Special toolholding system supports large-scale, automotive production.
By Charles Bates
Shrinkfit presetter systems that include a presetting machine, PC interface, a clamping and presetting assembly, an induction-heating unit, and a cooling system are finding their way to automotive production floors.
A shrinkfit holder and cutting tool assembly is practically as rigid as integral-shank tooling, while also providing quick toolchanges, simple regrinding of the cutting tool, and superior machining results.
Shrinkfit-toolholding use within the auto industry has not yet reached the popularity it has in the aerospace industry. Most automakers have viewed incorporating such tooling in the production environment as too difficult and time-consuming. Also, a major roadblock was the lack of a system that could preset shrink-to-fit tooling in the quantities required to support large-scale automotive production. That is until now.
Briney Tooling Systems of Bad Axe, Mich., along with Kaiser Precision Tooling of Elk Grove Village, Ill., and Speroni SpA, a presetter manufacturer based in Italy, have developed a shrinkfit presetter system that not only meets high-production needs, but also provides a practical method of setting shrinkfit tooling 4 more accurately than previous methods.
As developed, the Briney Tru-Axis presetting system includes a KPT/Speroni presetting machine, a PC interface, a clamping and presetting assembly, an induction-heating unit, and a cooling system. Users access tool data from the presetter, measure the cutting tool in the presetter vise, update the tool-length information, and transfer the data to set a servo-driven stop. They then remove the cutting tool from the vise, insert it into the induction-heated holder and against the preset stop. In just seconds, gripping takes place.
As the holder cools, it grips the cutting tool, and the presetter then verifies the tool-assembly length. The heating, cooling, and checking process takes minutes, and Briney applies the concept to a range of toolholder styles, including HSK, ABS, FL, and V-flange.
For production machining and automotive customers, the combination of Briney shrinkfit toolholders and KPT/Speroni tool-presetting systems provides several benefits. These include good concentricity and tool gripping for improved machining; consistent toolchange procedures and presetting accuracy; control of tooling costs; and total tool management.
"Measurable benefits for shrinkfitpreset tooling in automotive applications are impressive," says Chris Gust, project manager at Briney. "These systems increase productivity at any spindle speed, prolong tool life, reduce toolchange time, and improve machining quality through concentricity, rigidity, and balance." Two of the most significant installations of Briney shrinkfit tooling are at a major automaker's engine plants where the savings in tooling costs has easily justified the purchase of the systems.
Three years ago, the automaker's engine-plants needed optimal toolholdingsystems for a six-cylinderengineproduction line. According to manufacturing engineering managers, the engine plants considered everything from tapered-shank, ABS, FL, HSK, EPB, NTK, and hydraulic holders to collet systems and shrinkfit toolholding. The plants chose shrinkfit HSK toolholding, which provided the necessary rigidity, repeatability, durability, cost, ease of use, dependability, simplicity, and presettability (speed, accuracy, and repeatability).
"A shrinkfit toolholder and cutting tool assembly is nearly equivalent in rigidity to integral shank tooling while allowing quick toolchanges, simple regrinding of the cutting tool, and superior machining results," says Gust. A shrinkfit toolholder provides 3.66 greater resistance to axial pull and 3.2 more resistance to rotational or torsion forces than do conventional toolholding systems.
As an engineer at one of the automotive plants puts it, "We insisted on shrink-to-fit because we have had excellent results using that style holder in the past. Wherever we've replaced a currently used toolholding system with shrinkfit holding, it has markedly improved tool life, reduced chatter, and eliminated tool slippage (pullout). It is so dependable, we often use it as a troubleshooting tool in problem areas to help us differentiate between machine-caused problems and toolbased problems." One such problem area was a core-drilling operation experiencing persistent tool breakage.
To drill cores in two separate engine sizes produced on one line, one of the plants ran a 0.826-in.-diameter drill at 900 rpm, 195 sfm, and feeding at 14 imp. This tappet-bore-drilling process — considered a roughing operation — was costing the plant thousands of dollars in machine and toolbreakage downtime. Engineers tried changing the cutting data, but this had a negative effect on production rates.
After the incorporation of shrinkfit toolholding, core-drill performance shot up from 5,100 pieces/tool to 75,000. Furthermore, the number of tools used per 1,000 engines went from 2.35 to less than 1. Tool cost per 1,000 engines dropped from nearly $600 to less than $40, and the annual cost of downtime from toolchanges plummeted from more than $34,000 to less than $10,000. Production on the other engine showed similar dramatic improvements in costs and tool-related downtime.
Why a shrinkfit system?
The advantages of a shrinkfit toolholding system include:
Simplicity. Shrinkfit holders are one piece; no additional parts are needed. This reduces the spare parts and space required to store the accessory parts as with other toolholding methods.
Rigidity. Once a tool is installed into a shrinkfit holder, the two become as strong as one. They are essentially one piece and have all the benefits of a one-piece tool/holder system, including the ability to be removed for regrinding the cutting tool.
Concentricity. An even, symmetrical grip on the tool produces TIRs of 0.0002 in. or less.
Thin profile. Shrinkfit holders can reach into places that many other holding systems cannot.
Labor. Cleaning and setup of shrinkfit tooling is less labor-intensive because of its simple, one-piece construction. There are no additional parts to disassemble, clean, and reassemble, and setup does not require repeated attempts to attain accuracy.
Cost. Shrinkfit holders are comparable in cost to other holding systems. But given the lack of perishable parts (O-rings, snap rings, coolant washers, collets, collet nuts, tang drivers, and spindle seals), they are effectively less costly to maintain, clean, and set up.