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The Bumotec s191H From Starrag: Complete Firearm Slides Produced In One Machine Cycle

The Sports Gun Industry will never be the same.

W&D Staff

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Accuracy: Probably the most important aspect of sport shooting. It is seen on the range, in the field, and even in the Olympics. Exactness is shooting’s time-honored metric. There are numerous factors that can impact accuracy, including stance, aim, breathing, distance to the target, control, backdrop and, of course, the firearm itself.

While Starrag has no control over the “human” aspect of shooting, it does play a key role in helping produce a precise firearm slide that is both efficient and affordable.

Up until recent years, machining of firearm slides has often been produced on machining centers equipped with tombstone fixtures. Blank material is brought to the machine where the clamped part undergoes milling and, in some cases, EDM machining. The net shape is then deburred and hand finished. It sounds simple, right? But after taking a closer look, this process is rife with setups and always includes more than one machine to finish one slide. Starrag’s approach is different.

Bumotec machines stand apart from other machining centers thanks to flexibility and productivity.

The Bumotec s191H is able to produce firearm slides complete from 17-4 stainless steel material in just 45 minutes unmanned. Using a quick mill strategy comprised of small tools, high-speed linear motors with a direct drive torque spindle, the slide is finished and ready for sand blasting in less than one hour. Deburring and decorative operations are easily incorporated into the numerical control (NC) program. The machine’s 1.2 G accelerated drives with 30,000 rpm spindle motor produce quick cuts that generate smooth-to-the-touch surface finishes. Additionally, high pressure through the tool coolant blasts chips away from the slide’s hard-to-access areas, such as the firing pin. This allows for long gun drilling operations to be performed. A slotted feature is included in all slides that guides the barrel. Machining centers struggle to produce this square slot due to tool radius in the corner. At this point, the slide is often removed and taken offline to an EDM for electric discharge machining. This is an extra step that introduces costs. That’s not the case with the Bumotec s191H. The s191H easily broaches the slotted feature, producing sharp clean corners. Time is saved, and the need to use an EDM is eliminated, delivering part-to-part consistency.

U.S. firearm manufacturing market

According to the 2020 edition of its Firearm Production Report issued by the industry’s trade association NSSF®, 11.4 million firearms were produced in the United States or imported in 2018, the latest available statistical year.

Other statistics from the report include:

  • Nearly half (48%) of all rifles produced and imported (less exports) in 2018 were modern sporting rifles.
  • Since 1990, an estimated 19.8 million modern sporting rifles are in circulation today.
  • According to reports such as ATF Firearms Commerce in the United States, ATF AFMER and Congressional Research Service data, there are an estimated 434 million firearms in civilian possession in the United States.
  • Firearm and ammunition manufacturing accounted for nearly 12,000 employees producing over $3.9 billion in goods shipped in 2018.

Slide manufacturing can be considered a form of “Art”

Firearm manufacturing in the United States is a big business. But manufacturing slides affordably and efficiently can require endless hours to get it right.

Slide producers who regularly engage with Starrag say that the way a slide feels in the shooter’s hand is very subjective. By the time producers get to a point where the firearm can be tested, countless hours of design and testing have already gone into producing the slide. Often, the slide is fired thousands of times only to be redesigned or significantly augmented. The Bumotec s191H saves time during this prototyping phase. “With the s191H, slide designers can change features in the program ‘on the fly.’ This shortens the time it takes to get to a finished design,” said Greg Dunkley, Starrag Vice President Sales Precision Engineering North America. Simulation of NC programs offline with computer-aided manufacturing packages are a great benefit. At this point, tool selection is optimized during simulation ensuring the best tool-cutting path. Starrag’s customized tool management module complements part-programming with easy-to-read intuitive tool menus — again saving time. Another significant cost saver is Starrag’s unique work-holding system. Because the Bumotec s191H uses collets and a jaw vice, any major or minor change to the slide does not require new work-holding or custom fixtures. This is generally not the case with machining centers. As an extra benefit, a Renishaw part probe is stored in the (90) station tool carousel. It’s called up during the program and used for measuring critical features such as the front and rear sight guides.

After 61 operations, the finished slide is unloaded with Starrag’s integrated automated pallet tray system.

11-step process in Starrag gun slide manufacturing

The CNC process starts with a bar puller advancing rough bar stock through the Bumotec s191H’s main spindle passage, followed by 11 steps:

  1. The main spindle clamps the bar.
  2. One end of the slide is machined complete.
  3. With half the slide finished, the work-holding sub turret, which is equipped with a sliding jaw vice and tail stock, clamps onto the finished half of the slide.
  4. The sub turret vice pulls the slide out to its finished length.
  5. The vice releases and indexes out of the way.
  6. The work-holding sub turret rotates the tail stock into position onto the end of the slide. With the tail stock supporting the slide, feeds and speeds are advanced to machine the inside and outside the body of the slide.
  7. The tail stock moves out of the way and the vice rotates back into position.
  8. The vice clamps onto the body of the slide.
  9. A parting tool separates the slide from the rough bar.
  10. The jaw vice indexes the slide into a vertical position, allowing the back part of the slide to be finished.
  11. With the slide finished, it automatically is loaded onto the pallet tray and the cycle begins again.

Always a question of costs

Part of the unique value proposition of any Bumotec machining center is finishing a part complete in one cycle. The slide is no different. For owners of Bumotec machines, this means that one person operates one to several machines. The strategy is to have anything that needs to be done to the part — except heat treat or painting — performed on the Bumotec. This is where gains can truly be measured. Higher margins can be realized using a Bumotec machining center by reducing manpower, ancillary machines, large work-holding inventories and changeover times. Together, this equals an efficient, robust and profitable formula.

For anyone interested in producing slides COMPLETE from bar or raw blank lights out, then the Bumotec s191H is THE fast and proven choice. The Bumotec s191H’s inherent rigidity coupled with its unique kinematics will help achieve cycle times that are right on target to meet performance and profitability metrics.

Be sure and check out the slide video on the Starrag TV YouTube Channel: Precision part machining in one.

High-precision machine tools for greater productivity

Starrag Group is a global technology leader in manufacturing high-precision machine tools for milling, turning, boring and grinding workpieces of metallic, composite and ceramic materials. Principle customers are internationally active companies in the Aerospace, Energy, Transportation and Industrial sectors (Industrial Components, Luxury Goods, Med Tech). In addition to its portfolio of machine tools, Starrag Group provides integrated technology and maintenance services that significantly enhance customer quality and productivity.

The umbrella brand Starrag unites the product ranges Berthiez, Bumotec, Dörries, Droop+Rein, Ecospeed, Heckert, Scharmann, SIP, Starrag, TTL and WMW. Headquartered in Rorschach, Switzerland, the Starrag Group operates manufacturing plants in Switzerland, Germany, France, the UK and India and has established a network of sales and services subsidiaries in the most important customer countries.
www.starrag.com

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