thermal pads for the HBP

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firesped
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Location: Tucson, AZ

thermal pads for the HBP

Postby firesped » Sat Jul 22, 2017 7:55 pm

I switched out my bed to use thermal pads instead of the clips. I am wondering what is the proper orientation for the pads. do I just want them in the 4 corners?
RL name: Michael Nolen
printers:
raise3D N2 kickstarter Early Bird
Trinus Deluxe (running smoothieware on Azteeg X5 GT board)
Monoprice Maker Select v2

EldRick
Posts: 307
Joined: Thu Jun 22, 2017 5:55 am

Re: thermal pads for the HBP

Postby EldRick » Sat Jul 22, 2017 8:43 pm

What are "thermal pads"?

Jetguy
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Location: In a van, down by the river

Re: thermal pads for the HBP

Postby Jetguy » Sat Jul 22, 2017 10:00 pm

Silicone rubber heatsink pads sold in bulk on amazon and other places. It comes as a sheet. https://www.amazon.com/400mm-205mm-Sili ... B007PPEW52

Jetguy
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Joined: Tue Mar 22, 2016 1:40 am
Location: In a van, down by the river

Re: thermal pads for the HBP

Postby Jetguy » Sat Jul 22, 2017 10:02 pm

Often used in squares between the glass and aluminum plate. As shown on one of my custom hand built 3D printers.
Attachments
GinoPads-Checkerboard.jpg

Jetguy
Posts: 2642
Joined: Tue Mar 22, 2016 1:40 am
Location: In a van, down by the river

Re: thermal pads for the HBP

Postby Jetguy » Sat Jul 22, 2017 10:11 pm

To answer the question
I am wondering what is the proper orientation for the pads. do I just want them in the 4 corners?
RL name: Michael Nolen


You use the 4 corners if you find that the aluminum plate is not flat compared to the glass which will be flat.
If you have a better aluminum plate is near perfectly flat, then do the checkerboard pattern.
What you don't want is a plate that rocks on high center spot so again, 4 corners or checkerboard both works.

So to the probable next question is what about thermal transfer?
The answer is actually counter intuitive, the pads create a super tiny air gap that actually helps not hurts for a more even heat transfer. This actually helps spread the heat more evenly by allowing micro-convection currents between the aluminum heater plate and glass. Again, you might think using a giant full sheet of pad would be best. That doesn't work because you get air bubbles and find all the high and low spots anyway. Using checkerboard works again, if your bed is reasonable flat and limited warping. 4 Corner method still works for heat transfer even though people think just by looks it won't. Again, just the facts, glass is a poor conductor of heat. So we have this giant insulator sheet we just put on top. Because it's bad at thermal conduction, a hot spot where the heat is higher under one spot does not spread through the glass well. By placing a thin air gap, yes, it takes time for the heat to transfer, but it still does transfer, and because it is another layer that tends to spread the heat laterally, this evens out the surface temp of the bed and prevents hot spots.

firesped
Posts: 849
Joined: Mon Mar 21, 2016 9:23 pm
Location: Tucson, AZ

Re: thermal pads for the HBP

Postby firesped » Sun Jul 23, 2017 12:03 am

I went to your website and saw the example and put triangle pieces in the 4 corners. Before I had put pads in the center and was causing in consistent heat spots below the prints. my bed seems to be more level as well. which is also part of the entire reason I moved to this method. since the glass bed floats on the thermal pads and doesn't warp like the bed will when it heats up. a glass bed that is clipped to the HBP will bend with the HBP.

I just printed off a single .25 mm layer to check how level my bed was. 7 1/16 inches by 7 7/16 inches. didn't look like there were any thin spots but there was a lot of fuzz on top so I need to figure out how to deal with that.
RL name: Michael Nolen
printers:
raise3D N2 kickstarter Early Bird
Trinus Deluxe (running smoothieware on Azteeg X5 GT board)
Monoprice Maker Select v2

cullymoto
Posts: 44
Joined: Tue Jan 31, 2017 7:32 pm

Re: thermal pads for the HBP

Postby cullymoto » Mon Jul 24, 2017 6:54 pm

Stupid question alert!
These thermal pads have adhesives on both sides no?
How do you remove the plate without ruining the thermal pads each time?


firesped
Posts: 849
Joined: Mon Mar 21, 2016 9:23 pm
Location: Tucson, AZ

Re: thermal pads for the HBP

Postby firesped » Mon Jul 24, 2017 10:17 pm

there is no adhesive, it just sorta sticks to the metal plate and the glass.
RL name: Michael Nolen
printers:
raise3D N2 kickstarter Early Bird
Trinus Deluxe (running smoothieware on Azteeg X5 GT board)
Monoprice Maker Select v2

Iamkar33m
Posts: 81
Joined: Fri Dec 01, 2017 2:53 pm

Re: thermal pads for the HBP

Postby Iamkar33m » Mon Jan 15, 2018 7:23 am

Anyone wants the raw data on thermal pads, here they are:

image (2).png


16 data points captured on the bed from a 4x4 grid with a non-contact IR thermometer w/ "peak hold" turned on and a 5 second "sample" was taken from each data point.

1) Control test: Heated bed to 100°c and took measurements directly from the bed heater without a build platform.

2) Stock test: Heated bed to 100°c, let it sit for 10 minutes and took measurements from the stock glass build platform w/ Buildtak surface facing upright & clipped at the front at 2 points.

3) Thermal Pad test: Heated bed to 100°c, let it sit for 30 minutes and took measurements from stock glass build platform w/ Buildtak surface upright secured in place by four 100mmx100mm thermal silicone pads placed at as close to the 4 corners of the build platform as possible.

TL;DR: The build platform temperature is bad enough without adding thermal pads.

GWC
Posts: 4
Joined: Wed Jan 10, 2018 11:27 pm

Re: thermal pads for the HBP

Postby GWC » Mon Jan 29, 2018 2:32 am

Great work and thanks for sharing.

What is the brand of thermal pad and part #, thickness of the pad need to understand he heat transfer value?

Any place where there is no pad, there is air and will yield low temps due to resistance.

firesped
Posts: 849
Joined: Mon Mar 21, 2016 9:23 pm
Location: Tucson, AZ

Re: thermal pads for the HBP

Postby firesped » Mon Jan 29, 2018 3:27 am

when I finally got my printer back up last summer after I blew it up. I found that triangles in the corners works best. you actually don't want the pad below the print if you can help it.
RL name: Michael Nolen
printers:
raise3D N2 kickstarter Early Bird
Trinus Deluxe (running smoothieware on Azteeg X5 GT board)
Monoprice Maker Select v2


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