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Wire EDM Cutting

January 1, 2013 By a-j

Wire EDM (submersible)

edm1            edm2

Maximum cut size 12″ x 16″ x 15.5″ thick
Maximum workpiece 24″ x 36″ x 15.5″
Maximum workpiece weight 2200lbs
Standard tolerance +/-.0002″
Taper cutting to 30 degrees
Dielectric medium, deionized water

Process

A traveling brass wire is energized with a high frequency DC Current to produce a 10,000 degree centigrade spark at rates up to 500,000 cycles per second. As long as the work piece is electrically conductive, the hardest of materials are vaporized. Heat treating tool steel, before making parts out of it, eliminates the slight distortion that typically occurs after making parts. The EDM  process allows cutting parts from materials that are already hardened. This is one of many advantages offered by the electrical discharge machining process.

Unlike the sinker, (or ram), EDM which is typically used to burn shapes in to work pieces from one side at a time, (blind), the wire EDM process must go through the  work piece. The wire is then controlled by the upper, and lower diamond guides, being driven by the CNC section of the machine. On parallel cuts these axes move in unison, but another advantage of the process is that they also function independently. This allows the wire to “lean over” at angles up to 30 degrees, tracing two different geometries through  the part (upper, and lower). Its similar to flossing your teeth, except the wire is always a straight line.

Control

edm3
The wire EDM process in “rough cutting” leaves a finish, and accuracy that is far superior to plasma, water jet, or flame cutting, but we don’t stop there. The rough cut, in order to apply more power to the wire, is relatively slack. This shows up in profile corners, and although invisible to the eye, we know its there, and the process for precision wire cutting, is similar to the sinker electrodes orbit. That is to take multiple “skim” cuts with a tighter wire, at progressively lower power settings. This produces finish and accuracy that is unsurpassed by any other methods. Typical profile tolerance at this point in on the order of +/- .0001”. Internal profiles are accomplished by ram burning, (or drilling) start holes through which the wire is threaded, and then processed normally.

If there is a “down side” to wire EDM it is that it is quite slow, and one other detail that occurs now and then, is trying to accomplish a sharp inside corner. No matter how small a wire you use you have to leave a small (.005”) radius on a inside corner. Sometimes we are not allowed to “relieve” that corner with the wire, to allow the fitting of a theoretically sharp part. Never the less when you want to build a complex punch, and die profile, and control the clearance between them at +/-.0001 the wire EDM, quite often, is capable of doing work that is impossible by any other means. The cost of EDM does not lend itself well to production work, but is highly justified when a EDM’d dieset, or EDM’d mold cavity starts producing thousands of accurate, and complex parts.

Wire EDM (non-submersible)

wire edm danbury ct           edm6
The wire EDM process creates debris. Flushing is necessary to continue cutting efficiently, therefore both systems produce flushing pressures upwards of 300 psi. To remove this vaporized material. In a non-submersible machine, flushing is limited to getting flushing into the wire kerf. When cutting a part that is not solid, red sparks can be seen where the wire is exposed, and without coolant. This indicates unstable cutting and a probable wire break. For this reason non-submersible machines don’t lend themselves well to interrupted cutting.

The top photo above exhibits a bright blue/white submerged spark. This would continue even if the part were not solid (interrupted cut). Although the spark is quite hot, the wire, and the work piece are cool, and unlike the non-submersible method, the wire is not exposed to atmosphere.

Filed Under: Portfolio Tagged With: Portfolio

Sinker EDM

January 1, 2013 By a-j

SINKER

AgieCharmilles  Form 30 Ram (sinker) electrical discharge machine
Maximum Workpiece size                               39” X 27” X 12”
Maximum Workpiece Weight                         2,000 lbs.
Maximum Tank Size                                         47” X 31” x 20”

Sinker2

Geometrically similar to hobbing, copper and graphite electrodes are “sunk” into soft or hardened conductive materials such as punches, cavities, and bearing races. Unlike the wire EDM process, machining does not have to go completely through the work piece, and unlike conventional milling, little force is exerted on the parts or electrodes. This allows for extremely delicate shapes, holes, and finishes, on parts before, or after, heat treatment.

Electrodes

Sinker3

Today’s technology offers a wide variety of electrode materials containing graphite, tungsten, copper and silver, in the various combinations necessary for optimum “burn” conditions, in various conductive materials. Most of these conditions are pre-defined by the technology in the machine itself.

 

Process

The basic process in a CNC sinker is to make the job specific electrodes (cut from customers .sat solid file format) slightly smaller. This allows a higher power burn process in the initial plunge into the work piece, leaving a rather coarse surface finish and an unfinished part.  At that point, the machine powers down slightly and begins one of several predefined orbits of the electrode, thereby improving the finish, and bringing the part closer to size.  This process is usually repeated many times, with the same electrode.  Each time at a lower power setting and an orbit of greater amplitude, bringing us closer to the final tolerance and finish. At this point, a “finishing electrode” (usually identical to the first, but still sharp) is typically used to bring the part to final size. This process may be repeated several times as necessary for some of the more exotic powder metals or carbides.  Although it seems tedious, machining these super-hard materials before the electrical discharge machining process was developed, was limited to what we could do with a diamond grinding wheel.

Medium

Unlike the de-ionized water medium used in wire EDM, sinker EDM uses an oil based die-electric fluid (basically a highly refined form of kerosene with rust inhibitors, etc.)  Very large filters constantly remove particles from the 10,000 degree centigrade sparks that are discharging, at rates up to a half million sparks per second, but the work tank itself is not a very clean environment. This is not conducive to submerging whole mechanical assembly’s in the work tank or many of our high precision indexing systems I would like to use. Typically parts are washed after the sinker EDM process

Conventional ram EDM 

Sinker4

Non CNC ram EDM has its place for applications, such as burning start holes in hardened material to allow threading of the wire for the EDM process, and for more simple work, such as burning out broken taps or burning logos in mold cavities. One of our machines is dedicated to start holes for wire work, where hollow brass electrodes, of various sizes, rotate with water flushing up to 1,000 psi down their center, rapidly penetrating hardened tool steels. These machines are typically referred to as “hole poppers” in the industry.

sinker5

 

 

Filed Under: Portfolio

CNC Milling

January 1, 2013 By a-j

Milling Danbury, CT   CNC2

2 Million dollar vintage Pescarolo race car, broken motor mounts, parts unavailable. Digitized and made from 7075 high tensile aluminum. Back to racing again.

Milling Danbury CT   Milling Brookfield CT

Upper A-Arm mounts for same car. CNC milled, and then EDM wired.

Milling Danbury CT   Milling Brookfield, CT

Additional CNC Milling machines:

CNC7   CNC8

CNC Plasma cutting. Up to ¾” thick steel. 18” x 38” Travel.

CNC9

Aciera F55 retrofit with modern Delta Tau control. Extremely accurate CNC mill. Those Vertical box ways are not bolted on like most machines, they are ground into the heavy  machine frame, With the horizontal box ways for the “Y” axis on the top of the machine. The body of these Machines is made like a giant gauge block, making them extremely accurate, and rigid.

milling brookfield ct   CNC11

CNC12

Most of the parts we make are under non-disclosure agreements so we can’t save, or publish any photos of them.

Filed Under: Portfolio

Custom Machinery

January 1, 2013 By a-j

Machine Shop Danbury CT    Machine Shop Brookfield CT

Machine Shop Brookfield, CT    Custom4

Custom5    Machine Shop Danbury, CT

These are just a few of many machines we have built over the past 30 years. Most of which were conceived, and designed, in house, to our customers requirements. The most successful projects have been those where we have had complete control over concept, design, function, manufacturing, programming, optics, pneumatics, and assembly.  Although a process can be complex,  the development of such machines is easy if you prove each step, as you proceed.

The real challenge is in knowing which is the next logicial step in the development, and proceeding only when you have not violated any “rules” of mechanics, inertia, forces, wear, etc. Nothing can left to chance with so much going on at high speed.

 

Filed Under: Portfolio

CAD/CAM Drawings

January 1, 2013 By a-j

cad        CAD2

Whether generated in house, or your design, digital drawings, and surface models allow us to generate tool code directly from your geometry (step translation recommended). Full 3D modeling allows extensive analysis of machinery (when 2D becomes inadequate). All numeric machine code is post-processor generated which is less costly and error free. The most successful equipment we have built has been that which we ourselves designed to our customers’ requirements. Disciplines include stamping, insert molding, extruding, deep vacuum, high temperature applications, vibratory feeders, structural design, pneumatics, hydraulics, or whatever else it takes to resolve your needs. Typically, nothing is done outside for both reliability, and security.

CAD3

Filed Under: Portfolio

Portfolio of Services

Wire EDM Cutting

Sinker EDM

CNC Milling

Custom Machinery

CAD/CAM Drawings

About Us

A&J Machining Services - A&J Electronics - Machine Shop Manufacturing · Metals · Tools · Service A & J Electronics was created in 1980 by husband and wife team Arthur and Jacqueline Marsilio. What initially started out as an at home electronic assembly business, quickly grew into both that and a full service machine shop, necessary to support the fixtures and production aids required for assembly lines. In 1989, the business relocated to its own 10,500 square foot building, where … more

A&J Machining & Welding

56 Delmar Drive
Brookfield, CT 06804
P: 203-775-6621
F: 203-775-2574

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