Bed heater and temperature sensor



  • Hi,

    I am finishing up the build of a FolgerTech FT5 using all of the 713maker upgrade parts.

    I ordered the bed heater as suggested by 713 and it arrived today.

    It is self-adhesive and goes into a recess on the bottom of the 6mm thick solid aluminum bed provided by 713.

    The heater comes with a built in temp sensor.

    However I would think that sensing the temp of the heater itself would not track the temp of the aluminum bed. I would think the bed would lag behind the heater.

    So my question is this: Should I attempt to fit a temp sensor to the aluminum bed itself on the top side, away from the heater?

    Does the potential lag even matter?

    Thanks.

    Frederick



  • Monitoring the heater has the advantage of preventing it from overheating, even if it comes off the bed plate. If the bed is large and thermally conductive, as it sounds from your description, the difference in temperature between the heater and the plate will be pretty small. In the end you're going to test the temperature settings that work best for whatever printing surface you use and whatever filament you use, so it really doesn't matter if there's a little offset between the bed plate and the heater.



  • @mrehorstdmd said in Bed heater and temperature sensor:

    Monitoring the heater has the advantage of preventing it from overheating, even if it comes off the bed plate. If the bed is large and thermally conductive, as it sounds from your description, the difference in temperature between the heater and the plate will be pretty small. In the end you're going to test the temperature settings that work best for whatever printing surface you use and whatever filament you use, so it really doesn't matter if there's a little offset between the bed plate and the heater.

    Everything you said makes good sense.

    I think the only issue of any potential importance is when starting with a cold bed and being sure that the bed is up to temp before the printing begins.

    It shouldn't be too hard to determine how long it takes for the bed to reach the desired temp and stabilize from a "cold start".

    Thanks.

    Frederick



  • You can account for warmup time in your startup script. With an AC heater it typically doesn't take very long to get up to temp and aluminum conducts readily. In my case I set the first layer temp about 10c hotter than I use for the rest of the print. It heats the bed and then homes the printer then heats and primes the hotend. By the time the print starts the bed has been hot for a few minutes and a surface read of the bed shows about 5c cooler than the thermistor reports. Which is still hot enough.

    Once you know the offset between thermistor and the bed surface and you have tested by printing to determine the temp needed you could set a time delay in your script to wait that long before starting the print.



  • @phaedrux said in Bed heater and temperature sensor:

    You can account for warmup time in your startup script. With an AC heater it typically doesn't take very long to get up to temp and aluminum conducts readily. In my case I set the first layer temp about 10c hotter than I use for the rest of the print. It heats the bed and then homes the printer then heats and primes the hotend. By the time the print starts the bed has been hot for a few minutes and a surface read of the bed shows about 5c cooler than the thermistor reports. Which is still hot enough.

    Once you know the offset between thermistor and the bed surface and you have tested by printing to determine the temp needed you could set a time delay in your script to wait that long before starting the print.

    Thanks for the information.

    I have a cctree build surface on top of glass on top of the aluminum. It does eventually heat up nicely but it takes several minutes.

    Perhaps now with a heated bed I don't need the cctree build surface.

    The manufacture of the aluminum bed said to NOT print on it directly.

    Still I can surly compensate for any time delay or temp difference.

    I've done three test prints and they have all been fine - no warping as I experienced before the heated bed.

    They are hard to remove until the bed has cooled down so perhaps a bit too much adhesion.

    Thanks.

    Frederick



  • I should have mentioned I use sheet of PEI laminated to aluminum tooling plate. So the heat transfer is pretty good compared to having an extra sheet of glass in between.



  • @phaedrux said in Bed heater and temperature sensor:

    I should have mentioned I use sheet of PEI laminated to aluminum tooling plate. So the heat transfer is pretty good compared to having an extra sheet of glass in between.

    Well I googled PEI and got back "Prince Edward Island" - so I don't think that is what you meant.

    Do you have a link?

    Frederick



  • @fcwilt No, sorry, as lovely as Prince Edward Island is this time of year, I was referring to the material Polyetherimide, also known as Ultem. It's a very common print surface nowadays due to it's ready adherence to other molten plastics when it is heated and for its ability to release the bond again when cooled.

    https://reprap.org/wiki/PEI_build_surface



  • @phaedrux said in Bed heater and temperature sensor:

    @fcwilt No, sorry, as lovely as Prince Edward Island is this time of year, I was referring to the material Polyetherimide, also known as Ultem. It's a very common print surface nowadays due to it's ready adherence to other molten plastics when it is heated and for its ability to release the bond again when cooled.

    https://reprap.org/wiki/PEI_build_surface

    Thanks for the feedback.

    Just to see how it compares with what I am using I have ordered three sheets for my printer.

    Time will tell.

    Frederick



  • @fcwilt said in Bed heater and temperature sensor:

    cctree build surface

    The CCTREE build surface appears to be polycarbonate, which should function comparably.



  • @fcwilt said in Bed heater and temperature sensor:

    @phaedrux said in Bed heater and temperature sensor:

    @fcwilt No, sorry, as lovely as Prince Edward Island is this time of year, I was referring to the material Polyetherimide, also known as Ultem. It's a very common print surface nowadays due to it's ready adherence to other molten plastics when it is heated and for its ability to release the bond again when cooled.

    https://reprap.org/wiki/PEI_build_surface

    Thanks for the feedback.

    Just to see how it compares with what I am using I have ordered three sheets for my printer.

    Time will tell.

    Frederick

    I have a printer at the makerspace with a 0.7 mm thick piece of PEI on the bed. It has been in use for 3+ years and no one has managed to destroy it, and believe me, if there were a way to destroy it, they would have found it by now. About 2 years ago one person used the wire brush for cleaning the nozzle to "clean" the bed. I marked all 4 sides of the brush handle "for cleaning nozzle only" and it hasn't happened again.

    Tape is too thin and will tear. The 0.7 mm thick stuff I used costs about $20 on amazon.


 

Looks like your connection to Duet3D was lost, please wait while we try to reconnect.