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Author Topic: Machining metal problem - Have I missed a setting in Mach?  (Read 1165 times)

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Machining metal problem - Have I missed a setting in Mach?
« on: February 12, 2015, 02:54:05 PM »
Recently my classes have started to machine in metal using our classroom table top CNC mill. Student's machine their part in a scrap piece of wood.  Everything runs fine and  the part is produced beautifully.  The problem arises when we switch to machining metal.  After the first pass we start to notice that the subsequent passes do not line up with the first.  (This does not happen machining in wood).  As the part progresses, the variance gets greater and greater.  At one point, we witnessed the y axis stop and start again while in motion, and another time, the axis stopped, reversed, and then continued in a forward motion.  Here's our question, is there a setting in Mach3 that we are missing, something that needs to be checked when cutting harder materials?  Our motors are rated at 420 oz/in so we assume that they are powerful enough for the task, and mechanical connections are tight and triple checked.  We're at a loss and any help is greatly appreciated with this issue. 

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Re: Machining metal problem - Have I missed a setting in Mach?
« Reply #1 on: February 12, 2015, 05:06:36 PM »
Try reducing the acceleration in motor tuning and see if that helps.
Hood
Re: Machining metal problem - Have I missed a setting in Mach?
« Reply #2 on: February 13, 2015, 04:34:37 PM »
The rating of stepper motors for torque is essentially at 0 speed. The actual torque you get at higher speeds is very dependent on the voltage rating and inductance of the motor and the voltage rating of the drive and power supply. A high voltage motor with high inductance on a low voltage drive and power supply will be gutless at higher speeds.