Stealth and supersonic are two attributes of the most dominant and complex military combat fighter jet in the world, Lockheed Martin’s F-35 Lightning. These words also describe the ultra-precise Starrag machines, with more than 60 installations involved in the creation of each Lightning jet.

It takes a single pilot to maneuver the $100 million jet, but it takes thousands of Joint Strike Fighter (JSF) partners to construct the F-35 Lightning.

“It’s heart stopping when you attend an air show or are at a stadium when the U.S. military conducts a flyover with the F-35,” says Starrag Chief Sales Officer Alexander Attenberger. “We swell with pride knowing that Starrag plays a role in the JSF program, which is planned to continue for possibly another 50 years.”

Starrag machines produce a wide range of JSF specialized components using steel, aluminum, and titanium.

Starrag and the JSF

Starrag joined the F-35 program in the early 2000s when it worked on titanium parts with a U.K.-based customer. Starrag previously had developed tailored machines for machining parts for other aircraft for this customer and other manufacturers.

“Starrag’s extensive experience of machining titanium was extremely competitive, particularly in regard to tool costs,” the largest ongoing machining life cycle cost, says Starrag Managing Director Dr. Bernhard Bringmann. Work soon evolved into Starrag’s Big Titanium Profiler (BTP) machining center with 16ft x 6.5ft (5,000mm x 2,000mm) pallet sizes to accommodate JSF stringers. Today, 23 BTPs are in production factories in the U.K. and Australia.

With 737ft-lb (1,000N•m) twin spindles and a tool magazine with more than 400 pockets, the BTP 5000/2 simultaneously mills titanium tail-fin components: 27.6" to 31.5" (700mm to 800mm) wide, 2.0" (50mm) thick to tolerances within 0.00118" (30µm) and to surface finish qualities of Ra 1.6 (for 5-axis tasks) and Ra 0.8 (3-axis). Starrag’s quality turnkey solutions include constructing a 6.5ft (2m) deep machine foundation to ensure stability.

“With our ongoing support, there is no reason why our JSF customers shouldn’t continue to maintain such high accuracies day-in and day-out for the next five decades,” Bringmann says. “For every machine and flexible manufacturing system (FMS) we provide, we work very closely with the customer to provide the perfect machining solution to achieve the best quality and cost-effective end result.”

Gantry-type 6-axis machines

Starrag brand Droop+Rein FOGS overhead gantry-type 6-axis machining centers support high-speed die finishing for the JSF, especially because of fixed, fork-type heads with 221ft-lb (300N•m) spindles. Starrag continuously developed its FOGS models to efficiently rough machine a range of steel and titanium F-35 components using various heads.

For carbon fiber, a Starrag FMS, based around FOGS machines, is housed in a large, temperature-controlled building. It accommodates certain panel configurations that need surface milling, routing, and drilling in a single setup before being cleaned and passed along to an integrated coordinate measuring machine. The workpieces sit in fixtures on the pallets that are moved under constant vacuum to the inspection machine.

In addition, the FMS features an enhanced control software, Starrag’s kinematic management system that enables the FOGS machines to hold tolerances of 50µm across their entire 15.7ft x 9.8ft x 5ft (4,800mm x 3,000mm x 1,500mm) working envelope while cutting in fully interpolative 5-axis mode. Even the earliest machines installed continue to hold specified volumetric tolerances. Initially established with five machines, the FMS now has nine machines served by a 90-pallet Fastems system.

Starrag’s workable concept of interchangeable machined parts was also born from the JSF program. With parts being manufactured from around the world, the JSF program required all components to meet very stringent tolerance interchangeability specifications. Starrag, which had similar accuracy specifications for production of the Eurofighter Typhoon jet, met those stringent interchangeability standards. Initially supplying a tailored horizontal machining center, Starrag added volumetric compensation routines to a standard FOGS model to complete these complex tasks.

Starrag’s expertise, coupled with customer input, creates optimized production solutions. In addition to machine build quality, this ongoing quest involves CNC software, fixtures, and workholding, as well as tool design and development.

“Our solutions not only have to provide immediate results in terms of lowest cost per part at the expected quality level, but they also have to sustain over the part’s life cycle. In JSF’s case, this could mean another 50 years of flight,” Bringmann says.

Starrag Group

The grinding wheel spins up to speeds, contacts the surface it’s treating, and sparks fly. Why? What’s happening when the wheel or belt makes contact with the workpiece that sends shards of glowing material into the air? How does an abrasive actually cut material to make those sparks?

Creating sparks?

Many manufacturing processes use abrasives to achieve required finishes because of the material used or need for lower cycle times. And, while the visuals are different, sparks coming off of a grinding process are effectively the same thing as chips coming off of a cutting process.

When a cutting tool traverses a piece of material, whether it’s a high-speed steel end mill working along a block of steel or a carbide insert traversing a shaft on a lathe, the material coming off the workpiece can clearly be seen. The cutting tool penetrates the material and removes a curled chip determined by the size of the cutting point or tool area.

New or recently sharpened cutting tools form chips easily, and those chips often have a metallic color. As the tool continues to run, chips get darker – usually a deep blue or black. As the cutting edge of the tool starts to wear and become dull, penetrating the work surface becomes more difficult, requiring more energy to make chips. Duller tools generate more heat through friction, causing the chips to change color.

Increasing frictional heat from dull tools can deteriorate workpiece finish, causing it to lose form or geometric accuracy. At this point the tool must be re-sharpened or replaced.

Abrasives can accomplish the same thing as a conventional cutting tool – making chips and removing material. The sparks coming off the workpiece are the same sorts of curled chips encountered with a lathe or mill, just much smaller.

Fundamental differences

Conventional cutting tools travel at relatively low speeds compared to abrasive cutting tools – Surface speeds are typically used when referring to both types of cutting tools and even if a knee mill’s spindle is running the same revolutions per minute (rpm) as a grinder’s spindle, the surface speed will most often be different (see Table 1).

Most conventional cutting tools have smaller diameters than common precision grinding wheels, so their surface speeds would be a few hundred feet per minute versus several thousand for a larger grinding wheel (see Table 2).

Surface speed directly affects stock removal. The more often a cutting point contacts the material, the quicker the stock comes off or the higher the stock removal rate will be.

An abrasive cutting tool has more cutting points than a conventional tool – For large, indexable conventional tools with replaceable or resettable inserts, the number of cutting points contacting the work is limited to a single point. On a standard end mill tool, the cutter is making contact with the part on a very limited area, usually a single flute. Abrasive cutting tools or grinding wheels make hundreds of cutting point contacts at once, allowing an abrasive tool to better penetrate the work material and work more efficiently.

Abrasives are typically 2x to 6x harder than the steels and carbides used in conventional tools – Modern aerospace materials are lighter, stronger, and more difficult to machine due to wear-resistant properties, so cutting tools need to withstand those properties. Difficult materials can cause excessive and premature wear on conventional tools, but today’s abrasives are designed to hold up to these materials, effectively making chips, removing stock, and machining newer materials (see Table 3).

Depth of cut (DOC) – Abrasives in precision grinding applications may achieve 0.005" or smaller depths of, where cutters can reach 0.25" cutting depths. Although some specialized grinding operations can hog material, conventional cutting tools hold the advantage over abrasives in DOC. The tradeoff is conventional tools taking large, deep cuts leave very poor, rough surface finishes. Taking the deepest cut possible with an abrasive cutting tool, the finish will generally be better because more cutting points are in contact with the work.

Abrasives also offer very high material removal rates from optimally applying many more cutting points to material in the contact zone. Modern grinding wheels use advanced grains and bonds which improve stock removal, reduce cycle time, and/or extend wheel life.

Also, traditional cutting tools with inserts still need to be taken out of production to have inserts indexed or sharpened. Abrasive cutting tools or grinding wheels can self-sharpen, so they are only briefly out of production for occasional truing or dressing to restore a profile or face condition.

Making chips

As an abrasive grain contacts a workpiece surface, it immediately meets resistance. The work to be ground tries to prevent the abrasive from penetrating the material and making a chip. To overcome that resistance, the system must generate sufficient force, and the machine operator must apply downward forces to make the abrasive penetrate the work surface, or sliding or friction will result.

The wheel speed and machine horsepower must also be sufficient to cause the abrasive to create a chip. Tougher materials require higher horsepower – the higher the tangential forces, the higher the horsepower needed.

The battle occurs where the abrasive meets the material. The force applied by the grain trying to create a chip is fighting against the resistance of the material. If the applied forces are equal to or less than the resistant forces, grinding is minimal or non-existent, resulting in a lot of friction and heat, loss of finish and accuracy, and metallurgical damage.

However, if applied force exceeds resistant force, chips form more readily and grinding occurs. If the force applied by the abrasive is too high, the grain and bond holding it together may break down and cause premature wear of the abrasive cutting tool. To avoid this, pay attention and find the right balance between required grinding forces and chip size.

As the abrasive rubs against the workpiece, there’s a natural tendency for the abrasive to dull. When the abrasive begins to lose its sharpness, it’s more difficult to penetrate the work surface and forces intensify. This condition can accelerate abrasives dulling, increase forces, deteriorate finish, diminish accuracy, and cause metallurgical damage (burn). Most grinding problems can be traced to a dull abrasive remaining in the wheel, belt, or disc too long.

The most efficient grinding (or sanding) occurs when abrasives are sharp so it’s important to:

• Use abrasives with more mild/friable grains that fracture readily, don’t easily dull
• Use appropriate bond type and grade (hardness) to release abrasive grain before dulling
• Use coolant, other agent to reduce friction, slow dulling process
• Physically remove dulled abrasives before problems occur
• Ensure operational factors are appropriate to optimize abrasive; speeds, feeds, etc. set to maximize performance, life
• Abrasive products are made with a variety of abrasives and bonds so the products can be matched to the grinding forces and conditions encountered in a given operation.

Norton | Saint-Gobain Abrasives

About the author: David Goetz is corporate application engineer, Norton | Saint-Gobain Abrasives. He can be reached at david.s.goetz @saint-gobain.com.

Stainless steel materials differ by content, property, and machinability. Machining stainless steel requires tools with various geometries and tool materials to cover the three main application groups: ISO P, M, and S.

For more effective stainless steel machining tools, producers search for appropriate answers to growing industrial demands. Global cutting tool leader ISCAR’s latest products clearly supports this conclusion.

In cutting tool design, the type of stainless steel is a major factor for forming cutting geometry, choosing tool material (particularly carbide grade), and deciding about coolant supply.

Turning tools

ISCAR’s three new chip formers for ISO turning inserts determine the profile of an insert rake face; are designated R3M, M3M, and F3M; and are applicable to rough, medium-duty, and finish turning. Usable in negative and positive turning insert designs, typical features are a specially shaped deflector for better chip control and a wavy surface to prevent chip hammering. 3D modeling of chip flow contributed to forming the deflector during the design stage. To identify the chip former, there is an engraved contour around the hole of the insert and each chip former is characterized by the number of contour curves.

ISCAR experts say the combination of the most advanced carbide grades with its SUMOTECH post-coating treatment gives the new chip formers higher performance and increased tool life.

In parting and grooving, ISCAR launched two new carbide grades with PVD TiAlN coating for machining stainless steel: IC1010 for medium-to-high cutting speeds and IC1030 for low-to-medium cutting speeds.

Rotating tools

Technical capabilities of cutting tools are largely determined by their properties. In stainless steel drilling, ISCAR developments resulted in two new carbide grades: IC806 and IC5500. IC806 with PVD coating is mainly for deep drilling difficult-to-cut heat resistant stainless steel (ISO M and ISO S groups). IC5500 features a new substrate and CVD coating for high performance in drilling ferritic and martensitic stainless steel (ISO P group).

The family of milling cutters with round inserts now includes tools intended for machining profile surfaces, especially the working surfaces of blades in turbomachinery. Two design versions include one produced from grade IC5820 for machining austenitic, duplex, and precipitation-hardening stainless steel (ISO M and ISO S groups). The second version, made from carbide grade IC5500, is for milling ferritic and martensitic steel (ISO P group), and considerably increases cutting speeds.

To improve performance in machining austenitic, duplex, and precipitation-hardening stainless steel (ISO M and ISO S groups), a family of five-flute solid carbide endmills use the vibration-proof principle known as ISCAR’s CHATTERFREE. Variable angular pitch and different flute helix portions now include a sub-flute wear control mechanism allowing for more aggressive ramping and enhanced chip evacuation. Made from a new PVD coated hard submicron carbide grade IC608, the combination of the chatter- free approach, the sub-flutes, a reinforced taper core, and the advanced wear-resistant grade in the endmill design delivers increased performance.

Effective cooling

With stainless steel, effective coolant supply influences performance optimization. ISCAR continues to develop indexable cutting technologies with coolant channels directed to the cutting edge with many tools designed to enhance high pressure coolant delivery.

Demands for more and more efficient tools for machining stainless steel require an appropriate response from the cutting tool manufacturer. High competence and expertise, multiplied by an innovation initiative, is the decisive point here and the way to progress. ISCAR remains determined and will continue following this practice in future cutting tool developments.

Iscar USA
https://www.iscarusa.com

Potentially flammable and hazardous chemicals such as acetone and isopropyl alcohol are often stored in 55-gallon or larger drums for dispensing into smaller containers or at the point of use. Environmental, health, and safety directors often must identify the best type of pump to transfer these liquids as the wrong type of pump, or worse, employees tipping and pouring out contents, can be catastrophic. Accidental release of toxic or highly flammable materials can cause worker injuries, fires, and explosions.

SDS, GHS

Hazardous chemicals must include safety data sheets (SDS) and globally harmonized system (GHS)-compliant labels. The United Nations established GHS to create a worldwide, unified system to identify and communicate information about hazardous chemicals.

The SDS details potential environmental hazards, what to do in the event of small and large spills, and suggestions for treating injuries related to inhaling or coming into physical contact with chemicals. The SDS also identify required personal protective equipment (PPE) and safe storage guidelines.

Depending on the chemical substance, SDS can include descriptions of severe injuries, transgenic damage to cells and organs, and the possibility of death. For example, the SDS for the widely used solvent acetone mentions its extreme flammability and how it “burns with yellow bright flames… Vapors can flow along surfaces to distant ignition sources and flash back… even minimal static discharge can ignite acetone vapors.”

With such dire consequences in mind, proper storage and handling are outlined to prevent dangerous situations. For flammable and combustible liquids, that advice is consistent across most SDS and states:

• Avoid breathing fumes or vapors
• Keep away from heat, sparks, open flames, or hot surfaces (to avoid ignition)
• Keep containers tightly closed
• Bring in grounding or bonding devices for the container, receiving equipment
• Use explosion-proof electrical, ventilating, or lighting equipment (to avoid ignition)
• Take precautionary measures against static discharge (to avoid ignition)

Most states and municipalities have further adopted NFPA 30 Flammable and Combustible Liquids Code and OSHA 29 CFR 1910.106, fire codes addressing flammable liquid equipment, handling, storage, and use.

Ensuring safe delivery of chemicals requires proper safety training, use of PPE, and in some cases, further engineering controls.

Although SDS don’t state it directly, most – if not all – requirements spell out the need for a specialty pump to transfer flammable or combustible chemicals to smaller containers or at the point of use to maintain workplace safety.

Transfer equipment requirements

Whether mandatory or guideline, ensuring safe chemical transfer requires a sealed or closed-loop pump system that keeps vapors from escaping the container and prevents personnel contact. Systems must be designed using materials and seals that can withstand extended contact with the chemical and must include grounding wires to prevent static discharge. A sealed pump dispensing system enhances safety by eliminating spills, enabling environmentally safe transfer.

Eliminate ignition sources

A flame, hot surface, static electricity, or a spark generated by electricity or mechanical work can ignite combustible and flammable liquids, so it’s critical to eliminate external ignition sources when handling them. Highly volatile solvents are more hazardous because any vapor – volatile organic compounds (VOCs) – released can reach ignition sources several feet away and flash back to the liquid.

In transferring flammable liquids from large containers (>10L) to smaller ones, the flow of the liquid can create static electricity that could result in a spark. Static electricity build-up is possible whether using a pump or pouring the liquid. If the bulk container and receiving vessel are both metal, it’s important to bond the two by firmly attaching a metal bonding strap or wire to both containers and to the ground, which can safely dissipate the static charge.

Containers used to transfer Class 1 liquid (flammable with a flash point lower than 100°F) and Class 2 and 3 (combustible with a flashpoint higher than 100°F) must be grounded or bonded to prevent electrostatic discharge that could act as an ignition source. NFPA 30 Section 18.4.2.2 also requires a means to prevent static electricity during transfer/dispensing operations.

Selection guidelines

Chemical compatibility databases and guidance make selecting the correct pump for each chemical or formulation in aerospace manufacturing straightforward while maintaining workplace safety.

The correct pump for each application is often determined by the materials that will contact the chemicals. Each chemical has specific characteristics, so selecting the appropriate gasket, housing, and hose is critical for safety and equipment longevity. In addition, flammable liquids require a groundable pump. Established pump manufacturers compile detailed chemical compatibility databases that document the type of pump, gasket, hose, and whether the chemical needs to be groundable.

If the chemical is in the database, the pump often comes with a one-year warranty as it has been tested or the chemical manufacturer verified compatibility. When a chemical isn’t on the list, the pump manufacturer will review the SDS and, if necessary, conduct tests to determine the right pump.

Chemical compatibility testing

Testing can be as simple as soaking the standard gaskets in the chemical for 5 to 7 days. Because vapors are volatile, they are frequently more harmful than the liquid itself. When appropriate, vapor tests are conducted in which the elastomer gasket options (Viton, EPDM, Nitrile, and Santoprene) are suspended over the liquid. Pumps are then built, tested with each elastomer, and if none of these gaskets work for the application, designers can select Teflon or Kalrez gaskets.

With some complex aromatics, aliphatics, and flammable liquids, the plastic pump housing may also need to be tested. This test is a 60-day soak in the chemicals to see if the parts swell or bind with each other, which will cause the pump to fail.

By following the NFPA, OSHA, and other regulatory bodies’ recommendations, personnel can avoid hazards outlined in the SDS that could lead to physical injuries, chronic respiratory ailments, and even death.

Fortunately, protecting workers from harm can be relatively straightforward with proper safety training, the use of PPE, and applying engineering controls to prevent dangerous spills and chemical accidents.

GoatThroat Pumps

About the author: Nancy Westcott is president of GoatThroat Pumps. For more info., call 866.639.4628, 646.486.3636, or email info@goatthroat.com.