Inside Story Issue 2

Founded in 1977, Roembke Mfg. & Design, Inc. (www.roembke.com) is one of North America’s leading designers and manufacturers of tooling used primarily for high-precision molding of rubber materials ranging from LSR to high-consistency elastomers such as EPDM, FKM and Vamac. The parts are used mainly in automotive and other tightly-specified applications such as medical manufacturing.
Issue 2
3rd Quarter
2006
A Mitutoyo America Publication
Family owned, with more than sixty employees and six manufacturing cells, the ISO 9001-certified company occupies more than 62,000 square feet in modern facilities located in the Ossian Industrial Park about 15 miles south of Fort Wayne, Indiana.

The driver behind the design of most Roembke Mfg. molds is precise flash control. According to Gregory J. Roembke, Executive Vice President, “Customer requirements can vary from having extensions on the parts that will deflash easily and consistently, to parts with only a 0.002” maximum extension as they come directly from the mold.”

The degree of design freedom required by the complex, interior shapes often found in Roembke’s molds makes these features virtually impossible to achieve using conventional machining processes which employ a rotating tool or workpiece. As a result, both wire and sinker types of electrical discharge machining (EDM) are an indispensable part of the company’s operations.

Eight years ago the decision was made to bring most EDM work in-house in order to achieve the tightest possible control over the process. And, ever since then, EDM has been the subject of Roembke’s Continual Process Improvement (CPI) initiative.

At first, EDM earned a grade of “Needs Improvement”
According to Scott Shutt, Roembke Technology Development Director, “When we first started in-house EDM processing, there were some very apparent snags. First, the EDM came equipped with fixed electromagnetic fixturing. In operation, the electromagnet generated heat, heating up the dielectric fluid and causing growth in the fixture, and ultimately, in the parts. This threw off our very tight tolerances (some parts are held to ± .0001).”

Also the process was moving extremely slowly. Shutt observed, “The actual burning process was very efficient, but watching the EDM slowly probe to locate each workpiece before each burn had us looking at each other saying, bummer.”

A second factor slowing the pace was the fact that the EDM was idle during the electromagnetic fixture’s extended parts loading sequence which involved draining the dielectric fluid, turning off the magnet, removing finished workpieces, cleaning the magnet, loading a new set of workpieces, filling the fluid and turning the magnet on again.

According to Roembke, “It was obvious that there was a huge waste of time-and-motion. We decided to apply our CPI process to see if we could do better.”

The problematic electromagnet was a relatively easy fix. According to Shutt, “We went to a permanent magnet instead of an electromagnet. We found a magnetic pallet-and-receiver system with the receiver bolted solid to the EDM and capable of repeating to 80 millionths. This set-up gave us a couple of advantages. First, we eliminated the tolerance headaches associated with heat. Second, the pallet was now portable. This meant we could load pallets of workpieces off-line. This got the CPI group thinking, if off-line loading of workpieces could be integrated with off-line acquisition of centerpoints, then nothing would prevent the EDM from burning continually, pallet after pallet, without stopping to pick up locations.”

Insight: CMM enables separation of functions to free-up the EDM
What was needed was a separate machine, dedicated to acquiring workpiece centers – a pallet-load at a time – and with the ability to communicate location data back to the EDM.

Shutt explained, “We realized that a coordinate measuring machine (CMM) uses a probe just like an EDM, except much faster, while being easier to program. Shutt continued, “Since both CMM and EDM are CNC devices, we reasoned it should be possible to get them talking to each other to transfer locations. We just needed to be sure we could get each machine to index the same pallets with sufficient accuracy and repeatability.”
The EDM manufacturer, Mitsubishi, confirmed the feasibility of the concept – now Roembke had to find the right CMM.

Required: production floor CMM plus software
Describing their CMM selection strategy, Troy K. Smith, Roembke Vice President of Customer Development, explained, “We spoke with a short list of major CMM makers with a focus on three issues: We needed a machine able to run 24/7 on the shop floor as opposed to an isolated clean room or lab; we needed software to tie things together; and, we needed strong product support. All this pointed to the Mitutoyo Bright 504 CMM with its accuracy, speed and reputation for reliability.

The Bright 504 CMM came with standard Mitutoyo GEOMEASURE 6000 software. Middle link software was used to translate GEOMEASURE into a language understood by the EDM. Use of the middle link software, however, resulted in programming redundancies which Roembke ultimately eliminated by writing a sub-routine within GEOMEASURE, enabling it to communicate directly with the EDM.

The next productivity-enhancement initiative was to switch from GEOMEASURE to a graphically-driven CMM software able to directly interface with common CAD formats such as ACIS, CATIA, ProEngineer, SDRC and Unigraphics. The intent was to pull 3D models directly from native CAD programs into the CMM part program utilizing native CAD tools to reduce programming time and the possibility for error.

Mitutoyo understood Roembke’s intentions and determined that its MCOSMOS software package provided the necessary capabilities. Shutt elaborated, “While MCOSMOS is real intuitive and we quickly became fluent with it, our objective for multiple CMM applications resulted in some pretty challenging programming. But Mitutoyo fully supported MCOSMOS. Their technical people were always available to us, and Mitutoyo also provided advanced training at their M3 Solution Center in Mason, Ohio.”

Shutt quantified the productivity improvement resulting from the current CMM/EDM set-up. He said, “As a typical example, a run of 50 mold inserts that would have taken two-and-a-half hours when using the EDM’s on-board probe to pick-up centers now takes only twenty minutes using the Mitutoyo CMM.”

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