October 2012 / Volume 64 / Issue 10|
Limiting tool vendors boosts efficiency
By Christopher Tate, Mitsubishi Power Systems
Selecting cutting tools may seem like a simple process, but without a plan it can become complex, needlessly costly and a source of machining errors. As part of an operations improvement plan in the combustion shop at Savannah Machinery Works, a startup operation, our team set two goals for selecting cutting tools: provide a system that minimizes opportunity for tool-selection and tool-usage errors and streamline the procurement process.
The first step toward error reduction was limiting toolcrib items and vendors. This was made easier because we were starting from scratch. We grouped cutting tools into categories by machining process and selected one toolmaker for each of four categories: indexable tools, solid-carbide drills, solid-carbide mills and threading tools. (We wanted different vendors for each category.)
Selection was based on the toolmakers’ experience with power generation and aerospace manufacturing and high-temperature superalloys, catalog offerings and technical support. The last item was heavily weighted as we needed to develop new machining processes.
After selecting toolmakers, we met with their application engineers and identified tools for our materials and processes. We focused only on proven tool technology and tool series that offered the largest size range.
For the indexable mills subcategory, we avoided proprietary inserts and tool bodies where possible so inserts could be sourced from other manufacturers, if needed. For indexable turning tools, we selected CNMG and CCMT 4xx series inserts so we could quickly find suitable substitutes, if needed. In both cases, we selected two insert grades: one for machining steel and one for nickel. By limiting choice, we minimized the opportunity for errors.
We met with technical representatives from the solid-carbide drill manufacturer, who helped us select tools proven for our work materials in a large range of sizes. This is because we drill a large range of diameters and depths using only one series of drill.
For solid-carbide mills, we initially chose a large toolmaker with an extensive catalog, but repeated delivery problems made us look elsewhere. We turned to a small toolmaker we were using for specials. We did not initially consider them as the main supplier because we were unaware of their full capability. We knew they had a lot of experience in aerospace and power generation, but we discovered they also stock a large number of catalog items.
Courtesy of Savannah Machinery Works
This company now makes and reconditions all of our solid-carbide mills. Our relationship with them has proven very beneficial. They are a 4-hour drive from our plant, so we can issue a purchase order during the first shift and have the tools on a machine for the second shift.
Our regrind program works much better now because each tool is returned in the original box, eliminating any confusion. Tools are also reconditioned using the same machines and programs used to manufacture them, so, except for size, the tools are essentially the same as new.
We don’t perform a lot of threading, but when we do we use thread mills exclusively. We work with expensive, difficult-to-machine materials and any rework is costly; therefore, we don’t tap production parts. For this category, we selected a toolmaker experienced in thread milling.
As we developed new machining processes, we scheduled training classes with the toolmakers. Machinists, programmers and engineers were instructed on selection, assembly and cutting parameters for each tool category. Catalogs and technical manuals were placed in each manufacturing cell and in the toolcrib. Toolcrib attendants, who requisition tools, were paired with the toolmakers’ inside technical representatives. This level of personal contact helps prevent ordering errors.
Limiting the number of vendors and items has reduced complexity and improved productivity. This doesn’t mean, however, that we are not open to finding new sources. As in the case where we changed milling tool suppliers, adding new items only requires creating a report that lists the items we purchase from a manufacturer and cross referencing them with the new manufacturer’s part numbers.
Limiting toolmakers does, however, have some drawbacks. It could, for example, limit the willingness of vendors to introduce different technologies. Also, we have decided, in rare instances, not to use a tool that saves only a small amount of cutting time so we don’t introduce a different tool manufacturer to the toolcrib.
However, these rare situations typically occur only in the machining cells, where our cycle times are measured across multiple shifts. In addition, the small cycle-time inefficiencies are generally insignificant and are easily outweighed by the system’s benefits.
Our system works well in part because the engineering staff works directly with our counterparts in the supply chain and operations departments. Because we share a common goal, the system is easier to maintain—which is particularly important as more people join the SMW team. CTEAbout the Author: Christopher Tate is manufacturing engineering lead for machining at Mitsubishi Power Systems, Savannah (Ga.) Machinery Works, a global builder of gas and steam turbines. He has 19 years of experience in the metalworking industry and holds a Master of Science and Bachelor of Science from Mississippi State University. E-mail: firstname.lastname@example.org.
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