heat bed problems

Hello,

I am just building my first custom sourced printer and am having trouble with my mk3 alu dual heatbed. It takes forever to heat up past 90C and then plateaus at 102C. I need 110C for abs. I am using an led power supply 12V 29A that's adjusted to 12.85V but drops to 12V under load. My heatbed resistance is 1.2 Ohm but the terminals on my heatbed only draw 10.5V when heating up. There is no glass on my bed, just kapton tape since it's aluminum and i'm using an inductive sensor. Could anyone kindly help me resolve this issue ?

Thanks,

I've seen a lot of people complaining they can't get past 90C with the aluminum heatbeds without insulating the bottom of the bed with cork or some other heat insulator. But that is just what I've seen as I don't have an aluminum heatbed.

Edited 1 time(s). Last edit at 06/07/2016 02:09PM by PDBeal.

Measure the voltage at the PSU terminals which you say is 12V under load, the voltage on the electronics power input connector, the voltage at the bed heater output terminals of the electronics, and the voltage on the bed terminals which you say is 10.5V. From those measurements, work out where that 1.5V is being lost and take steps to reduce it. Also, add thermal insulation under the bed.

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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].

This is silly, but output terminals would be D8 right ?

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blahhh10
This is silly, but output terminals would be D8 right ?

I think that is correct if you are using RAMPS.

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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
Measure the voltage at the PSU terminals which you say is 12V under load, the voltage on the electronics power input connector, the voltage at the bed heater output terminals of the electronics, and the voltage on the bed terminals which you say is 10.5V. From those measurements, work out where that 1.5V is being lost and take steps to reduce it. Also, add thermal insulation under the bed.

Thanks!
You've saved me days of menu-chasing for hotbed settings, on my knock-off model anet.

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blahhh10
I am just building my first custom sourced printer and am having trouble with my mk3 alu dual heatbed. It takes forever to heat up past 90C and then plateaus at 102C. I need 110C for abs.

Unless you print inside a warm enclosure you won't be able to do much with ABS anyway. If the bed isn't warm enough (105C), prints won't stick, and if the enclosure isn't warm enough (45-50C), prints will delaminate. You need both to print ABS reliably (and of course, a flat, level bed with the right covering).

Unless you spring for a silicone or kapton heater you'll probably continue to have problems heating up to ABS print temperatures. About 0.4 W/cm^2 areal power density (or more) seems to do the job in a reasonable amount of time.

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

I print ABS at 65c on BuildTak with a simple box enclosure around my printer

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My updated Instructable on our Prusa i3 Build
[www.instructables.com]

I said you can't reliably print ABS without a warm enclosure. You might get away with small stuff, but try something a bit larger and see what happens.

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

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the_digital_dentist

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blahhh10
I am just building my first custom sourced printer and am having trouble with my mk3 alu dual heatbed. It takes forever to heat up past 90C and then plateaus at 102C. I need 110C for abs.

Unless you print inside a warm enclosure you won't be able to do much with ABS anyway. If the bed isn't warm enough (105C), prints won't stick, and if the enclosure isn't warm enough (45-50C), prints will delaminate. You need both to print ABS reliably (and of course, a flat, level bed with the right covering).

Unless you spring for a silicone or kapton heater you'll probably continue to have problems heating up to ABS print temperatures. About 0.4 W/cm^2 areal power density (or more) seems to do the job in a reasonable amount of time.

I read some great things about rubber pipe insulation tape. I will also be adding abs juice for sticking. Do you recommend cranking the input voltage up to 13.5V at rest since I have read that this may fry the voltage regulator of the arudino?

Rubber pipe insulation tape may not hold up well at 105C. That stuff is usually used for hot water pipes, but they don't normally get anywhere near 105C. The adhesive and the rubber may start to break down- check the specs before applying it to your printer.

You are right to be careful about increasing voltage to the Arduino board. You might consider using a separate power supply for the bed heater. It doesn't have to be regulated, or even DC (if you also add an SSR), so you can just use a transformer.

Insulation on the underside is OK, but if you have to add it to get up to print temperature, I think the heater is under powered. I prefer the brute force approach to bed heating. Use plenty of power (0.4 W/cm^2 or more) and the bed will heat quickly and the PID system will be able to regulate the temperature easily. You have to be set up to deliver the power input to the heater- adequate power supply and adequate MOSFET or SSR to switch it, and adequate cabling.

My printer's bed is 317 x 305 x 6.35 mm cast aluminum, has a 450W (about 0.5 W/cm^2) heater attached, 5 mil kapton print surface (no glass!), and no insulation on the underside of the bed. It gets to 105C in about 5 minutes (depending on the ambient temperature). My heater uses 24V and I power it with a big transformer, but if I were building another printer (currently designing one), I'd use a line powered heater. I use an SSR driven by the controller's MOSFET to switch power to the bed heater.

I don't use ABS juice - just print on clean (wiped with acetone at room temp before printing) Kapton. If the bed is flat and evenly heated, that's all you should need.

Edited 1 time(s). Last edit at 06/11/2016 11:39AM by the_digital_dentist.

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

I think I'm going to go with the heater mat you suggested. I found one at 0.7W/cm^2 but it is just 150mm x 150mm. My aluminium printbed is about 210*210mm. Do you think the 150mm one should be big enough or should I go with one that is 200 x 200 mm heater mat ?

Also am really confused with all the relay information. I plan on ordering a 12V silicon heated bed (since I have 1 12V power supply for everything) and sticking it to aluminium sheet. I want to control it with my ramps board. What do you guys suggest is the best wiring method for this ?

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blahhh10
I think I'm going to go with the heater mat you suggested. I found one at 0.7W/cm^2 but it is just 150mm x 150mm. My aluminium printbed is about 210*210mm. Do you think the 150mm one should be big enough or should I go with one that is 200 x 200 mm heater mat ?

The heater should be about the same size as the bed plate, otherwise the temperature drop toward the edges will limit you to printing only in the area directly above the heater- your 210 x 210 bed will effectively become a 150 x 150 bed. That's OK if you don't mind it, but if you're expecting to use the whole bed you'll be sorry.

Select the bed heater that delivers the necessary heat first, then start selecting parts to switch power to it. Using a line operated heater can simplify things in terms of power supply and relay, but you have to be careful to wire it safely.

Low voltage heater:
AC operation- use a transformer and DC-AC SSR (no heatsink required). Controller board drives SSR, SSR switches power from transformer to heater.

DC operation: connect to printer power supply (if sufficient rated current) or separate DC supply. Use MOSFET on controller to switch power to bed if the MOSFET and PCB can handle the current, or use DC-DC SSR possibly mounted on a heatsink, depending on the SSR. Regulated power is not necessary for bed heater- a DIY power supply can consist of a transformer and bridge rectifier, but its easier/cheaper to just power the bed from the transformer.

Line voltage heater:
Use DC-AC SSR with no heatsink to switch AC line power to the heater. Ground printer frame, wire bed heater carefully to prevent possible shock hazard.

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

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the_digital_dentist

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blahhh10
I think I'm going to go with the heater mat you suggested. I found one at 0.7W/cm^2 but it is just 150mm x 150mm. My aluminium printbed is about 210*210mm. Do you think the 150mm one should be big enough or should I go with one that is 200 x 200 mm heater mat ?

The heater should be about the same size as the bed plate, otherwise the temperature drop toward the edges will limit you to printing only in the area directly above the heater- your 210 x 210 bed will effectively become a 150 x 150 bed. That's OK if you don't mind it, but if you're expecting to use the whole bed you'll be sorry.

Select the bed heater that delivers the necessary heat first, then start selecting parts to switch power to it. Using a line operated heater can simplify things in terms of power supply and relay, but you have to be careful to wire it safely.

Low voltage heater:
AC operation- use a transformer and DC-AC SSR (no heatsink required). Controller board drives SSR, SSR switches power from transformer to heater.

DC operation: connect to printer power supply (if sufficient rated current) or separate DC supply. Use MOSFET on controller to switch power to bed if the MOSFET and PCB can handle the current, or use DC-DC SSR possibly mounted on a heatsink, depending on the SSR. Regulated power is not necessary for bed heater- a DIY power supply can consist of a transformer and bridge rectifier, but its easier/cheaper to just power the bed from the transformer.

Line voltage heater:
Use DC-AC SSR with no heatsink to switch AC line power to the heater. Ground printer frame, wire bed heater carefully to prevent possible shock hazard.

Yeah I was thinking of ordering a 200 x 200mm heater on 12V. It would be 240 W or 0.6W/cm^2 which = 20 Amps. For this I wanted to buy a second 12V, 29A led power supply and use a SSR to connect the ramps d8 terminals and the heater together while plugging the 2nd power supply into my 11A power terminals on ramps. Would this work?

It should work, but you may need a heatsink on the SSR depending on its internals. You'll need some pretty heavy cable to connect to the bed heater. Since you're using a separate supply, using 24V instead of 12 would reduce the required current and allow smaller, more manageable cable to be used.

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

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the_digital_dentist
It should work, but you may need a heatsink on the SSR depending on its internals. You'll need some pretty heavy cable to connect to the bed heater. Since you're using a separate supply, using 24V instead of 12 would reduce the required current and allow smaller, more manageable cable to be used.

If I bought the 24V 29A power supply, I would obviously need a 24 V heater but what else would need to change from 12V ? Could the ramps 11A power port accept cables from a 24V power supply ?

Also, the cables with the heater mat would come supplied so I wouldn't change them to fatter ones. Here is the link.[www.aliexpress.com] Could you kindly let me know if you think it or 24V version with same specifications would be a good purchase for my p3steel ?

Edited 2 time(s). Last edit at 06/11/2016 06:36PM by blahhh10.

Also forgot to add, would this ssr with a heatsink do the trick ? [www.ebay.com]

Edited 1 time(s). Last edit at 06/11/2016 05:54PM by blahhh10.

I wouldn't trust RAMPS or Arduino boards to handle 24V without checking each and every component first.

The relay looks OK for switching 24V to that heater. The leads are probably a little thin, but you can try it and see how it goes. If you lose a little power to heating the leads you still have plenty of power for the bed, so it will probably be OK.

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

About that bed... Are you going to be using tooling plate or a thin piece of aluminum with a glass plate, or something else? I recommend 1/4" cast tooling plate. It is rigid and flat enough to print on with just a layer of kapton tape- no glass needed. Thin plates are extruded and never flat, and will bend, especially if you have a 4 point leveling system.

Do you have a 3 point or 4 point leveling system? I recommend 3 points- 4 point systems bend the bed plate and undercarriage. 3 points actually level the plate (assuming you have a flat bed plate).

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

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the_digital_dentist
About that bed... Are you going to be using tooling plate or a thin piece of aluminum with a glass plate, or something else? I recommend 1/4" cast tooling plate. It is rigid and flat enough to print on with just a layer of kapton tape- no glass needed. Thin plates are extruded and never flat, and will bend, especially if you have a 4 point leveling system.

Do you have a 3 point or 4 point leveling system? I recommend 3 points- 4 point systems bend the bed plate and undercarriage. 3 points actually level the plate (assuming you have a flat bed plate).

I will be using a thick 3mm aluminum plate covered with kapton tape above the heater. I have the ability to use either system, I will use 3 point though. Either way I have an inductive sensor to bed leveling is the least of my problems for now.

If I bought a 24V, 30A led power supply, 24V 200x200mm 240W heater and the relay I linked above, would I just have to plug the power supply and bed into the in's and out's of the relay and the relay connectors to d8 of my ramps board and I should be good to go? If not, could you help provide some clarity and maybe a wiring scheme before I make any purchase ?

Before you glue the heater to it, check the flatness of the bed plate. Set the edge of a steel ruler against it and see if there are any gaps. 3 mm sheet isn't usually very flat, but since the bed is relatively small you may be OK.

24V 30A is over 600W, more than enough to run the 240W heater. Use the diagram provided by the relay seller and you should be good to go.

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

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the_digital_dentist
Before you glue the heater to it, check the flatness of the bed plate. Set the edge of a steel ruler against it and see if there are any gaps. 3 mm sheet isn't usually very flat, but since the bed is relatively small you may be OK.

24V 30A is over 600W, more than enough to run the 240W heater. Use the diagram provided by the relay seller and you should be good to go.

If I went with 12V 30A psu and 12V 240W bed, would this relay work perfectly?[www.makerfarm.com] I apologize for making you repeat yourself but am really confused with relays

There are two ways to regulate bed temperature. bang-bang is like using a thermostat- you set the desired temperature and the heater turns on until that temperature is exceeded, then it turns off until the temperature has fallen below the set temperature at which point the heater turns back on. The temperature fluctuates around the set temperature by whatever hysteresis is in the system. Bed temperature variations can show up as Z axis artifacts in prints.

The other way to regulate temperature is to use the same method that the hot-end uses- PID control. PID regulates the temperature and keeps it very stable at or near the set temperature. PID is preferable to bang-bang because it minimizes temperature variation, which helps prevent Z artifacts in prints.

That's a mechanical relay that will click each time it is activated. That's OK for bang-bang temperature control, but if you try to use it under PID temperature control, the clicking will drive you nutz (it will be clicking several times per second). Mechanical relays have limited number of operations before the contacts fail. PID would probably kill the relay pretty quickly.

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

nvm

Edited 2 time(s). Last edit at 06/12/2016 01:46PM by blahhh10.

Firstly, I apologize for making you repeat yourself but this will be the final confirmation bunch of questions

If I go with 24V 30A psu [www.ebay.ca] and 24 V silicon bed and the power expander I linked above from reprap.me, (this might be silly) but would I have to attach anything in the 11Amps terminal of my ramps board since it can't handle 24V? Also would this power expander allow me to use PID instead of only BANG BANG

Also just got it. If I used a 24V power supply and heater I would need an SSR to control the voltage to the ramps to 12V but the current would be fine. If I used 12V power supply and heater, I would need an SSR to control the current but the voltage to the board would be fine. Either way I assume the wiring to the ssr between, the bed, board and psu would be the same, is this correct ?

Thanks again for everything

Edited 8 time(s). Last edit at 06/12/2016 10:53PM by blahhh10.