March 2020 - 02: Measuring tool performance By Arthur Turner

How do we improve tool life?

It’s a time old question that we all want to know the answer to.

In the incomprehensibly competitive cutting tool market, sales engineers will all tell you to invest in the latest high-tech cutting tool solution with a new grade, coating, geometry or edge prep.

There may even be some conscientious engineers that will take a closer look at your set-up, machine tool, machining strategy and then try to enhance tool life and machining parameters from a ‘different angle’.

But who can tell us when it’s time to change a tool? 

It’s a question that is raised in factories every day, and we get many different answers. Why do we need to know?

Well, the answer to that one is apparent for any engineer worth his or her salt.

For businesses running series or batch production, the benefits of reduced downtime, consistent production quality and gaining an element of certainty on machine up-time can be the difference between whether you just paid your staff a Christmas bonus or not.

We are always looking at cutting edges to provide us with an indication on tool life and no doubt there are some Scrooges out there looking at the cutting edges with the meticulous detail of a seasoned crime scene investigator.

For a for a few years micromachining specialist KERN has offered its U-view tool measurement system for in-process inspection of the cutting edges of endmills and drills with inspection capabilities up to 540 times magnification.

In universities and research laboratories, the main way of testing tools has been by using workpieces on fixed dynamometers and extracting force and torque measurements to determine tool fatigue and failure.

For manufacturing companies, this has not been an option.

The academic world doesn’t have the time and cost pressures of industry, so the use of cumbersome systems that make tool changeovers difficult and time consuming, have not been on the radar for manufacturers.
Today, there are new capabilities and technologies on the market that enable the accurate measurement of tool life.

The next generation technologies no longer need to be fastened to a dynamometer – making the new systems more appealing to industry.

Critically, the answer lies in the tool holder and more importantly the new innovations are not just for machining centres.

At the EMO 2019 exhibition in Hannover, two companies were displaying tool force measurement systems that can be applied to all manufacturing sites without too much need for scientific support.
KISTLER, a name that has been well known in academic circles for a long time demonstrated a number of solutions for both machining centres and lathes.

Their solution, a Piezo tool system, has been made in conjunction with PH HORN which has added RFID chips to their lathe tool holders.

These are then connected to a PC to continuously provide feedback on the forces being experienced at the tool edge.

This development while initially having an additional cost, will be paid back as soon as the user attains enough accurate information regarding what is happening at the cutting tool edge.

The forward-thinking users that implement such a system will rapidly yield a return by controlling cutting tool costs more accurately.

In KISTLER’s own workshops, screen displays have been changed from technical information to simple ‘traffic light’ displays.

By showing green, amber and red lights to indicate the cutting tool edge condition, KISTLER has implemented an element of complete simplicity that will no-doubt be more effective, as the operator doesn’t need to be highly computer conversant.
Moving on to machining centres, KISTLER is also paying its due diligence to rotary tool holders – achieving similar measurement capabilities.

This needs to be thought out a little more than on turning centres, as there are multiple cutting edges on an endmill compared to a turning tool.

The tool information displayed for milling applications is applicable for each individual tooth of the endmill, so the operator can clearly see if there is a problem with one tooth,

However, any issues will ultimately be shown up in either size or surface finish deviations.

Importantly, KISTLER say that all tools do not require monitoring.

This approach will not only limit implementation costs, but it will also prevent the unnecessary monitoring of non-critical tools in the process.
Another company investigating how tool wear can be displayed is PRO-MICRON GmbH who offer individual tool holders for use on a machining centre.

The information is initially for a very skilled operator or technician, but I am sure given time, the shop floor information can and will be simplified.

The expense of employing individual tool holders could prove problematic and restrictive to wide-scale roll-out, but PRO-MICRON has a solution.

The solution is to integrate the system into the spindle bearings.

This development can, over the next few years change how we look at cutting tools and give the users a better insight into what they are asking their cutting tools to do.

With this technology, tool life will gradually improve as users will be better informed on the value for money that they achieve with their cutting tools.