“We have seen as little as a 30 per cent in cycle times and a high end of 80 per cent reduction,” said Ball. “In the upper range, the cycle time reduction also takes into account a reduction in rest roughing and semifinishing.”

Industry experts were also asked about grades and geometries for Swiss-type turning tools. “A grade specifically for use in Swiss-type turning is WSM21, a mono-layer PVD coating that is designed to withstand the low cutting speeds often encountered with small diameter components. Grades with thinner PVD coatings and sharp edges are generally best,” says Ludeking. “Although there aren’t any specific Swiss-turning geometries, those with aggressive chip control for light feed rates and depth-of-cut are often best for Swiss-type operations.”

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“Each of these devices can be ordered with special options that might pertain to the application being performed. Special ID tolerances, extended nose lengths, extended land surface, over gripping geometry, or special ID shapes are all things that can be modified on a guide bushing or pickoff collet,” says Scott Laprade, marketing manager, Genevieve Swiss Industries, Inc.

“Swiss machines have three work holding devices in them if you don’t include the bar feed collets. The headstock collet, the guide bushing (which is what the stock feeds through during the cutting and is used for support), and the pickoff or sub-spindle collet which takes a parted-off work piece and can hold it for secondary operations on the sub spindle side of the machine.

“Today’s CAM software can be programmed to create an optimized roughing stage that uses a large DOC and light radial engagement to maximize metal removal rates. It’s a type of milling operation that is very well suited to pocketing and side profiling,” said Jay Ball, product manager for solid-carbide end mills – NAFTA at Seco Tools.

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The new Walter Cut G1011-P grooving tool from Walter USA, which can be used in Swiss-type turning, is internally cooled. “The G1011-P is designed so the coolant stream is released very close to the cutting edge, guaranteeing the best possible effect of the coolant, no matter what the supply pressure is,” says Kurt Ludeking, product manager of turning at Walter USA. “Compared to an external coolant supply, this ensures coolant at the cutting edge throughout the cut, especially important in deep, narrow grooves and parting operations

The amount of stepover that can be used depends on tool diameter and the number of flutes on the tool. For example, a 6-flute, 0.5-in. end mill cutting 4140 steel can use a 10 to 12 per cent stepover. With a 7-flute tool, the stepover is only 8 per cent. Moving to a 9-flute tool reduces the stepover to roughly 3 per cent.

Exsys Tool places its expertise with tooling for Swiss-type machines front and center. The company highlights its Decoflex tooling system for interchangeable tools.

Optimized roughing is not for every part; it’s very component driven. If a part is a complex, 3-D component, optimized roughing is not going to be the most efficient way to get the highest metal removal rate during the roughing stage. When it can be employed, however, it can have a significant effect on cycle times.

Rigid workholding also is important to minimize vibration in the part or, in the worst-case scenario, movement of the workpiece.

“There are many tools that were designed with the Swiss machine in mind, due to the limited tooling space and stations,” says Douglas Paoletta, president and owner, Encompass Swiss Consulting in Richmond Heights, Ohio. “Iscar’s Pentacut insert, which is a five-sided indexable tool, is one. One of the first ‘back turning’ tools, and still one of the best, is the Kyocera ABS/ABW series tool. Kennametal has one of the best ‘quick change series’ tools called the KM Micro,” adds Paoletta, whose company offers on-site training for shops and manufacturers interested in Swiss-type machining.

“Decoflex is a modular tooling system specifically designed for Swiss turning head stock machines…we have introduced a multi-headed collet chuck that will work in both directions of the spindle simultaneously,” says Scott Leitch, marketing manager with Exsys.

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As Swiss-type turning edges towards the mainstream, cutting tool companies continue to provide a steady stream of appropriate tools. Such tools have to be able to function in the confined work envelope characteristic of Swiss-type machines.

“Instead of encasing the tool in 180 degrees of engagement, which creates a lot of heat and a lot of pressure, better metal removal rates are achieved with optimized roughing because machinists can take a 2xD DOC and use a 10 to 12 per cent stepover, depending on material. This means you generate less heat and have less radial engagement, which means you can accelerate feed rate and surface footage rate. This is what reduces cycle time,” he added.

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Rego-Fix Tool, meanwhile, recently expanded its retrofit reCool coolant through system. Previously matched with live tooling on CNC lathes, the system can be now be used with static toolholders on Swiss automatic machines.

Optimized roughing uses a large DOC and light radial engagement to maximize metal removal rates. Photo courtesy of Seco Tools.

Today’s advanced optimized roughing is only effective if implemented properly. And while similar in nature to other strategies, optimized roughing entails specific best practices that shops must adhere to and common missteps they must avoid to achieve optimum results.

When it comes to the overall manufacturing process, optimized roughing can typically remove 90 to 95 per cent of the rough stock on a workpiece. This leaves only about 1 to 2 per cent of the tool diameter as finish stock for removal.

To sum up, Laprade cites an old retail truism. “Swiss tooling is a very ‘get what you pay for’ type of product. When you’re trying to continuously ‘split tenths’ you want something that is high quality and more importantly, repeats each time a job is set up or when a tool is changed. A good tool or tooling system will eliminate the need for an operator to chase a tolerance because the tooling wasn’t intended for it or is poor quality,” notes Laprade.

“Coolant delivery can be the key to success and direct delivery via coolant nozzles built into the tools can have benefits of better chip control and cooling of the component and chips,” says Kevin Burton, product specialist at Sandvik Coromant in Mississauga, Ontario.

The number of flutes determines the stepover percentage because it determines the chip spacing. Tool diameter also plays a role. For example, a 0.5-in.-dia. tool with 9 flutes has less chip spacing than a 1-in.-dia. tool with 9 flutes.

For the optimized roughing operation to be successful, a constant radial DOC must be maintained. This radial DOC also depends on the material being cut. For example, superalloys can have a radial DOC that is 5 to 7 per cent of the tool diameter, while tool steel under 50 HRC can use 7 to 10 per cent of the tool’s diameter as the radial DOC value.

“In Swiss applications where the parts and work envelope are generally smaller, through coolant when and where available is always a better option than relying on flood coolant,” says Garfield.

Horn, among other cutting tool companies, has new offerings for the Swiss-type turning sector. “Although Horn has traditionally been oriented towards small part Swiss type machining, we have introduced new tooling dedicated to Swiss-type turning grooving and milling applications. A recent introduction to our existing 274 line was the System 274 ‘µ’ finish for micro turning, grooving and back turning. In addition, our Graf line of Swiss tooling offer numerous options for holding with round shank holders and height adjustable quick change holders for most Swiss type machines, i.e. Star, Miyano and Citizen,” says Garfield.

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According to Ball, the best use of optimized roughing is in situations that use the full flute length of the tool. Roughing long, straight walls is a good example of this.

When the question is about the best kind of coatings on Swiss-type turn tooling, there’s further consensus.

Overall cycle time is dependent on the part. If a part is near-net forged, for example, it will not require as much roughing as a solid block will. Another example is a mould cavity: It requires much more time to be spent in the finishing stage rather than the roughing stage because a smooth 3-D finish is required.

During the roughing phase, the vast majority of material is removed from the part, typically leaving only what is required for the finishing phase.

“Most Swiss machines just use flood coolant [and have] a little stick out there shooting the oil where you’re cutting. That may or may not be an accurate way of getting [coolant] there. [The reCool system] brings the coolant in through the nut, and now you can go through your cutting tool, something that’s always been hard to do with a Swiss machine,” says David McHenry, engineering and technical manager at Rego-Fix Tool.

“At GenSwiss we recommend micro-thin PVD coatings that don’t change the edge conditions of the cutting tools when applied to them,” adds Scott Laprade, marketing manager, Genevieve Swiss Industries, Inc. (GenSwiss). “When working with small diameter parts you want the edges to remain as sharp as possible to prevent pressure build up which can lead to deflection of the work piece. Some coatings and processes deposit a ‘bead’ of coating on the edge of the insert which can round it off by up to a thousandth of an inch.”

As the number of flutes increases, the stepover must decrease to maintain surface finish at faster feed rates. If the stepover is too large, feed rates must be lowered, and more heat is generated with the larger amount of metal removed in each pass. By decreasing the stepover, faster cutting speeds can be achieved. This requires more passes, but the metal removal rates are still higher than at slower speeds because of the increased feed rates.

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Ball suggested milling chucks, shrink-fit holders, and high-precision collet chuck systems when using this milling strategy.

Optimized roughing improves metal removal rates (Q), reduces the amount of time spent in the roughing phase, and increases tool life, all while reducing the load on the machine, according to Ball.

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2. Understand the power of CAM. It is impossible to program an optimized roughing strategy manually. You need to use a programming software package that will control the cutting strategy. But not just any programming software will work; it needs to be the right software for this application. A program designed only for high-speed side milling will not perform optimized roughing.

GenSwiss’ recently released its Ti-Loc SwissClamp System “for rotary tooling in Swiss machines … it can be used for milling and slitting operations that utilize ER collets for tool holding,” explains Laprade.

1. Use the right machine. Machines used for optimized roughing need two things: fast spindles and rigidity. The spindles must generate the necessary revolutions per minute for optimized roughing’s feed rates. The rigidity of the machine minimizes vibration and contributes to part quality.

The holder needs to provide less than 0.0004 in. of runout. A precise holder ensures the accuracy of the process, whereas a less secure holder will cause undesirable levels of vibration at optimized roughing’s high feed rates.

There’s a general consensus that when it comes to designing tooling for Swiss-type turning, coolant through is preferable to flood coolant. Coolant through tools utilize high pressure (H.P.) for delivery.

Insert shape also plays a big role in Swiss-type turning “since we normally do not rough and finish turn parts. Parts that have undercuts, larger grooves, angles into smaller diameters, and other features like that, are studied to see if a different tool can provide the entire profile in one turn. If not then we have to look at segmenting the part into sections to process,” says Paoletta.

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4. Use the tooling manufacturer’s recommended cutting parameters. Do not rely on the default cutting speed and feed rate data from programming software suppliers. Cutting tool suppliers develop the recommended cutting parameters after research and through years of experience. Tool makers optimize cutting data for the tool’s design and specifications and for the material group you are working with.

“PVD coatings are most common due to the reduced heat factor in small part machining—small contact diameter, lighter feeds and good cooling. The required sharper cutting edges also dictate that PVD be used,” echoes Burton.

“Typically PVD coatings or uncoated tools are used for Swiss-type turning operations,” says Ludeking. “These provide the sharpest cutting edges, thereby reducing forces on the small workpieces. Also, these tools have higher edge toughness that helps them withstand the high forces generated when cutting at low speeds often encountered in small diameter components. Because CVD coatings require somewhat larger edge-rounding (hones), they tend to generate higher cutting forces that are detrimental to small components. On the positive side, new CVD coating technology is enabling smaller hones, making them good choices for higher speed operations or very abrasive alloys,” he adds.

“On the I.D, using coolant-through drills for instance, can gain you a 2x feedrate over a standard carbide drill or 3x to 4x a cobalt drill, while you can also increase your SFM for the tool,” he explains.

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The best use of the optimized roughing technique is in situations that can use the full flute length of the tool, such as roughing long, straight walls. Photo courtesy of Seco Tools.

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“There might be some additional corner picking that you need to get closer to near net shape before you can move on to finishing, but this strategy takes the bulk of the material out,” said Ball.

“Manufacturers have really paid attention to the growing market and needs of the Swiss turn industry, so there really is a lot available [that meets] the needs of the Swiss-type turn shops,” he continues. “Considerations in tooling must also be made in relation to the geometry of the part and a possible non-standard program format to create certain part features. Some Swiss machines are limited on stick tool stations. There are many new tools out there that combine several things like face, turn, groove for the O.D. or drill, bore, and thread for the I.D. By using these combinations we can free up tool stations allowing us to machine more complex or tooling intensive parts with the limited stations.”

“With any solid-carbide application in which you are trying to hold tight tolerances, the holders can make you or break you,” said Ball. “If you try to run these strategies and these processes in a collet that is not rigid or doesn’t contain the runout, you will struggle to achieve the metal removal rate and cycle time reduction this strategy can provide.”

“Maximizing the envelope is crucial given the tooling requirement to complete a part versus space provided,” adds Jim Garfield, regional sales manager, at Horn USA. “Swiss type multi-function tools can reduce the number of tools/holders required as well as reduce cycle times. Quick-change Swiss holders can reduce downtime when changeover is necessary due to tool wear or new part set up. Repeatability of center height when changing insert/tools is of utmost importance,” he adds.

“Niagara Cutter [a division of Seco] has a multiflute family of tools that is used for this type of cutting. They feature a 38-degree helix, large core diameters, and multiple flutes (6, 7, 9). The tools used for optimized roughing typically have some sort of corner protection (radius or chamfer) and are coated to provide both heat and abrasion resistance, typically an AlTiN coating,” said Bell.

“The H.P increases the tool life and reduces the need for intervention by the operator for chips wrapping on a part.

AE-VMS short series endmills designed for stable milling application, ideal for wide range of material like Carbon steel, Alloy steel and Stainless steel to Titanium alloys and Ni alloys.

“When turning the O.D. of a part, H.P. coolant pays big dividends on gummy/hard materials or long cuts where stringy chips are a problem,” says Paoletta.

3. Don’t cut too deep. A cutting depth of 2xD that takes the full length of the cut in one pass is recommended. The shallow radial stepover enables the depth of the cut. A larger stepover would require a shallower depth of cut to achieve the same metal removal rates. However, a cut that is too deep, more than 3xD for example, creates cutting pressures greater than the tool can bear and causes deflection.