The Details Matter in Tool Selection
- August 4, 2020
Cutting corners when choosing tooling may seem like a time saver, but can ultimately remove your margin
The science behind cutting tool engineering and design has grown immensely over the last 20 years. Advances in software and data analytics has created a tooling industry that has an answer (or three) for almost every process problem a job shop may encounter.
For those working in the aerospace, automotive and mould and die sectors, intense scrutiny must be applied to each tooling selection to get the most bang for your buck—and tooling can cost a significant amount of those precious bucks.
In many cases, companies are doing long runs or repeat orders for the same part, which leads them to believe they can skip the proving-out phase and simply order the same tool as before. Often, in this world of impossibly tight tolerances and nearly impossible-to-meet lead times, this becomes a source of problems without companies even knowing.
“It’s pretty safe to say that most customers when they buy a tool they have used successfully before aren’t going to do a full inspection on the new order, expecting everything to be the same as the first time,” says Tod Petrik, cutting tool applications engineer at toolmaker Haimer USA. “Maybe they check it for size to confirm the offsets. They don’t look for the minute variations in the new set of tooling, but I guarantee you they are well aware of the consistency problems when these tools suddenly let go, or harmonics and chatter start to become problematic when it went great the previous time.”
Petrik describes a situation faced by many job shops, where engineers believe the process is already optimized and measured, using the same tooling to cut the same material at the same speeds to the same specifications. So why all of a sudden is there runout or breakage?
“Even look at short-run work where they have repeat orders, maybe the first run ended a month ago. You had the job dialed-in, the speeds and feeds were honed, you made good parts and your customer was happy with the product,” Petrik explains, using an anecdote similar to circumstances he sees all the time.
In Petrik’s anecdote, a few months later an order comes in from the same customer for another run of that same product. You set everything up again from your library, you order the same cutting tool from the same supplier right from the old job sheet. You put it all together, hit “go” and you get nothing but problems. You scratch your head wondering what could possibly have changed.
For Petrik, the answer is easy—not every tool is created equal, even if it’s the same tool from the same manufacturer. Every production run from a toolmaker could have slight variations in its make-up, be it raw materials supplied from a different supplier, ingredients in a coating that differ by as little as a molecule, or the tooling you just received was produced in a different factory using a slightly different machine.
To the eye, none of these subtle variations are noticeable until you drop them into your machines and start making chips. There’s no red flag for this, no system on the machine that identifies the issue.
“It’s something that often gets overlooked and its especially hard for a job shop. If they make 10 parts in a morning shift and then the next 10 parts that afternoon are for a different run, how do they establish tool life parameters. How do they determine that they may be losing a lot of value in small increments?” he asks.
The answer is to not skip the details when setting up your tooling, and this means more than measuring the offsets.
“It’s not until you really start to focus on what’s happening in that part of the manufacturing process that you realize how much money and performance you leave on the table for competitors to sweep up,” he warns. “And if all of the people involved in programming and cutting parts don’t have a deep understanding of the cutting tools in use, there is not only a weak link in the chain, but likely a broken link. It’s costing you money. All of those things have as much influence as the latest and greatest technology.”
Testing the tooling
It’s not to say the tooling in these circumstances is of poor quality. It’s just that the complex nature of machining, when combined with the complex nature of tooling, means there is essentially zero margin for variation when it comes to repeatability.Add automation or lights-out machining into the mix and things get even more complicated. This means highly detailed testing should be done for every job and built into the timeline for each project.
For companies that have done all of this and still can’t decipher the issue, there is another avenue to take: a quick call to the McMaster Manufacturing Research Institute (MMRI) could be the first step on the road to consistent quality parts.
“There are so many different tools out there, how do you pick the best one?” asks Stephen Veldhuis, professor, director of MMRI and the Braley-Orlick Chair in Advanced Manufacturing Engineering.
MMRI is an industrial lab run by McMaster University in Hamilton, Ont. Its researchers focus on solutions to manufacturing industry challenges and optimizing the machining process. It’s home to 18 full time staff, four post doctorate researchers and a number of student researchers, all working to solve real-world issues faced by machine shops. It currently has the capacity for about 100 projects every six months but is planning to double that capacity in the near future. Some of its biggest clients include Honda, which has a particular focus on developing young talent, and voestalpine Rotec Summo Corp., an automotive tube supplier in Burlington, Ont. The institute gets some government funding to help manufacturers in a “dollar-matched” framework. “It makes us a fairly good deal compared to trying to do something internally with your own resources,” says Veldhuis.
“Most manufacturing companies can try to do this on their own, but it takes a huge amount of time, and they have all kinds of other issues associated with manufacturing and just running a business,” he says. “We find that [tooling issues] are a really good thing for us to work on. We take it back to the lab, put numbers to the behaviour and understand how the tool is interacting with workpiece.”
MMRI uses a science-based, systematic approach, running tests on a company’s tooling options and workpiece material to quantify the differences and see what aspect of that tool helped it to perform, and if more could be done to accentuate those aspects. Modern tooling has many properties—lubricity, wear resistance, toughness, hardness—and each tool has these factors in slightly different combinations. Finding the best balance of these properties is what will give you high performance in your process.
“We are collecting data on the cutting forces, vibration, surface finish, dimensions. A company would measure surface roughness with a profilometer and get an RA value. We can actually get a mapping of the surface almost down to an atomic level,” says Veldhuis. “It’s not always needed, but machining is very complicated, and sometimes those specifications matter. We have specialized instrumentation that allows us to study this that doesn’t make sense for companies to invest in.”
Many companies like to go it alone on this front, because the culture is to work at their own pace and direction. But the diversity of approach used at MMRI is good for a company.
“If you try to solve problems every day with the same approach, you will get similar answers. If we can take a different approach and look at different data, maybe we can find a better solution. We collect the data, analyze it, then use the company’s expertise to apply the results to their real-world process.”
It’s true, with the vast number of new entries in the market over recent years, tooling has become commoditized and the pricing can vary greatly. But tooling is where the rubber meets the road in manufacturing and can be source of significant value added if the selection process is optimized.
But, says Veldhuis, there’s a caveat—these gains are incremental. Understanding the tooling and how it interacts with your material and machine speeds will help you squeeze these incremental gains from every part, improving your margin with every chip you make. SMT