Deburring and finishing of machined and manufactured parts is a necessary but often overlooked step in the manufacturing process. As a result, some workshops still handle this task as they did in the last century, relying on manual deburring and polishing methods rather than more modern, automated and predictable methods. This is time-consuming and wasteful. This can lead to inconsistent part quality and even increase machine downtime, because operators need to polish the grinding wheel and drill press while their CNC controllers are idle. To make matters worse, at this stage of the manufacturing process, a simple error can mean scrapping a workpiece that takes hours or even days to produce.

This article has neither time nor space to explain in detail the dozens of deburring and finishing techniques available today, but it will cover some of the more common techniques. For example, Timesaver or an equivalent rotating brush machine is a good way to remove many flat workpieces. Belt versions of these machines perform similar tasks by aligning parts or abrasive grains, while drum and vibrating bowl dressers loaded with abrasive media can handle even the hardest parts on machining, stamping or laser cutting. glitch.

There is also thermal deburring, which is an unlikely process. It uses explosive charges to explode the burrs. Electrochemical Machining (ECM) uses electrolyte to dissolve burrs and perform it in a surprisingly accurate manner. Abrasive flow machining (AFM) is commonly used in the automotive and hydraulic industries to remove burrs and polishing of complex internal part features, just like sandblasting the surface of everything from camshafts to cargo ships.

Then there are belts, discs, brushes and other abrasive media, all of which can reduce burrs and rough surfaces. Norton | Nonwoven Abrasives Senior Product Manager Michael Radaelli is an expert in this area. Saint-Gobain Abrasives, Worcester, Massachusetts. He pointed out that the industry continues to develop stronger and more efficient abrasives, including the company's Rapid Prep XHD non-woven abrasive product line. “By using modern abrasive grains, bonding methods, and other technological improvements, the shop can often reduce the number of steps required to achieve the desired surface quality,” Radaelli said. "This helps to reduce labor time, abrasive inventory, especially operator fatigue during right-angle grinding."

He suggested that manufacturers make several common mistakes when choosing abrasives. For example, during deburring operations, operators must have the required skills and experience to ensure that they will not change the geometry and size of the part, so as not to inadvertently scrap the workpiece. This is usually the result of using coarse abrasives, applying too much pressure, or simply choosing the wrong abrasive. Similar problems may occur when removing parting lines on castings, or during mixing and finishing operations of welded products.

Radaelli pointed out various field tests of the new Norton products. After an emergency vehicle manufacturer switched to XHD abrasives, the cutting speed of its aluminum ladder production line increased by 26%, and the abrasive life was doubled. A well-known locomotive manufacturer cancelled two manual grinding operations on welded carbon steel structures. A computer cabinet supplier used non-woven abrasives to increase the weight of each wheel from 480 inches 2 to 1,040 square inches (3,097 to 6,710 square centimeters), with remaining space.

Non-woven abrasive technology is also becoming more and more popular in other finishing operations, especially cylindrical and centerless grinding. Radaelli said that there are many examples showing that Norton fast finishing non-woven fabric wheels improve the surface finish and significantly increase the dressing time compared to traditional resin bonds and ceramic grinding wheels. "If someone wants to remove 1/8 inch of material from the workpiece, this is not the right wheel for them," he said. "But in more common cases, customers are finishing finishing and want to improve productivity and part quality. We strongly encourage them to step out of their comfort zone and look at more modern high-performance abrasives."

Of course, these types of grinding operations can usually be completely eliminated. This is based on Maury West, vice president of sales and marketing at Cogsdill Tool Products Inc. in Camden, South Carolina, who pointed out that barrel polishing is an effective method that can produce single-digit Ra surface finish on almost any material. , Consistent size and work hardening. CNC lathe or machining center. More importantly, it has become easier.

"We launched our Universal Diamond Polishing Tools (UDBT) about a year ago, and they have been off the shelf ever since," he said. "It is usually a square shank tool with rounded corners, replaceable diamond heads and indexable heads, which can be adjusted 90o on the left or right in 15o increments. We also offer a standard Capto C6 holder This allows polished surfaces, contours, and inclined surfaces, and internal features can reach a certain depth if the hole is large enough."

West explained that UDBT can be used for any metal, up to HRC in the mid-1940s. Like all polishing machines, it works by "cold flow" processing the peaks of the surface, essentially turning mountains into smooth grasslands. Because it displaces the material, the diameter of the workpiece will decrease accordingly during the polishing operation. For softer metals such as aluminum and mild steel, 10 µin is generated for every 10 Ra roughness-in other words, polishing a shaft with a 100 Ra surface finish to 10 Ra or less will knock about 0.001" ( 0.0254 mm) metals that are harder than the diameter, such as stainless steel and tool steel, inconel and other rare metals, are about half of this amount.

For flat surfaces, West recommends the use of diamond polished face milling cutters (DBFM). As the name suggests, DBFM is similar to a face milling cutter. Its function is similar to that of a face milling cutter. It is designed to polish the flat surface with a replaceable diamond blade similar to the UDBT just described. "We have been able to obtain single-digit Ra surface treatments on 3'[0.914 m] long plates and eliminate the residual tool marks common to face milling cutters and shell milling cutters," West said. "It has proved to be more cost-effective and less time consuming than polishing or grinding. In addition, since polishing does not remove material, it is an environmentally friendly process."

Cogsdill also offers a variety of mechanical hole deburring tools, including one-piece "clothes peg" Burr-Off, spring-loaded Burraway and Micro Burraway, and Ellipti-Bur for curved or inclined surfaces. All of these use simple in and out actions to remove burrs on both sides of the hole in one pass, which can be performed on a CNC machine or manually. Provide carbide and high-speed steel blades with diameters from 0.040" (1 mm) to 2.0" (50.8 mm).

JW Done Corp., located in Hayward, California, is another supplier of hole deburring tools that specializes in removing burrs at deep intersections within manifolds, valve bodies, and other challenging areas.

General Manager Stan Kroll described the company's ORBITOOL cross hole deburring tool as a hemispherical tool surrounded by a polished metal ring or disc and connected to a flexible shaft: in manual or CNC operation, the shaft exerts constant pressure; fine teeth The tool can even remove very large rigid burrs; the disc protects the adjacent surfaces at the intersection of the holes.

"This is both self-correction and self-discovery," he said. "As long as the tool is in the hole, it will ride on the disc until it encounters a burr. Because the shaft acts as a spring, it allows the disc to slide over the burr, and then the tool removes the excess material there. We also have a double-sided ORBITOOL , You can remove the burrs on the top of the hole and any internal intersections."

In recent months, the ORBITOOL product line has increased. What used to be custom-made 12" (30.48-cm) long tools are now standard products. However, to maintain sufficient radial pressure, these tools have a shorter shaft diameter than their 6" (15.24 mm) long counterparts. Kroll explained that knives with diameters ranging from 0.055 to 0.375" (1.40-9.53 mm) are available in two lengths, and the method of operation remains the same. "The heavier shaft also allows the user to be more aggressive, which is useful for removing Heavy burrs in large diameter holes are especially important. "

Although they are not in the metal removal category, electroplating, painting and coating operations can also be considered as finishing processes. One of them is black oxide, which is a popular method of protecting the surface of parts. Some people call it gun blue. Unlike competitive and usually more expensive processes (such as nickel and chromium plating, powder coating, and most anodizing), black oxide hardly changes part size and can be completed with minimal equipment investment.

"Whether you are talking about black oxide or alternative processes such as zinc phosphate, you will see one to two micron accumulation." This is according to Jesse Vouk, general manager of Birchwood Technologies, Eden Prairie, Minnesota. Supplier of chemicals and equipment for other protective finishing technologies. "We also have a large number of room temperature products, mainly cosmetics, but also provide various levels of lubricity and corrosion resistance. For those who manufacture hardware products, some oil and gas components, and anyone who needs low-cost but durable protection This is a very good choice for people who want to treat drugs."

Since these processes are considered low-temperature processes and do not require electrodes, they can easily be performed internally, as with most electroplating operations. "Usually, there are several heating tanks on a production line, starting with alkaline cleaners to remove any processing fluids, oils and greases, and other contaminants," Vouk said. "From there, it enters the chemical solution, and for our medium temperature black oxide, it operates at around 200 to 210°F [93.3 to 98.9°C]. It directly replaces operating at up to 290°F [143.3°C] The traditional thermal black oxidation process is far less dangerous in terms of worker safety and waste disposal."