they may be the norm. For example, three dimensional machining in mold work may use a single tool and let it cut for much longer than one hour. For example, what happens if a three hour cutting time experiences a lube alarm after two hours of machining? This is where the reserve comes into the picture.
Stopping machining before all cutting is completed, when the tool is just fine, is not only inefficient, it can cause various flaws to the machined part. In such cases, machining will not stop, when the lube alarm comes on. In fact, the machining will continue normally for the remaining time, until machining with this tool is fully completed. From the time of the first lube alarm appearance to the end of the cutting, the lubricating oil will be taken from the reserve in the container. That is the basic design about having a rather large reserve.
In summary, until it is interrupted by the program or by manual interference, the slide lubricant will be taken from the reserve the moment the lube alarm has occurred. Practically, it means that the lube alarm light will turn ON when oil level indicator reaches ‘low level’, and it will remain ON until the oil level in the reservoir is increased. If any machining takes place when the light comes on, the machining will be completed, as long as there is sufficient supply of lube oil. Having a rather large oil reserve guarantees that even a long machining sequence will be completed.
While the lube alarm is active (red light is ON), no further machining will be possible after the control system detects program tool change function M06, program stop function M00, optional program stop M01, or program end M30. In order to continue machining after these functions, the lube alarm must be eliminated by adding more lube oil to the reservoir.
When the LUBE alarm is ON, machining cycle will be completed, but program will not continue until the lubrication oil level is increased
The CNC operator can turn a number of switches located on the operation panel to ON state or to OFF state, as necessary to achieve certain operating conditions. These are important switches, used daily, and there are many of them located within the operation panel.
Depending on the controls system (manufacturer’s preferences), these switches can be of two types:
| ▪Toggle switches | ... UP and DOWN |
| ▪Button switches | ... IN and OUT |
Both types work on the same principle - they both select one of two modes available. For example, you flip the switch up or down (for toggle switches), or you push the button once and push it again (for button switches).
Regardless of the switch type, either of the two selections will make the particular switch inactive (OFF) or active (ON) and its function disabled or enabled.
The English word ‘toggle’ means a ‘selection from two opposite options’. A typical household light switch is a good example - it can be either ON or OFF - other options are not possible. In CNC, the operation panel has quite a number of toggle switches, mostly offering a selection from two possible options. Operation panel toggle switches can be similar to a common light switch, at least in the sense that they can be operated by flipping the switch up or down. Toggle switches can also be of the push-button type - push once for ON selection, push once more for OFF selection.
Normally, all toggle/button switches are OFF and activated only as needed. The one exception is the Manual Absolute switch (if available), which should be normally ON. This is a special purpose switch and will be described later in this chapter.
Several toggle switches can be used in combination to achieve a certain desired result, but understanding each switch individually is most important.
In this chapter, the UP/DOWN type of switches will be shown, as they better show their state visually.
Optional Stop
Optional Stop switch is only one of several switches that require a part program input in order to be fully functional. When the miscellaneous function M01 is contained in the part program, the CNC operator may choose to use the Optional Stop switch by setting it to ON position or leave in the normal OFF position.
When the M01 is processed, the program processing will stop. To continue with the program processing, it is necessary to press the Cycle Start button.
Programmers often place M01 function at the end of each tool, with the possible exception of the last tool. It is up to the CNC operator to decide whether to use it or not. There are a number of situations when the Optional Stop switch is useful:
▪Checking tool for wear and other flaws
▪Part dimension check
▪Temporary absence from the machine (see note)
▪... any other activity not required for each part
Leaving machine with Optional Stop set to OFF should be combined with Feedrate Override switch set to zero - always observe safety rules
If the program includes mandatory program stop M00, program processing will always stop - no interference from the operator is necessary.
Single Block
All CNC part programs are always written sequentially, in the order of tasks and instructions needed to complete certain machining operations. Normally, for full production, the Single Block switch is set OFF, so the program processing is continuous. Setting the switch to ON position is useful particularly during setup, as it allows the CNC operator to process one block at a time.
During part setup, using the Single Block mode enables the operator to test not only the program itself, but also settings of tools and offsets, check clearances, depth and width of cuts, and other cutting oriented activities.
Well structured part program always helps during part setup. For example, a common program entry for a tool number three (T03) is:
T03 M06 (NEXT TOOL SEARCH AND TOOL CHANGE)
During single block mode, the next tool search command (T03) will be done first but immediately followed by the actual tool change (M06) - in the same block. There is no pause between the two functions - they will be processed simultaneously as a single block.
There is nothing wrong with the block or program for efficient production, which is always the main objective. On the other hand, the format may slow down the setup in certain cases. Consider a possible scenario that may benefit changing the program structure to two blocks.
If those two functions are programmed in separate blocks, there will be no delay during production, but during setup the two blocks will bring some benefits:
| T03 | (NEXT TOOL READY) |
| M06 | (TOOL CHANGE) |
As the tool search is independent of the actual tool change, it takes place first. Working