Modern Machine Shop

OCT 2018

Modern Machine Shop is focused on all aspects of metalworking technology - Providing the new product technologies; process solutions; supplier listings; business management; networking; and event information that companies need to be competitive.

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CNC TECH TALK MMS OCTOBER 2018 38 Processes and Programming AUTHOR | Mike Lynch Founder and President, CNC Concepts Inc. tool as it machines the first workpiece, each cut- ting tool will machine properly, and the first work- piece produced will be a good one. Here is the general process for trial machining: • Stop and consider what the cutting tool will be doing before it runs. For example, M01 (optional stop) is commonly used to make the machine stop after each tool. Also, trial machining is only required for critical/finishing operations. • Adjust each finishing tool's o„set(s) so that the tool leaves additional stock. • Run the tool, stopping the machine when it is finished. • Measure the machined surfaces. There will be additional material to remove. • Adjust the cutting tool's o„set(s) based on the target value for the most critical machined surface(s). • Rerun the cutting tool. This time, machined surfaces will be close to their target values. • Repeat for each finishing tool. Ensure That Roughing Tools are Leaving the Correct Amount of Finishing Stock While roughing tools do not require trial machin- ing, setup people must measure the surfaces they machine to ensure that the proper amount of material is being left for finishing. If they do not, finishing tools may have to machine much more (or much less) material than intended. In either case, the finishing tool will not machine properly. Look at the Process With repeated jobs and with our recommended methods, if experienced setup people are con- stantly struggling to produce a start-part, it should be taken as a signal that the problem may be with machining process. The issue(s) could be related to workholding and/or support methods, cutting tool and cutting-condition selection, or machining order. If a quality control person provides the go-ahead when the workpiece passes inspection, they must understand the related urgency. A CNC machine will remain idle until the first workpiece inspection is done. DEBURR ANY CROSSHOLE

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