Custom Heat Pad and thermistor question
-
@wingtip, I didn't say (I hope) that it would not work but rather that it makes no sense at all. Just keep it in mind if you run into odd problems down the road.
-
Let me approach this from a slightly different perspective just for argument's sake .... and I am not saying it won't work but just throwing ideas around.
So people spend money on special cast and machined aluminum print beds to get as flat an area as possible to print on. While average printed layer height may be 0.2 mm there are plenty occasion when I am printing 0.1 mm layers.
Cork is a natural product. Natural products such as wood are not known to be precision surfaces, they change based on humidity, temperature and the phase of the moon. Cork is also not produced in a precision thickness.
Your heat pad is not manufactured as a precision thickness part.
So you built a surface that is hopefully very level and flat and you add two layers of non precision parts to it. I am ignoring the fact that glass also has variations but you can't directly print on aluminum so some reduction in precision is unavoidable.
In your case you are introducing substantially more opportunity for error to the overall equation.
You could probably replace the aluminum build plate with a slab of wood and possibly get a good print when conditions are right but that doesn't make wood a good product for making a build surface out of. -
@jens55 I had a mirror but the guy cut it wrong so i am stuck with this glass that he says is just as accurate as the mirror being flat... and with auto mesh leveling it has to be better than my other printer which has no auto leveling at all...
-
@wingtip, yes, mirrors are made with standard glass so the two are functionally equivalent.
-
This is a thermal image of a Taz printer with a heater affixed directly to the glass bed.
Printing on that machine was very difficult due to the almost 30C variation in temperature across the bed (among other reasons).
This is a thermal image of the same heater mounted on a 1/4" cast aluminum bed that replaced the glass bed that broke (as glass will do under the right circumstances):
I think it clearly shows why you want to heat up the aluminum.
-
@mrehorstdmd .... wow!
-
@mrehorstdmd
What were you trying to print abs or something extreme like that? Im not... as i said, this method has worked on my other printer for years and is how ive made this one... The problem i usually have is the prints stick to well and i have trouble getting them to release.
Im not changing it all now after its been built as the alum bed is designed with the adjustment wheels in mind. mounting it directly to the alum sheet would require ordering another heat pad slightly smaller and restrict my building area even further after losing 20+ mm in x axis already due to binder clips.
It is what it is at this point and if there are issues then i will address it then. But the same setup has worked for me already for several years... -
The OP's aluminum is not a cast plate, but an extruded or rolled sheet which will not be flat enough to print on. That also means that if you were to put the thick glass on that aluminum, the glass will not heat evenly because of air gaps between the glass and the aluminum and the poor thermal conductivity of the air and glass. A thinner, more flexible piece of glass would be better in this case, at least for heat transfer, but then you have the problem of unflatness (which can be solved with flatness compensation and a sensor on the extruder carriage).
A closer to ideal situation is to put a piece of glass, probably not especially thick, on a piece of cast tooling plate with the heater attached to the bottom of the plate. The flat aluminum will contact the glass surface with fewer and thinner air gaps and do a better job of transferring the heat. This way you get flatness and good heat transfer.
Do you want to ride a bike with square wheels?
-
It's untraditional, but I think it will work. I guess I'm most worried there will be hot spots on the heater if it's not making great contact with the glass. It is 1500w afterall. Glass isn't a great heat conductor but the traces on the heater pad look pretty evenly spread out and close together. And that glass is thick as hell.
Don't forget to PID tune the bed heater.
-
@phaedrux
its 6061 t5 alum sheet that a machine shop drilled and milled to accept 4mm nuts in place. As for the airgaps its sandwiched with giant Fing binder clips to clamp it all together. Again this is the exact same method that is working on my other printer just fine. -
@wingtip hey I'm on your side! fire it up and show us!
-
@phaedrux Im getting there....
-
Looking here at the link suggested for setting up the bltouch, https://duet3d.dozuki.com/Wiki/Test_and_calibrate_the_Z_probe , it says on step 10
Open config-override.g and check that there are no G31 commands in it. If you find any, delete those lines and save the file.I do not have a config-override.g file. Should I?
- Board: Duet 2 WiFi (2WiFi)
Firmware: RepRapFirmware for Duet 2 WiFi/Ethernet 3.2.2 (2021-02-11)
Duet WiFi Server Version: 1.25
- Board: Duet 2 WiFi (2WiFi)
-
@wingtip said in Custom Heat Pad and thermistor question:
I do not have a config-override.g file. Should I?
It will get created after sending M500 to save any measured values. If it doesn't exist, don't worry about it. When you do the bed and nozzle heater tuning you'd usually send M500 to save those results. You'd also need to put M501 at the end of config.g to load that file again at startup.
https://duet3d.dozuki.com/Wiki/Gcode#Section_M500_Store_parameters
-
ok, i have the z offset set (not perfect till i try a print), and have the x,y offsets in. I have not done any pid tuning yet. should i wait to put the m501 into the config.g till i do the pid tuning?
and with the bl touch working now can i try some sort of mesh leveling to try to dial in the bed mechanical adjustments?? -
Yes if you've got the BLtouch working with G30 now you can do mesh leveling if you wanna see you the bed surface looks.
M557 controls the area to probe and the density of points.
You can add M501 now or wait until after you do the tuning. Up to you. BTW, be prepared to wait a while for the bed tuning to complete. It can take a long time with large beds. It'll be interesting to see how it deal with the unorthodox setup.
-
I think i am ready to try to heat up the bed.... Bare with me for all the dumb questions because 1) this is my first duet/reprap (coming from marlin), 2) My first AC powered bed with SSR..
I will post the config g below if someone can take a look at the heater section and make sure all looks good. If so i think the first command i want to enter to the console would be something like:- M303 T0 S100 ; where T0 is the bed and S80 is the cutoff or target temp??? Is this correct?
Configuration file for Duet WiFi (firmware version 3) ; executed by the firmware on start-up ; ; generated by RepRapFirmware Configuration Tool v3.2.3 on Wed Mar 03 2021 15:26:56 GMT-0600 (Central Standard Time) ; General preferences G90 ; send absolute coordinates... M83 ; ...but relative extruder moves M550 P"The Big One" ; 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 P0 S0 ; physical drive 0 goes reverse M569 P1 S0 ; physical drive 1 goes reverse M569 P2 S1 ; physical drive 2 goes forwards M569 P3 S0 ; physical drive 3 goes reverse M569 P4 S1 ; physical drive 4 goes forwards M569 P5 S0 ; physical drive 5 goes reverse M584 X0:3 Y1 Z2:5 E4 ; set drive mapping M350 X16 Y16 Z16 E16 I1 ; configure microstepping with interpolation M92 X395.52 Y80.00 Z400.00 E420.00 ; set steps per mm M566 X300.00 Y900.00 Z180.00 E120.00 ; set maximum instantaneous speed changes (mm/min) M203 X4000.00 Y4000.00 Z400.00 E1200.00 ; set maximum speeds (mm/min) M201 X400.00 Y500.00 Z20.00 E250.00 ; set accelerations (mm/s^2) M906 X1400 Y1000 Z1200 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 X655 Y440 Z400 S0 ; set axis maxima ; Endstops M574 X1 S1 P"!xstop+!e0stop" ; configure active-high endstop for low end on X via pin xstop M574 Y1 S1 P"!ystop" ; configure active-high endstop for low end on Y via pin ystop M574 Z1 S2 ; configure Z-probe endstop for low end on Z ; Z-Probe M950 S0 C"duex.pwm3" ; create servo pin 0 for BLTouch M558 P9 C"^zprobe.in" H5 F120 T6000 ; set Z probe type to bltouch and the dive height + speeds G31 P500 X0 Y-35 Z2.757 ; set Z probe trigger value, offset and trigger height M557 X15:215 Y15:195 S20 ; define mesh grid ; Heaters M308 S0 P"bedtemp" Y"thermistor" T100000 B3950 ; configure sensor 0 as thermistor 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 M143 H0 S120 ; set temperature limit for heater 0 to 120C M308 S1 P"e1temp" Y"thermistor" T100000 B4725 C7.06e-8 ; define E1 temperature sensor M950 H1 C"e1heat" 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 M143 H1 S280 ; set temperature limit for heater 1 to 280C ; 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 T0 -
M303 T0 S100 would tune the hotend heater on tool0 to 100c. T0 = tool0. This will also control the part cooling fan automatically to take it's cooling of the nozzle into account.
The bed would be M303 H0 S100. H0 = heater 0, which in your config is the bed.
But I think you should tune the hotend heater first so you can see what to expect. Just choose your normal printing temp.
-
@phaedrux said in Custom Heat Pad and thermistor question:
M303 H0 S100.
I dont have a part cooler yet for this so should i still try a tune on the hotend? Then try the bed?
M303 H1 S236 ; for the hotend
M303 H0 S80 ; for the bed, should i use a p variable for the pwm setting or does it just default to full 100% pwm?? -
Yeah if you don't have a part fan at the moment you can just use M303 H1.
PWM is 100% by default.
