Tuesday, October 14, 2014

5 Steps to Improving Production Economics

By Todd Miller, Manager of Product Marketing

The goal of any machining operation is to produce accurate parts at the lowest cost, thereby maximizing profitability. The traditional way to lower machining costs is to accelerate production rates with more aggressive machining parameters, usually focusing on faster cutting speeds. That approach, however, does not recognize significant cost factors including the expense of scrapped parts and production downtime. Use the following 5-step strategy to balance productivity and manufacturing costs.

1.  Focus on the Costs You Can Control
Some elements of manufacturing costs are beyond your control. Workpiece material type is dictated by the end use of the machined component. Likewise, costs for machine tools, maintenance, and the power to run them are basically fixed, usually involving ongoing payments. Your strategy for increasing production economics, therefore, should focus on the variable costs such as machining process elements like which cutting tools you use and the parameters in which they are employed.

2.  Find Optimal Parameters
There is a common misconception that simply increasing cutting speeds will produce more parts per period of time and thereby reduce manufacturing costs. While using higher cutting speeds can increase production rates, it may also result in higher tooling and machine tool costs. Finding optimal parameters is essential and requires a balance between reduced cutting speeds and proportional increases in feed rate and depth of cut. The ideal is to use the largest depth of cut possible to reduce the number of cutting passes required and machining time. At the same time, maximize the feed rate, albeit carefully so as not to negatively affect workpiece quality and surface finish requirements. When a stable and reliable combination has been reached, cutting speeds can be used for final calibration of the operation.

3. Reduce Machine Tool Costs
Higher speeds initially drive down machine tool costs because the machine tool is producing more parts per period of time, therefore more revenue can be applied against its fixed cost. However, as speeds rise beyond a certain point, machine tool costs begin to increase. Tool life becomes so short that the decrease of the machine tool cost has a smaller effect than the fast increasing costs of tooling and downtime for tool changes. In addition, extremely high cutting speeds and very aggressive machining parameters in some cases can add to machine tool costs for maintenance and even result in downtime caused by unanticipated machine failures.

4. Follow A Model of Efficiency
American mechanical engineer F.W. Taylor once developed a model for determining tool life that shows that for a given combination of depth of cut and feed there is a certain window for cutting speeds where tool deterioration is safe, predictable and controllable. When working in that window, it is possible to quantify the relation between cutting speed, tool wear and tool life. Following this model brings together cost efficiency and productivity and provides a clear picture of what to aim for when defining the optimum cutting speed for an operation.

5. Establish a Stable Machining Process
The key to maintaining productivity and part quality and avoiding scrap is establishing a stable machining process. Create an optimum production environment by choosing the tool material, coating and geometry best suited to the workpiece and operations at hand, and optimize the machining CAM program, toolholding systems, and coolant application. Be sure to integrate workhandling automation such as pallet or robotic part load/unload systems into the process as well, because handling of raw and finished part stock can consume significant amounts of machine downtime.

Want to learn more? Please contact me, and I’ll help you create a balanced production strategy for your operations. 

About the Author
Todd is the manager of product marketing for Seco Tools, LLC. He oversees the product marketing team and works with the company’s sales department to further enhance the customer experience. He and his team also support product introductions while working globally on new product testing to ensure customers gain access to the industry’s most advanced tooling as quickly as possible. In his spare time, Todd likes to bowl and cheer on the University of Michigan football team. 

Thursday, September 25, 2014

Simple Steps to Environmentally Aware Productive Machining

By Todd Miller, Manager of Product Marketing

In a world where energy is a rare, expensive commodity and pollution is a continually growing concern, there’s a growing need to machine components in a more efficient, environmentally responsible, “green” way. 

When machining complex components from high-performance workpiece materials such as nickel-base alloys, ultimate productivity in many cases is not of primary importance. The operations focus more on reliably producing dimensionally and qualitatively perfect parts. That is not to say economic and environmental considerations are irrelevant, but technological productivity and process security challenges are so prominent that efficient, green machining is not the top priority.

The story is somewhat different with simpler parts and more common workpiece materials such as steels and cast irons. Today, steels and cast irons make up the bulk of the materials machined worldwide, and all indicators show a stable situation in the tonnage that will be machined in coming decades. Employed across all industries, steel alloys offer a very good price-performance ratio in terms of cost, strength, and ease of machining.

Wide application and long familiarity have made the purely productivity-oriented aspects of steel machining less crucial. Manufacturers know how steel behaves and are rather sure they can create solutions that will guarantee good productivity.

As a result, our customers who machine steel are increasingly interested in the economical and environmental consequences of their machining operations beyond technological productivity issues.

Research institutes and universities around the world are examining ways to perform machining in a way that puts less load on the environment, namely using less energy and making less waste.

Part of the process involves gaining an overall perspective on the machining process. For example, we have found that workshops do not always realize that energy costs, specifically of electricity, are on the same or even somewhat higher level as cutting edge costs, expressed in cost per minute. Electricity costs include not only operation of a machine’s spindles and axes, but also CNC units and auxiliary equipment such as coolant and workhandling systems. 

There are many ways to reduce the energy consumed in the cutting process itself. Application of certain insert geometries, for example, can contribute to energy conservation. Where use of a sharper geometry is appropriate, 1-degree extra positive rake angle can reduce energy consumption by 1.5 to 2.5 percent.

Manipulating cutting speeds represents another opportunity to save energy. Productivity is the traditional goal in machining, and achieving it has almost always involved employing higher cutting speeds. However, one way to reduce energy consumption is to lower cutting speeds and proportionally increase feed rates and depths of cut.

If a machining application permits working with a combination of lower cutting speeds and higher feed rates and depth of cut, at least three benefits result. One advantage is that less energy is required to remove material from the workpiece. We have found that a one percent reduction of cutting speed reduces energy consumption by five percent; a one percent decrease of depth of cut combined with one percent increase of feed rate reduces energy consumption by two to three percent.  

Another benefit of lower cutting speeds can be longer tool life. Fewer cutting edges or inserts are consumed over a certain amount of time or over a certain number of workpieces. There’s a reason indexable tools have historically been called “throwaway” inserts; at the end of tool life, they end up as waste in the environment. At slower speeds in combination with other cutting parameter adjustments, however, fewer inserts are consumed to do the same amount of work.

A third advantage of the application of lower cutting speeds is a reduction in the heat generated in the metalcutting operation. In addition to contributing to longer tool life, reducing heat also lowers the cooling requirements of the cutting system and less coolant is needed. That is environmentally significant because used coolant is full of metals, lubricants and other contaminants and poses particularly troublesome and expensive disposal problems.

Of course, reducing the environmental impact of metalcutting operations goes far beyond tools and tooling systems. Complementary efforts to improve the environmental status of machining include recycling of chips and used carbide, moves to minimal-coolant or dry machining processes, and even research into use of workpiece materials that themselves require less energy to make. Productivity will always be the ultimate goal in metalcutting and manufacturing overall, but analytical thinking and simple actions can make productivity go hand-in-hand with resolution of environmental concerns.

About the Author
Todd is the manager of product marketing for Seco Tools, LLC. He oversees the product marketing team and works with the company’s sales department to further enhance the customer experience. He and his team also support product introductions while working globally on new product testing to ensure customers gain access to the industry’s most advanced tooling as quickly as possible. In his spare time, Todd likes to bowl and cheer on the University of Michigan football team.

Tuesday, July 22, 2014

Best Practices for Austenitic Stainless Steel (ISO M) Machining

By Don Graham, Manager of Education and Technical Services
Austenitic stainless steel, an iron-chromium-nickel alloy, provides enhanced strength and corrosion resistance for a wide variety of today’s demanding component applications. The benefits of this ISO M material, however, come with a downside. The alloy’s nickel content, which boosts its corrosion-resistance capability, also makes the material harder and therefore more difficult to machine. Fortunately, there are strategies that address this problem and help manufacturers significantly boost productivity in austenitic stainless steel machining operations. 
Milling Stainless Steel
Here are some of the most effective strategies:
Use sharp tools with carbide substrates. Traditionally, machinists assumed that because the austenitic stainless steel alloys were stronger, mechanical cutting forces would be higher, necessitating the application of stronger, negative-geometry tools at reduced cutting parameters. That approach, however, resulted in shorter tool life, longer chips, frequent burrs, unsatisfactory surface roughness and harmful vibration.  In reality, the mechanical cutting forces involved in cutting austenitic stainless steel aren’t much higher than those typical when machining traditional steels. Most of the extra energy consumption required to machine austenitic stainless steels is due to their thermal properties and work hardening characteristics. 
Metalcutting is a deformation process, and when deformation-resistant austenitic stainless steel is machined, the operation generates excessive heat. Evacuating that heat from the cutting zone is of primary importance. Unfortunately, in addition to being resistant to deformation, austenitic stainless steel also has low thermal conductivity. Because of this, the workpiece and chips generated during machining absorb very little heat, so, excess heat transfers directly into the cutting tools to severely shorten their working lives. 
Carbide tool substrates, on the other hand, combat this problem and provide hot hardnesses that endure the elevated temperatures when machining austenitic stainless steel. Paired with sharper cutting edges, carbide substrate tools actually cut the stainless steel – as opposed to deforming it – to reduce the amount of generated heat.
Take large depths-of-cut at aggressive feedrates. With austenitic stainless steel, the bigger the chip the more heat it can carry away from the cutting zone. The most effective way to generate big chips is through large depths-of-cut and aggressive feedrates. Larger depths-of-cut will also reduce the number of cutting passes required to complete a part – an important consideration because austenitic stainless steel tends to progressively strain harden during lengthier machining operations. 
There are practical limitations to these aggressive machining tactics, however. For instance, the power available from the machine tool, as well as the strength of the cutting tool and the workpiece, will ultimately determine how aggressive the cutting parameters can be. In addition, machinists should rethink the finishing process, which traditionally involves multiple passes at smaller depths-of-cut and light feedrates. The most effective strategy is to maximize machining parameters whenever possible, as this can improve tool life and workpiece surface finish.
Use appropriate coolant, applied under high pressure. Due to the problematic thermal properties of austenitic stainless steels, the application of coolant during machining operations is almost always crucial for favorable machining results. The coolant must be of high quality, with at least eight or nine percent oil content in an oil/water emulsion – compared with the three or four percent oil content typical for many machining operations. The higher the pressure at which coolant is delivered to the cutting zone, the better it will do its job. Specialized delivery systems, such as Seco’s Jetstream Tooling, that delivers a high-pressure stream of coolant directly to the cutting zone are even more effective. 
At Seco, we’ve developed several advanced products and strategies that address ISO M austenitic stainless steel machinability – and will continue to do so as the use of these high-performance workpiece materials grows. If you have any questions or would like more information on how our tools and machining strategies for austenitic stainless steels can boost your productivity, please don’t hesitate to contact me.
About the Author
Don is the manager of education and technical services for Seco, responsible for all educational activities for the NAFTA market, new product testing and various other technical functions. Outside of work, he enjoys making maple syrup, restoring antique tractors and farming. 

Friday, June 6, 2014

Resolving Opposing Concepts in Production Economics

By Patrick de Vos, Corporate Technical Education Manager, Seco Tools AB
To gain maximum productivity and economic benefits in your metal cutting operations, it’s essential to evaluate the processes in light of overall production economics. The goal is to ensure reliability of the machining process while maintaining high productivity and low production costs. Achieving those goals involves an examination of several opposing concepts.

Macro Versus Micro
The traditional approach to maximizing metal cutting results involves a narrow-perspective micro model based on 1:1 optimization of one tool in one operation. Macro models, however, consider manufacturing processes from a broader perspective. These models focus on the total floor-to-floor time required to produce a given workpiece. 

The macro perspective considers the interrelation of all the steps in a manufacturing process. A simplified example involves two machines employed in series to produce a component. If machine tool A is optimized to boost its output but the results from machine B can’t be improved, parts from the first machine will sit waiting for the second as semi-finished inventory, increasing costs. In this case, simply optimizing cutting costs (rather than output) on the first machine would lower machining cost overall while maintaining output. 

On the other hand, in a situation where machine B sits idle waiting to process parts from machine A, increasing the output of the first machine will increase total output. Much depends on whether the shop organizes production flow in a line, batch, or parallel sequence. 

Cost Versus Productivity
After evaluating the process from a macro viewpoint, shops can optimize operations on an individual basis with the goal of achieving high metal removal rates at the lowest possible cost. The process involves selecting tooling best suited to machine the part’s features and then employing the largest depth of cut and highest feed rate possible. Those parameters, of course, are subject to constraints regarding available machine power and torque, and the stability of workpiece fixturing and tool clamping. 

Shop personnel then can use cutting speed to fine-tune the machining process to achieve minimum cost, maximum productivity or a compromise result. Initially, machining time drops and productivity rises with increasing cutting speeds. After a certain point, however, costs again start to rise. Above a certain cutting speed, tool life becomes so short that the cutting edge requires frequent replacement. At that point, the decrease of the machining time cost has a smaller beneficial effect than the increasing cost of tools and changeover time. Somewhere between the extremes there is a cutting speed where the two costs balance to result in a minimum total cost.

Quality Versus Productivity
Standards for part quality continually become stricter, but the quest for quality sometimes is overdone. Pursuing unnecessary high quality wastes money. Manufacturers can drastically reduce costs and dramatically increase productivity just by fulfilling the given requirements for part precision. 

Productivity Versus Reliability
Similarly, focusing entirely on maximum productivity in terms of lower cycle times can negatively affect the reliability of a metal working process. A process that is run constantly at the limit may exceed that limit at a cost of scrapped workpieces and lost time. Understanding tool wear and failure modes is essential. Wear-related phenomena generally are gradual and predictable, while other failure modes, such as tool breakage, lack the predictability required to maintain a reliable cutting process.

Individual Factors Versus Overall Results
Typically, more than 50 to 70 individual factors can have an appreciable effect on product quality, production time, and cost. Typical factors that should be analyzed include tools/tooling systems, workpiece configuration and materials, equipment process capabilities and data, human factors, peripheral equipment and maintenance issues. Environmental factors such as energy consumption and disposal or recycling of worn tools and machining waste must also be examined, in addition to employee safety considerations. 

Universal Versus Specialized Tooling
An accepted way to increase productivity in an individual operation is to engineer specialized tooling for that specific process. Spending the time and money involved in such an effort may be worthwhile when the expense can be amortized over a long production run. However, balancing productivity, reliability and tool cost considerations in the small-batch situations that have become more frequent today requires versatile “universal” tooling that offers flexibility over a broad window of application. These tools reduce downtime by minimizing the time needed to switch in a new tool when the workpiece changes. They also eliminate the need to set up and test run a new tool. 

In summary, the choice of tooling and machining parameters for a single operation is dependent on how that operation fits into the total manufacturing picture. The choice should be biased toward what is desired in terms of productivity, cost efficiency and reliability, and what best fits a broad view of the production process.

About the Author 
Based in Sweden, Patrick is the corporate technical education manager for Seco Tools AB with global responsibilities for the technical education activities that help train Seco employees and customers worldwide. He led the creation of the Seco Technical Education Program (STEP) and since its launch more than 145,000 people worldwide have participated in the program. He has been with the Seco organization for more than 30 years, and during that time he has trained more than 50,000 people in over 55 countries. He is also the author of the book “Metal Cutting, theories in practice.”  

Friday, May 16, 2014

Productive Tradeoffs in Rough Turning

By Chad Miller, Product Manager – Turning and Advanced Materials 

Maximizing productivity in rough turning operations requires a balance of tradeoffs between the properties of the cutting tool substrate as well as the characteristics of its chipbreaker geometry. 

Seco M6 Roughing Geometry
A tool’s cutting edge must be harder than the material it cuts. High hardness, especially at elevated temperatures generated in high speed machining, will prolong tool life. A harder tool, however, is also more brittle. Uneven cutting forces encountered in roughing, especially in interrupted cuts involving scale or varying depths of cut, can cause a hard cutting tool to fracture. Instability in the machine tool, fixturing, or workpiece can also precipitate failure. 
On the other hand, boosting a tool’s toughness by including a higher percentage of cobalt binder, for example, will enable a tool to resist impact. But at the same time, reduced hardness also makes a tool subject to rapid wear and/or deformation in higher-speed operations. The key is to balance tool properties in light of the workpiece being machined. 
For example, Seco’s TP0500 grade is engineered for maximum hardness and wear resistance and trades off some impact resistance or toughness for faster speed capabilities. It is best suited for higher-speed roughing on workpieces without interruptions and on stable machining setups. The TP3500 grade, on the other hand, is designed to provide long, predictable tool life in unstable conditions. To gain toughness, the grade trades off some heat resistance and high-speed capability. 
Incidentally, Seco’s Duratomic coating enhances the performance of both grades. The aluminum and oxygen in the coating’s outer layer are arranged on the atomic level to maximize hardness, toughness, and lubricity, allowing cut material to flow freely minimizing heat buildup.
While the substrate material and coating of a cutting tool provide a foundation for roughing operations, the tool’s chipbreaker geometry enables fine-tuning of tool performance.
Seco TP0500 Grade

Just as with tool materials, tradeoffs are involved in the engineering of tool geometries. A positive cutting geometry and sharp cutting edge reduce cutting forces and maximize chip flow. However, a sharp edge is not as strong as a rounded one. 
Geometric features such as T-lands and chamfers can be manipulated to strengthen the cutting edge. A T-land – a reinforcing area behind the cutting edge – set at a positive angle can provide sufficient strength to handle specific operations and workpiece materials and minimize cutting forces as much as possible. A chamfer squares off the weakest part of a sharp cutting edge, at the price of increased cutting forces. 
“Hard” chip control geometries guide the chips through a relatively acute angle to curl and break them immediately. These geometries can be effective with long-chipping materials but place extra load on the cutting edge. “Soft” chip control geometries put less load on the cutting edge, but generate longer chips. 
Good examples of differences in roughing geometries are the M5, M6, and MR7 designs from Seco. Listed basically in the order of their capability to handle increasing DOC and feed rate in roughing operations, the inserts are negative in overall geometry in that they have perpendicular flank faces and are engineered for two-sided use. 
Seco M5 Roughing Geometry
The M5 geometry combines high edge strength with comparatively low cutting forces. At the insert nose, the tools have a 0.30 mm wide, 5˚ positive T-land followed by a 20˚ transition area to the insert’s rake face. The rest of the cutting edge has a 1˚ negative chamfer preceding a 0.31 mm-wide, 5˚-positive T-land before an 18˚ transition to the rake face. The chamfer boosts edge strength, and an open chip groove facilitates the flow of ductile long-chipping alloys. The M5 geometry suits a variety of workpiece materials including steel, stainless steel, cast iron and superalloys.
The MR7 geometry, in comparison, is engineered to handle heavy interruptions and tough applications such as roughing forgings/castings with skin and oxide scale in steel, cast iron, and stainless steel. To maximize edge strength, the tools have a wider 0.35 mm, 0˚ T-land at both the nose and the cutting edge with a shallower, 17˚ transition to the insert’s rake face. While the wider, flat T-land and shallower transition angle provide increased strength, they also generate higher cutting forces because the tool overall is less sharp. Together, the geometry features provide strength comparable to that of single-sided inserts for heavy roughing operations.
A combination of geometric features places the performance of the new M6 geometry between, and overlapping, that of the M5 and MR7 tools. The 4˚-positive T-land at the nose is 0.25mm wide, not as wide as the M5 or MR7 tools, and there is a 19˚ transition to the rake face. The 0.30 mm-wide, 0˚ T-land on the cutting edge is followed by a 21˚ transition to the tool’s rake face. This chip-control configuration combines strength and a wide chip control groove to expedite flow of the cut material. 
Although the three geometries differ in details and areas of application, they share an engineering strategy aimed at protecting the cutting edge, minimizing cutting forces and maximizing efficiency of chip evacuation. The tools illustrate how tradeoffs and combinations of geometric features can positively affect the final results of roughing operations. 
About the Author
Chad manages Seco's turning and advanced materials product lines, including all CBN and PCD products. When he's not helping customers implement advanced metalcutting solutions, you can find him training for and running 5K, 10K and 1/2 marathon races and triathlons.