MEC325 Lab Report
Wire Electrical Discharge Machine (WEDM)
Date: March 26, 2014
Group Leader:
Team Members: Matthew Stevens ID 108469622
Group Number: 20
Regiment No.: D
Instructor: Dr. Qing Chang, Dr. Noah Machtay, Nikita Timofeev
Department of Mechanical Engineering SUNY at Stony Brook
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Table of Contents
i.
Objective………………………………………………..3
ii.
Introduction…………………………………………......3
iii.
Principles and Practice………………………………..3-4
iv.
Design Procedures and Result………..…………………4
v.
Conclusion…………………………………………….4-5
vi.
Appendix……………………………………………...6-7
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i.
Objective
The objective of this lab is to learn what a Wire Electrical Discharge Machine (WEDM)
is, how to operate a WEDM, and write a G-codes, M-codes, and T-codes by hand that utilizes the
unique features of a WEDM.
ii.
Introduction
In the modern day of technology, manufacturing technologies has allowed for the
improvement and advancement of our lives. Many products formerly not possible to make are
now easy to mass produce under new manufacturing technologies. Traditional methods of
machining in a lathe or milling machine are effective for softer metals and larger cuts that do not
require high tolerance or small cuts. A wire electrical discharge machine excels for cutting any
metal that conducts electricity regardless of hardness, smaller intricate shapes, and taper cuts,
quicker, less expensive and more accurate solutions than conventional machining.
Several main features make such a machine desirable. The most useful feature of the
WEDM is the ability to cut hard materials since it is a non-contact cutting process. A WEDM
cuts any material that conducts electricity by running a current through a thin wire. The wire
creates microsparks that eats away at the metal. This process is entirely non-contact based, so the
machine will cut any workpiece regardless of hardness. Some materials that would traditionally
be difficult to machine using conventional machining methods like carbide, inconel, titanium,
hastelloy are great uses for a WEDM. Next, since the WEDM only uses a wire, productivity time
is faster since there is no need to change tools or finish the surface off. In fact, WEDM are great
for creating burr free parts. Finally, the cutting wire is mounted on two separate heads that can
move independently of each other, providing the WEDM with up to 5 axis cutting capabilities.
Because of these features, WEDM is commonly used to time sensitive prototyping, parts with
splines or high tolerances, large series production molds, and custom tool inserts.
Not all machining jobs are best performed with a WEDM however. Since a wire is used
to cut the material, all cuts must go through the material. If a design calls for a cut that stops
midway in the part, then the WEDM will not be able to achieve this.
iii.
Principles and Practice
Wire electrical discharge machining (WEDM), is a non-contact based operation that
works using the principle of spark erosion to cut through often very hard materials like steel
carbides, so long as those materials are electrically conductive. The setup involves two
electrodes –one being a threaded wire for electricity to pass through and another being the work
piece–immersed in dielectric fluid, fluid which normally acts as an insulator. If current is passing
through the wire and if both the wire and work piece come close enough, the electric field in the
volume of dielectric fluid between the two electrodes will exceed the strength of the dielectric
and cause a voltage breakdown– a voltage at which the insulative dielectric fluid becomes
conductive. [1] (Wiki Wire EDM) A small amount of material is vaporized from the work piece
which will cool into solid particles and be flushed out by pressurized flow of the dielectric fluid.
This phenomenon of spark erosion does not utilize the pressure contact-based methods of
conventional machining using lathes, mills, and so on. If the wire and the work piece (the two
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electrodes) do come into physical contact, passing current will only result in a short circuit and
no useful spark erosion.
In practice, for effective spark erosion in a WEDM machine, wire material and diameter,
the type of dielectric fluid used, purification and de-ionizing of the dielectric fluid, “ON/OFF”
duty cycle regulation, and so on must be optimized. Standard 0.0098” diameter brass wire was
used and is most common, but brass-zinc, molybdenum, steel, and tungsten wires are used of
sizes from 0.004” to 0.014”. [2] (Buhlmann Fundamentals) Brass offers a balance between
conductivity, good tensile strength, and “flushability” which wire choice depends on. De-ionized
water was used as the dielectric fluid. The dielectric fluid is cleansed of the solid particles from
the work piece by a filter and of dissolved ions by what is often resin, which ensures it returns to
its insulative behavior ready for the voltage breakdown during the next ON cycle. The
“ON/OFF” duty cycle control the ON time the current is active and the OFF time when it is
inactive and when flushing occurs, both in microseconds. To increase linear speed and reduce
job time, ON time can be increased or OFF time can be decreased at the increased risk of wire
breakage which is checked using the color bar of operation and verifying it’s at the edge of the
green zone. [3] These factors can be accounted for in the “Condition Search” submenu and are
listed as a header on top of the G-Code for the job. ON/OFF times can also be altered in real
time.
iv.
Design Procedures and Results
Our design objective was to create a tapered object resembling an I-Beam within our
given 1”x” square, which we were able to accomplish by programming G-Codes for each
independent head to create the entire part profile. Our strategy was to utilize the top head for
tracing the top (larger) profile, with the bottom head tracing the bottom (smaller) profile. The
wire was threaded arbitrarily at the vertical midsection of our work-piece, and then code was
written to bring the wire into the desired position in the profile. This simplified our coding
process, as we had to calculate coordinates for half the profile and used symmetry about the
midsection to determine the remaining coordinates. For a detailed part drawing and complete
listing of the G-Code used see Appendices A1 and A2.
Our approach was successful in the lab, as our code produced the desired tapered profile.
Specifically, our selection of the point where the wire was threaded was particularly useful when
given an arbitrary 1”x”1 square within a larger piece of material. As we expected, our final
product possessed the smooth tapered profile that we set to produce, with sharp edges forming
the edges of the profile. The part came from the tank with very limited burrs and excess material,
with the only noticeable excess occurring at the region where the threaded wire first started to
trace the part profile.
v.
Conclusion
Our approach to utilize the 4-Axis movement of the heads to design the taper was
successful. We experienced first-hand the power and flexibility of WEDM machining, as our
part was produced within 25 minutes with the intended design and a smooth burr-free finish. As
expected, our final measurements were within the expected tolerances specified by the AQ300L
WEDM Machine and possessed the smooth tapered profile between the top and bottom faces of
the part. It is quite easy to see how proper utilization of this equipment can produce some of the
complex part geometries, seemingly with ease and minimal error.
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Our approach to utilize the 4-Axis movement of the heads to design the taper was successful. We
experienced first-hand the power and flexibility of WEDM machining, as our part was produced
within 25 minutes with the intended design and a smooth burr-free finish. As expected, our final
measurements were within the expected tolerances specified by the AQ300L WEDM Machine
and possessed the smooth tapered profile between the top and bottom faces of the part. It is quite
easy to see how proper utilization of this equipment can produce some of the complex part
geometries, seemingly with ease and minimal error.
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vi. Appendix
A1. CAD Drawing Dimensioned CAD Drawing of our design.
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A2. G-Code the G-Code used to form the profile of our design. This code does not include the
conditions that were implemented during the lab.
G01 X0 Y0.125:G01 X0 Y0.175;
G01 X-0.355 Y0.125:G01 X-0.275 Y0.175;
G01 X-0.355 Y0.275:G01 X-0.275 Y0.275;
G01 X-0.305 Y0.275:G01 X-0.225 Y0.275;
G01 X-0.305 Y0.475:G01 X-0.225 Y0.475;
G01 X-0.355 Y0.475:G01 X-0.275 Y0.475;
G01 X-0.355 Y0.625:G01 X-0.275 Y0.575;
G01 X0.355 Y0.625:G01 X0.275 Y0.575;
G01 X0.355 Y0.475;G01 X0.275 Y0.475;
G01 X0.305 Y0.475:G01 X0.225 Y0.475;
G01 X0.305 Y.275:G01 X0.225 Y0.275;
G01 X0.355 Y0.275:G01 X0.275 Y0.275;
G01 X0.355 Y0.125:G01 X0.275 Y0.175;
G01 X0 Y0.125:G01 X0 Y0.175;
G01 X0 Y0:G01 X0 Y0;
M02;
CITATIONS
[1] Jameson, E., 2001, Electrical Discharge Machining, Society of Manufacturing Engineers,
Dearborn, MI, pp. 1.
[2] Moulton, D., 2012, “Wire EDM – The Fundamentals”,
http://www.buhlmann.be/worknews/fundamentals.pdf
[3] Machtay, N., 2014, “Wire Electrical Discharge Machining Introduction: Sodick AQ300L”,
http://mysbfiles.stonybrook.edu/~nmachtay/classes/mec325/wedmintro/index.html
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