plate, cut it to size and drill the holes. But I'm looking to save some time.

brnrd Wrote:
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> Can anyone recommend a supplier of an aluminum bed
> around 5 mm or 3/16" thick for the Mendel without
> a notch? I think the notch takes away useful build
> area on the bed. I'm thinking of drilling a hole
> in one of the corners to use as dump location if
> needed. So far, I've found that I don't need it
> with SF 040-041 skirt feature. Also, I don't want
> to have holes drilled for heating resistors.
>
> I suppose I can just buy the plate, cut it to size
> and drill the holes. But I'm looking to save some
> time.

Onlinemetals.com cuts to size. Not sure if it's precise enough, but it's cheap enough to be worth a try.

OnlneMetals Aluminum Plate

AgeingHippy Wrote:
-------------------------------------------------------
> Hmm... I am afraid I am not particularly trusting of posts where the poster is not a registered user
> on this forum...

I guess you are referring to the post about Cassidy's heated bed? I saw that on ebay too, and in the description the seller scion_imports says he will send out instructions to anyone that asks for them, which I did and he has. I'm not going to release them here; that's up to him. It's quite a neat, simple, robust design, using heated wire. Contact him through ebay here:
[cgi.ebay.co.uk]

My two cents worth on heated beds, mine in particular:

In order, from bottom to top

220mm x 220mm 1/4" Acrylic - Kapton Covered - 4 x 5/16" round rare earth magnets press fit flush to the surface in the corners. You can print PLA cold on this, although I don't do that any more.

Four 1/2" diameter PEEK rods cut to 15mm, drilled out 5/16" hole, 4 x 5/16" round rare earth magnets press fit flush to the bottoms. These sit on top of the acrylic, and hold the bed firm, but also allow it to be removed.

Four layers of corrugated cardboard, cut to 220mm x 220mm, corners cutouts 15mm x 15mm, placed on top of acrylic bed. These insulate the bottom side of the bed so that heat loss is reduced. It more than doubles the heating rate. The acrylic is not affected either way. If the insulation is there, it does warm up a bit, but not much.

1 Printed PCB heated bed, glued to the tops of the PEEK with Krazy glue, Etched copper side down.

1 1/8" Pyrex (Borosilicate) Glass, cut to 8" x 8", held to PCB with four strips of Kapton diagonals on the corners. This is sufficient to hold the bed flat to the glass. The PCB bows convex on the solid copper side, so taping in the corners makes it really ideal. I got the glass from McMaster-Carr for about $27.00.

I print directly on the glass, without Kapton. Temperatures from 100c to 120c work well for ABS. Haven't tried PLA lately, so I don't know how that would go yet.

Once the print is complete, the glass need only cool to just below 100c to allow easy removal. Usually I just blow on the bed, and the part starts to pop up (always wear safety glasses, just in case).

Odd that you can print ABS directly onto glass. I found that it does not stick at all: [hydraraptor.blogspot.com]

Different ABS? Different glass?

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[www.hydraraptor.blogspot.com]

I also failed to make ABS stick on glass but I never got passed 100 C at the time. I used window glass that I bought from a local stained glass shop. Is Pyrex that much different from window glass?

That's the weird thing. I can't get it to stick below 100c either, but above this temperature, it's on there pretty good. It's really a great little discovery for me. On thing to note is that a slight cool breeze will ruin a good part with this setup, so keep the machine away from doorways and windows.

I picked up a small ceramic heater for $9.00 this morning, and I think I'm going to build a chamber.

If you want to see the setup in action... [wildseyed.com]

CdnReprap Wrote:
-------------------------------------------------------
> brupje: If you connect those 2.2Ohm resistors(4x)
> in series you should have 8.8~9Ohms, if you run
> that off ~18V (pretty common laptop PSU) you
> should be at/about the right temp for PLA.


Running these at 12V I get about 55C with glass on aluminium PLA doesn't stick very well at this temp at all. I have everything plugged into a multi plug. I using a universal laptop adapter so I could step it up to 18V would this still be drawing a low enough amount of power to not blow my multi plug? Electronics is not my thing hence the questions

Edited 1 time(s). Last edit at 06/03/2011 11:48PM by NelsonRap.

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__________________________________________________________________________
Experimenting in 3D in New Zealand

I just installed the heated bed I got from [botmill.com]
It was totally plug and Play .. It is a replacement bed for the Botmill . All I need to do was unbolt the bed that was on it and bolt on the new heated bed, level it and place the tape on it . It has it's own adjustable power supply so to can set the heat to the temp you want . The first day I ran this for 10+ hours . It held the temp very steady the whole time.

Hmm. Another positive post for Botmill from an unregistered user. Be careful ordering from this company. There are much better alternatives.