Electro Motive (EMD) is a global provider of diesel power engines for marine propulsion, offshore and land based oil well drilling rigs, and stationary power generation. Electro-Motive is the only diesel engine manufacturer of its size to have produced more than 70,000 engines. This success stems from product reliability, serviceability, load acceptance capability, low operating costs and ease of maintenance with standardized components.
EMD utilizes three large Kolb Pentamat bridge mills in a FMS line to machine 20 cylinder crank cases that go into diesel engines they manufacture. The 286”(7M) travel X axis on these machines require linear encoders for position feedback to the Siemens 880 control, in order to maintain the required accuracy on these long travels.
The Kolb bridge mills, had incorporated Hedenhain LB optical linear tape encoders in the original design of these machines, for this purpose. Since these linear encoders need to be installed near the ball screw, contamination of the linear optical encoder from lubricant oil and coolant ingress became a constant problem.
The Newall representatives presented the attributes of Newall’s electromagnetic inductive technology and the advantages vs. optical glass and tape technology. After the presentation, EDM quickly became a believer. “Inductive is the way to go for these machines”. “If these (Newall SHG linear encoders)work the way I think they will, it will save us a tremendous amount of downtime. Tearing down these machines to clean glass scales puts the machine out of commission 3-5 days on average.”
The first replacement Newall SHG-TT encoder was installed on the first Kolb bridge mill in the spring of 2011. EMD verified the positioning accuracy with a laser interferometer upon the completion of the installation to be within +/- .001” in the required 220” of travel, with .0002” repeatability, well within their requirements and the SHG-TT specifications. The SHG-TT has been running with no contamination issues since. EMD ordered another SHG-TT to schedule replacement on the second Kolb machine, and intend to replace the third when available scheduled downtime (or downtime due to failure of the existing Heidenhain LB optical linear encoder) permits.
Mr. Docauer of EDM stated that with the success of this SHG-TT repalcement program on these Kolb bridge mills,they intend to replace all linear optical scales on other machines in the plant as they fail.
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