User:DaveX
Contents
My Wallace Build
My Wallace is currently in a mostly 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 172x218x220 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, using $3.34 42V 49A Protected Mosfets from [[1]].
- 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 4/4/2/4 for noise and speed in Teacup on a Teensy
- A version of Wildseyed_Simple_Hot_End]
- Big delay due to several life events.
- Wired up the extruder and hot end assembly with a ribbon cable using Nophead's male D9 connector per Mendel90_Build_Manual#Extruder_Wiring and [[3]]
- Filed flats on my steppers & re-fit the connectors and pulleys for less slippage
- Teacup ported to Teensy 2.0 / ATmega32U4 on https://github.com/drf5n/Teacup_Firmware on the Gen7 Branch. Many changes pushed upstream into Teacup
- No endstops for now: I jog to the center until a piece of paper binds and then start with a G92 x0 y0 z0.1
- Filament reel hanging from a long L-shaped stick wedged behind the desk.
Things to do:
- Tune things.
- Document Pololu_Electronics#Teensy_Breadboard as Teensy Breadboard.
- Test the hotend temperatures. My PLA seems too hot and liquidy at a setting of 185. It seem to flow and stick at 165.
- Assemble and install a heated bed
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.
- Do file/use flats on your stepper motor shafts. They don't need to be much, but without flats the pulleys and couplers might slip.
- Make the hobbed bolt groove well defined so the filament does not ride up to different diameters and change the steps/meter extrusion calibration.
My Wallace Rod Sizes
My NEMA14/6mm Wallace ended up with my smooth rod pairs as 350x300x430, which produces travel of 172x218x220 with my extruder, as can be seen in the set of huge pictures in User:DaveX/WallacePics With an ~110mm Accessible Wade's extruder assembly, and 65mm(=30+35) for the x-end sockets for a NEMA14/6mm bar Wallace, it looks like I'd need about 380mm for a 200mm working length along the X axis. A narrower extruder than I used could allow up to 40mm additional travel in X. For 200mm of motion in Y, it looks like I'd need to allow for 2x20mm for the bed mounts plus 62mm for the NEMA14/6mm base, or 282mm of smooth rod. 36" (914mm) bars minus (375mm + 282mm - 4mm kerf) would leave 257mm for Z, allowing 200 for the base, bed, extruder, hotend, etc., as listed on the spreadsheet would leave a total build volume of about 200x200x57mm. Since changing/upgrading Y looks the most simple, one might choose to cut a pair of 36" rods as 380x(914-380-370=160)x370 for a build volume of about 202x82x170mm, while planning to cut a pair of 282mm+ rods out of a third smooth rod to get the full 200mm of Y travel. DaveX 19:22, 18 February 2012 (UTC)
For a NEMA14/6mm rod machine, the threaded rod sizes could be: (In parentheses are examples for smooth rods of 380x282x370, or build volume 200x200x170 DaveX 17:07, 8 February 2012 (UTC))
Calculations
# R code for estimating feed rates, etc.: stepsPerSec <- 15570 *16/20; # per http://reprap.org/wiki/Teacup_Firmware#Distances_as_expressed_in_steps for a 16mhz chip stepsPerM <- c(13576,13576,400000,160423) maxFeedPerMin <- stepsPerSec / stepsPerM * 1000 *60 safetyFactor <- 1/(4*2) # divide by 4 axes, and factor of 2 maxFeedPerMin * safetyFactor # == 6881.2610 6881.2610 233.5500 582.355 mm/minute maxFeedPerMin * safetyFactor /60 # == 114.687684 114.687684 3.892500 9.705591 mm/second maxMMperMin = c(6881,6881,233,680) ## Teensy w/ 4,4,2,4 microstepping on a Wallace 2012-10-13 #Steps/sec at max feeds: maxMMperMin/60*stepsPerM/1000 # == 1556.941 1556.941 1553.333 1818.127 # Resolution: 1/stepsPerM*1000 # == 0.073659399 0.073659399 0.002500000 0.00623352 mm/step