Leadtime Killers OF RAM EDM

Oct. 1, 2004
The prime suspects are setup and programming.

The prime suspects are setup and programming.

In some instances, integrated-tooling systems reduce ram-EDM part and electrode handling and setup as much as 40%

Additive technology like Makino's High-Quality Surface Finishes (HQSF) lowers the resistance of a ram-EDM's dielectric oil and delivers improved part-surface quality, fast finishing, and diminished re-cast layers.

Makino's off-line planning-and-assembly software EDCAM Professional reportedly reduces overall ram-EDMprogramming time by 70%.

Combining integrated tooling with automation in a cell system, such as this one from Makino, further compresses ram-EDM-setup time.

It's typically the same M.O. in every shop with a ram EDM. Long leadtimes kill a machine's productivity, so the faster operators set up and program a job, the quicker they can push the start button. To help them do so, today's EDM OEMs offer several leadtime-compressing technologies, some of which include integrated tooling, automation, and special programming packages.

Integrated tooling and automation speed workpiece and electrode setups. Integrated tooling systems let shops accurately transfer electrodes or workpieces from other types of machines to a ram EDM. An added measuring station with a presetter confirms and stores workpiece and electrode data and transfers it to either a cellmanagement computer or to the machine itself for job execution.

"If a shop isn't using an integrated tooling system, especially for workpiece holding, they aren't going to cut leadtimes," says John Bradford of Makino, Mason, Ohio. In some instances, he's seen shops reduce part and electrode handling and setup as much as 40% by incorporating a table-type integrated-tooling system.

To further compress setup time, shops should combine integrated tooling with automation in a cell system. According to Bradford, between 1985 and 2000, overall average setup times for Makino's customers have dropped 80% through the use of integrated tooling in conjunction with automation.

For customers, Makino equips its Level-Three integrated robot cell with a VMC for machining electrodes, a ram EDM, a 3R Workmaster robot, and Mitutoyo CMM for automatic process verification of both the VMC and electrode specifications.

When it comes to programming, operators consume valuable leadtime making several critical decisions for successful ram-EDMing results. These include determining the number of electrodes for the job, electrode undersizes, types of orbits, optimal power settings, whether to use flush or not, jumping/pulsing parameters, and part-surface-finish requirements. To speed this decision-making process, EDM companies, such as Makino, offer interface tools that simplify programming inputs and software that manages the overall EDM process.

Smart Page is a simple interface tool on Makino's controller. On the program-creation side, operators can go as deep as they want into Smart Page's question-and-answer section. At minimum, they input electrode undersizes, starting-tool number, material combination (graphite to steel or graphite to copper), orbit shape, machining depth, and burn locations. The interface also includes advanced machining methods such as 3D swiveling, undercutting, incline bottom-angle orbiting, thread splitting, and more.

For job scheduling, operators use Smart Page, along with onboard scheduling software, to link and run up to 20 programs. It also permits queing jobs to run and then dropping others into the lineup after the machine starts.

Beyond Smart Page, Makino's EDCAM Professional off-line planning-and-assembly software starts at the CAD/CAM side and lets users import electronic data as it pertains to electrode and workpiece positions. The data transfers to the EDM for running simulations, selecting strategies and uses of electrodes, and simulating dry runs. According to Makino, the software slashes overall programming time by 70%.

The software accepts electrode designs as wireframes or 3D surfaces. Users select data such as representations of the electrode shape or orbiting type, which automatically imports to the machine. They then enter customer specifications for roughing and finishing electrodes and electrode-identificationmanagement information, such as offsets, either from a CMM or a cell controller. Once completed, the software automatically generates NC code.

"This off-line programming eliminates input errors," says Bradford. "Some builders offer off-line systems, but they are usually a reflection of the machine's controller set into a software desktop package that still requires the same thought and manual input for the machine itself."

Beyond setup and programming
Increasing ram-EDM productivity doesn't stop at setup and programming. EDM OEMs also provide shops with technologies that compress actual burn time for both roughing and finishing operations. Four such technologies include Makino's Super Spark and Rib-Head, both for roughing, and its Super Spark II and High-Quality Surface Finishes (HQSF) additive technology for finishing.

Super Spark is a program input that internally converts a ram-EDM's jump into a more uniform and efficient working cycle to speed roughing time by 40% without operator intervention. The technology is effective when using large electrodes or multiaxis machining where the EDM cannot physically move at high speeds.

Makino's Rib-Head is a dual head for roughing when linear depths exceed an inch and created vacuums hinder high-speed movement. The head generates a suction and evacuation plunge, maintains consistent gaps, and eliminates wasted time out of the burn that occurs with a slow Z-axis retract. Jump speeds increase from a standard 200 to 1,600 ipm with the Rib-Head.

Using the same technology as Super Spark, Super Spark II reduces finishing times 20% to 40%. It keeps electrodes in the burn longer but effectively evacuates chips without the use of flushing. According to Bradford, shops combining Super Spark and Super Spark II cut operational time up to 60% for a savings of about $30,000/yr, based on typical volume and hourly rate estimates.

HQSF technology, actually for both roughing and finishing, introduces semi-conductive particles into the gap to aid in the transfer of spark energy from the electrode to the workpiece. Basically, it lowers the resistance of the ram EDM's dielectric oil. The results are improved partsurface quality, fast finishing, and a diminished re-cast layer.

Traditional surface finishes improve in a practical amount of time with HQSF. For example, a 10-µ finish improves to a 5-µ one, and recastlayer thickness drops by approximately 50%, all of which reduces part-polishing times by 30% as compared with standard finishes.

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