Wire EDM Bandsaw

July - December 2024

Before my final semester at Northeastern, I had been getting a bit obsessed with wire EDM machines. I was even considering building one myself, so you can imagine I was excited to see that one of the available capstone projects was to build custom wire EDM machine! The market for WEDM machines is dominated by extrememly capable machines with 6 figure price tags, and we had around 1/20th of that budget. In order to finish the project within a few months and on budget, we addressed a niche use case that required a smaller, much different set of requirements.

Client’s requirements

  • Cut a metal 3D printed (DED) part off of a 18” build plate - previously a bandsaw or angle grinder was used
  • Cuts must be flat within ±.020”
  • Adjustable cut height
  • Affordable (<$3000 w/o power supply)

Responsibilities

  • Work with group of 6 to brainstorm novel format of Wire EDM machine
  • Design X/Z axis, wire tensioning, end effector subassemblies
  • Lead design and build of machine over extreme timeline
Capstone day group pic
Full system

Subsystem: X/Z Stage and Wire tensioning

  • X/Z stage driven with geared stepper motors and EtherCAT drivers
  • Hand calculations used to determine vertical displacement of wire due to X axis flex
  • 2 servos run closed loop with load cell to control wire tension and speed
  • Wire tensioning was inconsistent, so a planetary reduction was added to servos to increase precision and torque
  • Further iteration necessary to reduce skipping on output wire tensioning assembly
Wire tensioning test
X/Z Stage

Subsystem: End Effectors

  • End effectors were suspended on cantilevered beams to reach through 18” diameter build plate
  • Water blocks mount diamond wire guides, nozzles, pulleys, and NPT fittings
  • CFD used to determine correct nozzle orifice size, hand calculations used to determine necessary post-pump pressure
  • End effector designed to be extremely compact in order to fit around workpiece in COTS stainless steel tank, significantly reducing cost
  • Machinability of water block was crucial, as it was done in-house
  • More bracing on end effectors was added to deal with inconsistent wire tension
Nozzle/water block pressure test
Water block - my favorite part on the machine

What I Learned

  • On large projects, splitting up the system and doing subsystem testing is critical
  • Test early and often
  • There is always a way - even if it’s me buying a 3D printer with personal funds and running it around the clock to make stand-ins for machined parts
  • Good project management means communicating failures early and delegating work, even if I’d prefer to do it myself
  • Any engineering assumption made will be tested and could cause failures