User:DaveX

My Wallace Build

My Wallace is currently in a partially assembled state with these pieces:

• Wallace, NEMA14/6mm Printed by http://www.fabbr.com/
• Pololu steppers per http://www.pololu.com/catalog/product/1209 1A, 1400gf-cm (20 oz-in)
  • Some (too-small, but shimmed with paper,) PLA LM6UUs per http://www.thingiverse.com/thing:16464
  • Replaced the LM6UUs with steel ones, but they still seem pretty stiff. In trying to get the Y axis to move, I think I burned out a stepper.
  • 350x300x430mm smooth rods makes a build volume of 172x218x22 and an overall envelope of 405x531x442mm (per notes in Wallace_Build_Manual#Dimensions, and measurements shown in the pictures at User:DaveX/WallacePics
  • Pegboard bed: 274x313mm
• Greg's hinged accessible per http://www.thingiverse.com/thing:8252 hobbed with an M5-ish SAE 10-32 tap per my notes at Talk:Wade's_Geared_Extruder#Filing_and_hobbing_the_bolt
• A shorter Wildseyed_Simple_Hot_End, since the air-fitting's locking fin seemed small compared to Wildseyed's pictures, per Talk:Wildseyed_Simple_Hot_End#Air_hose_Adapter_machining
• Pololu_Electronics#Teensy_Breadboard using Pololu_stepper_driver_boards running ATMEGA32U4-ported Teacup
• Old ATX power supply
• Initial plastic: Natural PLA from http://thefutureis3d.com/node/113 through Ebay
• Pololu_Electronics#Teensy_Breadboard
  • Thermistor circuits modeled after Pololu electronics
  • Heater circuits, modeled after Pololu electronics
• Wallace, ATX and electronics mounted on a 18x24" piece of MDF
• Put the Z steppers in series, so x,y,z circuits all use similar current: 0.7A drives the axes with cool steppers and Pololus. Pololus tuned to Vref=0.28V for 0.7A peak current, 70% of stepper rating, for 70% of 1400 g-cm torque and 50% of motor heating.
• Setting microstepping for XYZE as 4/4/2/16 for noise and speed in Teacup on a Teensy
  • Determining max feedrates. (x,y,z,e)=6881,6881,233,170 with above microstepping Teacup stutters on interrupts if you set the rates too high. See [[1]]
• A version of Wildseyed_Simple_Hot_End]
• Big delay due to several life events.

Things to do:

• Wire up the extruder and hot end assembly with Nophead's male D9 connector per Mendel90_Build_Manual#Extruder_Wiring and a ribbon cable -- my build moves and heats, but is using unreliable, too-short alligator jumpers.
• Continue the Pololu_Electronics#Teensy_Breadboard experiment
  • Adjust my Teacup port to the Teensy http://www.pjrc.com/store/teensy_pins.html for a 100K beta=4036 thermistor. Teacup has multiple thermistor tables
• Test things.
• Print something.

Mistakes

• Don't assume a metric rod in the US is 1m long.
• Don't overcurrent the steppers. Pololu's drivers can do a nice job of limiting the current, but can overdrive the 1A/coil steppers if you want them to. I think I had damaged my Y stepper earlier by trying it on a circuit for the higher current extruder, then since I was fighting too much friction on Y with the new steel LMUU6s, I upped the current until a new failure: odd pulsing due to thermal overload of the Pololus. By adding a heatsink I was able to increase the current further, compounding my problem, as I still didn't get motion on Y. Then I noticed that the holding torque on X driven by a much lower current was much stronger than the holding torque on Y. My Y stepper was weak and feverish, compared to my strong and cool X stepper. Bummer. I ordered a replacement and spare. In the future it might be good to Thevinin-ize the stepper and set the current with a dummy resistance load. A couple of fat resistors would be much cheaper than a stepper-shaped heater.
• Don't strip the nut-trap on the Z-axis couplers.