January 2, 2014
Deburring is a time-consuming but necessary fabricating operation. Metal fabricators that can minimize the time spent on finishing have a competitive advantage because they are getting parts out quicker to customers.
Deburring—it’s the metal fabricating chore that most shops can’t get around.
As long as concerns about edge or surface quality exist, fabricators will have a need for someone to tackle deburring chores. That doesn’t mean it has to be the time -consuming activity that normally eats away at a shop’s production efficiency, however.
Sometimes a simple change in consumables can do the trick. Other times it might call for a move away from manual deburring to automation. The key to attaining a new level of productivity is for someone within the manufacturing process to take the time to focus on the deburring task and ask, “Is there a better way?”
Here are three short stories, based on real-life manufacturing challenges, that illustrate how companies found that better way to deburr parts.
A metal fabricator has to deburr the edges of torch-cut sheet metal to clean them up and make them more presentable for the customer. A time study reveals that the employees doing the grinding with a right-angle grinder are having to stop the job much too frequently to replace the abrasive discs. Shop management obviously wants more grinding and less disc replacement, so it looks for a new way.
Resolution: In this case, the metal fabricator went with a better grade of abrasive disc, which was designed to provide more edge durability and more aggressive material removal (see Figure 1).
The high-performance flap disc has a full zirconium grain that is engineered to retain a good cutting edge even as the abrasive is being removed during the grinding process. The disc’s multiple layers of coated abrasive material expose sharp, fresh grains as the leading edge of the disc is used up.
The cloth design prevents premature grain shedding on challenging edges. The aggressive grinding action allows the operator to let the tool do the work without the need to push the abrasive disc into the material, causing premature grinder failure and operator fatigue.
In the future, if the fabricator is looking for even longer consumables life, it could consider trimmable abrasive flap discs. The composite backing, which holds the abrasive cloth, can be trimmed back to reveal more abrasive material as the grinding edge gets worn down by use. To trim the backing of these types of discs, the tool operator only has to run a sharp metal edge against the backing until the desired diameter is achieved. In some instances, the backing can be trimmed up to 0.375 in. from the original diameter.
A fabricator works with tubing that has rough edges after being cut to size. To facilitate safer handling and proper fit, the ends of the tubing must be deburred. Manual deburring is the means by which the edges are prepped before shipping, but the fabricator wants more consistency and productivity in this part of the shop.
Resolution: The fabricator found a more automated approach to the task with a crimped-wire wheel brush, a pedestal grinder, and a simple workholding jig (see Figure 2). The operator is now able to quickly deburr the tubes by rotating them in the jig. The brushes deburr the OD and the ID simultaneously and more consistently than the previous manual operation.
The crimped-wire brush is the most appropriate for this job. The wire is crimped to allow individual strands to support each other, which makes it suitable for light- to medium-duty applications. Anything more substantial, such as a knot-wire brush in which heat-treated straight wire filaments are twisted together into what looks like a rope, could slightly deform the thin-wall tubing.
The life of the wire wheel brush also can be extended by flipping the brush. All the machine operator has to do is remove the brush from the spindle, flip it 180 degrees, and remount it. By reversing the rotational direction, the sharpest side of each filament is exposed to the workpiece. An additional advantage is that flipping the brush also evens out the brush wear.
A manufacturer of aluminum pump housings has a problem with burrs on the parts after face milling. It was relying on manual deburring with an assortment of air tools at a burr-bench. However, the manual process led to part inconsistencies on precision-machined components. The company wanted to reduce scrap caused by the manual process and introduce a more consistent method of deburring.
Resolution: The manufacturer selected an automated deburring brush that is used in its CNC milling machine (see Figure 3). The 2-in. nylon- filament brush is run at 1,750 RPM and proves effective in removing residual burrs from the milling process.
The use of this type of brush is especially convenient for manufacturers using CNC equipment because the abrasive brush can follow existing machine programs with some minor tweaks. For example, the tool path for a disc brush is very similar to a face mill’s tool path. The parameters that have to be adjusted are spindle speed, feed rate, and depth of the interference (which is called depth-of-cut in cutting tool programming). In some operations, it might be necessary to take two passes across the part with opposite directions of brush rotation.
Unlike a cutting tool, however, the nylon abrasive brushes do not require exact positioning. The brushes conform easily to a surface and are extremely forgiving. Positioning within 0.020 in. of the ideal location typically produces acceptable results, although this window varies with more challenging applications.
The FABRICATOR® is North America's leading magazine for the metal forming and fabricating industry. The magazine delivers the news, technical articles, and case histories that enable fabricators to do their jobs more efficiently. The FABRICATOR has served the industry since 1971. Print subscriptions are free to qualified persons in North America involved in metal forming and fabricating.