What is tool management for?
As soon as you need more than one tool per work piece, you will have to consider how you will manage to carry out the process on the correct spot and get the plunge depth correct despite the different lengths, diameters and shapes. That means that the control must “know” which tool is in the machine at any given time and how long and thick etc. that tool is. There are various methods for replacing the tool which require a few different ways of proceeding.
Without tool replacement – TR
This is the simplest scenario. Only one individual tool is used per CNC program. This sounds like a drastic limitation but in CNC processing, it is not that serious, at least when the material being used is thin sheet material. One can drill holes with varying diameter, then use a tool for the smallest hole and mill a circle for the larger ones. In this way, you can get a surprising amount done with one individual tool.
If more tools are required to be used one after the other, the processing will be distributed across several programs. Each processing step should be carried out individually. In between steps, the tool will be manually changed and thereafter, the zero point will be measured once again. In this instance, the tool list needs only one individual tool (T1). You can enter the tool data into the list (Menu “Configuration – > Tools”).
Calibration configuration menu
This is only relevant for the representation on the screen. Because the work piece offset is measured again after each change, the tool length entered is irrelevant and you can also forget about the tool number.
The best thing to do is to select the “Ignore Tool Replacement” setting under “Configuration -> Machine -> General” so that no unnecessary requests for tool replacements are received. You will have to have changed the tool already before starting to fit the program anyway.
General configuration – manual tool change
Manual tool replacement (direct)
Even if you do not have the “luxury” of an automatic tool replacement system, you can still process programs with several different tools. In this scenario, set the “Configuration -> Machine ->General” to “Manual Tool Replacement”. In addition, you will have to add at least as many tools to the tool list as are to be used in the program, i.e. T1 to T10, for example.
Directly installed tools
If the tool spindle does not have a change system with tool holders (usually ST = Steep Taper, HSC = Hollow Shaft Cone), rather, the tool is directly set in the collet of the motor shaft with the shaft, then it is referred to as a direct change. The advantage is that this can be made with any cost-effective tool spindle. The disadvantage is that the tool can be positioned in a slightly different position after every change and with differing shaft diameters every time, the collet will also have to be changed. This requires more time and usually the tool length has to be measured once more after each change.
For this reason, it is highly recommended that you purchase a tool length control feeler for direct changes. This is the same as for the height sensor as described above, only it is permanently mounted onto a specific part of the machine. There are also combination length and height sensors and the same sensor can be used for both purposes. A sensor usually has one magnetic foot which is mounted permanently onto the machine.
The sensor is used there for measuring the length of the tool. For mobile applications of measurements of the height of the work piece’s surface, the sensor can be removed from the foot and placed on the work piece. If on the other hand, two separate sensors are used, they can both be connected to the same hardware entry (series circuit) because the sensors will never be required at the same time.
No height sensor
If you do not own a length sensor, it is better to use the “No Tool Replacement” method and separate the program from it so that each step of the process is carried out with only one tool separated
No height sensor macro
In order to carry out a longitudinal measurement automatically after every tool replacement, you should install the surveying macros as described in Chapter 27 “Working with Height Sensors”, pg 42. Thereafter, the “G79” macro must be adjusted for your machine so that the control knows where the length sensor is situated, how high it is and at which speed is it allowed to proceed.
Using “Configuration -> Macros”,
Calibration configuration menu
Select macro “G79” and then press the “Edit Macro” button to open the Editor. Parameters #0 to #6 determine the parameters for the longitudinal measurement. Enter the appropriate values for your machine and save these. Note that you should check the functionality of the signal inputs before the first use, by pressing the sensor with your hand and monitoring the reaction of the inputs on the Diagnosis page.
When working with several tools, it is important to remember that the tooling length compensation is activated. It will ensure that the length of the tool is recognised and added to the programmed Z values. The length compensation must also be activated in particular while you are measuring and setting the work piece offset (either with a height sensor or with the “Scratch Method”). Ensure that the work piece offset is set up by pressing the button which is displayed next to the “G43” offset button.
Manual tool change with tool holders
The tool replacement process will proceed a little more efficiently if the machine has a replacement system with tool holders and pneumatic or hydraulic clamping. Some machines are also equipped with threaded pulling studs which have to be removed by hand. Each tool is first placed in a tool holder (usually ST = Steel Taper, HSC= Hollow Shaft Cone though there are other systems). In an actual tool change, the mountings for the tool spindle will also be changed. The tool remains in “its” mounting as long as it is not frayed or broken.
This has the advantage that the longitudinal measurement only has to be taken after a new tool has been placed in the mounting. This can be carried out either automatically as described above with a length sensor or manually with an additional length gauge (the easiest scenario involves a callipers) outside the machine. The length is then entered into the tool list and will only be looked up there during the actual tool change.
How is this measured?
The actual length is the tool is actually irrelevant; it is only the difference between the tools which monitored. You can measure e.g. the distance of the point to a specific reference plane for all tools, for example until they are flush with the HSC cone. It is important that the same reference plane is selected each time. The front of the collet chuck nut is therefore unsuitable as its precise position is dependent on a tightening torque.
Easy to enter onto the list
The manual change with the work tool does not need any special macros or other adjustments when you enter the tool lengths into the tool list manually (Configuration -> Tool -> Change -> Length 1). If you have a length sensor, you can install the G79 macro as described above and adjust it. It will then be used not with every tool change but only when necessary, either with the MDI input or by selecting the “with length measurement” option in the Tool Change dialogue box (Main window, “Tool Change” button, on the left). As described above, you should note that the tool length compensation (G43) is activated.
Automatic tool replacement (direct)
If the tool spindle has a pneumatic or hydraulically operated mechanism where the collet chuck does not have to be opened and closed manually, you can change the tool automatically. Of course, in this scenario you will also need a magazine in which several tools can be placed.
Types of magazine
There are securely positioned (linear) Tool Change Magazines, wherein each tool is retrieved from a different position depending on the use of the X, Y and Z positioning of the spindle, or a mobile magazine can be used (a revolver). With a mobile magazine, collection will always take place from the same X/Y/Z position, however an additional drive is available for selecting the tools
HSC tool change in series
Because for direct change in the collet chuck, the tool’s exact position is not the same every time, after every change, a tool length measurement must be carried out. Therefore a length sensor is always required. The settings for “Configuration -> Machine -> General” has to be set to “Automatic tool change”.
The M6 and G79 macros for the revolver magazine and robotic arms
For the actual tool change, the M6 macro has to be installed and adjusted. The length measurement itself requires the G79 macro. Specialised knowledge is required to programme the automatic change. In the reference book, you will find examples for macros for a simple, linear magazine and a revolver magazine. More complicated systems, e.g. linear magazine with several rows or revolvers with additional robotic arms are possible. It is however, recommended that you request professional assistance to programme and adjust this type of change system.
Automatic tool change with tool holders
If the tool is not placed directly in the collet chuck but in a tool holder, the length measurement after every change with a tool holder is not required. For series production, this has the advantage of shorter cycle times though it is the most expensive system available. Just as with the automatic direct change, more types of magazine are conceivable.
A length sensor is not completely necessary. If the tool lengths are measured by hand and entered into the tool list, then nether the sensor nor the G79 macro is necessary.
Copyright © 2017 by Benezan Electronics. All Rights Reserved