Production Machining

SEP 2017

Production Machining - Your access to the precision machining industrial buyer.

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productionmachining.com :: 17 Helping Precision Machine Shops Be More ProducƟve and Proftable I lived in northern Georgia for five years, and whenever questions of distance came up, the answer was always "miles." Sometimes, it was qualified by, "as the crow flies." When I returned to Ohio after my Georgia assignment, I was amused to learn that questions of distance were almost always answered in terms of time, such as "that's about a half an hour away." That is a typical Ohio response. I am often asked my opinion about a material's machinability, and I have found that I have to assess the person's motivation, job title and location before I can answer the question. I often find, when listening to managers and estimators here in the U.S and Canada, that they tend to answer the machinability question with "cycle time," which, since it is derived from both material and the configuration of the part to be produced, can lead them to a conclusion that is not 100 percent correct. Some engineers are satisfied with surface feet per minute, as they can compare that to other materials and jobs they have run. Others ask, in the case of steel, as a percentage of 1212, or in the case of brass, compared with C36000 (360 Brass). Surface feet per minute is one factor in calculating cycle time and distinct for each material, but it is surely not the whole picture. On some of the more difficult-to-machine alloys, the question of, "What is its machinability?" is best interpreted as, "How bad will my tool life and downtime be?" That is, unless it is an actual machine operator. The most experienced machine operators always ask, "What are the chips like? How will they behave?" So what do we mean when we say machinability? What is it that others mean? What is the truth that we really seek? What do we really want to know, and where can we find that? In this case, how we answer is dependent on our location, just as being located in Georgia or Ohio gave us clues as to how to best describe distance. Purchasing If you're located in the purchasing office, machinability is a presumed attribute of the material required and of no apparent consequence. Price per pound and delivery are the sole concerns. And yet, purchasing decisions can have a profound effect on machining performance. Changing suppliers in search of lower cost per pound or faster delivery What Machinability Means Depends on Where You Are By Miles Free – Director of Technology and Industry Research changes the material and the way it performs in your shop processes. Different suppliers use different recipes, processes, practices and technologies to deliver a bar that meets the broad requirements of the specification. But your shop may be optimized in one narrow band of that specification. Shopping for price rather than aiming for supplier stability throws the variation of the entire world at your shop people to deal with. Limiting suppliers for each item is the best way that purchasing can assist the shop in achieving its goal of consistent, efficient machining. Shop Supervisor If you are the shop supervisor, you don't just have one material to deal with. You have many. You are looking for simplicity and stability in a complex world. For the shop supervisor, it is the ability of the material to travel through the shop, starting as bars and ending as parts with the least amount of aggravation and trouble needed! While that implies the machining performance of the material, for the supervisor, a host of other deliverable attributes can, if not properly provided, sabotage his version of machinability. If the packaging is wrong, if tags are missing, incomplete or illegible, then the amount of aggravation and trouble increase and the supervisor loses production. Are missing, incomplete or illegible tags a factor for machinability? Unexpected downtime is not a positive for machinability in the shop. Dimensional variance, lack of straightness and deformed ends of bars are not machinability issues, per se, and yet, they cause the operation to slow down, be delayed or take extra time to produce, not counting the extra efforts needed for inspection and product validation. Continues on page 20

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