Welcome to "Sinumerik Live – application technology simply explained" – part of our
video series with the aim of presenting short individual topics on using SINUMERIK in practice!
Today, the topic is "Tool management – milling: Reference points, tool parameters and clamping
options".
We start with the systematics involved with tool holders and the extensive clamping options
available.
How does tool management function in principle?
What is it – and why do I need it?
And then of course specifically the tool management functionality of Sinumerik Operate – which
is the core topic on today's agenda – and finally, a summary of what has been discussed,
naturally using the correct tools and the correct tool holders.
How are both combined, how are they brought together to be used in practice – and how
does everything function together in the machine tool?
The systematics of tool holders and the associated clamping options.
A tool holder represents the perfect connection to the machine, in other words, tool holders
are the connection between the tool itself and the machine.
For this, two requirements must be satisfied.
On one hand, fast and safe tool changes must be guaranteed, and naturally a high accuracy
when machining the workpiece.
These tool holders are standardized in order to ensure that these two requirements are
satisfied.
In Europe, the two most widely established types of tool holders are steep taper and
hollow taper shank.
There is an additional variant from the family of steep taper holders known as the BT tool
holder.
In Asia, the BT is just as widely established as the steep taper is here in Europe.
These only differ in the length of the taper and the shape of the collar.
But otherwise, this type also belongs to the class of steep tapers.
So let's take a look at the steep taper tool holder in detail:
These types of tool holders are drawn into the spindle by the draw bolts.
Force is transmitted through the static friction between the peripheral surface of the taper
and the spindle – and in turn, to the tool itself.
This design has the advantage that it is very rugged and high forces can be applied during
the machining process.
But it is unsuitable for high speeds as a result of the spring assembly that also rotates.
Further, different draw bolts are required depending on the particular machine tool manufacturer.
The hollow taper shank itself is very compact – and in this case, it is clamped at its
inner surface.
The torque is transmitted to the tool through internal surface friction and grooves.
It has the advantage that extremely high speeds are possible – and the tool can be very,
very quickly clamped and released from the spindle.
And it has a collar, which guaranties that the tool holder lies flat directly on the
spindle.
However, the lateral force that can be applied is somewhat limited with this design.
There are three main ways in which a tool is clamped.
These are clamping, pressing-in and shrinking.
A collet chuck is used to clamp the tool firmly in place.
This is combined using a collet chuck and union nut.
The two are assembled and then screwed to the actual tool holder.
And the tool is then clamped in the collet chuck using
the union nut.
This type of clamping guarantees that the tool is clamped precisely centered – one
hundred percent at the center.
This has perfect radial eccentricity as the design is completely symmetrical around the
axis of rotation.
Of course, it is the somewhat more costly version as several parts are required.
The Weldon tool holder is the next type.
A Weldon tool holder has a bore and a lateral clamping screw.
The tool is inserted in the tool holder, and fixed using the clamping screw.
The advantages are that it can be very quickly used, it is straightforward and also very
favorably priced.
But the tool must also have a clamping surface where the clamping screw can engage.
Unfortunately, however, there is some inherent imbalance because it is not one hundred percent
symmetrical around the axis of rotation as a result of the lateral bore.
There is another type of clamping known as the Morse taper.
In this case, torque is transmitted exclusively through the friction at the lateral surfaces
– however, this type of clamping is hardly ever used on state-of-the-art CNC machines.
A pressed-in connection is another type of tool clamping.
Here, the tool with the clamping device is pressed into the tool holder using a hydraulic
press.
To press a tool into the tool holder, we need the tool holder itself, and an appropriate
collet chuck – one that corresponds to the diameter of the particular cutting tool which
is to be inserted.
These two elements are then inserted into the tool holder.
These are then slightly pressed together and inserted in the hydraulic press.
This press has various adapters corresponding to the size of the tool holder being used.
The tool holder is now connected to the collet chuck up to the end stop – and the cutting
tool is firmly connected with a predefined force, ready for use on the machine tool.
The tool is released by carrying out the steps described above in the inverse sequence.
The press is used to release all of the clamping force.
We do this by putting the tool in the hydraulic press and starting the release operation.
The tool is then removed and the complete clamping assembly is again broken down into
its component parts.
And the tool is now released.
The third tool clamping variant is where the tool is shrunk-in – also known as the warm
or hot process.
The principle is simple.
The tool holder is inductively heated up so that it expands.
The precisely machined bore is expanded by a couple 100th millimeters, and the tool – that
is also precisely machined – slides into the bore.
As the assembly cools down the tool is clamped with a very high friction and form-locking
connection that cannot be released.
It can only be released by heating it up again so that the tool can be removed.
As stated before, the clamping force is exclusively established as a result of the temperature
differences.
The advantage is that it has a perfect radial eccentricity, far more precise than that of
a collet chuck, for example.
This design has absolutely no mechanical elements that can have a negative impact on the radial
eccentricity.
All that is required is a tool holder and the tool itself.
The disadvantage is that this technique requires expensive equipment to heat up the metal – and
of course, to cool it down again.
I require two different pieces of equipment for this, and naturally, special work protection
equipment – at the very least, special heat resistant gloves, because the metal is often
still too hot to handle with bare hands, even after it has cooled down.
And of course, you must warn your fellow workers, as they might not be aware that the tool holders
lying around can be hot.
Tools are shrunk into the tool holder using a shrinking unit.
The tool holder is inductively heated up.
Heat resistant gloves are the most important piece of protective equipment here as they
protect your hands against temperatures of several hundred degrees Celsius.
We are now going to connect the tool to the tool holder.
To do this, we place the tool in the shrinking unit – the tool holder – und move the
shrinking unit over the opening and heat this up.
And the tool drops into the tool holder.
After the tool holder has been heated up, it is mandatory to cool down the tool with
the tool holder.
After the drying phase, the tool is removed and then ready for use in the machine tool.
It is firmly shrunk and has established a tight connection.
The tool is released in the same way that it is clamped.
For cooling, the tool holder and tool are placed in the cooling unit and the cooling
process ensures that the tool is cooled down to a safe temperature.
After drying, the tool holder and the tool can be removed – and
with the temperature at a normal level, can be placed in the tool cabinet.
Why tool management?
Everything must be well organized.
A machine tool is designed for effective and efficient use in production environments.
And the effectiveness of a CNC machine tool is also defined by the possibility of automating
tool changes.
In order that tools are changed smoothly without errors, tools must be sorted – in other
words, managed – both virtually in the CNC as well as physically in the tool magazine.
The CNC tool management must absolutely guarantee that the tools being used are correctly managed.
To ensure fast availability, all of the tools are located centrally in a tool magazine.
The tools in the magazine must be protected against the effects of machining, so that
the tools – specifically the tool holders that go into the spindle – are protected
from metal chips and cooling water, for example.
We make a distinction between virtual and real tool management.
The tool magazine itself serves as an effective and protected storage location for tools in
the milling machine – and ensures that the required tool can be quickly accessed.
The tool cabinet itself is located outside the machine.
The virtual tool management – in the control – ensures that tools are saved in a structured
and transparent fashion.
Tools from a magazine – as well as mounted and already measured tools in the tool cabinet
– can be emulated here.
We make a distinction between two different tool location management options: The fixed
tool location coding – and the variable tool location coding.
For the fixed tool location coding, the tool is always changed at a permanently assigned
location.
The tool is always replaced at precisely the location from where it was taken.
There are several reasons for this.
On one hand, it is naturally dependent on the design.
And of course, for oversized tools – meaning those with a diameter that exceed what is
permissible – they require free tool locations to the right and to the left so they don't
collide when placed in the magazine.
And naturally, to keep adjacent locations free.
The 3D probes, which are available in the machines for automatic measurement, are also
always assigned the same location – so that to a large extent they are protected against
the influence of machining, such as cooling water, chips and similar.
The variable tool location coding means that the tool is always changed at the next free
location in the magazine, which is closest to the tool change point.
This also has something to do with the tool preselection.
The next tool is ready, while the other tool is still being used.
As a result, the workplace can become a little bit chaotic, but only virtually.
This is actually called chaotic tool management, but it is an extremely effective method as
tools are placed at the next free location.
And it goes without saying that the control always knows where the tool is.
A new tool is created using the "New Tool" function.
Select the corresponding tool type here.
Confirm with "OK".
The name is entered here in the input field, which you always require for a tool.
So here, of course, the length is also entered.
The diameter.
And of course, the number of cutting edges.
And whether the cooling water should be switched on or not.
The tool is created as such in the magazine.
If a tool is no longer required, then it should be removed from the magazine.
And of course, this must be physically done in the real environment.
But when it comes to unloading, it is sufficient to simply select the "Unload" function.
It is then virtually removed from the magazine and placed below the magazine locations in
what is known as the virtual tool cabinet.
It is available with all of its data for further use when you reload it back into the magazine.
And already, it's back at the location from where we unloaded it.
If we wish to write a program to machine a workpiece at the machine, then we require
the tool that has just been created – and then we select the appropriate machining technology:
"Milling", for example "Pocket milling".
And we then select the required tool using "Select tool".
Confirm with "OK".
It is stored at the top under "T".
We then press "Accept" and in ShopMill we can see that it is available.
We proceed as follows to insert a tool into a G code program: We position on a line where
the tool is to be called.
"Tool call".
The appropriate tool is selected.
We confirm with "OK" – and the tool is already called with the appropriate tool change command.
What have we learned?
Clamping, pressing-in and shrinking techniques to assemble tools, tool holders and tool adapters.
Using machine and workpiece coordinates and tool data.
The structured, virtual representation of tools and saving tool data.
Classifying and creating tools.
Updating tool data sets.
Interaction between SinuTrain and Sinumerik.
Exchanging tool data sets in offline programming.
And naturally, using tools from the list, our virtual tool cabinet.
And that's it for today.
Thanks for watching.
See you next time.