Tooling and workholding adjusts for output of small parts
As demand for small parts continues, tooling and workholding has changed. Vises to hold parts for milling have gotten smaller to accommodate parts that can be overwhelmed by clamping force. Also, adjustments have been made so the parts aren’t handled as much.
John Zaya, product specialist for BIG Daishowa Inc., Hoffman Estates, Ill., defines microtooling as 3 mm or 1/8th of an inch. “Everything becomes more and more critical,” he said. “On a smaller toolholder size, the leeway is much smaller.
“When you’re working with medium- to large-parts, you’re working with one part at a time. On a five-axis machine, you want that part to be held in one position.”
With small parts, he added, “You want to approach it to be more efficient, with less handling of parts. You’re trying to eliminate part handling by the operator.”
Various factors have led to the evolution of tooling and workholding for small parts.
“Competent workholding is about rigidity and to get to that point, the clamping device needs to interact as best as possible with the workpiece,” said David Jones, precision workholding product manager for Emuge-Franken USA, West Boylston, Mass. “With small workpieces sometimes there isn’t enough surface area available to properly hold it for the operation being performed. This is especially the case when higher transferable torque values are applied in the operation on the workpiece.
“So, to start,” he added, “there needs to be a full understanding of the application between the workholding supplier and the end user, and sometimes compromises on speeds and feeds must be brought to the table for these smaller parts.”
Scott DeVinney, global product manager for turning at Pittsburgh-based Kennametal Inc., shared this view: “Aspects of a tool design that generally don’t cause much concern can require extensive consideration when designing tooling for small parts,” he said. “As each feature of a particular tool design decreases in size, you begin to run out of real estate for certain insert clamping styles, navigating coolant to the cutting edge can be a challenge, and quick-change locking mechanisms may require a redesign to adhere to these smaller requirements.
As for workholding, he noted, each new part can provide its own unique challenges. “But it always comes down to utilizing strong and stable workholding that will not impede access to the part being manufactured.”
Over the past five years, improvements have occurred. With workholding, for example, more companies are offering smaller-based systems. “There are more and more fixturing systems set up around small parts,” said BIG Daishowa’s Zaya.
Inspection is another factor. To meet tighter performance tolerances and requirements, inspection equipment also has become more precise.
“I believe one improvement which often gets overlooked is inspection,” explained Emuge-Franken’s Jones. “The norm for many years has been temperature and humidity-controlled environments and now, like many aspects of the machining world, the inspection machines themselves have become even more accurate. This is important when you market micron-sensitive workholding assemblies, where each individual item in that assembly requires the utmost diligence when performing component inspection. If one element is off by a few microns, it will show up in the final assembly tolerances.
Finding an inaccuracy at the point of final assembly inspection, or during the physical testing phase of a workholding assembly, Jones said, is the second most expensive time to identify it. The most expensive time is when you are on the customer’s shop floor, which Jones noted is “nothing anyone wants.”
There have also been new designs for machining small parts.
“Inside the machine, the tooling is in very close proximity to each other, so you must be conscious of how oil or coolant is delivered to the cutting zone, how oil or coolant lines are routed, and how operators will gain access to change inserts, clamps or remove the toolholder itself,” DeVinney said. “These machines have many moving pieces, and all of them must work simultaneously without interfering with each other.”
Emuge takes a different tact. “For Emuge, it’s really the same approach regardless of the workplace size,” Jones said. “Surely the part geometry is perhaps ground zero for designing the workholding device.
“However, similar to any workholding project, there are always machine or table connections, tooling paths, speeds, and feeds, etc. that have direct influence on the outcome of the part manufacture. So Emuge’s approach to smaller workpieces is the same as it would be for any workpiece.”
Difficult-to-machine materials such as Inconel and stainless steels also have to be taken into account, as do next-generation manufacturing technologies.
The available real estate afforded to the workholding is inherent to small workpieces. Add in some difficult geometries and the workholding supplier will have its hands full, according to Jones.
He said: “One of the toughest discussions to have with an end user is when you need to tell them they may need to revise or slow their processing of the workpiece because the proposed transferable torque values exceed the values the workholding can provide on such a small workpiece.”
When it comes to manufacturing advances over the next five to 10 years, BIG Daishowa’s Zaya expects breakthroughs in artificial intelligence to impact tooling and workholding for small parts.
“It will be interesting to see how some of that may change,” he said. “CAM pathways may become less based on programmers’ input and more based on the machine’s knowledge of the cutter, the holder, the workholding, the part material, and even its own kinematics.”
Additive manufacturing, meanwhile, continues to become more prevalent and sophisticated. But high costs have limited its applications, at least for now.
“It’s truly an amazing technology, with a lot of promising benefits, but it’s also a very expensive technology,” Jones attested. “Ultimately, finding a fit technologically and financially may be a little tricky for a while to come, but that corner will be turned at some point in the future.”
Another trend that’s taking shape: increasing spindle capacities.
“They’ve been steadily increasing over the past decade, with many manufacturers now offering machines up to 38-mm capacity,” DeVinney said.
And he predicts further increases are coming.
“Otherwise, you’re likely to see machines with more tooling stations, more driven tooling, more cutting axis,” DeVinney added. “All of these increases allow operators to complete complex parts in a single cycle and eliminate some of the custom tooling required in years past.”
Regardless of the application specifics, companies expect the advancement of tooling and workholding for small parts to continue.
“The future of machining small parts is bright,” said DeVinney. “Cutting tools have significantly advanced in recent years, and those improvements are being realized now.”
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