D3D v20.04.27 Data Collection
Build
- For the bed, because bed holder carriage nut catchers are printed upside down, best way to smooth is using a longer bolt to suck in a nut to clear the excess plastic. Possibly a different production engineering (machine redesign or part redesign) can solve the dirty nut holes
Bed Lift Capacity
- Bed itself is about 24 lb:
- 17x17" -1/16" plate
- 9' of 2x1/16" strip = all of 1/16" is 10 lb
- one 1/8"x18"x18" plate = 11.4 lb
- Rods - 2 lb (8' of 8 mm)
- Insulation - at most 0.5 lb from D3D_v20.04_Calculations
- 6x6" plates of 1/8" steel are 1.3 lb each
- How many can we lift?
- It should be, based on former results - 14 lb based on D3D_v20.04_Data_Collection#Bed_Weight_Holding_Capacity because we have 2x the motors, 2x the weight, and excess hold was 7 lb, so with double motors this should go to 14.
- Data:
- 4 plates (5 lb)
- 6 plates (8 lb)
- 8 plates (11 lb)
- 10 plates (13 lb)
- 12 plates (16 lb) No. Went up <1" then dropped.
- 14 plates (18 lb) No. Went up a little then dropped.
- 16 plates (20 lb)
- 4 plates (5 lb)
Run
- RAMPS 1.4 doesn't handle 2+2 series+parallel z motors. It is fine to drive 2 in series - bed lifts. Adding the other side just causes skipped steps.
Counterweight
- Used 3x10.5" slabs of 1" on each side - 4 kg almost exactly.
Heating
Hysteresis of Bed
- Hysteresis - at 14 ambient, set to 55C goes to 82C.
- Set to 99 at 16 ambient - temp goes to 112 on second cycle.
- Set to 135. Parts of bed bubble up. So put metal plate on to keep thermal expansion down, baking in the bed with glue to bed contact. At 120, temp went down to 117 after putting on 33 lb of plate. 25 plates of 1.3 lb. With plates on, overshoot is to 142C.
- Without the metal plates, overshoot goes to 146C.
PID Autotuning
- Enabled Bed PID autotune. Autotune fails - Marlin_Bed_Temperature_Overshoot#Errors. But stock PID values result in the following 2 data points:
- Set to 67, overshot to 73. Then fell to 67 and vershoots to 68. Stable at 68. Flashes quickly on/off.
- When set to 99, overshoots to 103. Great.
Turned on slow PWM:
- define SLOW_PWM_HEATERS // PWM with very low frequency (roughly 0.125Hz=8s) and minimum state time of approximately 1s useful for heaters driven by a relay
Works great: setting to 91 overshoots to 95. Falls to 89. Stabilizes at 91. Great results, default PID settings for bed work quite well, even on Slow switching of less than 1 Hz.
Energy Usage
At 17 ambient, bed set at 91C has on-cycles of about 1 second. 5 cycles take 42 seconds - or about 1.4 second in 8 seconds of full power. Divide 1800W by the duty cycle to obtain about 315 average wattage for the bed.
Z Motion
Never seen it before: Z axis moves only in one direction no matter what direction i make it go. So for example, upon homing, it keeps going into the head.
This may be something with the counterweights?
Undetected Quality Control Issues
Controller passed basic quality control of the controller: all motors working and endstops triggering.However, this was the first time that the Z driver went one direction only, whether told to move up or down. It was not a bad driver, so I replaced the RAMPS board. Unfortunately, fried the Arduino voltage regulator as I forgot to convert RAMPS from 12V to 24V operation, and Arduino regulator was hit with 24 volts for an immediate smoke cloud. Replaced Arduino (still works but regulator is fried, so it can't take a 12v input any more). After testing the Z motion - it works - moves both up and down. Success. Not a problem to drive 4 stepper motors in series - on 24V.
The issue was either the RAMPS board or the Arduino itself. Did not get a chance to test the arduino before regulator fried. After regulator fried, tested the Arduino. It may have been the issue - as it didn't drive the Z axis properly. So it's likely that the RAMPS board is good, and the suggestion for next time is to replace the Arduino first before replacing the RAMPS.