More powerful heated bed? May 23, 2015 06:30AM |
Registered: 8 years ago Posts: 37 |
Re: More powerful heated bed? May 23, 2015 07:01AM |
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Re: More powerful heated bed? May 23, 2015 07:08AM |
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Re: More powerful heated bed? May 23, 2015 07:54AM |
Registered: 8 years ago Posts: 37 |
Re: More powerful heated bed? May 23, 2015 08:13AM |
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Re: More powerful heated bed? May 23, 2015 08:58AM |
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Re: More powerful heated bed? May 23, 2015 10:49AM |
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Re: More powerful heated bed? May 23, 2015 05:09PM |
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Re: More powerful heated bed? May 23, 2015 06:11PM |
Registered: 9 years ago Posts: 977 |
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VTE
I was reading somewhere that installing the MK2 upside down puts down more heat. Is that true?
Float glass is much more likely to break from thermal shock than borosilicate glass. Use borosilicate glass, 3mm is a common thickness and works well.Quote
VTE
The thin glass from picture frames, is that stuff going to break when heated and cooled? That glass is not tempered.
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VTE
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Not sure what else to do, I am positive that the heat distirbution is screwing up my prints. I can put my hand on the bed 1" away from the edge when the thermistor is reading 120C... Thats a 50-60C differential!!!! This is not right!
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Re: More powerful heated bed? May 23, 2015 08:25PM |
Registered: 8 years ago Posts: 37 |
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AndrewBCN
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VTE
I was reading somewhere that installing the MK2 upside down puts down more heat. Is that true?
No. That on the other hand explains why you are having such poor heat transfer between the heatbed and the glass. You do have your heatbed upside down, don't you?
Float glass is much more likely to break from thermal shock than borosilicate glass. Use borosilicate glass, 3mm is a common thickness and works well.Quote
VTE
The thin glass from picture frames, is that stuff going to break when heated and cooled? That glass is not tempered.
Quote
VTE
...
Not sure what else to do, I am positive that the heat distirbution is screwing up my prints. I can put my hand on the bed 1" away from the edge when the thermistor is reading 120C... Thats a 50-60C differential!!!! This is not right!
...
Fix your heatbed orientation first, then come back with your new measurements. Also make sure the heatbed thermistor measures the temperature of the borosilicate glass (heatsink thermal compound is your friend...). Oh yes, one last thing: I would not try to measure temperatures with the palm of my hand, bad idea. A $15 infrared thermometer is recommended.
Re: More powerful heated bed? May 23, 2015 10:20PM |
Registered: 9 years ago Posts: 977 |
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VTE
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Hi, I said I was just reading somewhere, I never run it that way.
Here is where I read it.
[reprap.org]
Re: More powerful heated bed? May 23, 2015 10:46PM |
Registered: 8 years ago Posts: 37 |
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AndrewBCN
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VTE
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Hi, I said I was just reading somewhere, I never run it that way.
Here is where I read it.
[reprap.org]
The wiki sometimes contains information written three or more years ago and that has not been updated. Thanks for pointing out that bit of information which I thought was not very clear. I have updated it, hopefully it will not lead to such confusion anymore.
Just to clarify this again: the MK2A and MK2B PCB heatbeds, when used together with a piece of borosilicate glass as recommended nowadays, should be mounted with the side with copper traces UP (i.e. in contact with the glass).
Re: More powerful heated bed? May 24, 2015 01:35AM |
Registered: 9 years ago Posts: 977 |
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VTE
Hi, thank you for the quick response.
I am mounting them up. Here is the issue that I noticed, the PCB is not perfectly flat, the middle is bowed up and the corners are about 0.5mm away from the glass, this is where the problems seem to stem from. Poor conduction due to little or no contact. I was thinking bonding, squashing, gluing, or somehow fixing the heater to the glass. I feel like that is the only way I can get the even distribution of temperature.
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Re: More powerful heated bed? May 24, 2015 04:14AM |
Registered: 8 years ago Posts: 5,232 |
Re: More powerful heated bed? May 24, 2015 04:30AM |
Registered: 8 years ago Posts: 37 |
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AndrewBCN
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VTE
Hi, thank you for the quick response.
I am mounting them up. Here is the issue that I noticed, the PCB is not perfectly flat, the middle is bowed up and the corners are about 0.5mm away from the glass, this is where the problems seem to stem from. Poor conduction due to little or no contact. I was thinking bonding, squashing, gluing, or somehow fixing the heater to the glass. I feel like that is the only way I can get the even distribution of temperature.
...
I agree with you that proper heat transfer between the PCB heatbed and the borosilicate glass depends essentially on good contact. Air as we know is an excellent insulator so any gap between the PCB and the glass will act as a heat barrier. I use 6 or more bulldog clips to insure a good contact between the heatbed and the glass. However, I haven't really done a lot of testing with printing big objects, the largest things I print are usually 10cm wide at most, and I usually print them around the center of the bed.
When using a 12V power supply to heat up an MK2A heatbed it is essential to verify the resistance of the heatbed with a good multimeter. You really want a resistance no higher than 1.1Ohm with the heatbed cold. With that kind of resistance my heatbeds usually reach 65C within 5-8 minutes and 110C within 15-18 minutes; I consider these times acceptable.
Obviously if you feed the heatbed more power it heats up faster, but I am OK with the approximately 120W I am feeding mine.
Re: More powerful heated bed? May 24, 2015 06:52AM |
Registered: 9 years ago Posts: 977 |
Re: More powerful heated bed? May 24, 2015 07:29AM |
Registered: 10 years ago Posts: 14,672 |
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AndrewBCN
Borosilicate glass is much harder than float glass and does not bend anywhere as much.
Re: More powerful heated bed? May 24, 2015 11:38AM |
Registered: 8 years ago Posts: 5,232 |
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dc42
One disadvantage of glass is that because of its low thermal conductivity, it is difficult to get reliable temperature measurements on top of it.