Weighing Options in Deburring

Investigating the tools, equipment, and technology surrounding the deburring of gears

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In the gear deburring process, the operator must determine the method, or tool, that will  be used. Three tool options exist for performing this task — grinding wheels, brushes, and carbide tools. Reference 1

GRINDING WHEEL METHOD
If you’ve chosen to use a grinding wheel for deburring, the next step is to choose the proper grinding wheel for the task ahead of you.

There are a number of different grinding wheels, which are differentiated from each other by the grit.

A larger grit number indicates a finer grit; conversely, a smaller grit number indicates a heavier grit. The size of the burrs and chamfers on the gear will help in determining which wheel should be used. Smaller burrs require a finer grit, again, a higher number. To remove larger burrs, you would choose a wheel with a heavier grit. Grit values for gear deburring purposes generally range from 320 to 57.

One advantage to using a grinding wheel for gear deburring is that it will often provide the desired cosmetic appearance, if that is a concern.

For the sake of both consistency and resources life (the grinding wheel), it is essential to set up the grinding wheel properly. To ensure a proper setup of the grinding wheel, make sure the point-of-contact of the grinding wheel is the same as the approach angle of the grinding head.

Here’s an example: Using a protractor, set the approach angle for the grinding head at 45°. Then draw a line through the center of the grinding wheel, and a line drawn 45° to the first line (See Figure 1). After following these steps, the grinding wheel should be properly set up.

Chamfer size will be dictated by the size of the burr that will be removed from the gear. However, grinding wheel grit, spindle speed, and the amount of pressure applied to the gear by the grinding wheel also can affect chamfer size. Grinding wheel speed will be written on the wheel itself (most often 15,000 to 18,000 RPM).

BRUSH METHOD
Brushes are often an effective method for removing small burrs found on gears (See Figure 2).  There are two varieties of brushes — wire and nyon — that are commonly used in deburring.

The wire brushes are produced in three different bristle configurations — straight, crimped, and knotted. The diameter and length of the wire bristles will dictate how aggressively the brush will deburr the part.

With nylon brushes, abrasives such as aluminum oxide or silicon carbide (in a range of grits from 80 – 400) are often added to the bristles during the manufacturing process.

Deciding which type of brush to use, whether wire or nylon, often depends on the specific needs of the deburring application. Brushes are sometimes used to as a follow-up method to remove small burrs that still remain after a more aggressive method was used to remove a large burr.
 
 

CARBIDE TOOL DEBURRING
Deburring gears with carbide tools is the newest of the three methods mentioned here. This process holds several distinct advantages over grinding and brushes.

First, carbide tools, spinning at 40,000 RPM are able to complete the deburring process in a fraction of the time of grinding wheels (15,000 – 18,000 RPM). Similarly, carbide deburring avoid the time-consuming set-up process described above with grinding wheels. Figure 3

Carbide deburring tools are also carry more capabilities than the other two methods. For example, they allow the user to deburr cluster gears, or gears that have the root of the tooth lose to the shaft or hub.

DEBURRING MACHINES
With deburring machines, the process is carried out through a system of “floating” heads, each with viariable-speed motors. Contained within these heads is an air-operated adjustable counterweight system that can adjust the amount of pressure being applied to the part by the deburring medium.

These heads are fitted with grinding wheels, brushes, or carbide tools, and allow for fast and easy swapping of the deburring tools. This ease of reconfiguration offers versatility in being able to process a number of different parts on one machine. Reference 2.

MACHINE TYPES
The dry machine is so named because the deburring operation is performed dry. These machines are often equipped with a dust collection system. Deburring on a dry machine is best accomplished if the parts are clean and dry prior to deburring.

With a wet machine, a non-foaming rust preventative is applied to the part during the deburring process (see Figure 4).
The wet machine carries several advantages over the dry machine:
• Increased tool life
• Parts leave the machine clean and dry with rust preventative applied (see Figure 5), eliminating the need for extra handling and equipment for post-deburring operations
• Dust and slivers generated by the deburring process are eliminated
• Burn marks on gear teeth are eliminated

MACHINE PRODUCTIVITY
The productivity of a deburring machine can be greatly increased by the addition of various forms of automation. Power conveyors allow for the automatic loading and unloading of parts.  Additionally, programmable servos provide for placement of the deburring heads.

"Pick and place" units, or robots, can transfer parts from the load conveyor to the work-holding chuck (power-operated clamping). They can also remove the deburred parts from the chuck and place them on the unload conveyor (see Figure 6). Installing turnover units facilitates deburring of two sides of a part in an automated system. Vision systems can identify the location of the burr on the part (see Figure 7).

In addition to increased productivity, the flexibility provided by these automation devices permits efficient processing of a variety of parts through one machine because change-over from one part to another is not complicated and can be done quickly. A single, automated machine can therefore efficiently deburr a number of parts, reducing the need for multiple machines (see Figure 8 and Figure 9).
 

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is president and owner of Machesney Park, Illinois-based Chamfermatic, Inc. He can be reached at (815) 636-5082 or chamfer96@comcast.net.