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Feed Rates
The WELturn microcontroller unit is able to drive the lathe axes at rates ranging from about 10mm/min to in excess of 700mm/min in increments of 1mm/min. (700mm/min is the maximum recommended by Emco). The microcontroller has stepper motor acceleration control to prevent steps being missed, and therefore tool position lost, when sudden fast movements are required. The lathe does not have a measuring system which feeds positional information back to the PC. Dimensional accuracy depends on initial setting of the tools, measurement of the diameter of the billet and the stepper motors responding to every step and not missing any of them.
In NC code, cutting feed rates can be entered either in mm/min or in mm/rev or, for Imperial (inch) machining, inches/min or inches/rev. A mixture of /min and /rev can be used in a program for a part. WELturn does not require a special G code to tell it which units are in use. It assumes that if a metric feed rate (an F value) is 1 or greater, then feed in mm/min is being used. If a feed rate (an F value) is less than 1, it assumes that feed in mm/rev is being used.
For Imperial (inch) machining, if a feed rate (an F value) is 1/25.4 inches or greater, then inches/min is being used. If less than 1/25.4 inches, WELturn assumes that feed in inches/rev is being used.
Cutting feed rates in mm/rev (or inches/rev) are most commonly used and are to be preferred. As a single step of the stepper motors which move the tool along the X and Z axes is 1/72mm (0.01389mm), the lowest cutting feed rate in mm/rev should be 0.01389mm/rev. If a lower cutting feed rate is set, the tool will not be cutting but rubbing for part of a revolution of the billet and this may have an adverse effect on tool life and surface finish.
Finishing Cut Directions
Speeds and Feeds for Turning and Parting with Indexable Tipped Tools
Surface Finish - Depth of Cut
Surface Finish - Feed Rate