by Shop MT staff
Tool wear: you can’t avoid it, but understanding what causes it and how it happens, and selecting the right cutting tools can reduce wear, extend tool life and reduce tooling costs.
“When we speak about tool wear, we mean the gradual wear of cutting tools due to regular operations; it is nothing unexpected,” says Dr. Moshe Goldberg, who supports training and engineering in Iscar Tool’s marketing division in Tefen, Israel. Goldberg was in Canada recently to speak at a manufacturing conference and to speak to local customers at Iscar’s Canadian facility in Oakville, ON.
Cutting tool wear is an important issue for manufacturers and cutting tool suppliers, says Goldberg.
Cutting tools are subjected to challenging conditions during metal cutting – extreme heat (1000°C), high stresses and high friction – which means that today’s tools must be built to maintain strength at high temperatures, and exhibit high toughness and hardness. In short, cutting tools must be designed with wear resistance.
“We say to customers ‘don’t try to push the limit of the cutting tool.’ The cost of the cutting tool only constitutes three per cent of the production cost. You don’t save anything by prolonging the tool life when the cutting edge is no longer sharp. In fact, you’re defeating the objective; you’re generating poor performance, you’re damaging your machine and your workpiece and you end up with excessive tool wear. Instead, if you replace the cutting edge tip, you’ll save yourself a lot of work and be more productive,” advises Goldberg.
Reducing tool wear is a big focus of R&D for cutting tool manufacturers, including Iscar. Researches and engineers at the company’s Tech Centre in Israel dedicate much of their time assessing tool wear and developing technologies – new surface treatments and new tooling materials – that can minimize it.
“We know today from observation that tool damage is a result of high stress, high friction, high temperatures exceeding 1000°F. Gradual wear is flank wear – the portion of the tool that comes into contact with the finished parts gets eroded – crater wear – contact between the chip and tool erodes the space – and built-up edge, an ongoing process of the material being deposited and removed on the cutting edge.” says Goldberg.
“Fracture and temperature failures are premature failures, so you can’t predict these types of problems. Fracture is something you should avoid and it normally occurs as a result of human error or poor fixture design or simply by operators not following instructions for tool set-ups.”
Instead, manufacturers would be better off with the gradual wear – e.g. flank and crater wear and built-up edge – that is unavoidable but manageable because it leads to “the longest possible use of the tool. Fracture wear damages the workpiece, damages the cutting tool, the machine and the spindle. You create excessive heat and this type of failure should be avoided at all costs,” advises Goldberg.
While cutting tool manufacturers can’t prevent this type of failure, they can reduce tool wear and have done so by developing new surface treatments and coatings, new tooling materials and innovative edge preparation processes.
Images courtesy of Iscar. Coatings can enhance tool performance.
Goldberg cites Iscar’s Sumo Tec insert grades as an example of modifications (e.g. post treatment coating process) that can be done to tool substrates to enhance tool performance and extend tool life.
“The reason we put the emphasis on this post treatment process of coating is that by having this CVD (chemical vapour deposition) technology, we reduce surface tension and stress, have less friction and less generated heat. We improve toughness and we get better chipping resistance. We also reduce the phenomenon of built-up edge.”
Ultimately, understanding tool wear and using cutting tools with technologies that can combat such wear will lead to longer tool life, high machining productivity, lower operating costs and, ultimately, a stronger competitive edge.