Tips for Improving Wire EDM Productivity
Originally posted Moldmaking Technology, October 2001
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?
Regular Maintenance For EDM
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.
OEM Parts/Wire/Consumables
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.
Preventive Maintenance Planning
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 a typical WEDM machine. A good preventive maintenance program can help keep a Wire EDM system running consistently.
"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... 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."
Tooling for EDM
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.
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.
CAD/CAM Software
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.
Working on the Weekend - Lights-Out Machining for EDM
Weekend and unattended production time can make a major difference in Wire EDM productivity. To run reliably without constant operator attention, a Wire EDM system should be set up with dependable automatic wire threading, automatic rethreading after wire breaks, stable flushing, reliable workholding, proven cutting conditions, and enough wire and consumables to complete the planned work.
- Use automatic wire threading to move from one opening or feature to another unattended.
- Plan workholding, slug retention, and flushing so jobs can finish without intervention.
- Confirm wire supply, filters, resin, contacts, and wear parts before starting long runs.
- Use proven programs and conservative unattended settings when reliability matters more than maximum speed.
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!
