Silicone Heater

dc42

Your power density ia 750/900 = 0.83W per sq cm, which is very high (I usually recommend 0.4W per sq cm). With that power density, a thermal cutout is mandatory. I heard that Keenovo can integrate a thermal cutout into the heater, which would make it easier for you. I'm not sure whether Shenzhen Ali Brother Technology offer that, so I've just asked them.

Deler

Hi @dc42
So you are recommending a heater with 360W. Actually I was thinking to install a cut-off thermal attache it to the heater it self (since it is easier to replace incase of failure).
But still I am lost about which brand should I buy

A Former User

@deler said in Silicone Heater:

There are not much specification to compare.

That makes it difficult to make a recommendation. All I can add is that I have some silicone heaters in the price range of the cheapest option, and the quality matches the price tag as with most cheap things from AliExpress. I.e. the edges are jagged and the adhesive is poorly applied - I don't have any means of determining if the 3M branded adhesive is indeed the real deal either. and you want to consider what happens if the heater comes loose. The thermal cut-off should be integrated for that reason, and I wouldn't worry about replacing it unless its the single use thermal fuse that melt.

Thermal images show the heater is not laid out with any care for anything but time, but thank to relatively thick aluminium I still get a reasonably even heat distribution.

mrehorstdmd

The self-stick heaters from Keenovo use 468MP adhesive. I have found that it lasts about 2 years before it starts letting go. I recently received a new heater for UMMD. I ordered it without adhesive and will use high temperature silicone to attach it to the bed.

When I inquired about the adhesive-free heater, the Johnny Tang at Keenovo sent me a couple links to user guides for the heaters that I had never seen before. They recommend putting a bead of silicone around the edges of the heater once it has been stuck to the bed plate. Maybe that prevents the adhesive from letting go of the plate (maybe..?). Here are the links:

https://keenovo.store/blogs/how-to/how-to-achieve-a-perfect-installation-of-a-keenovo-heater-pad-to-your-3d-printers-build-plate

https://keenovo.store/blogs/how-to/how-to-remove-from-a-3m-adhesive-backing-installation

This is what happens when the heater lets go of the bed plate:

alt text

Air is a great thermal insulator. When it gets between the heater and bed plate the heater gets very hot- it toasted the silicone in the black area. The adhesive let go of the plate and stayed on the heater in the burned area. I don't think this sort of thing will be a problem with high temperature silicone (purchased for $6 at a local auto parts store), but if it ever lets go of the plate, I'll post pictures on my blog. This is why the TCO should be on/in the heater and not the bed plate.

I have found that the same approximate 2 year limit applies to the 468MP holding the PEI on the bed plate, too.

Deler

thanks @mrehorstdmd for the great info

gorf26

Any one have a link to a 120v thermal cutout I have been looking but most I come up with are for 220v.

thanks gary

jhonf441

Hello, i have looked for a 110V fuse but I can not find it, my question is if I use a 1800W heater at 110V I could use a 250V to 10A fuse and the other doubt, the fuse must be touching the hot surface and must have a nominal temperature, being Is the maximum safe temperature that the heater can reach?

A Former User

You can use a fuse with a higher voltage rating no problem, they are usually just physically bigger than what would be needed at a lower voltage.

The rated temperature is the temperature at which you want the fuse to disconnect the heater, so it should be above your normal printing temperature and below the temperature you think would pose a fire risk.

jhonf441

Thanks, the fuse must be touching the heater?

dc42

@jhonf441 said in Silicone Heater:

Hello, i have looked for a 110V fuse but I can not find it, my question is if I use a 1800W heater at 110V I could use a 250V to 10A fuse ...

1800W at 110V is 1800/110 amps, which is a lot more than 10A. So no.

Do you really need 1800W? How large is the bed?

gorf26

On mine the heat pad is 330 x 330 110volt

haven't hooked it up yet but working on it now want to be safe...

Thanks gary

mrehorstdmd

@jhonf441 fuses are selected based on current, TCOs based on current and temperature.

An 1800W heater is going to take 16A, so you'd need a fuse rated for at least 20A.

A TCO has to be rated to handle the current you'll be pulling through it, so again at least 20A. They usually self-heat, too, so if you want the bed to operate at 100C you have to get a TCO that's rated for a temperature higher than 100C. Check the data sheet of the TCO for the formula to calculate the TCO operating temperature based on current draw (16A) and your bed's operating temperature.

1800W is a lot of power to pull from a 117VAC outlet. Are you going to blow a circuit breaker?

gorf26

Would this one be OK?

https://www.digikey.com/product-detail/en/SDF+DF152S/317-1136-ND/1014765/?itemSeq=294889851

Thanks gary

Phaedrux

@gorf26 said in Silicone Heater:

Would this one be OK?

https://www.digikey.com/product-detail/en/SDF+DF152S/317-1136-ND/1014765/?itemSeq=294889851

Thanks gary

That looks ok provided you won't be using bed temps of 120c on a regular basis.

Holding Temperature 128°C (262°F)
Rated Functioning Temperature 152°C (306°F)

jhonf441

@dc42
Hello, they are actually 1800/110 amps, but I had calculated 1800 / 250A and approached the commercial value available at 10A so the fuse I find is at 250v, the bed is 600mmx570mm I had already read about 0.4W per square cm but that was according to what I read for beds 4mm thick and aluminum, I have 8mm thick stainless steel, and the reason is that I had enough problems with aluminum, I did not get it was completely flat or curved when heate.
The size of the silicone heater is made to the same extent as the bed.

gorf26

No I use 60°C so should be good then

thanks gary

Surgikill

@mrehorstdmd I just put an AC heater on my printer. I'm looking for fuses and a TCO. Can you point me to any? It's a 110V/1100 watt heater, so I'm thinking 12a fuse.

I'm looking at this for a TCO. A little pricey but seems like it would fit the bill.
https://www.digikey.com/product-detail/en/cantherm/L5015224DELB0XE/317-1557-ND/3135080

Phaedrux

@surgikill said in Silicone Heater:

A little pricey

You might be able to find the same part at a different reseller. Digikey encourages selling in bulk. Check for any regional electronics outfits that may carry them or something similar.

If you're in Canada, check https://www.be-electronics.com/searchresults.asp?Search=thermal+cut+off&Submit=

gtj0

These are the ones I use...
99C : https://smile.amazon.com/gp/product/B07K358CKK/
or
128C : https://smile.amazon.com/gp/product/B0195UX2KA/

sinned6915

Deler-

I have Ali Rubber heater, 800W, 350x350. I know, crazy stupid big, I ordered from the printer BOM before I understand what I do now. Its been great. I honestly don't go over 100C. I know a bunch of people who swear by them and their service.

I dont understand how the Keenvo are better other than their marketing- its a resistance heater with nichrome wires.

suggestions- get it made with a couple of holes for post install thermistor or thermal fuse additions later.

you CAN fix a nicked heater wire by carefully excavating and wire wrapping the ends and covering in RTV.

and dont forget supplemental ground to the bed.