CNC Tips & Techniques, Page: 1   2   3   4   5   6   7

CNC Tips & Techniques (p. 2)

What is the difference between a 2.5 and 3 axis machine?

An axis is a direction of motion controlled by the CNC machine control. It can be linear (motion along a straight line) or circular (a rotary motion). The number of axes a machine has determines it's machining capabilities. A 2.5 axis machine really has three moving axes, but only two axes can move together (most machines sold today are full three axis machines). For machining centers, a three axis machine will have three linear axes. A four or five axis machine will have three linear axes as well as one or two rotary axes. (Article)

How wise it is to use wear offsets for different diameters on a lathe?

 ...I assume that the problem is caused by a tool pressure difference from one diameter to another. Additionally, I'm assuming that as the finishing tool wears, tool pressure changes again, requiring one or more adjustments during each tool's life. First of all, I urge all programmers to program the mean value of each dimension for all coordinates used in the program. This gives you the best shot at being able to hold size for all dimensions with one wear offset. (Article)

What are the benefits of constant surface speed?

For Fanuc controlled turning centers, G96, of course, specifies constant surface speed mode, while G97 specifies rpm mode. In constant surface speed mode, the spindle speed in rpm is automatically determined by the CNC control based upon the diameter a tool is currently cutting and the speed specified in surface feet per minute (or meters per minute in metric mode). This mode is only used for single point turning tools (boring bars, turning tools, grooving tools, etc.), when diameters to be machined change substantially throughout the work piece. There are (at least) four benefits to using constant surface speed mode for appropriate applications. (Article)

Why can't I load all programs from one file?

With all Fanuc controls, including the 6M , a parameter controls when the control will stop reading a program coming in from your DNC device. By my 6M documentation, it appears to be parameter number 306, bit number 3 (it's label is NEOP - don't ask me what that stands for) for a 6M control. Please check this in your own documentation to confirm. If bit 3 (the fourth from the right) is set to a 0 (as I believe it is on your control), the control will stop reading a program as soon as it sees the first M02, M30 or M99. Since your subprogram ends with an M99, the control doesn't continue reading the main program, even though it's part of the file being sent. If this bit is set to a one, the control will continue reading all programs until it sees an end of file character, which is a percent sign (%) for Fanuc controls. (Article)

How can I confirm that the right pallet is in position?

 Many machining centers, especially horizontal machining centers, come with a two-pallet pallet changing system. The operator loads one pallet while the other is in cycle. It is quite important, of course, that when the operator activates the cycle, the correct pallet is in the machine. A mistake in this regard can be disastrous. Unfortunately, most machine tool builders provide little in the way of pallet confirmation. Again, if the wrong pallet is in the machine, the control will simply activate the program, ignoring the problem. If your machine has parametric programming capabilities, it is quite easy to add your own pallet confirmation system. We're showing the example in Fanuc's custom macro B, but with a little ingenuity, you should be able to apply this technique with just about any version of parametric programming. (Article)

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