WHAT MAKES WEDM FUN FOR YOU?

The Great artwork that is produced on the machines is one for me!

   Let’s start at the beginning, all of us have a story and this is a little of mine. When I was an apprentice, I was selected to learn to run the NEW LeBlond Makino EC 3025. It was the 1st wire EDM in our shop. What really got me excited about machine was a 4-axis sample part, it was the one and a two on the backside. John Aldridge was the service technician who was training me it was a great experience for a young apprentice in 1990.

It was John’s program to demo the capability. John is still with Makino today and we even worked together for a short time. Doing intricate parts on a wire machine is very satisfying and I have seen many art pieces the talented tool makers and operators have created. In this post I am going to share some pictures of what I have made and some I have found during my WEDM Journey! I hope you enjoy what you see!

Send WEDM Tech Wize your Favorite Art works! An we will add to the Collection!  george@gipintl.com

Pagoda cut on a Makino EDM U53K

NOT a WEDM – But could be and it is so COOL!

Remember send WEDM Tech Wize your Favorite WEDM Art works! An we will add to the Collection!  george@gipintl.com

Calculating EDM Wire Costs with WEDM Tech Wize

Calculating EDM Wire Costs

 How to Calculate EDM Wire Costs

WEDM costs can vary depending on many factors, one main factor is the wire you are using as your electrode! Plain Brass wire is the most popular and you would like to think the price would not change by much between vendors. This is of course not the case because the market of users is always looking for a better deal! So, can you find a cheaper EDM wire? SURE! Will it work maybe?

Frankly, I don’t think buying the off brands for pennies less a pound is a good idea if you want to run 24/7 and have no issues. The buyer beware of where the wire is being made and if it is guaranteed should be a priority. It is not just the wire cost that might get scrapped, but the Tool Steel and time already put into the part or parts that are set-up in the machine that could be scrapped! Then the WEDM machines run time that could be wasted at $175.00 - $250.00 dollars an hour that adds up Fast!   

How to Figure out Cost of Using Brass or Coated EDM Wire

To figure the cost of using brass or any coated wire e.g. Plasma by GIP, you need to know your initial cost. 

  Let's start with the brass price per pound at $5.25. Then the diameter size since .010” is the standard we will go with that. Next thing you need to know is how many yards are in a pound of wire? That would be 1,193 yards per pound  for .010” wire. ( Side Note: Which would equal 13,123 yards on a 11 Lb. spool.) Since the WEDM is spooling off wire in yards per minute (or Meters per minute) we need to look at the E-Code for that amount.  

  Doing some quick math - if 1,193 yards equals 1 pound of wire, at $5.25 a pound the cost per yard would be $0.0044 cents per yard. With this number you can  calculate the wire cost per job once you know the amount of minutes the cut time will be. That is of course just one of the costs that need to be add to the job quote, but it is an important one to make sure you can make a profit on the job.  

The question is when is coated wire the better choice to make money? 

Well, if you need to get more parts done faster then coated wire can help you! See example:

Figuring a 30% faster cut time the difference is $0.80 cents per minute higher cost, but you also need 

to figure you now have 12 more minutes of time to make more parts. If you made 36 parts in 24 hours,

Now you could make those 36 parts in 16.8 Hours so you could now make 15 more parts in the same period. 

So, in 7.2 hours, how much more money can you generate in the extra time? It will all depend on the job!  

Get a Free EDM Wire Cost Calculator

If you would like to get a copy of the full excel spread sheet, fill out the request form below with your contact information and we will send it to you by e-mail.

This is all a part of the service from GIP as we plan to build the best EDM Supply company with todays GIP High Performance EDM Wire made by BEDRA & ThermoCompact as the cornerstone. 

Let us know how we can help you and what you would like to see in the future editions of 

WEDM Tech WIZARD.  

“May your Sparks always be ON-TIME!”

The Physical Properties of Eroded Surfaces Encountered In Wire EDM - Part #2

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The Physical Properties of Eroded Surfaces Encountered In Wire EDM – Part #2  Continued from “The Role of Metallurgy in EDM Wire”

 It might be easiest to start this discussion by considering what are the potential physical surface properties which have been suggested to control the wire flushing efficiency in WEDM.  Flushing in the WEDM application involves removing the solid debris created by each individual discharge which in fact is created one at a time in rapid succession but never two simultaneously.  The discharge envelope collapses under the pressure of the liquid dielectric medium (D.I. Water in most cases) after the ON-time and OFF-time cycles are completed by quenching the debris converting it to solid particulate.  

Those candidate surface properties controlling the wire’s contribution to flushing are:

1. “Vaporization Temperature” (represented by eroded surfaces’ Boiling Point) as suggested by the traditionally accepted theories of  WEDM  Heat of Sublimation as characterized by the energy per unit volume needed to transform the material affected by each individual discharge. If you will recall the Post of “Five Myths of EDM” the first candidate property cannot be the surfaces’ “vaporization temperature” because, as discussed in that Post, there is no such animal since metals vaporize over a very wide range of temperatures and not at some arbitrary fixed temperature. 

So that leaves 

2. the Heat of Sublimation as the only viable candidate. You need to know, as illustrated in the previous Post, that sublimation is defined as the process whereby a substance transitions directly from the solid to the gas state, without passing through the liquid state.  The Heat of Sublimation is the heat required to accomplish that transition and has the correct units, e.g. KJ/cm3, which relate to the WEDM process where one is trying to remove unit volumes of the workpiece.  

This Skim pass shows an example of the Discharge during the WEDM process: This is easy Flushing! www.gip-edmwire.com

  Each discharge introduces a finite amount of energy into finite units of volume at both ends of the discharge envelope, i.e. at the wire and the workpiece. So, what is the relationship of Heat of Sublimation to flushing efficiency?  We just said that each discharge introduces a finite amount of energy into the discharge envelope in the gap between the wire electrode and the workpiece, some fixed portion of that energy will be delivered to the wire and the balance to the workpiece.  We will have the most efficient flushing of the wire debris if the maximum proportion of wire debris is from solidified vapor, i.e. smaller sized particulate.  That maximum will be determined by the Heat of Sublimation of the eroded wire volume, i.e. the lower the energy required to accomplish the transition the higher the probability it will happen.  The same is true of the workpiece but unfortunately one has little control over that since the workpiece is a given and not a choice.  As we will see later, that does not mean this parameter cannot be used to understand the performance of the workpiece. However, we do have control over the physical properties of the wire surface as determined by one’s choice of wire type.

   The following chart lists the volumetric heats of sublimation of the metallic elements.

Volumetric Value Chart for Metallic Elements www.gip-edmwire.com

Unfortunately, the volumetric heats of sublimation of metallic alloys are not readily available but one can assume they logically would be similarly ranked in the same order and magnitudes as those of the predominate alloying element of a given alloy system, e.g. iron in the case of tool steels or zinc in the case of brass alloys.  We will have more to say about the metallurgy of the brass alloy system which is critical to the WEDM application in a subsequent Post, but for now just consider the ranking of the metallic elements.  We are not so interested in the absolute values of the heats of sublimation but rather to their relative magnitudes.  For example, the relatively low value of zinc explains its predominant role in the WEDM application.  Although we have and will be focusing on the implications of this chart to the wire debris contributing to the total debris being flushed, note that the chart can also be used to better understand the simplicity or difficulty of using WEDM to erode various workpiece materials.  Note that aluminum has about half the value of iron (Tool Steel).  Do you suppose that has anything to do with the faster cutting speed of eroding aluminum parts as compared to tool steel parts?  The problem is aluminum flushes so efficiently it also obstructs the filtration system with its very fine debris particulate.  Guess why that might be!  Now that you understand the heart of our concept of approaching wire type selection, we will move on to the metallurgy of brass wire in the next edition of WEDM Tech Wize. “May your Sparks always be ON-TIME!”

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The Role of Metallurgy In EDM Wire - The Technology of Flushing

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The Role of Metallurgy in EDM Wire

The metallurgical properties of the wire and the workpiece are equally important to the mechanics of flushing in EDM, and as most of you are aware, EDM needs great flushing.

Thus the role of metallurgy in EDM is quite extensive. Not only do the physical properties of surfaces influence flushing by determining the particulate size of the eroded debris, but the electrical properties of the wire and workpiece control the energy transfer process at the gap.

The fracture mechanic properties of the wire, control its breakage frequency which in turn controls the electrical circuit integrity.

As everyone here knows, when the wire electrode breaks in WEDM, no current flows, and no metal can be removed as the only thing that vaporizes is profits.

Which type of wire cuts better?

Keep reading it will be worth the time!

Critical EDM Wire Properties

•Zinc Concentration/Melting Point of Eroding Surface

•Fracture Resistance (a.k.a. Fracture Toughness) 

•Electrical Conductivity 

•Handling Characteristics, Particularly For AWT

We can now focus on the critical wire properties in WEDM, from the metallurgical perspective. We will be looking at zinc concentration and melting point of the eroding surface, fracture resistance, electrical conductivity, and handling characteristics.

The handling characteristics, more specifically the wire straightness, is critically important to those machine without annealing units as part of there automatic wire threaders, so older machines! As you might suspect, this property is also related to metallurgical phenomenon, but this really in the domain of wire manufacturers, so we will not be digging into it here.

The Annealing unit have made this much less an issue as they have solved the problem of the wire not threading EVERYTIME!

The Technology of Flushing

 If you take nothing more than this away from my article, you will be well on your way to understanding the metallurgy of EDM wires.

Earlier I said there is no such thing as a vaporization temperature for metals. However vaporization as a process is critically important to EDM, and the property that controls it is known as the heat of sublimation. Do not be intimidated by this complicated sounding name; it is quite simple concept which we will consider momentarily. In the meantime the fact is, the heat of sublimation determines the flush-ability of wire and workpiece.

Low values yield good flush-ability; high values yield poor flush-ability. Zinc and zinc alloys have low values and therefore provide good flush-ability.

The following two sentences tell you much of what you need to know about wire selection.  

When considering EDM wires, the one with surface with the highest zinc content will cut the fastest, IF, that surface with the high zinc content is thick and tenacious enough to survive the erosion process.

The tenacity of the surface is directly proportional to its melting point with a minimum 550oC required for superior performance. 

Notice I capitalized the “if” because it is a very “big” if. Thick and tenacious are relative terms that can only be fully judged after the fact. Thickness is important because there must be enough of the eroding surface available to make it through the gap.

Tenacity is important because the large values of the physical and hydraulic forces that exist in the gap of wire EDM are capable of deforming and/or removing some of the surface. It is literally possible for the surface to be “blown away.

Hopefully not like this!

The Melting Point

Hence the importance of melting point. Higher melting points prevent the surface from being softened and distorted by the large hydraulic and mechanical forces imposed on the wire. Why 550oC? Because we know it works. The application of these principles will become more obvious when we review the metallurgy of brass in a few minutes.

In the meantime let’s look at this concept of heat of sublimation to see if we can make some sense of it. All matter exists as one of three phases: as a solid, as a liquid, or as a gas (vapor). You are no doubt familiar with the process which describes the transformation of a solid to a liquid, i.e. melting, or a liquid to a gas or vapor, i.e. boiling. However it is also possible to transform a solid directly to a gas or vapor, and that process is called sublimation. Although the terminology may not be familiar to you, the process may well be.

Consider for a moment two blocks of ice, one wet ice (frozen water ) and the other dry ice (solid carbon dioxide).  

Phase Changes of Ice

Consider what will happen if we apply heat to the two blocks of ice. The wet ice will melt forming droplets of water. It turns out there will also be some water vapor in equilibrium with the liquid water as there will always be a gaseous phase in equilibrium with a liquid phase although the amount of gas may be minuscule. If we were then to withdraw the heat, and go so far as to freeze what remains, we would find smaller pieces of solid ice and a snowflake or two formed from the vapor phase.

In the case of the dry ice, the application of heat will cause the dry ice to vaporize without forming any liquid phase (hence the term dry ice). The block would slowly disappear as it sublimed. If one were to then refreeze that which now existed, one would have absolutely nothing since the carbon dioxide gas would have diffused away and could only be returned to a solid state if it were subjected to extreme pressure and cold.

Now let us take one step back toward the world of EDM by considering two solid blocks of “Metal M” and a “Metal V.”

Let us say “Metal M” is similar to H2O and has a tendency to melt first and form very little vapor phase. Such a metal would be characterized as having a high heat of sublimation, i.e. it would take a lot of energy to transform it directly from a solid to a vapor. Let us further say “Metal V” is similar to dry ice (CO2) and has a tendency to vaporize very readily. Such a metal would be characterized as having a low heat of sublimation, i.e. it would take a relatively small amount of energy to transform it directly from a solid to a vapor.

Just as we did with the ice, suppose we were to now to withdraw heat form these examples and were to freeze, or in metallurgical parlance, to quench these systems. In the case of “Metal M,” we would get relatively large pieces of solid from the liquid and relatively small pieces of solid form the vapor in a manner similar to the way the wet ice behaved. In the case of “Metal V,” we would get the same relatively small pieces of solid as we got from the vapor phase of “Metal M,” but none of the larger pieces of solid that previously came from the liquid phase.

If you were wondering what the point of this discussion might be, consider the fact that the sequence we have just described is analogous to what goes on during the EDM process.

The electrical discharge in the EDM process generates an intense heat locally and melts and/or vaporizes a small volume of both the wire and the workpiece. This all occurs in a plasma envelope which eventually collapses under the pressure of the dielectric fluid, thereby quenching the liquid/vapor phases that are present. The solid particulate thus formed is the debris in the gap which must be disposed of (flushed away) in order to maintain the electrical conditions necessary to reform additional discharges. Let me assure you it is much easier to flush the smaller particulate than it is to flush the larger particulate, as you can well imagine. In addition the larger particulate can form a conductive path to initiate a D.C. arc which we will see later can cause instantaneous wire breakage.

Returning full cycle to where we started, it is very helpful to have some knowledge of the relative heats of sublimation of the materials we must deal with in WEDM because that will give us an idea of their relative flush-abilities.

The next edition of WEDM Tech Wise we’ll provide just that sort of information. “May your Sparks always be ON-TIME!”

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