Bed heater tuning questions

Tpmoses

@Phaedrux
The printer was built by the previous person that held my job. Its used to make Positives for fiberglass molding. He never got it really working, Ive gotten good prints off it but its a constant clean up of shoddy work, pretty much rewired the entire thing as best I can with what I have access to.

Firmware was updated to the 3.2 on 1-5-21
Here is config.g

; Configuration file for Duet WiFi (firmware version 3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.2.2 on Fri Jan 22 2021 11:13:01 GMT-0600 (Central Standard Time)

; General preferences
G90                                                ; send absolute coordinates...
M83                                                ; ...but relative extruder moves
M550 P"Caymas 3D Printer"                          ; set printer name

; Network
M552 S1                                            ; enable network
M586 P0 S1                                         ; enable HTTP
M586 P1 S0                                         ; disable FTP
M586 P2 S0                                         ; disable Telnet

; Drives
M569 P8 R1 T2.5:2.5:5:5 S0                         ; physical drive 8 goes forwards
M569 P6 R1 T2.5:2.5:5:5 S1                         ; physical drive 6 goes forwards
M569 P2 S0                                         ; physical drive 2 goes forwards
M569 P5 R1 T2.5:2.5:5:5 S0                         ; physical drive 5 goes forwards
M569 P3 S0 										   ; physical drive 3 goes forwards 
M584 X6 Y8 Z2:3 E5                                 ; set drive mapping
M671 X-10.0:1200.0 Y450.5:450.5	S3				   ; Set z motor relative locations 
M350 X16 Y16 Z16 E16 I1                            ; configure microstepping with interpolation
M92 X320 Y320 Z640 E80                    ; set steps per mm
M566 X200.00 Y200.00 Z12.00 E120.00                ; set maximum instantaneous speed changes (mm/min)
M203 X3000.00 Y3000.00 Z340.00 E4000.00            ; set maximum speeds (mm/min)
M201 X200.00 Y200.00 Z20.00 E250.00                ; set accelerations (mm/s^2)
M906 X2000 Y2000 Z2800 E800 I30                    ; set motor currents (mA) and motor idle factor in per cent
M84 S30                                            ; Set idle timeout

; Axis Limits
M208 X0 Y0 Z0 S1                                   ; set axis minima
M208 X1170 Y1100 Z1100 S0                          ; set axis maxima

; Endstops
M574 X1 S1 P"!xstop"                                ; configure active-low endstop for low end on X via pin xstop
M574 Y1 S1 P"!ystop"                                ; configure active-low endstop for low end on Y via pin ystop
M574 Z1 S2                                         ; configure Z-probe endstop for low end on Z

; Z-Probe
M558 P1 C"zprobe.in+zprobe.mod" H5 F240 T3600      ; set Z probe type to unmodulated and the dive height + speeds
G31 P500 X0 Y-69.85 Z1.55 	                    ; set Z probe trigger value, offset and trigger height
M557 X100:1170 Y100:1100 S100                      ; define mesh grid

; Heaters
M308 S0 P"spi.cs2" Y"thermocouple-max31856"        ; configure sensor 0 as thermocouple on pin bedtemp
M950 H0 C"bedheat" T0                              ; create bed heater output on bedheat and map it to sensor 0
M307 H0 B0 S1.00    							   ; disable bang-bang mode for the bed heater and set PWM limit
M140 H0                                            ; map heated bed to heater 0
M303 H0 S60											;Tune for 60C
M307 H0 R0.168 C358.6 D7.17 S1.00 V24.2
M143 H0 S120                                       ; set temperature limit for heater 0 to 120C
M308 S1 P"spi.cs1" Y"thermocouple-max31856"        ; configure sensor 1 as thermistor on pin e0temp
M950 H1 C"e0heat" T1                               ; create nozzle heater output on e0heat and map it to sensor 1
M307 H1 B0 S1.00                                   ; disable bang-bang mode for heater  and set PWM limit
M303 H1 S200										;Tune for 200c
M307 H1 R2.211 C192.4 D8.94 S1.00 V24.2
M143 H1 S320                                       ; set temperature limit for heater 1 to 320C
M500

; Fans
M950 F0 C"fan0" Q500                               ; create fan 0 on pin fan0 and set its frequency
M106 P0 S0 H-1                                     ; set fan 0 value. Thermostatic control is turned off
M950 F1 C"fan1" Q500                               ; create fan 1 on pin fan1 and set its frequency
M106 P1 S1 H1 T45                                  ; set fan 1 value. Thermostatic control is turned on

; Tools
M563 P0 D0 H1 F0                                   ; define tool 0
G10 P0 X0 Y0 Z0                                    ; set tool 0 axis offsets
G10 P0 R0 S0                                       ; set initial tool 0 active and standby temperatures to 0C

; Custom settings are not defined

; Miscellaneous
M575 P1 S1 B57600                                  ; enable support for PanelDue
M911 S10 R11 P"M913 X0 Y0 G91 M83 G1 Z3 E-5 F1000" ; set voltage thresholds and actions to run on power loss

M501

M303 H0 S100
Auto tuning heater 0 using target temperature 100.0°C and PWM 1.00 - do not leave printer unattended

Then

Auto tune cancelled because target temperature was not reached

The tuning cancelled itself after 25 minutes of trying. Lately it takes about an hour to get up to heat. I did S100 because everything I print on this machine is ABS and needs 110C generally.

Phaedrux

Try tuning again, but try a more conservative temp to start with. Try 50c. Or whatever temp it can get up to within 20 minutes or so.

How well insulated is the bed and heater?

What wattage is the heating pad?

How thick is the plate?

Tpmoses

@Phaedrux

The bed is a 1/4" aluminum base plate with 1/2" of cork, then the silicone mat then the print surface another 1/4" aluminum plate on top. Not how I would have made it, but its what I got.

I'm not sure the wattage of the pad, it was apparently custom made in china. Similar ones online are around 750W

Tpmoses

@Phaedrux I will attempt to tune it again in the morning, its not going to cool by the time we close today. I will update when I run the tuning.

Phaedrux

Yeah that's a big plate.

Another option might be to add a thermistor embedded in the plate itself that way it has a better idea of the heating and cooling speed. The problem with such large heat sinks and powerful heaters is that the thermistor is on the pad itself, so it gets hot fast, but then then cools down as the plate takes the heat, and then once the plate is hot, it takes a long time to cool down.

Tpmoses

@Phaedrux This was the result of the calibration this morning, I'm going to attempt to start a print and see if I am having the same temp drop issue.

; Heater model parameters
M307 H0 R0.181 C263.693:263.693 D7.71 S1.00 V24.1 B0
M307 H1 R2.211 C192.400:192.400 D8.94 S1.00 V24.2 B0

H0 is the bed

Tpmoses

@Phaedrux After calibration to 60C, I attempted to warm up to 110C and it is stopped and hovering at around 79.3C, I tried to adjust it like the tutorial saidby reducing the Gain value, but no change. any Ideas?

Phaedrux

I think the heater may be a bit underpowered for that size of bed.

How much did you reduce gain by? What values were used?

Tpmoses

@Phaedrux The gain is at .168, the dead time I lowered to 1.5. about to run a print to see if it will hold temp.

MikeS

750W heater are commonly used on Voron with bed size of 350x350. I think 1100x1100 is too much for this poor heater...too much surface that exchange heat with cool air. If you print abs then an enclosed chamber is a must, more with that size of print area. Probably you need 3 or 4 of this 750W heater to reach 110°C in a reasonable time and mantain it during printing.

hamel

I agree that you are underpowered. I use a 1600W heater for my 450mmx450mmx8mm Al plate with insulation and thermal breaks.

I would check to make sure that you are getting the power you expect. Make sure you are running the correct voltage for the heater as well.

Tpmoses

@MikeS The Bed was holding heat fine until we had a power surge in the building, had to replace the wire to the bed. The entire printer is in a popup canopy with walls to act as the enclosure, but for example, it reached 110C, has been printing for about 14 minutes now and is already dropped to 100C

Tpmoses

@hamel 750W was a guess, I didn't build this printer the person who built it has left the company and didn't leave any specs. after more research there are similar ones on alibaba that are around 2000W but they run on 220V. I'm working on finding the receipts to find out what it is.

Phaedrux

@Tpmoses said in Bed heater tuning questions:

I'm working on finding the receipts to find out what it is.

That would be the best bet. The wattage could be pretty much anything and you can't tell by looking at it.

If you're familiar with Ohms law you could measure the resistance of the heater and then figure out the current and wattage.

Can you post some photos of the bed and heater so we can get an idea of what you're dealing with? Also the SSR and wiring.

You might be able to use bang bang instead of PID tuning it, but you might still run into the problem of it not heating fast enough and causing a heater error.

Adding a thermistor to the bed plate itself might be the easiest thing to do since it will give the PID algorithm some better data to tune with.

Tpmoses

@Phaedrux I will as soon as I can, Bed is to hot to take it apart. Wiring wise there is not much to show, As it stands, Power comes from the wall. Ground goes to common. Neutral runs through the SSD Hot wire is connected to the bed through a DIN Block, So the only things between 120V power and the heater is the SSD and one DIN block. The Guy who built it had both the bed heater and the extruder heater as well as some powers supplies for the board and Z driver all on one 120V in. We had a power surge that toasted a length of wire to the bed, I had to rewired it also adding a ground to the bed. (kept getting shocked) I then moved bed power to the 120V in that ran the X and Y power supplies. Printed fine.

The bed started to have issues holding temp on Monday, Seemed that it was not getting enough source power, so I ran a separate 120V drop and put it in its current config.

There is an integrated thermistor in the heat mat itself.
I've never used Bang Bang mode before, I'm not as worried about the slow warm up as I am the temp starts dropping the second the printer does anything but sit still.

Phaedrux

@Tpmoses said in Bed heater tuning questions:

We had a power surge that toasted a length of wire to the bed,

Might be time to inspect the heater pad itself if possible.

Tpmoses

@Phaedrux I cut the wire to have a pigtail and tested it with my meter, still has continuity. The length of Wire that I cut out had no continuity on the live wire. but still had it on the neutral, When I replaced the wire I also added a ground to the bed that connects to common.

Tpmoses

@Phaedrux I have talked to my boss, he is open to me replacing the mat, and my best guess at doing that and avoiding future heartache is to replace it with 4 say 500x500mm ones. any suggestions? I'll know if I go that route I need to get 3 more SSRs but I'm not sure what type of heaters I should get that wont make my boss mad at me for spending too much money.

Tpmoses

I am also not sure how I would integrate that into the duet 2 wifi board

Phaedrux

Well the only thing that makes bosses more mad than spending money is spending good money after bad money. Buy once cry once.

Having 4 smaller zones might be beneficial if you aren't always printing full volume parts. Only heating a sector might be faster and cheaper to run. But remember you're still attached to the other sections of the bed and they will draw a lot of heat away.

There's also the added complexity. Controller 4 heaters for the bed on the Duet you'll need enough ports and still need to figure out how to tune it for all heater function.

https://duet3d.dozuki.com/Wiki/Choosing_a_bed_heater
https://duet3d.dozuki.com/Wiki/Spurious_heater_faults_and_how_to_avoid_them
https://duet3d.dozuki.com/Wiki/Tuning_the_heater_temperature_control

https://keenovo.store/

That's where I would buy my heater pads from. They will do custom options too.