Hey there!

i opinion is I need a 3D printer to find out but I would like to flash my bang is better than yours just look at it

On my Ender 3 Pro I left the Bang Bang when I switched to the Btt skr e3 mini 1.2. I have no issues with it. The temperature is only fluctuating by a couple of centidegrees. I guess it will not improve that much changing to PID.

I plug my bed to a lab power supply. I made a Voltage/Temperature calibration curve. That's it: constant current and constant temperature; no noise, no fluctuations whatsoever.

@@urano1988 do you manually set the bed temp or did u put the curve into firmware? how does that work

For large 4-point constrained PCB beds it can be really dramatic. With the PCB bed from my BLV cube kit, you could see it moving by eye if you parked the nozzle over the middle.

I'll have to do that!

@@CNCKitchen And it would be super to compensate this in firmware during print with automatic z-baby stepping :D Like mesh bed leveling, but temperature mesh compensation.

@@JanVokas That would be really neat, but you would only be able to compensate for the bed lifting/dropping. If your bed were warping during the heat cycling, you could compensate for the first couple layers, but after that, the part geometry will result in unpredictable part movement.

@@Kineth1 You are correct, but what if the mesh compensations were applied to the X, Y and Z? This might be harder to predict, however! Perhaps, piezoelectric sensors could be placed under the print bed to monitor any bed deflections and compensate in real time!

I might have a closer look at that though I don't think that the steppers are a problem due to their discrete steps, though who knows what happens to the microsteps?

@CHEP I think you might be on to something there. I had a problem in my printer with the Z-axis not moving enough upon layer change. The firmware would indicate the correct height but the actual height was about 20-25% lower. This only happened to me when I would print ABS with the bed at 105C so drawing a lot of current. When I would print PLA with smaller bed temp it would print just fine. My fix was increasing the Z-motor Vref voltage. I too believe that a minute 1-1.5C variation in bed temperature wouldn`t affect the print quality that much. This needs further investigation.

@@CNCKitchen Full steps on stepper motors are fairly accurate when stationary. Any microstep step is not precise and can be within a small number of actual microsteps of the position you think your at. Take a strip of paper and rip it in half, now do the same thing again and again and again and again. You now have 16 smaller pieces of paper. You have increased resolution but the resolution does not equal precision. Each piece of paper is not precisely torn, not precisely the same size as the others. With the ripped paper you can separate two objects by 3 micro-pieces of paper and the position will be more accurate than if you were limited to 1 full strip of paper. But, the spacing is not precisely 3/16 of the full paper strip. It may in fact be closer to 2/16 or 4/16 because our paper micro steps are not precise. Microsteps increase resolution of movement and smoothness of movement at low speeds. You don't get something for nothing though. With microstepping as the RPM increases the potential power output of the motor decreases. Some stepper drivers will 'morph' steps from n-microsteps to full steps as RPM increases (all done internally, you are still sending microsteps to the driver). This gives you the best of both worlds. Increased resolution, increased low speed smoothness and all the power out of the motor at high RPMs. Please see my post about indicating to your bed when the bed it stationary and heated to measure any deflection in Z. My suspicion is that if your bed is deflecting with a 2C delta T then it is due to it being held at the corners thus any thermal expansion/contraction can only be relived by the center of the bed bowing in the Z direction.

Best comment exactly what I thought. Its a power issue. Electrical noise affecting the steppers. If say a second power supply was used for the bed heat this would also fix it.

@@HeyBirt ripping a piece in paper in half ??? please put down the crack pipe buddy, you've had enough.

Thanks!

Still shows 300.000. 🙈 can't be the true amount. I think it stays at 300k for a while to celebrate?

@@REDxFROG some time ago youtube stopped showing precise sub counts

The issue with that kind of a measurement is that your indicator is also growing and shrinking as the temperature fluctuates, and needs to be accounted for.

@@TurkishLoserInc introduce a thermal insulator, such as a 3d printed object. if the effect is real it doesn't matter whether or not the dial indicator is directly in contact with the bed

in case one part of the bed doesn't expand and another part does i would use multiple dial indicators to take into account that distortion

@@ikbendusan Laser interferometry should be able to illustrate minute changes in form and placement.

@@TurkishLoserInc Let's be realistic, if a change of 2C disturbed the test indicator that much it would be utterly useless in real life.

the first line too.

Spoiler: the conclusion is to not bang if you don’t want z wobble.

He is a real resource. Totally agree.

Good idea. Just put some tape on the bed or use a thick raft and it should be fine.

✌

Glad you enjoyed it!

Great to hear!

My lack of money made me go the complete opposite direction for my 1st printer: an entirely scratch built project, not even a clone, only just similar to the i3 style in montion design (and even that just similar - mine runs on lead screws all the axis), and Marlin on it. Sure as heck is quite the ambitions project and I have quite a bit on my hands to tune and test, tho I'm glad to report to anyone that cares that it's indeed moving and heating correctly right now!

I don't think it's that. It must have something to do with the "power shocks" on the Mainboard itself. They are strong and happen less frequently than mini burst of PID.

It is, at least on the original printer that bed pid was implemented for in Marlin, the mendel max. It had a 250w heater and a glass bed. The math is all in the git commit to prove it.

The slow nature of temp sensors could mean the temp swing is greater than indicated.

@@stephenmcdonald3781 the temp sensors are super quick? It only depends on often you poll it. You could basically get 5 different values within a second when you heat it up. However the temperature transfer in the bed is slower and thus you will get a different temperature through the entire bed. The temp sensor can only tell what's in the center of the bed.

Good point and this is also what you can find on the RepRap Wiki. If the thermal mass is big enough, Bang-Bang can be fine.

even with a large thermal mass for example if the glass isnt thermally bonded (bed clips) there is still maybe an isulation gap causing the metal plate to flex under the glass causing the glass the pulsate with the metal plate though on my large printer i use bang bang, with thermal tape under the glass and its fine

@@meky0 Wouldn't it be the reverse? If the glass is bonded to the metal, it's forced to follow the erratic motions of the metal. If the binding is loose, the glass bed can sortof ignore whatever the metal underneath is doing. Not too sure about this though.

@@CNCKitchen The original pid bed implementation in Marlin was specifically because of a glass bed. The heater side of the glass swinging around in temperature by just a little while the top was more stable would cause bowing that led to banding. Although that was with a 250w heater, which is a bit large.

Thanks!

👌💪

That's it ! Nothing to do with thermal expansion/contraction. More like voltage fluctuation affecting the board...the power supply, and consequently the motors. Bang-bang control create two distinct levels...while PWM control spread out the influence.

The voltage of the PSU drops a bit but if it's powerful enough the impact shouldn't be too big.

@@CNCKitchen but you should check the voltage/current on the Mainboard traces itself. The bed instantly sucks full power causing little spikes which could also drain/hit capacitors and cause a quick shortage of current. The fan of a JGAurora A5 always lowered the rpms once the bed banged. But of course I'm not as much inside this tech as you are. Just trying to guide thoughts in another direction.

@@CNCKitchen Could ultimately be skewing the thermistor though. Would be interesting if you could rule this out. You could remove the heatbed (leave it attached, but don't actually print on it - i.e., just leave it sitting behind the machine). So you have the same electrical load, but you're not heating the actual print surface.

Same here on another printer.

OK Nancy

I was looking for this reply 😂💕🤘

#TeamTarantino

Great to hear!

you must be mistaken, everyone knows that prusa's are perfectly engineered printers with no flaws that never have problems and turn out perfect prints every time and are completely worth the 100% markup.

Cheers!

On Marlin or on RRF? Because the RRF system has been made significantly better recently.

@@malloott repetier firmware, I'd think marlin and others would have similar ways with repetier and server you can update the eeprom live

Yes, I find I get the best and most sane PID values by hand tuning on the bed. Especially with AC powered beds that have large thermal mass. If you go to Wikipedia for PID control there is a graphic on the right hand side about halfway down about PID tuning that explains almost everything you need to know in one graph. It shows how the P, I, and D affect the setpoint, rate, and oscillation.

This reminds me of the old days, when I PID tuned my first quadcopter with simple trim-pods.

Yes, I think it is actually an extruder problem: not enough extruder heat element current when bang bang turns full on for longer than a pwm pulse.

Let us know if that solved your problem!

@@CNCKitchen Unfortunately not. It seems to be a mechanical issue but I can't seem to figure out what it is. Would you mind looking at this test print and telling me if this is a mechanical or a settings issue? imgur.com/a/49pm0M9

That is also my guess. Bang Bang has a very high impact on the Mainboard especially when using the mosfets from the board and not exter Al mosfets with seperate cables. I speak from experience. Bought a used JGAurora A5 which had bang bang and no separate mosfets. You could hear the power loss on the cooling fan. Also it affected the print quality each time the 300x300mm bed banged power. But it's just one possible reason.

I'm inclined to go this way as well. With steel and aluminum expansion coefficients in the 10-30 micrometer range per C and a fluctuation only being within a single degree, one would need a fan actively cooling the board itself to produce those kinds of results. I think the hysteresis board management is drawing power from the heater, motors, or both and causing the issue, not the bed flexing.