Maintaining A Wire EDM Machine MoldMaking Technology [PDF]

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2/1/2006 | 9 MINUTE READ BUILD | EDM | MOLD MATERIALS

Maintaining a Wire EDM Machine

To achieve the ultimate capability and level of productivity from your wire EDM on a consistent, re reliable basis, regular maintenance is a required task. BRIAN R. PFLUGER, EDM PRODUCT MANAGER, MAKINO

Over the past three decades, wire EDM (electrical discharge machining) has advanced an

transformed into an everyday, commonly relied upon process. The capabilities and perfo

today’s wire EDM machines continue to develop and improve in the three main machini characteristics: speed, accuracy and surface finish.

Gains in machining speed have reduced overall process cycle times while also delivering

repeatable dimensional accuracy. These wire EDM machines can automatically thread w

0.001 inches in diameter through holes barely larger than a human hair. And they can p

like surface finishes with micro-machined part details so minute that they require a mic with the human eye.

In order to accomplish this capability and level of productivity on a consistent, repeatab

basis, these modern technology marvels must be maintained on a regular schedule, acco manufacturers’ recommendations.

Maintenance Intensive

A wire EDM machine may be one of the most maintenance intensive pieces of equipmen

shop environment. This should not be a concern, as this does not downplay any of the m

productive capability nor indicate any excessive downtime. It does, however, elevate the disciplined preventive maintenance schedule.

For example, a highly-tuned automobile racing engine will not produce at its rated horse

performance levels without regular care and scheduled maintenance. A wire EDM mach

much in the same manner, and will not perform to the speeds, finishes and accuracies th for if not properly maintained.

The main difference between wire EDM and other traditional machining processes in re

maintenance is that it must be done as a proactive and preventive measure. Adherence t maintenance at recommended intervals is crucial to the process performance!

Due to the electro-mechanical nature of wire EDM machines, there are several items in n

that routinely wear and require cleaning and/or replacement. If certain machine compo properly cared for, machining speeds and accuracies will rapidly decay.

The most important reason to properly schedule and perform this routine wire EDM ma

ensure consistent and repeatable machining results for the aforementioned machine tra

accuracy and surface finish. This level of maintenance also prevents machine failure an machine downtime.

There are several wire EDM machine tool manufacturers, and there are some significan

the machine design of each. But the importance and type of basic items that need to be m

wire EDMs are very similar. When planning and scheduling wire EDM machine mainten actions can be grouped into short interval and long interval items.

Short Interval Items Short interval items vary in occurrence from weekly to monthly.

1. Automatic Wire Threading System: The automatic wire threading (AWT) system per

threading of the wire via a water jet column. It is the single most important automa

wire EDM machine. Utilization of an AWT system will extend the unattended operat

machine. AWT units typically require cleaning and alignment checks of mechanical sensors to ensure reliable operation.

2. Power Contacts: These two contacts deliver the electrical cutting power to the wire.

both on the upper and lower machine heads—will erode over time, resulting in a si

decrease of machining speed. They require a simple indexing and cleaning, and eve replacement.

3. Belts and Rollers: These items make up the wire transport system. They require eith

indexing, or replacement to prevent wire slippage or wire tension problems that ca inaccuracies.

4. Brake/Clutch Roller: This roller is the most critical item in the wire transport system

create and control the proper tensioning of the wire. If wire tensions are not held to parameters, workpiece inaccuracies, exces-

sive wire breaks and excessive wire lines on the workpiece may result. This unit is t

maintained with the aid of an OEM (original equipment manufacturer) supplied pro calibration cycle.

5. Wire Guides (2): These guides—either diamond or sapphire—are located in both the machine heads. They are used to align and locate the wire within the machine. The

most important item within the machine because they deliver and transfer the mac

accuracy into the workpiece. They require cleaning to prevent misfeeding, clogging inaccuracies and failure.

6. Wire Alignment: This procedure is typically required after wire guide cleaning with

OEM supplied jig or fixture, and is performed to calibrate and align the wire within

verticality. If the wire is not properly aligned for verticality, machined results will c positional part locations will be inaccurate.

7. Wire Collection Box: The wire is only used once within the machine, and will accum

bin that will need to be emptied periodically. The spent or used wire should be rout

emptied per manufacturer recommendations. The spent material can typically be r an industrial materials scrap recycler.

8. Machine Seals: Many machine designs require cleaning of a door and tank seal to en

integrity and longevity. Seals will need to be replaced once they become degraded b service life and can no longer sufficiently prevent or control water leakage.

9. General Cleaning: With the intricate wire EDM process, debris is typically scattered throughout the work tank. Over time, this debris can accumulate and build up into

is difficult to clean. Scheduling a monthly machine cleaning using a standard cleane

large buildups of debris. Less overall time will be required the more frequent the cl

Generally, the cleaner a machine is kept, the less likelihood there is for unsuspected arise. This also may extend the life of some long interval consumable items.

Long Interval Items Long interval items vary from bi-monthly to yearly. 1. Machine Filters: Replacement of the main water filters will be required and should

needed (most machines will typically generate an alarm when the filters are deplete

intervals are purely dictated by the type of work, workpiece material and thickness

being performed. Many machines also contain a safety filter for the AWT system tha

replacing periodically (six to 12 months). The filtration system on a wire EDM is fun necessary because it controls the amount and size of particles/debris that can exist

through the flushing system during machining. If this debris is excessive and of a la size, machining will be very unstable and inefficient.

2. De-ionization Resin: This is a special resin that is used to control the conductivity of

the machine. If the conductivity or resistivity of the water is not controlled and sust

level that the machine requires, machining will become very unstable, and final res

inaccurate. The de-ionizing (DI) resin is replaced when needed (most machines will

generate an alarm when the resin is depleted). There also is a conductivity/resistivit requires cleaning to ensure proper level readings.

3. Water Level: Over time, the water level in the machine reservoir will become low fr

and will need to be replenished. The quality of the incoming water (tap water is typ affect the life of the DI-resin.

4. Belts, Rollers and Pulleys: Certain machine designs require periodic replacement of

rubber rollers and pulleys. Replacement may be required due to physical wear of th

from wear of replaceable bearings. It is very important that these items be maintain

and/or replaced by specific procedures and intervals suggested by your machine too

Failure to keep these items within operational specifications will result is part inacc machine downtime.

5. Wire Choppers: Some machines contain a wire chopping unit that cuts the used or s

small pieces. Maintenance on this unit will include the sharpening or replacement o

and dies. The results of allowing these cutting edges to become excessively dull will

workpiece inaccuracies, excessive wire lines on the workpiece and machine downti

6. Cabinet Filters: Some machine designs require the changing or cleaning of an air fil

filters are commonly found on intake fans of the electrical/generator cabinets and w

These filters should be inspected, cleaned and replaced at regular intervals specifie these filters become excessively clogged, air flow will be restricted, which will lead and failure of the equipment.

7. Machine Seals: Due to specific seal designs, some seals and/or gaskets may require a

replacement to ensure proper machine operation. The seals/gaskets that typically re

attention are the work tank door gasket and the lower arm tank seal plate. Proper m

care of the lower arm sliding seal plate is especially important because as this seal w increases, machining accuracies also may be degraded.

8. Machine Floats: Most manufacturers recommend a yearly inspection and cleaning o operational and safety float switches. If these floats become excessively dirty, their fail, resulting in damaged machine electrical components and water spillage.

9. Water Reservoir: The quality level of the water within the machine can become deg

and heavy sediments also can build up in the water holding tanks. Contaminants fr

agents also can change the pH levels of the water, all of which can affect the perform

machine. Most wire EDM manufacturers recommend that the water be drained and

reservoir cleaned yearly. Insufficiently monitoring and maintaining the reservoir sy

in excessive machine corrosion, sedimentary buildup and machine component/pum

10. Machine Lubrication: Check with your machine’s OEM on recommended intervals a

for machine lubrication. The most common items that require attention are the ball linear guide way systems. Be sure to use the proper lubricants that are specified by

Improper lubrication of the machine will lead to workpiece inaccuracies and the ev replacement of costly machine mechanical components.

General Cleaning Importance

Good cleaning habits and care of a wire EDM machine is highly recommended. Regular a cleaning of the machine also can extend the life of some consumable items.

Care should be taken when selecting a cleaner. It is recommended that a general, all-pur

cleaner/degreaser be used for general cleaning. A mild, watered-down solution of acid (t

cleaners are phosphoric acid based) is used for the cleaning of more heavily soiled mach

When using any cleaner, it is best to apply the cleaner to a rag and not directly spray cle

machine. This will result in using less cleaner as well as controlling the contamination o reservoir.

Do not allow caustic or acidic cleaners to sit on some surfaces too long as they may etch,

damage surfaces. And avoid getting cleaners on attachment points where power cables c

machine heads, as cleaners can act like a corrosive agent and degrade the power cables.

After cleaning, be sure to wash and rinse cleaned surfaces with water. This will ensure t are properly removed prior to operation.

Keep in mind, the underlying concept and operating strategy for wire EDM is to maximiz

machining time. With a properly maintained wire EDM machine, the goals of maximizin time and greater overall process efficiency can be more easily achieved and realized.

Due to machine design differences, the type and time intervals of machine maintenance

highly recommended to check with and follow the maintenance specifications, intervals

supplied by your machine OEM. If maintenance requirements, procedures or intervals a

contact your OEM or refer to your machine’s maintenance manual for more information