Bonded Heat bed for 12"

[Chadd]

Just curious if anyone would be interested in a 300mm x 300mm heat bed that is bonded to 3.2mm aluminum sheet?

Thinking of ordering one for myself and with shipping it may be worth ordering 5 at a time. That would leave me with 4 extras, these are 12/24v. The price would be ~$86 each plus shipping from me to you once they arrive.

I am looking at this to help with my Z banding issue. I have narrowed most of the problem down to the heat bed and print surface "glass" warping up and down as the heat is turned on and off. I replaced my Y axis plate with aluminum and that helped quite a bit with with Z homing issues but I still have some banding while printing with the heated bed on.

[BLKKROW]

Wouldn't the aluminum act as a heatsink and pull heat away from the heat bed?

[tsteever]

I too am getting some z banding and haven't been able to fix it. I was thinking of getting a more powerful sower supply or replacing the z rods with 6mm lead screws. I will be watching this thread to see what the best route would be to combat this issue.

[Chadd]

Wouldn't the aluminum act as a heatsink and pull heat away from the heat bed?

Most people print directly to the AL plate so you want the AL to transfer the heat from the element efficiently.

https://www.youtube.com/watch?v=UBneHZyadBQ

[Chadd]

I too am getting some z banding and haven't been able to fix it. I was thinking of getting a more powerful sower supply or replacing the z rods with 6mm lead screws. I will be watching this thread to see what the best route would be to combat this issue.

Well here is my plan of attack for the Z banding.

1. Replace plastic tube Z axis couplers with metal ones.

2. Replace the threaded rod as mine have wobbled since new.

3. Change from a mechanical relay to a SS relay so I can setup PID on the heated bed to hopefully get rid of the up/down movement of the build plate while the heat comes on and off.

4. If none of the above work I will change to Bowden extruder to take the filament pulling up the X carriage out of the equation and replace the heat bed with a bonded aluminum heat bed.

5. If none of those work I will take the electronics and extrusions off the printer and throw away the piece of crap wooden frame and start from scratch.

[pichuete]

well i have done Steps 1 and 2 with no significant improvement . im pretty sure that in my case the heated bed is causing my banding . my layer offsets are not in a particular pattern . .as we usually see when Z banding is caused by threaded rods wobble .

Im curious about the SS relay but i dont know how this work . for what i understand the rambo board (what i have on my printer) is capable of doing PWM on the HB . but im not sure if it can handle the current .

Also im planing to convert my I3v 12" to all metal similar to the new model that colin have on makerfarm (Pegasus) maybe if more users are interested in this solution we can work together to come with a good design.

[lakester]

idle speculation...

(FWIW..., the one mod I was contemplating was the addition of the bearing/guide for the top end of the z-rods..., haven't tried it yet)

..., back to speculation...

I wonder if a firmware mod might be worth a shot, specifcally, one that tweaks the "hysteresis" assumptions regarding bed heating.

My intuition doubts that the periodicity of heating cycles substantially change the overall expansion/contraction of the glass or overall structure in a fashion that would correlate with the z-banding issue. The heating system is more or less responding to the behaviour of the portion of the system with the least thermal mass, i.e., the heating pad itself. Is it really plausible that the overall structure responds significantly with the same periodicity?

I'm guessing that heat cycling correlates poorly with what is essentially a geometric effect in the form of z-banding.

Just the same..., maybe it would be worth reducing the hysteresis built into the heating algorithms and see if it changes anything wrt z-banding.

Again..., my feeling is that there is a geometric problem at work here, independent of heating..., but maybe if the heat cycling were tweaked..., it would help settle the issue once and for all.

0.02USD

(additional thought: heck..., for the sake of experiment, what if we disabled heating altogether, and did a z-banding test print with PLA on blue tape?)

[Chadd]

I tried the bearing/guide on the top of the Z rods and it made the problem much worse.

These two videos show the difference between ON/OFF heat bed vs PID.

ON/OFF

https://www.youtube.com/watch?v=0T5BE5XC2-8

PID

https://www.youtube.com/watch?v=RRSI2TJ3Trs

Those aren't my videos but some I came across. You have to figure with a 12" bed it would be even worse.

idle speculation...

(FWIW..., the one mod I was contemplating was the addition of the bearing/guide for the top end of the z-rods..., haven't tried it yet)

..., back to speculation...

I wonder if a firmware mod might be worth a shot, specifcally, one that tweaks the "hysteresis" assumptions regarding bed heating.

My intuition doubts that the periodicity of heating cycles substantially change the overall expansion/contraction of the glass or overall structure in a fashion that would correlate with the z-banding issue. The heating system is more or less responding to the behaviour of the portion of the system with the least thermal mass, i.e., the heating pad itself. Is it really plausible that the overall structure responds significantly with the same periodicity?

I'm guessing that heat cycling correlates poorly with what is essentially a geometric effect in the form of z-banding.

Just the same..., maybe it would be worth reducing the hysteresis built into the heating algorithms and see if it changes anything wrt z-banding.

Again..., my feeling is that there is a geometric problem at work here, independent of heating..., but maybe if the heat cycling were tweaked..., it would help settle the issue once and for all.

0.02USD

(additional thought: heck..., for the sake of experiment, what if we disabled heating altogether, and did a z-banding test print with PLA on blue tape?)

[lakester]

Cool demo of the problem (thx!).

2 questions:

1. What does "PID" refer to? (Sorry..., been puzzling on that...)
2. What is the table structure of the Mendel90 in the vids? What are its similarities to the MakerFarm wood+glass table?

I tried the bearing/guide on the top of the Z rods and it made the problem much worse.

These two videos show the difference between ON/OFF heat bed vs PID.

ON/OFF

https://www.youtube.com/watch?v=0T5BE5XC2-8

PID

https://www.youtube.com/watch?v=RRSI2TJ3Trs

Those aren't my videos but some I came across. You have to figure with a 12" bed it would be even worse.

[super fly]

PID=Proportional Intregal Derivative
It's a feedback controller based on current change, future change, and past change. Each term is weighted to come up with an output (this is where PID tuning comes into play). I use one to controller my smoker temperature.

Also, here is a pretty lengthy write up on z banding. To be honest I haven't completely read through yet as I don't have my printer yet. I saved the link just in case I needed it later.
https://www.evernote.com/shard/s211/...c268dcdd2d687e