• Second Z belt

    Thomas • 04/25/2021 at 18:11 • 0 comments

    Should be expected, when probing bed, z axis moves up and down quickly which caused binding.

    If you were able to only print in vase mode on a perfectly flat surface, you can get away with no binding issues. But to allow proper bed probing and z motion (z-hop, etc.), a second belt was added to support the opposite side of the bed.

    Parts:

    • 5mm stainless steel rod (mcmaster)
    • 625 bearing
    • 6mm belt (ran out of space for 10mm belt)
    • printed belt attachment block + 2 M5 bolt
    • GT2 6mm pulley/idler

  • Spool holder

    Thomas • 03/17/2021 at 02:09 • 0 comments

    Spool holder with bearings

    - 608Z bearings
    - 8mm aluminum axle
    - M5 preload screw


  • Z-axis stiffness

    Thomas • 03/12/2021 at 03:40 • 0 comments

    Z-axis is stiff when attempting to rotate in the y direction.

    Also very stiff when pushed in the Z direction on the supported side (held by the belt and stepper). However, the non-supported side does have flex. Its essentially acting as a cantilever bed as the carriage isn't fully constraining that end.

    With about 10lb of force applied, Z on unsupported side will move up and down about 0.9mm.

    On the plus side the linear rail on the unsupported side is not binding yet. Normally you want belts or screws driving both carriages to avoid binding (https://reprap.org/forum/read.php?397,756640, https://drmrehorst.blogspot.com/ has great info, eg two z motors is not ideal).

    TODO:

    - measure flex with unsupported side carriage removed (to simulate a cantilever bed). Another option might be to put dual carriages on the supported Z linear rail and use triangular support of the bed.

    - extend 2020 to meet face of L bracket, see if it provides additional stiffness

    - measure max weight Z axis can hold

  • Z-axis pulley system

    Thomas • 02/25/2021 at 05:25 • 0 comments

    Z-axis pulley division:

    • 200 step per revolution motor (1.8°)
    • Stepper shaft has 16T pulley -> driving 80T pulley -> driving 20T pulley -> connected to belt
    • Reduction = 5:1
    • Final 20T pulley pitch diameter = 12.73mm (reference)
    • 12.73mm * pi / 200 / 5 = 0.03999mm

    Each full step should move z-axis 0.03999mm (a number that divides into 0.2mm would be better, but it should be close enough).

    Can be divided down with microsteps 1/2, 1/4, 1/8, 1/16: 19.996, 9.998, 4.999, 2.4995um

    6mm belt on first stage, then wider 10mm belt on second stage for higher load:

    • 6mm = 2.8kg working, 56kg breaking strength
    • 10mm = 4.4kg working, 88kg breaking strength

    Hopefully bed weight will be <4.4kg.

  • More extruder

    Thomas • 11/21/2020 at 23:03 • 0 comments

    BMG clone extruder



    PTFE tube can be trimmed to length and inserted at the bottom, to reduce flex past the gear teeth

  • Hotend heatsink

    Thomas • 11/19/2020 at 04:19 • 0 comments

    Designed to accept 7mm heat break, secure with set screw.

    Titanium heat breaks are available.

  • Modular extruder board

    Thomas • 11/19/2020 at 04:10 • 0 comments

    Board built up.

    Has white LEDs and one red LED for heater on. Red connected to heater 24V, but may make more sense to connect it to hotend fan.

  • z-axis pulley blocks

    Thomas • 09/17/2020 at 03:15 • 0 comments

    80T pulley bought and some machining done on it:

    Two bearings inside the block on the left.
    80T 6mm and 20T 10mm on 5mm shaft.
    Stepper motor on right mounted on 36mm standoffs.