The goal of any machining operation is to produce accurate parts at the lowest cost, thereby maximizing profitability. The traditional way to lower machining costs is to accelerate production rates with more aggressive machining parameters, usually focusing on faster cutting speeds. That approach, however, does not recognize significant cost factors including the expense of scrapped parts and production downtime. Use the following 5-step strategy to balance productivity and manufacturing costs.
1. Focus on the Costs You Can Control
Some elements of manufacturing costs are beyond your control. Workpiece material type is dictated by the end use of the machined component. Likewise, costs for machine tools, maintenance, and the power to run them are basically fixed, usually involving ongoing payments. Your strategy for increasing production economics, therefore, should focus on the variable costs such as machining process elements like which cutting tools you use and the parameters in which they are employed.
2. Find Optimal Parameters
There is a common misconception that simply increasing cutting speeds will produce more parts per period of time and thereby reduce manufacturing costs. While using higher cutting speeds can increase production rates, it may also result in higher tooling and machine tool costs. Finding optimal parameters is essential and requires a balance between reduced cutting speeds and proportional increases in feed rate and depth of cut. The ideal is to use the largest depth of cut possible to reduce the number of cutting passes required and machining time. At the same time, maximize the feed rate, albeit carefully so as not to negatively affect workpiece quality and surface finish requirements. When a stable and reliable combination has been reached, cutting speeds can be used for final calibration of the operation.
3. Reduce Machine Tool Costs
Higher speeds initially drive down machine tool costs because the machine tool is producing more parts per period of time, therefore more revenue can be applied against its fixed cost. However, as speeds rise beyond a certain point, machine tool costs begin to increase. Tool life becomes so short that the decrease of the machine tool cost has a smaller effect than the fast increasing costs of tooling and downtime for tool changes. In addition, extremely high cutting speeds and very aggressive machining parameters in some cases can add to machine tool costs for maintenance and even result in downtime caused by unanticipated machine failures.
4. Follow A Model of Efficiency
American mechanical engineer F.W. Taylor once developed a model for determining tool life that shows that for a given combination of depth of cut and feed there is a certain window for cutting speeds where tool deterioration is safe, predictable and controllable. When working in that window, it is possible to quantify the relation between cutting speed, tool wear and tool life. Following this model brings together cost efficiency and productivity and provides a clear picture of what to aim for when defining the optimum cutting speed for an operation.
5. Establish a Stable Machining Process
The key to maintaining productivity and part quality and avoiding scrap is establishing a stable machining process. Create an optimum production environment by choosing the tool material, coating and geometry best suited to the workpiece and operations at hand, and optimize the machining CAM program, toolholding systems, and coolant application. Be sure to integrate workhandling automation such as pallet or robotic part load/unload systems into the process as well, because handling of raw and finished part stock can consume significant amounts of machine downtime.
About the Author
Todd is the manager of product marketing for Seco Tools, LLC. He oversees the product marketing team and works with the company’s sales department to further enhance the customer experience. He and his team also support product introductions while working globally on new product testing to ensure customers gain access to the industry’s most advanced tooling as quickly as possible. In his spare time, Todd likes to bowl and cheer on the University of Michigan football team.
Email: [email protected]