Heated Bed slow heating wont go past 68 degrees

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AwesometroN
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Heated Bed slow heating wont go past 68 degrees

Post by AwesometroN » Fri Nov 11, 2016 12:02 pm

Built a v3, everything on it has been working perfectly except for the heated bed. I've given it upwards of 35-40 minutes and it still wont go past 66-68 degrees.

Hot end heats up in less than 2-3 minutes so I'm not sure what to be testing for the bed.

I've seen a lot of discussion in regards to people using a different power supply. But before I go through the annoying task of that I wanted to see if I wasn't missing anything basic.

It's the standard v3 equipment so the onyx bed, stock power supply (which I made sure was set to 115v), I tested power and I'm getting about 11.5V to the bed, etc.

I saw some discussion in the v2 section about changing firmware settings but I thought I'd let the community weigh in first before jumping down too many rabbit holes at once.

Thanks in advance!!

Edit: I did forget to mention that I can get it past 68 by covering the plate with an insulating cover, but it still feels far less than ideal to have to sit and wait and then grab it out of the way at the last minute before it starts...

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Re: Heated Bed slow heating wont go past 68 degrees

Post by Xenocrates » Fri Nov 11, 2016 1:31 pm

AwesometroN wrote:Built a v3, everything on it has been working perfectly except for the heated bed. I've given it upwards of 35-40 minutes and it still wont go past 66-68 degrees.

Hot end heats up in less than 2-3 minutes so I'm not sure what to be testing for the bed.

I've seen a lot of discussion in regards to people using a different power supply. But before I go through the annoying task of that I wanted to see if I wasn't missing anything basic.

It's the standard v3 equipment so the onyx bed, stock power supply (which I made sure was set to 115v), I tested power and I'm getting about 11.5V to the bed, etc.

I saw some discussion in the v2 section about changing firmware settings but I thought I'd let the community weigh in first before jumping down too many rabbit holes at once.

Thanks in advance!!



There are a number of options here. It is unlikely to be the power supply (If it is, it is because that one is flawed or maladjusted, not under powered). The firmware has a number of tweakable values, starting with PID Drive Max (make sure you get the bed rather than the hotend one, usually). This can be set to 255 as a maximum value, and should increase the on time of the circuit. However, it is getting close to the rating of the Rambo's fuse at that on time. Ensure you have good ventilation through the top if you start seeing any other issues, as there is some amount of additional heat to dissipate and the Rambo is operating at the edge of it's capacity with that current.

You can also boost the P parameter, or weaken the I and D parameters in the PID equation to increase effective power and re-tune the control loop. I do not suggest using the auto-tune for this, as it will often time out and gives values that are far from ideal. You can also use the dead-time heat manager, and tune that instead of PID. However, I do not suggest using bang-bang and especially not bang-bang with delay control. these are likely to cause major over and undershoots on temperature due to the lack of granularity in their control system.

Beyond that, insulating the bottom of the bed better, however you do it (Aerogel, fiberglass, and painters tape have all been used with some success), will improve your efficiency in heating.
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Re: Heated Bed slow heating wont go past 68 degrees

Post by AwesometroN » Fri Nov 11, 2016 2:15 pm

I went back through the Firmware and the PID Drive Max is already set to 255.

I'll try to look into adding additional insulation underneath.

Even when covering the glass my temp seems to max out at 91.

So I guess I'll just keep trying things and update this as I find stuff out, I'm sure I can't be the only one experiencing this.

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Re: Heated Bed slow heating wont go past 68 degrees

Post by morgandc » Fri Nov 11, 2016 4:05 pm

I have the same issue, can't get past about 88 on mine. I switched to Bang Bang to skip PID control tuning and the firmware decouples prior to reaching any higher.

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Re: Heated Bed slow heating wont go past 68 degrees

Post by Noircogi » Fri Nov 11, 2016 4:56 pm

If you don't want to go to the effort of installing a higher-voltage PSU along with an SSR and regulator, you can get some performance improvement by turning the voltage of your stock PSU up to about 13.5 volts. You'll see around 0.6 volts drop at the Onyx due to the driver FETs and wiring, so you'll end up with it running at about 12.9 which would be significantly better than the 10.9 or so you're probably seeing if your PSU is currently set to 11.5V.

If you do install a higher-voltage PSU for your Onyx, it's critically important that you get a "good" DC SSR. Make sure to get either an Auber 100A or a Crydom 40A. Most of the others may be counterfit or bad and will fail in the "ON" state which can burn your house down.

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Re: Heated Bed slow heating wont go past 68 degrees

Post by prestonh » Tue Nov 15, 2016 12:51 am

For a few bucks and several hours of work I added a cork insulation under my bed. I can get the bed to 110c in 30 minutes, all firmware settings and PSU are stock. Still takes time to heat up, but it gets there.

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Re: Heated Bed slow heating wont go past 68 degrees

Post by morgandc » Wed Nov 16, 2016 10:53 pm

I actually can't get past 53c running with the fan s on full near the plate. Sounds like I need to insulate...

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Re: Heated Bed slow heating wont go past 68 degrees

Post by AwesometroN » Thu Nov 17, 2016 12:33 am

I've seen a few other threads showing their insulation, seems to be the non-standard standard practice for setting these up, I will probably add in some forum links to the build manual for people building theirs since it's definitely a lot easier to insulate the bed before running wires.

As for my v3 I only get 2-3 times a week to mess with it so I'm planning on taking pics and showing results after I insulate mine, hopefully by Friday.

I'm also getting a new Heater Decoupling error that's driving me crazy. The thermistors are tested and working but about 10-15 mins into a print the bed starts losing too much heat and the whole thing decouples and shuts down. I'm guessing it's the fans, but at this point I'm feeling less certain of anything.

Solutions I'm finding for it seem to be all over the spectrum from Slicer software to fan hardware. So I figured I'd at least insulate it first and then try to tackle the next fire...

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Re: Heated Bed slow heating wont go past 68 degrees

Post by Eric » Thu Nov 17, 2016 3:20 pm

People rarely mention what their ambient temperature is in the printer room. The colder the air flowing above and below the bed, the more the heater has to fight the environment. The top end of the bed should go down as the ambient temperature goes down!

Could be why we're seeing an uptick in this kind of complaint as we close in on winter. Clearly underbed insulation helps. On the top side, an enclosure would keep out cold drafts and trap waste heat from the bed and hot end.

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Re: Heated Bed slow heating wont go past 68 degrees

Post by AwesometroN » Fri Nov 18, 2016 5:27 pm

So, insulated the bed. It's warming up slightly faster. Like 5 minutes faster to get to 60-70 instead, but still 25-30 mins.

Ambient temp in our machine shop is around 25-30 C.

The new issue I'm having is that on certain prints, once the hot end fans kick on they cool the bed down by a good 20-30 degrees and the system errors out and the heater decouples.

I am printing with PLA, so the fans are fairly necessary.

For sake of ruling things out, when I set the bed temp to zero and use my FabLam plate my prints come out just fine. So it's definitely something in the bed temp affecting things, and no, I can't just keep my heated bed turned off, I will need to use it later.

Any new ideas? I'm still trying to learn the Kisslicer/Octoprint combo which I've read might help, but I might do some more digging and then make a new thread if I don't find anything...

Update: Using Kisslicer/Octoprint seems to be the workaround for the fans cooling off the bed too much. I'm getting some super ugly prints, but I think that has more to do with the presets I loaded from mhackney's Kisslicer profiles than the printer.

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Re: Heated Bed slow heating wont go past 68 degrees

Post by teoman » Sat Nov 19, 2016 11:05 am

Check power cables connected to the board.

If they have started to burn up due to a poor connection, that will inhibit the bed from reaching temp.
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Re: Heated Bed slow heating wont go past 68 degrees

Post by geneb » Sat Nov 19, 2016 12:36 pm

My v3's bed stays where I set it - 60 to 80c, depending on what I'm running. The fan's don't overcome it. I'd strongly suggest checking the wiring.

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Re: Heated Bed slow heating wont go past 68 degrees

Post by AwesometroN » Tue Nov 22, 2016 7:51 pm

Update:

Checked the wiring, reflowed the connections just to be extra sure. Still getting 11.6-12v to the board, stopped using Matter Control, still getting a temp drop of about 12 degrees when the fans are on for multiple layers near the bed, however it's not as severe as before so it's not triggering a Heater Decoupling. For now it seems to be heating a little faster and is much more stable than it was prior to all the TLC I had to show it.

So thanks for the input.

Now onto the next fire, which is turning knobs one at a time in KISSlicer to output something that isn't a filament starved inconsistent disaster...

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Re: Heated Bed slow heating wont go past 68 degrees

Post by geneb » Tue Nov 22, 2016 10:03 pm

I'm wondering if you don't have a weak power supply. What do you read on the bed pads when you're heating it up to temperature?

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Re: Heated Bed slow heating wont go past 68 degrees

Post by AwesometroN » Wed Nov 23, 2016 4:42 pm

So I spent all day yesterday doing yet another minor tear down of the printer, cleaned up and re-flowed my pads again, flashed my EEPROM, and re-tested all of my wiring yesterday and all of my concurrent tests I'm getting a solid 12v and "improved" heating times. I even started doing tests on Matter Control again to rule out software and I'm no longer getting Heater Decoupled after the fans kick on for a few minutes.

It still takes a "while" (10-15mins) to preheat, but I'm no longer needing to cover it to get it up to/past 60. I'm still seeing a drop of 10-15 degrees when the fans kick on full for multiple layers close to the bed, but not as severely as it was before.

For the sake of trying to be more objective, I've also been working in a school lab with dozens of various types of printers, (they're really bad about buying "flavor of the month" instead of finding one good consistent model), this is my first Rostock which I've been building on my own outside of the lab so I might also be a little spoiled as to how long I expect a glass bed to heat up, considering some of them will hit 100C in less than 5 mins. So I could also just be comparing apple to oranges and refusing to accept it.

The ambient temp in the machine shop where I'm building this is also around 22-25C, so I'm guessing that's part of why it takes it so long to heat up first thing in the morning and why the fans might be cooling the bed off so much. Insulating the bed seems to be an almost imperative step though, as my bed easily retains it's temp now and after the first pre-heat only takes 5-10 mins tops to get back up to 60+.

I still haven't pushed it up to 100C though, so I still don't feel completely out of the woods.

TL:DR - I might have fixed it by reflowing my pads and insulating the bed, but I don't wanna jinx it.

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Re: Heated Bed slow heating wont go past 68 degrees

Post by erniedoors » Wed Dec 14, 2016 8:10 pm

Please tell us if you fixed it! I Just built mine and checked everything for errors, still can't get past 78ºC.
I read somewhere me might have defective beds (since the power supply is the stock one, not the old ATX) So it might be worth getting a replacement

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