Fab Machine

Specs v0.1

General

  • Motion system is shipped disassembled and fits inside a box which is pallet sized (euro pallet 800x1200mm)
  • Several end effectors will be shipped with the system, and more can be created locally
  • Will be built with the local facilitator / fablab manager
  • EASY to maintain: assembly, diagnose, fix
  • Robust & resistant in terms of humidity, temperature and dust
  • Easy to use (interface) to be define (user-friendly CAD/CAM software)
  • Safe

Machine architecture sketch Machine architecture sketch

Power

  • 48v DC machines
  • Globally, 1500 W is a safe total draw. India is the lower limit, running 6A x 250v AC.
  • In many countries, 2000 W is a safe lower bound, but this would exclude North America (standard wall outlets are ~1700W)

Space & time

  • Unit: mm (standard in 98% of countries)
  • Precision: ~0.15 mm repeatability is a good target (about 5 thou)
  • XYZ working volume:
    • Footprint (XY): maximum, disassembled fits in a EURO pallet, 1200x800mm
    • (Z): 100mm
    • One thought is to ship 1 'big' machine and the parts for 1 'small' machine (or vica versa), where the remaining parts are made on the completed machine
  • Resolution: To be defined
  • Cut speed: To be defined
  • Should be happy with 1/64th End Mills

End effectors

  • Router module:
    • 1kW spindle, using off-the-shelf brushless motor w/ DC inverter from main DC lines. closed loop speed control with Back EMF Measurement
    • Aiming for 20 000 RPM max
    • 1kW leaves 500 W 'left over' for motion control, losses during transform. Should be enough.
    • 'Jonathan Ward' style spindle w/ ER20 or ER25 collet (ER11 should be sufficent. "ER11 Extension" is a good search term for sourcing, this type is comabitble with standard skateboard bearings)
    • Some kind of Probe (piezoelectric?) will allow auto-squaring / leveling features, so that machine assembly errors do not directly translate into parts made on machine.
  • Laser (diode) module
  • Universal module: knife, pen, 2D printer head, extruder

Connectivity

  • USB vs WIFI : To be defined
  • Browser-based, configurable interface (MODS)

Control

  • Sam Calisch's stepper controller board requires further development but could be helpful for this machine
  • Kinematics coordination: on-hardware in C, or within MODS?
  • TBD! Network or Graph? Centralized node connects to motors / end effectors over UART?
    • Helpful if each axis can be communicated with (i.e. online, or via serial) individually, so that debugging can be done one-axis-at-a-time?

Assembly

  • The Prusa i3 has some nice assembly design features that might be useful in the design of this machine.
  • Assembly is a great opportunity for learning

Schedule v0.1

September -> December

  • prototype MODS / Machine interface and networked machine control
    • use existing hardware, or design (i.e. do Jens' Hittori machine, but move forwards on controls / interface side)
    • this means adapting a stepper driver (jake is partial to using Sam's xmega 8e5-based board) and some spindle driver (jake has a brushless motor controller) for use on-network
    • how, when and where things like acceleration control and motion planning happen is an open discussion
    • network architecture is an open discussion
  • build a stronger spec for the machine and its end effectors. size? materials used? capability?

January -> April

  • a 'complete' prototype fabkit machine. motion systems, rev'd controllers, and a 1st end effector

April -> FAB14

  • documentation!
  • likely, more work on controls, and interface
  • end effector expansion
  • fancy things, like probing and geometry correction
  • a 'complete' machine is shipped to FAB14!

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