Machining Toolholders - Productivity Engineering Applications

 

Lesson 105 of Industrial Engineering ONLINE Course.

Refer to Industrial Engineering Case Studies Collection for case studies and productivity engineering applications

Process Improvement via Toolholder Change to Shrink Fit

Case Study 16 of  Industrial Engineering ONLINE Course

2017

The story of toolholder change at Wescast Industries Inc., the world’s largest manufacturer of cast exhaust manifolds and turbocharger housings for passenger cars and light trucks.

The annual cost-savings for change of toolholder,  from the additional tool life on Wescast’s 16 CNC machine line, factoring direct and indirect labor costs as well as tool change savings, was $78,269.

The new toolholder was Haimer's shrink fit toolholder. The regional manager for HAIMER USA, presented Wescast  with a proposal that would guarantee both increased productivity and tool life versus their current collet chuck holders. He promised  reducing cycle time by 5% for all round tools with the guarantee that Wescast would net a minimum increase in tool life of 25% for all tools using shrink chucks.

The Test

To test the proposal, one machining cell (8 machines) and five cutting tools was used to conduct a study.  The part was cast iron exhaust manifolds. In four machines, the existing collet chuck holders were left to run as usual, without changing cutting parameters. In the other four machines, HAIMER shrink fit chucks replaced the pre-existing collet chucks with adjustments to feeds and speeds to generate the 5% improvement for each tool. During the following three months, data was carefully gathered as all machines continued operating across three shifts, six to seven days per week. Data including cycle times, tool life and tool change times were recorded.

Results – Tool Life

After three months, the data was examined. The improvements in tool life from the tools in shrink fit chucks were profound, achieving an average life increase of 60% across all five tools. Tool life, which was measured by the number of manifold pairs the tools could produce, increased anywhere from 25% to 100% depending on the tool. The annual cost-savings from the additional tool life on Wescast’s 16 CNC machine line, factoring direct and indirect labor costs as well as tool change savings, was $78,269.

HAIMER claims the significant increase in life is a bi-product of their systems runout accuracy, balance integrity, taper accuracy and inherent ability to maintain the aforementioned properties from one tool change to the next.

https://www.haimer-usa.com/news/blog/blog-articles-pages/2017/71917-shrinking-costs.html


Top 10 reasons to use HAIMER shrink fit technology

https://nraoiekc.blogspot.com/2020/05/process-improvement-via-toolholder.html

Application of Tribos  Toolholder for Productivity Improvement

Hard Milling - Productivity Improvement Using Tool Clamping Solution

A combination of toolholding used to get the most performance from its small-diameter tools.

Impact Forge in Columbus, Indiana, faced a toolholding challenge.  The shop  runs small tools at long overhang lengths on jobs that involve not just restricted tool access, but also hard material.

The application is machining  forging dies. that have been repaired through flood welding. Process engineering programmer has to develop process plan for material  with hardness reaching as high as 50 Rc.

Roughing and finishing occur on  Okuma horizontal machining centers. Roughing is done using a 1-inch diameter end mill in a setscrew holder. Finishing the fine details of the dies calling for end mills as small as 0.030 inch in diameter. Deep cavities and small relief angles for the cavity walls require a toolholder slender enough to let these small tools get close to the walls to do their work.

Slender shrink-fit toolholders were first tried. The shrink-fit holder uses thermal expansion and contraction. The holder is heated to open the bore, which then shrinks during cooling to clamp around the tool. The shrink fit’s clamping force is proportional to the amount of expansion and contraction, which is proportional to the size of the bore. As the tool holding bores are small in case of small tools, the clamping force was small. The shrink-fit holders are not able to clamp the  the tiny tools if the cutting force became too high at the high speeds used. The toolholder became the limiting factor for productivity of the machine.

Search for the solution to the problem led to the trial using  the “Tribos” system from Schunk (Morrisville, North Carolina). The proprietary tool clamping  system uses metal spring-back to clamp the tool in a way that is similar to shrink fit, except that it uses mechanical force to open the bore instead of heat. The other part of  solution was to hold the  Tribos extension within a hydraulic toolholder. The shop used “Tendo” hydraulic toolholders, also from Schunk. A hydraulic toolholder uses hydraulic pressure to deliver its force. The toolholder contains a reservoir of hydraulic fluid. By tightening a screw, the user applies pressure to this fluid, and that pressure is in turn distributed around the metal sleeve, or bush, that holds the tool’s shank. The compression of this flexible bush clamps the tool. In addition, the hydraulic fluid provides vibration damping as a secondary benefit. This damping for the tool life improvement according to shop's process planners.

The Tribos  toolholder’s bore has a natural shape that is considerably distorted from being a perfect circle. Instead, the shape has three lobes. The clamping device applies force to the toolholder to push this shape closer to being a circle and the tool can be inserted. Releasing the force then lets the toolholder spring back, concentrically clamping the tool.

With this tool clamping and holding solution, the shop was able to run one of the 0.030-inch Melin ballnose tools in 50 Rc steel at 8,500 rpm, 20 ipm and 0.003-inch depth of cut.  The parameters were used and productivity improved substantially.


https://www.mmsonline.com/articles/hard-milling-with-tandem-toolholding
https://nraoiekc.blogspot.com/2020/06/application-of-tribos-toolholder-for.html

Rego-Fix ER Collets for Tools  - Productivity Improvement Case Study

Case Study 34

October 2011

A manufacturing engineer at Smith & Wesson, took a hard look at the company's revolver frame machining operations and realized that toolholding was not allowing machine tools to run at their maximum RPM.  The culprits were cutting tool deflection and runout, so machines have to be run slower during heavy milling to maintain part quality. In case of aluminum revolver frames  machined on 4-axis horizontal milling machines with CAT 40 spindles with standard ER collets for holding cutters,  machine spindle speed during rough milling operations was restricted to just 5,000 RPM on machines rated to run at 10,000 RPM.

https://mfgnewsweb.com/archives/4/34555/Applying-Technology-oct11/Tooling-Helps-Firearms-Manufacturer-Hit-Production-Target.aspx

https://nraoiekc.blogspot.com/2020/06/rego-fix-er-collets-for-tools.html

Productivity Improvement Through Tool and Toolholder  Change - Corogrip 

Case Study 35 of  Industrial Engineering ONLINE Course

Fermer Precision (Ilion, New York) machines a variety of precision parts from aluminum, cast iron, powdered metal, carbon steel and low-carbon steel for automobiles, firearms, medical products and train brake systems. The company uses a Mori Seiki SV-500 and two OKK KVC 600 vertical machining centers for drilling, reaming and chamfering operations. A typical drilling operation requires drilling nine holes in six workpieces mounted in a single fixture.

The powdered-metal core drills presently used were supposed to last 200 parts per drill, but they were only averaging 120.  Operators were at risk of burning their hands when removing the tooling from the shrink-fit toolholders. If tools with steel shanks were used instead of  solid carbide, the coefficient of expansion of the toolholder and the tool's steel shank are too close to the same and hence there was difficulty in removing the tool.  In most cases, you need to use a mallet and a drive punch to remove the tool. After removal of  the drill, the toolholder still could not be used for another 1.5 hours till it . cools down enough for handling and then retooling. During the reheating and cooling of the shrink-fit toolholder, operators ran the risk of injury. 

The long retooling times are forcing the firm to keep on hand three times the number of toolholders actually needed for drilling. One is cooling, one is working and the third one is ready for the next change. The company was looking for alternatives and  DoAll and Sandvik Coromant (Fair Lawn, New Jersey) team came out with a suggestion.  The solution suggested was a hydromechanical clamping toolholder and a dual-grade drill with high toughness and good wear resistance—Sandvik's Delta C GC1020 drill and the Sandvik CoroGrip toolholder.

The key to the new drill's performance is the sintering of two substrate materials together at the drill tip. The grade at the tool center provides toughness and withstands tension and pressure on the drill point. The grade at the tool periphery provides wear resistance at high surface speed. This combination results in high speeds and feeds without sacrificing edge security. The CoroGrip high precision chuck for high speed machining offers twice the clamping force of shrink-fit chucks and three times that of ordinary hydraulic chucks.

The tooling combination demonstrated dramatically longer tool life. The average number of parts each drill handled increased from 120 to 300. The increase in tool life varied from 50 to 200 percent on tool life in different applications. 

The runout on the CoroGrip is 0.002 mm and is another benefit.

Feeds and speeds on the machines remain unchanged with the new drill and toolholder. A typical operation is drilling several 0.4313-inch diameter holes, 1 ¾ inch deep at 250 sfm in low-carbon steel workpieces.

Fermer technicians were happy with the safe, easy and quick tooling setup with the CoroGrip chucks. The toolholders are fitted with a tool and ready for insertion into the machines in just 15 seconds which is  360 times faster than the setup time required for the shrink-fit toolholders.

Fermer no longer needs to inventory more toolholders. The gloves and mallet are no longer necessary to change drills. During tool setup there are no forces exerted on the clamp or the tool pot, since only shop air is applied to move internal toolholder components.

The design of the CoroGrip toolholder optimizes balance and torque transmission. The combination has increased overall productivity and the quality of our products according to executives of Fermer.


2001 article
https://www.mmsonline.com/articles/retooling-saves-time-and-space

Collet for Corochuck 930 with Mechanical Locking - Productivity Improvement Use Case

Case 36 of  Industrial Engineering ONLINE Course

2019-11-26

Collet for CoroChuck® 930 maximizes pull-out prevention

The new collet features mechanical locking interface


Cutting tool and tooling system specialist Sandvik Coromant has introduced a new collet for its CoroChuck® 930 high-precision hydraulic chuck. Designed to suit Weldon shanks, the new collet features a mechanical locking interface to prevent tool pull-out or movement when producing expensive components and/or machining with challenging cutting data

“Being 100% assured of zero pull-out for Weldon shanks when producing high value-added parts, such as aerospace frame and engine components, is paramount in the highly competitive manufacturing arena,” says Mats Backman Global Product Manager at Sandvik Coromant. “Production engineers and managers are under constant pressure to minimize scrap and maximize bottom-line profitability. These thoughts were the driver for developing the new collet.”

The mechanical locking interface acts between the collet and chuck, and between the collet and shank. Having confidence in no pull-out when both collet and chuck are locked enables increased productivity in heavy-duty applications. Further benefits include easy assembly into CoroChuck 930 chucks, both slender and HD versions, while high run-out accuracy is assured with cylindrical clamping of Weldon shanks. In addition, coolant supply through the collet provides secure and reliable coolant delivery to the tool.

Ultimately, this new solution will benefit any machine shop seeking trouble-free machining in heavy applications. No pull-out or tool movement protects against the potentially sizable cost of reworking or scrapping an expensive component. Pull-out effectively changes the gauge length of the tool mid-cut, leading to the generation of features with incorrect dimensions or crash marks.

Example of the potential gains on offer - Customer Use Case

A customer case trial saw CoroChuck 930 (featuring the new collet) used for a milling operation on a CNC turn-mill machine. The objective was to produce a twin-screw from 42CrMo4 alloy steel. At cutting data of 3220 rpm spindle speed, 1500 mm/min (590 in/min) feed speed, 10 mm (0.394 inch) axial depth of cut (nominal), and 20 mm (0.787 inch) radial depth of cut, the mechanical locking interface generated a stable process with no pull-out. In addition, productivity increased due to longer tool life.

Collets are available to suit an assortment of common Weldon shank sizes. Accessories include assembly tools and anchor screws.

For more information please visit: https://www.sandvik.coromant.com/en-gb/products/corochuck_930/pages/default.aspx

https://www.sandvik.coromant.com/en-gb/news/press_releases/pages/collet-for-corochuck-930-maximizes-pull-out-prevention.aspx


https://www.sandvik.coromant.com/en-gb/products/corochuck_930/pages/default.aspx

https://www.sandvik.coromant.com/en-gb/news-and-media/press/pages/press-releases.aspx

https://nraoiekc.blogspot.com/2020/06/collet-for-corochuck-930-with.html