Heated Bed Advice

I have the red PCB heated bed and would like to clarify the construction, before i start routing wires etc for my Mendel REPRAP

From what i have read in previous posts

1. I cannot print directly onto the PCB - the side that says "HOT DO NOT TOUCH" etc
2. Glass is best as a surface above the PCB.
3. The glass must be pyrex or some form of toughened glass so that the heat does not shatter it
4. Kapton tape can also be used - but needs to be re-applied after a build

Are the above statements correct?

Also,
I have MDF boards. Do i need to insulate these boards from the heat?
I have seen bulldog clips used to hold the glass on to the PCB - are there other ways and does anyone have a solution to "hot swap" glass plates at the end of a build.

Finally
I am looking for a place to buy the glass i need in the UK. Anyone on these shores know of a good retailer or willing to send me pyrex glass or similar which they use themselves.

Thanks
Griz

A Heated Bed(glass) video for you.

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__________________________________________________________________________
"I like to be, what I like to see, in you and me.
I am the Stallion, Mang."

ISTAR Scope Club

I use standard 3mm picture frame glass on my aluminium heated bed, can't help with suppliers over there as I moved to NZ 10 years ago but any glass shop of which there will be plenty in your local yellow pages.

I use bulldog clips to hold it in place and have several pieces of glass so I just swap them over as you need to let them cool before the printed objects can be removed

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__________________________________________________________________________
Experimenting in 3D in New Zealand

grizgrand Wrote:
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> I have the red PCB heated bed and would like to
> clarify the construction, before i start routing
> wires etc for my Mendel REPRAP
>
> From what i have read in previous posts
>
> 1. I cannot print directly onto the PCB - the side
> that says "HOT DO NOT TOUCH" etc

You can print there, but it is best to cover it with Kapton, to protect the finish on the board. Complete cooling will be required to remove the part.

> 2. Glass is best as a surface above the PCB.

Yes. Glass is very good, especially if you don't want all of your parts branded with a reverse image of the hot surface warning. I use Pyrex (Borosilicate) glass, which is used in things like test tubes, and other heat resistant lab equipment. The picture frame variety also works for some ppl, but I have no experience with those types.

> 3. The glass must be pyrex or some form of
> toughened glass so that the heat does not shatter
> it

I would wear protective eyewear if I were you

> 4. Kapton tape can also be used - but needs to be

I find that there is no need for kapton on glass. Some ppl have trouble sticking the initial print filament. I do a really low pass on the first layer, and don;t have any problems with PLA or ABS, at any speed (reasonable speed)

> re-applied after a build
>
> Are the above statements correct?
>
> Also,
> I have MDF boards. Do i need to insulate these
> boards from the heat?

You should put at least a couple of layers of corrugated cardboard below the PCB. This will trap the hot air close to the surface of the PCB, and make the heating more efficient in the direction of the glass.

> I have seen bulldog clips used to hold the glass

See the video above. It's mine, and I use kapton tape in the corners to secure. I've only needed to do it once. Very durable.

> on to the PCB - are there other ways and does
> anyone have a solution to "hot swap" glass plates
> at the end of a build.

On bare glass, you only need to drop the temp 30' or so to pull the part off. like two minutes. Changing out glass is risky IMHO

>
> Finally
> I am looking for a place to buy the glass i need
> in the UK. Anyone on these shores know of a good
> retailer or willing to send me pyrex glass or
> similar which they use themselves.
>
> Thanks
> Griz

You can order from McMaster-Carr here in the US. but of course it won't be cheap. Look for old toaster ovens with square doors. Those are Pyrex too (why didn;t I think of that. There are also food warming plates the are 200mmx200mm, but the surface has a texture to it that may or may not be desireable.

I have yet to have a piece of glass shatter and I often put them in the freezer to aid cooling if I need the object in a a hurry. As I said I just use normal glass on a heated bed (60C) and swap them over at the end of each print

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__________________________________________________________________________
Experimenting in 3D in New Zealand

My heated bed was covered with kapton tape but as it wasn't quite flat I added normal window glass, with the corners cut off to allow for the bolts. it cost me a couple of quid from a local glazier.

the heated bed is held away from the wooden base by bolts and extra nuts, you can just see it if you zoom in on this picture:
[picasaweb.google.com]


hope this helps

peter

+1 on the window glass (my HW store called it picture frame glass). No breakage problem, and the print bed is dead flat now.

Thanks for the advice.

I bought my glass today (20 quid, local craft shop). It is heat-resistant and sized correctly to fit over the bed.

Just a few more days workn and this callsign will have a printer!

My heating element has stopped working so I thought I would heat the bed prior to printing with a heat gun, it craked all the away across

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__________________________________________________________________________
Experimenting in 3D in New Zealand

Most recently I've started using a sheet of borosilicate glass from mcmaster carr, 1/8in thick.

I sanded the top surface with 220 grit sand paper until it is quite scratched and cloudy. So far it looks like the perfect (though expensive) surface for ABS, though I haven't been able to completely run it through it's paces yet. I've been heating it to 110C or so.

Sanding the surface has made a huge difference compared to smooth, and I'm going to try a lightly sandblasted piece soon. It's too bad normal etching solution doesn't work on borosilicate glass...

So, is 110C enough to make ABS stick on sanded borosilicate glass? I wonder if sanding or etching window glass work too.

Window glass is an absolute crap shoot.

It's possible to get lucky and have a piece with low residual stress, and if it is heated slowly and evenly have no problems; but
i've had many different pieces of normal glass crack and shatter on me from 70C up.

Did some more testing.

I can get ABS to stick to sanded Borosilicate glass at 85C on up, though the best bonding is around 110. Anything much above 110C and the plastic starts to get squishy and the part deforms instead of peeling off the bed. Thin support occasionally doesn't stick well when printed fast (50mm/s+)

I've also tried coating the sanded glass with ABS dissolved in acetone. This works 100% perfectly so far, and is still fairly easy enough to remove the part once the glass has cooled.

Biggest thing printed on it so far is 5in deep, 1in wide, 5in tall.

110'C as measured from the bottom of the HBP is probably not high enough. I know that anything below 120'C for me will not stay put for long.

ABS on glass seems to be an extreme case of YMMV. I will try sanding mine, but in general I find shiny surfaces stick and matt ones don't.

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[www.hydraraptor.blogspot.com]

Attached is the result of a 10hr print at .25mm, solid, in abs. I coated the sanded bed in a very thin coat of abs dissolved in acetone. Carefully measured the surface temp to be ~112C while printing.

When the plate was hot I could practically pick up the printer by them, once it cooled they easily popped off.

Andrew Diehl Wrote:
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> Attached is the result of a 10hr print at .25mm,
> solid, in abs. I coated the sanded bed in a very
> thin coat of abs dissolved in acetone. Carefully
> measured the surface temp to be ~112C while
> printing.
>
> When the plate was hot I could practically pick up
> the printer by them, once it cooled they easily
> popped off.

Coating glass with abs sounds like a great idea. I will try it on smooth glass today and see if it works.

I'm printing a Wade extruder now and so far it looks like it works!

In the end, the corner near the motor mount lifted off the bed so the part is a little warp. It looks like it would work for parts 50 mm or less.

Edited 2 time(s). Last edit at 08/24/2011 05:58PM by brnrd.

I've started experimenting with window tinting film on glass as build surface. So far, results are really good.
The stuff is easy to find, cheap (pieces big enough for a PCB heat plate are scraps to an installer) durable, and comes with an adhesive back. Wondering what you guys think.

[sliptonic.com]

sliptonic Wrote:
-------------------------------------------------------
> I've started experimenting with window tinting
> film on glass as build surface. So far, results
> are really good.
> The stuff is easy to find, cheap (pieces big
> enough for a PCB heat plate are scraps to an
> installer) durable, and comes with an adhesive
> back. Wondering what you guys think.
>
> [sliptonic.com]

i would love to know how this works.

spad007 Wrote:
-------------------------------------------------------
> sliptonic Wrote:
> --------------------------------------------------
> -----
> > I've started experimenting with window tinting
> > film on glass as build surface. So far,
> results
> > are really good.
> > The stuff is easy to find, cheap (pieces big
> > enough for a PCB heat plate are scraps to an
> > installer) durable, and comes with an adhesive
> > back. Wondering what you guys think.
> >
> > [sliptonic.com]
>
> i would love to know how this works.

So far, it works fantastic. The PET is the best surface I've printed on yet. I printed about 15 of the same part in the same spot and I can't tell any deterioration in the material or the stickiness. Parts stick as well as kapton but pop off easy when it's cool.

I've applied the film to 3 different pieces of glass, gradually improving my technique for getting it on without bubbles. The best, so far, has been to:

1) thoroughly clean the class
2) Mist it with isopropyl alcohol
3) peel the backing and mist the adhesive side of the film.
4) float it into position and then squeegee it from the center out, pushing the alcohol out. A good quality squeegee is helpful.
5) let it sit for a day or two before heating it up. Heating it too early causes any remaining alcohol to vaporize and causes bubbles.

Cool to death..
I at times have applied tint to car windows following the directions on the package with (dish) soapy water
popping bubbles with sharp straight pins .
and heating the tint with hot air dryer .
never tried Isopropyl but no reason it can't work .
This seems to be a good idea going to try it

Thank You

I'm surprised nobody mentioned a scanner bed. Has anyone experience repurposing glass from a scanner?

I had an old scanner and tried to reuse the glass plate.
I made a line with a glasscutter to cut the plate to size.
With normal glass you need only a litle pressure on one side to get a nice cut.
I had to use a lot of force to get the glass cut. The result was 1000+ pieces of glass instead of just two.
So my old scanner glass was not usefull.

JanD

Probably toughened safety glass. I think that it is toughened after cutting.

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[www.hydraraptor.blogspot.com]

After my failed experiment with the scanner glass plate I tried a mirror I had laying around.
This is mounted on a alu bed heated with power resistors.

This has a funny effect when the extruder lays down the first layer of plastic.
This works nice for me with PLA at 65 C at the alu plate.
I have not (yet) worked with ABS.

I also tried printing on the backside of the mirror.
This sticks just as good as kapton tape, but after a few prints the mirror coating sticks to the part.

JanD

i saw this in this thread► [forums.reprap.org]
Mono coat needs to be shrunk on with heat gun.
as to A mirror the back side of some are coated with lacquer i have a first surface mirror i might try
the alloy coating on the face is all nothing between.. just thinking

There is one more thing to consider when trying to print ABS (and possibly PLA) on glass, and that is the shape of the nozzle tip. The larger the flat around the nozzle hole, the less likely it is that you will get the plastic to stick. I recently made three hot ends, identical in every way except for how I shaped the nozzles. Keep in mind that these (Wildseyed Hot End) use copper MIG welder tips.

The first tip, I just hammered flat, and did nothing except bevel the edges slightly. The second, I shrpened to a point, and then put in a slight flat, about half the width of the nozzle hole. The third, I sharpened, and put no flat at all.

The first tip failed horribly.The plastic just gets dragged all over the place, and does not stick at all.

The second tip stuck better, but whenever there was a rapid move (no print, or retraction), the plastic would curl off about 50% of the time.

The third tip, and this is usually how I make them, sticks well, and prints well.

I'd be interested to know the shapes everybody has, and what their success or failure has been. Maybe brass behaves different than copper? I know most other nozzles have some kind of flat at the tip.

My problem is that there is simply no attraction between glass and ABS. I can lay it down cleanly from the nozzle but it doesn't stick to the glass, so it can't turn a corner, let alone hold down an object that want's to warp upwards. On the other had when it sticks to PET and Kapton it sticks like chewing gum.

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[www.hydraraptor.blogspot.com]

... has someone tried with ABS solved in Acetone as paint on a glass surface?

I've seen something in this direction working good on plastic or aluminium, but don't know if it's adhesive enough on glass or simply will peel down when heated and printing on it ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Someone reported having success with printing ABS on sanded glass coated with ABS in acetone on another thread. I tried this on plain glass and although small parts stuck well, large parts peeled off at the corners resulting in warping.