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)

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

1. Hysteresis - at 14 ambient, set to 55C goes to 82C.
2. Set to 99 at 16 ambient - temp goes to 112 on second cycle.
3. 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.
   1. 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:

1. 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 91.

Links

• D3D v20.04.27