CNC Control Setup for Milling and Turning:. Peter Smid
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next). The illustration shows the meaning of soft keys when the Offset/Setting selection key is pressed.
Incidently, the meaning of the word soft-key is not related to its physical composition or the feel of one’s finger when the key is pressed. The word ‘soft’ is just a short form of ‘software’ - as in ‘software keys’. The implication is that it is the software of the control system that determines the meaning of each soft key, based on the selection key. That is the main reason why the soft keys are not identified in any way.
Navigation Keys
Regardless of the number of actual soft keys, there are also two arrow keys - one to the left and one to the right of the actual soft keys:
| ▪LEFT arrow key | ... Function Menu selection |
| ▪RIGHT arrow key | ... Operation Menu selection |
In conjunction with each other, these two arrow keys are used to navigate different pages and sub pages of the screen display.
As mentioned in the previous section, the actual functionality of each soft-key is always directly dependent on the currently active Selection Key. In other words, the selection shown on the screen above each soft key will be different for each selection key. The illustration below shows the most common key selections available:
POS Key
POS indicates settings related to various position displays. This is probably the most commonly screen used in part setup. The main modes that can be used are:
| ▪ABS | ... Absolute display |
| ▪REL | ... Relative display |
| ▪ALL | ... All displays |
| ▪MACH | ... Machine position display |
The two main displays - ABS and REL - are used the most. The absolute display is normally used during program processing - it shows the current tool position based on part zero location. The relative display is used mainly during setup, for activities such as setting work offset, tool length offset, and others. In this case, at a certain critical position (commonly at machine zero), the CNC operator sets the relative display to zero and makes the required offset measurement, for example, sets G54 work offset or G43 H.. tool length offset.
Both ABS and REL displays are usually shown in larger form than normally, so they can be seen from a distance during part setup.
MACH selection key shows the current tool position always measured from the machine zero (home position). This display is totally independent from any offset setting or part program data.
If you want to see both ABS and REL position displays, and MACH display as well, on the same screen, just press the ALL selection key. The display of each part is smaller, but all important data is shown on a single screen. In addition to the four modes, the control system also shows some current activities from the part program, such as current spindle speed, cutting feedrate, active program codes, etc.
PROG Key
PROG indicates the program mode. The contents of the screen - what you can actually do - depends on the selection of control mode, located on the operation panel of the control (described in the next chapter):
For the PROG key selection to work, either the MEM (memory) or the EDIT mode has to be selected.
In MEM mode, the currently loaded program can be monitored by viewing it on the screen. Current and next block can also be viewed. No program changes are possible in MEM mode.
If you want to make changes to the current program, you have to choose the EDIT mode from the Operation Panel. As these two modes are separate, there is no possibility of making a mistake, for example, by editing part program currently active.
In the EDIT mode, program can be edited, viewed on the directory screen, program can also be loaded into memory or deleted from the control memory.
Many controls even offer a feature called background edit, which allows programming of the next job, while the current job is running.
OFFSET / SETTING Key
Contrary to some beliefs, this is a dual function key -it does not mean Offset Settings - it means Offset and Settings !
Tool length and cutter radius offset can be set by selecting the OFFSET soft key. Work offset is set by selecting the WORK soft key. In order for either setting to work, the OFFSET / SETTINGS key has to be pressed first.
In this mode, various settings may also be done at the control. The most common setting is the selection of units - metric or imperial (mm or inches). Another setting may relate to mirror image and macros - several others are also available from this screen. Although these settings can be done at the machine, it is always important to follow this recommendation:
Settings that can be done at the control AND in the program, should always be covered by the program
SYSTEM Key
SYSTEM selection key is the entry into the inner workings of the CNC system. There is no harm looking at this display but making any changes is not part of general operator’s duties. Under the SYSTEM key selection, you will find Parameters Setting Screen, Diagnosis Screen, PMC Screen (PMC stands for Programmable Machine Control, which is a version of PLC - Programmable Logical Control). PMC/PLC is used by machine tool manufacturers for many different applications. One of the more common ones is connecting various devices together. For example, a transfer system between two CNC machines uses PMC/PLC, The same applies internally for almost all mechanical functions.
SYSTEM selection key should only be used for viewing various data - changes should always be left to qualified technicians
MESSAGE Key
Typical screens that appear in the Message mode relate to various alarms and operation. They may also show alarm history. Message screen will also appear when a macro program includes message to the operator via a part program.
GRAPH Key
An option on many controls - if available, it shows toolpath motions graphically. The main benefit of this optional feature is that a program can be graphically tested prior to actual machining.