Tips on Improving Wire EDM Productivity
By focusing on such aspects as maintenance, tooling and training, moldmakers can increase the productivity of their wire EDM significantly.
There are many areas inside the typical mold shop where productivity can be improved. The most obvious place to look at certainly might be the wire EDM (WEDM) itself. When was the last time the machine had a tune-up or a filter change? Just like your automobile, if you do not take care of certain items, poor performance and costly delays can happen down the road. Other areas inside the mold shop may require some more serious thought: programming methods, tooling methods, automation capability, people flexibility and overall ease of how your entire system runs.
Think for a second exactly how you would define "productivity." If your operator increases the servo control and cuts a set of electrodes or inserts fifteen minutes faster than previously, then yes, you are being more productive. On the other hand, if you must still manually set up the next set of parts with the WEDM sitting idle or the WEDM finishes the parts just after your operator has left for home - where has your productivity really gone?
Keeping a daily logbook next to the machine or on a nearby PC is a step in the right direction. We are all too busy juggling 15 other projects at one time. Face it, who is going to remember the last time the power contacts or filters were changed?
Preventive maintenance is the best maintenance. Keeping a diary of how long the wear parts and consumables last provides a history so that you know when to get off the race track and come in for a quick pit stop. Some WEDMs even have fairly accurate timers that can give you a heads-up notice.
The most important thing recorded in your logbook is the weekly WEDM machine "cutting hours." Each year you are given 8,760 hours. You don't have the option of buying any more time - you just have the challenge of deciding how to use it all up. The more weekly cutting hours that you can squeeze out of the WEDM is the best measure of your overall productivity.
The replacement parts and consumables that you use on your machine can help or hurt you depending on whom you buy them from. Saving money on some items is a good thing - but not if it causes accuracy or reliability problems. Certain parts and materials were OEM designed specifically for each model of machine. Check with your OEM application support or service engineers to make sure that you are not chasing a problem of poor performance or accuracy just because of a $20 part.
OEM Maintenance Contracts
Every mold shop has qualified repair people who must work on a variety of different machine tools and keep them all running so that the shop runs smoothly. However, it takes a lot of experience to know the ins and outs of your typical WEDM machine. A good preventive maintenance (PM) program can keep your WEDM running 24-7. David R. Kennedy III of Kennedy and Bowden Machine Co. (Nashville, TN) - an 87-year-old family tool shop specializing in injection molds for plastics - has this to say about his PM experience: "Over the years we followed the prescribed maintenance and kept our machine in good shape, but we began to have unplanned shutdowns due to worn or broken parts. Then our supplier's service department offered us an extensive PM program for our machine for just a little more than the cost of the parts. The service engineer not only replaced components and tuned up the machine, he also showed us how to better maintain and use our machine. Since the PM, we have experienced no loss of machining time, the machine cuts at the speed we originally experienced and threading reliability has improved immensely. We got more than our money's worth and will be repeating this program periodically to ensure we get the most for our machine tool investment."
In today's world, technology, hardware, software and machine features are changing everyday. Even so, it is people and not just machines that are the most critical part of a company's success and rate of growth. In many shops the current WEDM operator never attended an official OEM machine training class. Often it is the case that the first operator showed the second operator what buttons to push and how to set up a part. Later, the third operator runs the machine from the second operator's "years of experience."
Check to see if your supplier offers free operator training to companies purchasing a new wire EDM. Some offer it for as long as you own the machine. Sending an operator to one of the OEM demo centers for regular or advanced classes can turn your WEDM productivity in the right direction - not to mention improving the knowledge and morale of your WEDM department personnel.
Every WEDM comes with a basic table having a left, right and back rail. Depending on the size of the shop, you may have just a few - or maybe even a few hundred - pieces of tooling holders and fixtures. The key to obtaining greater productivity when it comes to tooling is standardization and palletization. By having everyone use the same type of system, setup times can be significantly reduced. Often we think it is just easier to set up and indicate a part on the back rail. It will only take "just a few minutes" to set up. Compared to the two or three hours of cutting time, it seems a very short time. This could not be further from the truth. Take a closer look at the amount of work that could fit on a wire EDM pallet or holder. There are many benefits to palletizing:
- Wire EDM is able to cut around the clock while someone presets parts on wire pallets.
- You are able to switch out parts quickly in just a few seconds.
- Table chuck repeatability within 0.000080".
- You are able to switch work from one machine to another.
- You can stop a part, then go to the hot job and back again.
- Standard tooling is used throughout the shop and CMM.
Just like standardizing your tooling, having only one programming system throughout the shop is a must in order to streamline the production of CNC programs. Each station should have the same software release level, identically configured PCs and should have the latest postprocessors for the specific type of wire EDM machines to avoid the editing of programs after post processing. Adopting a standard programming technique eliminates the programmers having to constantly interface with the EDM operators.
We truly live in a global economy today. There is one particular company that has divisions in North America, Asia and Europe. Through a common network system it has two or three programmers programming eight hours a day. A programmer often starts an urgent job in the afternoon and when he comes back the next morning the program is ready and waiting after being completed by a programmer 3,000 miles away at another division.
There also is a system available that enables slugs to be removed automatically between the roughing and finishing operation of your wire EDM. The package consists of a hardware device for knocking out slugs and a programmable software instruction that the EDM uses to make a triangular attachment in order to hold the slugs securely. It's easy to use and the best part is that it can be retrofitted on a select number of machines.
The system can save you time and money. Imagine that it's 11:30 p.m. - the workpiece that your operator loaded at 5:00 p.m. is done roughing all 10 pockets. But just because your operator turned in for the night doesn't necessarily mean that your wire EDM has an excuse to go to sleep. This system:
- Finishes the job unattended, day or night,
- Allows more possible machining hours per week,
- Allows more time for operators to perform other tasks, and
- More work is delivered to your customers - faster.
The system can handle slugs with a maximum slug height of 4.7 inches and slug weight of 2.2 pounds. For those who have larger slugs that must be removed manually, the standard software can be used to make the triangular attachment, helping to keep the slug rigidly in place. This can help to avoid marking up the finished part when removing the slug at the end of your machining program.
Working on the Weekend
Weekends are for the family. Weekends account for 104 out of 365 days - which equals 2,496 hours or 28.5 percent of one year's time. People working on the weekends is a thing of the past. Your WEDM must have one or more of the following in order to compete in today's global economy:
- Automatic wire threader (AWT) device to move from one pocket to another unattended.
- Automatic re-threading device (RTH) in case the wire breaks accidentally.
- Automatic restart device (ART) in case the main power to the machine goes down momentarily.
- Large 20/25 kg (44/55 lb.) wire spool option to handle the weekend operation.
- Automatic pallet changer or robot to load/unload workpieces at night or over the weekend.
Call your OEM and find out about what programs they offer for upgrading your existing wire EDM.
The EDM foreman at one European company that does work for Rolex had trouble justifying the purchase of a robot to upper management for many years. Management firmly believed that the WEDM was not a place where the cost of a robot could be justified. Eventually, management agreed to retrofit a robot on one of their existing machines on a trial basis. During the day, the operators continued to run the machine in manual mode. At 5:00 p.m., the WEDM was switched to automatic mode and the robot would finish various parts that were left waiting in the robot carousel. Management saw the WEDM productivity jump from 40 hours to 100 hours per week. This customer now states that they would never buy another WEDM without a robot.
Twin Wire EDM Machining
Until now, the choices available to operators involved in machining operations ideally requiring two different wires were limited. They performed both roughing and finishing with the same 0.004" diameter wire, thus slowing down the manufacturing process. Or they manually switched wires - cutting productivity as a result of a tedious changeover process. But this is now a thing of the past. Now, new wire EDM machines are designed with a fully automated dual-wire system, allowing operators the flexibility and versatility that they want without the need for manual intervention or changeover.
Without the need to change wire guides or to perform dual pre-settings, operators no longer run the risk of losing precision by manually switching wires. Instead, some wire EDM's are now capable of choosing for each cavity the optimum solution in terms of productivity and work schedule. And since operators now have a choice on how to best optimize the performance of their machine, they enjoy the kind of flexibility they never had before.
Twin Wire Benefits
- Automatic wire changeover on one and the same machine for flawless roughing and finishing in half the time.
- Just one second to change from one wire diameter to the other for a combined threading and changeover time of no more than 45 seconds - much less than manual intervention or switching to another machine.
- Precision remains unaffected by changeover whether operations involve roughing or finishing.
- Maximum versatility allows operators to schedule unattended machining jobs as they see fit (overnight, weekends).
The Next Move
It has been said that doing something is better than doing nothing. Start conversing with your co-workers. Talk to other companies and find out what they are doing to improve quality, communication and productivity inside their WEDM facility. But hurry up and do it now - the clock is still ticking.
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