The correct way to mount a silicone printbed heater?

Hello fellows,

I would like to implement a 3d printer setup with 5 to 8mm aluminium printbed and a silicone heater beneath it. It outputs 500W at 230V.

My question is how to mount the whole construction properly?

My ideas:

1. Safety: Ground the aluminum as well as all metal parts of the printer. I am aware and capable of the safety issue.
2. Thermal isolation: How should I do that? My current PCB bed is isolated with a layer of cork. However, I saw people using some sort of shiny foil under their silicone mats.

Thank you so much in advance! :-)

Edited 1 time(s). Last edit at 02/28/2016 08:18AM by mardy3d.

The silicone heaters usually have adhesive. If yours doesn't, you'll need high temperature pressure sensitive tape or high temperature silicone used for making gaskets for engines and available cheaply at auto parts stores.

Before you stick the heater to the bed, make sure the aluminum plate is cast tooling plate. It will come milled flat enough to print on. Extruded aluminum sheet, even 5-8 mm thick, is not flat.

The silicone covering on the heater should be sufficient insulation, but if you're operating from 220VAC, it is best to ground the printer's fame, including the bed plate. Make sure you correctly identify the ground lead from the power line or you could cause more problems than you prevent.

500W is a good power level for about 300 x300 mm plate. My machine has a 450W heater and is about that size and gets up to 105C for printing ABS in about 5 minutes. There is no insulation on the underside of the bed in my machine.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Under my silicone heater I have a sheet of 7mm cork with aluminium foil glued on top. The heater is smaller than the aluminium plate by 15mm all round to leave space for fixings and bed clips.

I didn't use tooling plate, but I was lucky and the 330mm diameter x 5mm sheet of aluminium that I ordered was flat enough. Someone else who ordered from the same supplier was not so lucky.

Edited 1 time(s). Last edit at 02/28/2016 09:27AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thank you very much for the good help!

In fact, I let the aluminium part be made on a CNC mashine.

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the_digital_dentist
500W is a good power level for about 300 x300 mm plate. My machine has a 450W heater and is about that size and gets up to 105C for printing ABS in about 5 minutes.

I am assuming that you're using 220VAC as well then? Did you integrate any thermal fuse or something similar? I find it somewhat troubleful to think of a thermal fuse (the ones I have here simply burn if T>200°C and would be connected in series to the silicone heater) connected to the aluminium bed.

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dc42
The heater is smaller than the aluminium plate by 15mm all round to leave space for fixings and bed clips.

For what do you need the bed clips exactly? So far, I printed directly on my (former) aluminium bed. Do you have an additional surface on top (e.g. glass)? Actually, that would be the best combination between a persistent print bed and the modularity of a removable one, I guess.

Yes I use a 230VAC bed heater. The bed temperature tops out at about 190C, so I don't have a thermal cutout. But you can get single-trip thermal cutouts very cheaply on eBay, they are used in microwave ovens.

The bed clips are for attaching the glass beds that I print on. This lets me remove the bed when the print is finished, put it somewhere to cool down (in the fridge eventually if necessary to release the print), and start a new print immediately on a different glass bed. This works well for the 330mm diameter glass beds that I use, but would be less practical with a larger bed size.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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dc42
Yes I use a 230VAC bed heater.

How do you control it? In normal thermostatic mode with relay or SSR or with some kind of PWM and triac?

I'm just curious as I'm thinking about multiple fan control and measure board with mains relay for 24VDC PSU and 230VAC heater bed triac.
I have this idea of putting my yet to be built printer inside a box, put some air through the electronics and motors to cool them and then filter it out the heated air with active carbon.

My bed heater is a 450W, 24V device that I power using a 0.5KVA transformer (big and heavy). I switch 117VAC power into the transformer using an SSR driven by a MOSFET under PID control on a SmoothieBoard. I turned the max PID frequency down to 7 or 8 Hz to keep it from blowing circuit breakers. I do not have a thermal switch installed to protect against excessive heat, but it would certainly be a good idea. One of these days, if I find one that can handle 20+ Amps, I will install it. The power switch to my printer is a 10A circuit breaker.

Edited 1 time(s). Last edit at 02/28/2016 12:43PM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

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Vuokko

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dc42
Yes I use a 230VAC bed heater.

How do you control it? In normal thermostatic mode with relay or SSR or with some kind of PWM and triac?

I'm just curious as I'm thinking about multiple fan control and measure board with mains relay for 24VDC PSU and 230VAC heater bed triac.
I have this idea of putting my yet to be built printer inside a box, put some air through the electronics and motors to cool them and then filter it out the heated air with active carbon.

I control it with a DC-AC zero crossing SSR, using either bang-bang mode or slow (10Hz) PWM.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I have a 30x30 cm silicone bed (12V) and I need to fix under my 3mm aluminium plate
On the top of the plate I'll place the borosilicate glass fixed with clips
Can someone suggest me how to fix it under the plate?(adhesive it's not present on it!!!)
Can I use this [www.amazon.com]
or you suggest other methods?

Look up the specs. If it's good at 120-150C it should be fine.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

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the_digital_dentist
Look up the specs. If it's good at 120-150C it should be fine.

It's the same used to fix PEI
so it should be fine!

I'd look it up anyway, just to be sure. People make mistakes that get copied by others all the time.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

If one uses aluminum and then borosilicate glass on top why not just stick the silicone pad to the glass? Let's say I don't need to swap glasses all that often.

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A silicon heater does not have a uniform thickness. There's the wires & thermister, you would need make a space for them.

Edited 1 time(s). Last edit at 03/11/2016 08:32PM by stephenrc.

You don't glue the heater to the glass for the same reason that the glass is a bad idea in the first place. It is a thermal insulator. That means the temperature will vary across its surface. We looked at a Taz 3 printer at the makerspace with a FLIR camera a couple months ago (silicone heater glued directly to glass bed plate) and saw 20C variation across the surface including a cool spot about 75 mm diameter right at the center of the bed.

The question you should ask is why are they supplying a piece of aluminum that is so thin it won't be flat and requires that you to add a piece of glass to print on the machine? Why not use a piece of aluminum that is flat enough to print on without having to resort to stacking glass on top of it to make the surface flat enough for prints to stick?

How many people actually need to swap glass plates? Really? When I was a kid I was impatient and would have wanted to throw another plate on there to start printing again right away. Like wine, I've matured with age, and don't mind waiting a little longer for a print to finish. I find I'm also much more particular about the quality of the parts, too, and that usually means printing at a leisurely 40-50 mm/sec. The world won't end if I can't start printing another part 30 seconds after I finish printing the last one. When printing parts that take hours to finish, what's a few more minutes more or less for the bed to cool off and warm up again?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I don't seem to find any such "silicone to glass" combo in the online literature. I am surprised by your results as I believed glass to be a pretty homogeneous material and I thought that if directly glued and assuming a good contact between the two it will only act as an insulator and heat up/down slower as the only downwside. There are so many people having good results on glass on top of ALU PCB I would think directly gluing the silicone mat to the underside of the glass would only improve on those good results.

I am curious about a comparison between a silicone-glass combo and a silicone-thin aluminum-glass combo and whether the latter is worse than the first one. I am not comparing a properly sized aluminum tooling plate with silicone heater underneath to silicone_heater-thin_alu-glass stack. I am quite sure that the silicone_heater-glass combo would end up on top.

This video shows a pretty even temp spread as far as I can tell.
This video makes a comparison between different printers and I can see a blue spot the kind of which you mentioned. They are, however, using glass ontop of thin (or not thick enough) aluminum plate - I believe it's the PCB heater kind.

I wish there was a comparison between a PCB-Glass and Silicone_heater-Glass.

Edited 9 time(s). Last edit at 03/12/2016 01:40AM by realthor.

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Quote
the_digital_dentist

How many people actually need to swap glass plates? Really? When I was a kid I was impatient and would have wanted to throw another plate on there to start printing again right away. Like wine, I've matured with age, and don't mind waiting a little longer for a print to finish. I find I'm also much more particular about the quality of the parts, too, and that usually means printing at a leisurely 40-50 mm/sec. The world won't end if I can't start printing another part 30 seconds after I finish printing the last one. When printing parts that take hours to finish, what's a few more minutes more or less for the bed to cool off and warm up again?

I've seen your megamax and all the particular description!(GREAT JOB!!)
Your "filosophy" and your experience are a very important example for 3d printing world!!
....and I totally agree your assumptions about quality printing, speeds etc.
But I want to have the chance of remove the printing platform at the end of each print, I've realized a good and rigid leveling system, but I can , for example have two printing platform that I can alternate!
Anyway the problem is another; you advise against the use of glass because of its poor thermal conductivity!
So I ask you if for example a 3mm aluminium plate is a good substitute (new configuration with 3+3mm plate, silicone heater on the bottom of the first and PEI on the top of the second)
Another chance can be carbon plate ( what do you think and know about..)
You have used on your printer an heated film, how did you stuck it?? (I think he have a pre-glued system from 3M)

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the_digital_dentist
I'd look it up anyway, just to be sure. People make mistakes that get copied by others all the time.

You can see that people who bought PEI use this adhesive (read comments)http://www.amazon.com/gp/product/B00CPRDDLY?keywords=PEI&qid=1457768582&ref_=sr_1_1&sr=8-1

What a great discussion!

My dream configuration would be to have a removable layer as well. It supports modularity with respect to: (a) printing the next print quicker and (b) trying out new print surfaces. Though, I can see the issue of having an alu + glass combo because putting a piece of glass on top of an alu plate could possibly lower the advantage of the alu plate (even heat distrubution, perfect flatness, inductive sensibility or contact between alu-glass as pointed out before).

For instance: I am not sure these days if I should invest in a PEI coating on top of my alu print bed to which the silicone heater will stuck on. Many people reported great results with PEI. With this option, however, the modularity would be lost all together because putting something on top of such a coated alu plate isn't that feasible. Also, sticking the silicone heater to the "wrong" (here: an eventually unnecessarily PEI coated alu plate) is annoying since one can't pull it off that easy.

A more modular possibility would be using a glass layer with a PEI layer on top of that (again, put on the alu plate). However, my inductive sensor doesn't sense the alu plate beneath the glass layer anymore and also, PEI is somewhat hard to order from within Germany. :-/

Edited 1 time(s). Last edit at 03/12/2016 07:57AM by mardy3d.

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mardy3d
A more modular possibility would be using a glass layer with a PEI layer on top of that (again, put on the alu plate).

That's exactly what I use. However, I use an IR sensor, not inductive. PEI is transparent to IR, so I painted the underside of the PEI matt black so that the IR sensor picks up the reflection from the top surface.

Apart from being able to start the next print immediately, the other reason I like a removable bed is that if the print sticks too well to it, I can put the bed+print in the fridge or freezer to encourage them to separate.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks!

The first and most important properties of the bed plate are flatness, and being level. The problem with stacking two 3 mm aluminum plates is that neither plate is flat by itself, so you can't be sure that the stack will be flat. Autoleveling can correct for a flat plate that isn't leveled into the printer's XY plane, but AFAIK, it can't correct for a non-flat plate. If you start with a flat plate, keeping it flat isn't too difficult. If you start with a non-flat plate, making it flat is very difficult. Cast aluminum tooling plate is flat.

If you absolutely must remove the plate, put your 3mm aluminum on top of the cast tooling plate, or just use a thicker piece of PEI and clamp it to the tooling plate instead of taping it down. That way at least the bottom will be flat and maybe the 3mm plate or PEI will conform to it when you clamp it down. Alternatively, design a mount to hold the tooling plate that allows it to come off the printer easily. Then you can use two cast tooling plates with heaters attached and unplug the heater when you remove the plate.

I have no idea about carbon plates. Exotic materials are not needed here. Flat material is needed.

I use self adhesive 5 mil kapton tape on the plate, and I don't use glue, hairspray, or other sloppy stuff to keep prints attached. I just clean it with acetone before printing and heat it adequately while printing. I use 2" wide tape instead of big sheets because prints are typically done at the center of the bed and that is where the most wear/damage to the kapton occurs. When the tape gets damaged I just replace the strips that are damaged, usually just the central two strips. They typically last for several months before needing replacement. I am still using the same roll of kapton tape I bought 3 years ago. 1 and 2 mil tapes are more common and much more fragile- they would have to be replaced more often.

Regarding the tape used to hold PEI... I was suggesting that you look up the specs on the tape from the manufacturer rather than rely on user reviews that are often wrong or not updated when things don't work after some time. Manufacturer's specs are always the first and most reliable source of information for industrial products (maybe not for 3D printers!). I spent 30 seconds searching and found this link to the data sheet on the tape directly from the manufacturer's site: [multimedia.3m.com]

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Temperature/Heat Resistance: 3M™ High Performance Acrylic Adhesive 200MP is usable for short periods (minutes, hours) at temperatures up to 400⁰F (204⁰C) and for intermittent longer periods (days, weeks) up to 300⁰F (149⁰C).

So based on the manufacturer's specs, I'd say that tape looks OK to hold the PEI on the bed plate.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I second the two ALU cast tooling plates with plugs that you switch for one another when you need that. And Kapton on top of the ALU. BUT that's the most expensive way to do it.
The cheaper way I'd use two glass plates with silicone underneath and change those with one another. I am betting two 6mm tooling plates will be half the price of most printers out there so I'd go for the glass if the printer is not 6-700+.

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Quote

Temperature/Heat Resistance: 3M™ High Performance Acrylic Adhesive 200MP is usable for short periods (minutes, hours) at temperatures up to 400⁰F (204⁰C) and for intermittent longer periods (days, weeks) up to 300⁰F (149⁰C).

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So based on the manufacturer's specs, I'd say that tape looks OK to hold the PEI on the bed plate.

......and do you think that I can use this adhesive also to fix my 30x30cm silicone heater on the bottom of cast plate?

Edited 1 time(s). Last edit at 03/12/2016 09:37AM by mdcompositi.

I think it would probably be OK, what do you think?

Back when I glued a silicone heater to a glass plate, early in my 3D printing education and before I knew better, I used high temperature silicone that is used to make automotive gaskets. You can buy the stuff at any auto parts store for very low cost. Here's one example: [www.amazon.com]

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]