Abrasive cutting wheels provide a quick and accurate way to cut through steel and other materials such as aluminum, titanium and Inconel when preparing many parts for industrial and manufacturing operations. However, selecting the right wheel for the application plays a critical role in ensuring proper results — and helping operations meet their goals.
While it is easy to view cutting wheels as a consumable and choose wheels based solely on the lowest purchase price, this approach overlooks hidden costs that can add significant time and money in an operation. Cutting wheel selection and use also has a substantial impact on safety.
Problems can arise when the wrong wheel is used or when the correct wheel is used improperly. Selecting the right cutting wheel for the job can reduce cutting time, extend product life, minimize product waste and material scrap, and help optimize operator safety.
Understanding the impact of cutting wheels on total costs
In manufacturing operations, time is money, and companies likely have customers waiting on them to deliver the final product on time and within budget. Wasted time, materials and consumables all add unnecessary costs to the equation. This makes it important to understand the total cost involved with the cutting wheels being used. Not only can it help save time and money, but understanding the true costs also helps determine profitability for each job. Of course, the true cost of a cutting wheel can vary greatly from operation to operation. It is dependent on many factors related to the overall application and how much cutting is involved. Some of the key factors that affect a cutting wheel’s total cost include the initial price, labor (time spent cutting as well as on wheel changeover), wheel lifespan and operator technique.
While the upfront cost of a cutting wheel is tangible and can be seen on an invoice, the most expensive component of the cutting application is the operator’s time. Labor time that is wasted or saved is less tangible but has a significant impact on an operation’s overall costs and efficiency. The number of wheel changeovers required is part of this, as wheel changeover can be extremely time-consuming depending on the application.
Take an operation that pays $1 per wheel but only gets five cuts out of each wheel, making the wheel’s cost-per-cut 20 cents. Compare that to an operation that buys a longer lasting wheel at $2 and gets 30 cuts out of each one. The material cost-per-cut is 7 cents. On the surface, the initial cost of the longer lasting wheel is double that of the $1 wheel. But the operation can buy fewer wheels per month, save significant labor time in wheel changeover and reduce their material costs.
This must be measured against the speed of cut for the wheel with the shorter life, since typically shorter life wheels cut much faster than long lasting wheels. This analysis will show the overall cost per cut.
Understanding a wheel’s true costs can help make that more tangible and identify potential cost savings. Productivity, throughput and labor costs are all tied together, and the choice of cutting wheel impacts all of these factors.
Choosing the wrong cutting wheel for the job can result in:
- Shorter wheel life: If the wheel is too soft for the base material or the application needs, there will be fewer cuts per wheel. This results in a higher cost per cut and increased total cost (for reduced wheel ROI).
- Increased labor: If the wheel is too hard it will not cut effectively. Users will get many cuts from the wheel but it will take considerably longer to make those cuts, increasing labor costs.
- More frequent wheel changeover: A shorter wheel life can also create bottlenecks in the process. Faster cutting helps maintain high throughput, since wheel changeovers greatly reduce value-added productive work time. Wheel life versus cut rate should be evaluated to determine overall costs.
- Too much pressure: When it’s the wrong wheel for the job, the operator may feel the need to use more pressure to get the work done efficiently. Excess pressure is one of the main causes of injury in metal cutting. In addition, too much pressure increases heat buildup, which can decrease wheel life and result in costly rework if the workpiece is affected by the heat. Aluminum, for example, has high thermal conductive properties, and excess heat buildup can warp the material. Too much pressure can also damage the right-angle grinder being used by pushing the motor too hard. An overheated tool could result in expensive repair, downtime or replacement. Wheel failure, grain loading, decreased productivity and damaging the workpiece are all possible outcomes of too much pressure on the wheel.
- Increased time for burr removal: Some wheels introduce more friction in the cutting process, which can produce more burrs and increase the time spent on burr removal. To avoid this issue, choose a very thin, fast cutting wheel that reduces friction to help reduce rework and time for burr removal.
- Issues with fit up: When the wrong wheel is used for the job, the cut may be less precise. This can result in issues with fit up during the weld, requiring operators to use more filler metal. This increases the cost of the weld and takes more time. Using a better wheel for the job can improve part fit up, for better weld quality and a lower rejection rate.
Choosing the right cutting wheel for the job
In order to choose the right cutting wheel, the first critical step for any operation is to identify their goals and pain points. Is the goal to increase throughput? To increase the time operators spend welding? To use less filler metal when welding? Certain products can help achieve goals faster and better. Working with an abrasives expert to conduct a full evaluation helps greatly in determining priorities and uncovering useful data. This process can be especially beneficial for operations that complete a high volume of cutting, those that are experiencing high cutting wheel costs or short wheel lifespans, or those that want to address safety concerns.
When choosing a cutting wheel, there are many options and factors to consider, including:
- Base material: This is the most important consideration when choosing a wheel. Cutting aluminum requires a wheel designed for that material to prevent loading. And cutting harder materials like titanium, Inconel, armored steel or high nickel alloy steel is best done with a ceramic wheel. Operations will waste a significant amount of time and money if the wrong wheel for the material is used.
- Wheel type: Type 1 wheels have a flat profile that allows a deeper reach. Type 27 wheels have a depressed center or raised hub that provides added clearance when working at a constrained angle.
- Wheel diameter: In the U.S., 4.5-inch and 6-inch wheels are the most popular sizes used on right-angle grinders. A 6-inch wheel will by nature provide more cuts over a 4.5-inch wheel and allow for easier access to hard-to-reach areas that could be interfered with by the tool profile.
- Wheel thickness: This plays a role for various materials. For example, with sheet metal, thin (.045 inch) and ultra-thin (1 millimeter) wheels are best. Ultra-thin 1 millimeter wheels cut quickly and produce fewer burrs because they generate less friction. A combination wheel could also be a good choice in some applications, as these are 1/8-inch thick wheels that can cut and safely do light grinding.
- Grains/grit and bonds: Some of the cutting grains commonly used in bonded abrasive cutting wheels are aluminum oxide, silicon carbide, zirconia alumina and ceramic alumina. Grains should be chosen based on the operator’s goals and requirements, including the materials being cut, potential heat buildup, and cost. The grit is the size of each individual grain. Various sizes of grit can be used, from coarse to fine, which helps define the cut rate of the wheel. Some grains and grit sizes are more aggressive and provide faster cutting when combined with the appropriate bond. The bond is the substance that holds the abrasive grain together. The strength or hardness of the bond determines how well the wheel can handle different materials. The bond also impacts the wheel’s lifespan and cutting rate. Harder bonds typically have a longer lifespan and are better for softer materials, while softer bonds have a shorter lifespan but shed grains more quickly, providing a faster cut. For the best results for a specific operation, consult an expert with your abrasive manufacturer to determine the appropriate grain, grit and bond combination for the most effective cutting wheel to meet your goals.
- Proper tooling: In most industrial and manufacturing applications, cutting wheels are used on right-angle grinders. Be sure that the tool amperage or horsepower is sufficient to maintain the cutting wheel speed. Higher powered tools are necessary to properly break down the harder bonds and grains in higher performing products. A tool that doesn’t have sufficient power means the wheel won’t perform as designed.
Keep safety at the forefront
Cutting wheels can greatly impact operator safety in any facility. Choosing the right wheel for the job plays a key role in safety, but it’s also important to properly train operators in the safe and efficient use of that specific wheel to help avoid injuries.
Abrasive manufacturers can provide safety and product use training. Weiler Abrasives provides SPOT safety training and also offers the Weiler Consumable Productivity (WCP) program. It evaluates, measures and compares wheel performance and calculates the true cost of cutting wheels, using real-life testing onsite at a user’s facility. It can help operations uncover and understand their true needs and goals.
Choosing the proper cutting wheel for the job and following best practices for its use can help operations reduce costs by improving operator safety, minimizing time spent on wheel changeover, prolonging the wheel’s effective cutting life, and decreasing rework and the amount of filler metal needed to produce a quality weld. In many cases, buying higher-priced, high-performance cutting wheels ultimately provides a lower overall cost of use and helps operations reach their goals.