Simplifying Operator Responsibilities - Dimensioning Methods

All companies expect quite a bit from their CNC operators. Minimum responsibilities commonly include workpiece load/unload, cycle activation, offset adjustments to hold size, inspections on completed workpieces, and reporting inspection results to the statistical process control (SPC) system.

Columns From: 2/1/1998 Modern Machine Shop,

All companies expect quite a bit from their CNC operators. Minimum responsibilities commonly include workpiece load/unload, cycle activation, offset adjustments to hold size, inspections on completed workpieces, and reporting inspection results to the statistical process control (SPC) system. Many companies want their operators to do even more, including machine cleaning and preventive maintenance tasks. Some companies even expect their CNC operators to program and setup their machines.

Two factors make it increasingly important to simplify the effort an operator must exert in order to complete their tasks. The first is related to our entry level work force. In almost every CNC course I teach, someone expresses frustrations about how hard it is to find qualified CNC operators. Most of these people say they are willing to hire anyone who is motivated, willing to learn, and will show up every day. If this is the case in your company, it is important to lower the required skill level an operator must possess in order to run your machines.

While some may argue that even entry level operators must be highly proficient, you will likely find it easier to lower expectations (simplify operator responsibilities) than it is to bring everyone to expert operator status right away. Do remember that even tasks that seem simple to you (or your experienced operators) will be very challenging to entry level operators. And anything that can be done to simplify their responsibilities will shorten the time it takes them to become proficient.

The second factor is time. CNC machine time is expensive. Even if you have expert operators that can handle anything you throw at them, every task they perform will take time. And generally speaking, the more complicated the task, the more time they'll need. Tasks an operator must perform while the machine is not in cycle (like workpiece load/unload) can be very costly. And overly complicated tasks (even those that can be done while the machine is in cycle) are error prone. Simplifying operator responsibilities can result in saved dollars and minimized mistakes.

Dimensioning Methods

One way almost all companies can simplify operator responsibilities is related to how their design engineers dimension workpieces. All CNC operators must, of course, be able to read and interpret a blueprint. However, inconsistencies in dimensioning methods can lead to inconsistencies in manufacturing processes, and can cause wasted time and increase the potential for confusion among CNC operators.

The drawing shows one example of an inconsistency in dimensioning that can lead to (among other things) inconsistencies in measuring devices used to check the workpiece. The keyway in this workpiece is used for exactly the same purpose in an entire family of shafts. However, note that sometimes the design engineer dimensions the keyway from the opposite side (probably the easiest for the CNC operator to measure with a slot micrometer). Sometimes they dimension the keyway depth (requiring a different measuring tool). And sometimes they dimension to the center of the shaft (requiring a measurement and a calculation to be made). Measurements for the purpose of adjusting offsets and/or SPC reporting will, of course, require the operator have the appropriate measuring tools and be versed in three different measurement methods. Note that this is but one example of inconsistent dimensioning that can cause wasted time (even for experienced operators) and can lead to confusion among entry level operators. Almost every product producing company has room for improvement in this area. When approached with this idea, design engineers may be reluctant to change their methods, especially if it means modifying a number of existing prints. They may feel that as long as the workpiece can be made from the print, manufacturing people (including CNC operators) should be able to figure out what needs to be done. Do remember that in value added terms, design engineering is a necessary support task. The company doesn't actual make money when drawings are made. Machining parts (which the CNC operator does) is a value added task. Anything that enhances value added tasks (like simplifying operator responsibilities) will improve the company's profit margin.

Over the next few months we'll be discussing more specific issues related to how you can simplify your operators responsibilities. Based on our exposure to the companies we've visited, many companies can benefit from the suggestions we give. However, by watching your own CNC operators, and by looking for problems their having, you will likely come up with many more ways of simplifying your own operators' responsibilities.

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