The Toolroom Lathe As An Alternative To CAM

The basic CNC lathe is not just for those who are new to NC.  The ability to quickly program a job at the control can provide a quick alternative to programming off line.

Article From: 4/21/2004 Modern Machine Shop, ,

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Entering the parameters

The operator doesn't program machine moves directly, but simply enters the parameters associated with each machining operation. Larger lathes in the TL line will also use this control. A milling version will be supplied with the company's latest toolroom mill.

Getting manual lathe operators comfortable with CNC is not the only benefit of a CNC toolroom lathe, says Haas Automation applications manager Jeff Endean. While programming a part using CAM software can produce a more efficient machining cycle, the ability to program the job quickly at the control can lead to greater time savings overall if the run of parts is small—or even if the run is somewhat large. Details of the part will determine where the break point lies, but based on users' experiences, Mr. Endean estimates the productive maximum quantity for a typical turned part to be as high as 120 pieces. If the run is smaller than this, he says, then it is likely that an operator can complete the job faster by entering parameters into the CNC and using the program that results, as opposed to waiting for the CAM department to generate a program that is more efficient.

The CNC on Haas's TL-1 toolroom lathe allows the operator to create programs using only the knowledge and information that a manual machinist would possess. An operator touches off the part to find program zero coordinates, then enters parameters relevant to the cut to allow the contol to create the tool paths. For an OD turning operation, for example, the operator enters values such as the intended diameter and the maximum depth of cut. Speed and feed rate default to conservative settings, but these can be entered directly as well. By inputting such parameters for one operation after another, the operator can create the program for a relatively complex part without any G-code understanding.

The G-code program is still there, however. It's written in the background. For users who do understand G code, the program can be called up and edited in this form.

This method of programming—entering part dimensions directly, without translating them for the machine—takes a variety of lathe operations that have traditionally been difficult and makes them easy to perform. Threading is an example. No expertise is required; the operator simply enters thread dimensions that can be found on the part print. Chamfering is another example; it can be performed using an automatically generated diagonal tool path instead of a manual adjustment to the tool block. Also, consider a turned radius. Instead of machining this feature using a tool with the radius ground in, the operator can simply enter the desired dimension and let the control produce this form by means of an interpolated arc.

Advantages such as these can make an intuitively programmable machine into a productive resource not just for the manual machinist, but also for users who are comfortable with G code or have access to CAM. Requiring the operator to enter only straightforward information about the part and the cut reduces the mental effort necessary to think through the correct moves for every feature.

Still, the opportunity to provide an easy entry into CNC is also significant. Though the TL-1 comes with handwheels, they are intended to be used infrequently by anyone familiar with the machine. Instead of using the wheels, it is generally easier to push a button and let the machine rapid to position electronically. The handwheels are there to a certain measure for psychological effect, Mr. Endean says. They ease the transition—during the first week or so—for an operator who is coming to CNC for the first time.

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