The Inside Story of Grinding Abrasives

Metalcasting technology emphasizes the material and structural developments that take place during melting and pouring parts, but what happens to those parts after they come out of the mold is also critical to production– and to the success of the foundry or diecaster. Finishing processes do not draw the same degree of inquiry, but there is a lot to know about grinding castings effectively and productively.

Automation answers many concerns about grinding of castings efficiently; that’s the hardware needed for the process. Understanding the consumable supplies involved requires more research and expertise than some metalcasters may assume.

Ask Justin Scarborough to discuss the practical considerations for grinding castings, and you’ll begin to learn more about the different types of “engineered grain abrasives” available to metalcasters to remove risers or parting lines, or unwanted marks on a casting surface.

Developing such products is the specialty of Norton | Saint-Gobain Abrasives, where Scarborough is an application engineer. Engineered grain abrasives is a broad term, covering different Norton product lines, which can be adopted according to the cast material, or to achieve different production objectives. Scarborough pointed out that foundries can select different abrasive products according to their process or performance needs – metal removal rates (MRR), for example, or total metal removal, or product longevity, or coolness during cutting.

That variety addresses foundries’ many production goals, but there are other objectives too. In 2024, following extensive development testing, Norton introduced a new series of abrasive materials.

The RazorStar products represent a new class of grinding materials, called engineered shaped ceramic grain abrasives, which provide a wider range of advantages for the users.  The innovation involves the formulation of the ceramic material, and the specific shape of the ceramic grains and their placement on the cutting belt or disc.

It was an intensive development program that, according to a Norton source, tested different grain shapes that could be manufactured and coated efficiently, and would be effective in grinding operations. Different grain geometries were evaluated before Norton settled on an engineered shape “with razor sharp tips.”  

“The new ceramic was developed to be more friable than traditional abrasives, to make more sharp cutting points,” Scarborough explained. “So, the grain itself fractures and keeps cutting with less force – which is better ergonomically, for off-hand applications, and it gives longer life for those applications, because the grains stay sharp instead of dulling and no longer removing metal under those low forces. But, at high forces, for automated or impact grinding, you can still take advantage of that shape to get longer life.”

The developers evaluated the engineered shaped ceramic grain abrasive in different product types, so that RazorStar material is available in fiber discs, quick-change discs and belts, according to the type of grinding process manufacturers use.

“In the metalcasting market we've done very well with off-hand and automated applications, but we’ve really excelled in automated applications,” Scarborough reported. “We've worked closely with OEMs; there are new automation set-ups that are going into the market with RazorStar products, and we are successful in converting automated machines that are already in service for our customers to RazorStar abrasives.

The products have been well received for hand grinding operations, too.

Cast steel products offered some of the first successes scored for the new products. Norton reported that a ferrous foundry customer detailed a need for an abrasive to use in an automated process to remove a high volume of steel from a part gate area, to replace bonded abrasive wheels used for a manual grinding operation. Among different abrasive products tested, a 36+ grit RazorStar belt removed the most material in the shortest time. It emphasized that the high metal removal rate was accomplished across a range of grinding speeds (up to 100 hp) of an automated grinding cell, even as the backing material stood up well to the pressure and force of the process.

The developers have also reported successful applications with hard metal castings. A foundry that casts cobalt-nickel-chrome alloys and grinds the parts with a robotic backstand grinding machine found cycle time improvement using a 36+ grit RazorStar belt with approx. 50 lbs. of pressure, grinding 30% more parts per belt, with reported total cost savings of 44%.

For high-value castings – specifically, stainless steel turbines – Norton’s research showed that the novel shape of the ceramic grain achieves notable metal removal rates without high pressure, so less heat is generated and thus the grinding process remains consistent and manageable.

Scarborough added that RazorStar has demonstrated success “even in soft metals, such as aluminum, where we can show that the performance is superior to other ceramic grains, including our own ceramic grains.”

He underscored the point that the performance of the abrasive can be defined to match the specific requirements from customers. “A cycle time to meet, or a product life, or whatever the customer dictates, … our job is to provide support for ‘speeds and feeds’ and those sorts of things, to make sure that we achieve what the customer is looking for… so it could be any combination of the benefits of the engineered abrasive that help achieve that.

“The customer also dictates how we approach optimization of their process if their if their goal is to produce parts as quickly as possible,” Scarborough said. “Parameters potentially change to achieve that, but at the same time, the customers will see the benefits.”

What improvements lie ahead for abrasive materials? Scarborough said finer-grit RazorStar products may be possible, e.g., for aerospace castings. Another area of development may be the chemistry around the ceramic grains, “to optimize it for different processes and products.

“And then we're always looking at the market needs, potentially for lighter grinding, or for you know maybe there's a new product developed that has even higher heat-sensitivity that we can adjust based on that. Our research and development team is continually working on product improvements, with feedback from the market, and from our product management team, and our abrasive management team.”