Part-On-Part Deburring 101
Q. We use vibratory finishing to debur stampings. We are a job shop, so part sizes and configurations vary with every customer. You recommended part on part deburring for one of our parts, and I am looking for more opportunities to use this method. Here are some questions I have: Do I always have to use abrasive compound? What are the largest parts you can do this way? Can parts get bent? Will different parts require different machine settings? Can I exceed the weight load limit of the machine? A.N.
A. The need for abrasive compound is to provide edge radiussing and better deburring. Light edge breaking—enough to blunt sharp edges—can be accomplished without abrasives. The burrs, however, are usually just rolled over if no abrasive is present. If the object is only to clean and/or polish, the use of abrasive compound can be detrimental. In that case, just use your normal flow-through cleaner/inhibitor or a burnishing compound. The process can burnish some parts almost as well as steel ball burnishing.
The size of parts may be limited only by how well a load of parts will roll over and interact with each other in the tub or bowl. It is also limited by the damage they may do to each other if they tangle up. I have seen steel bars about 1/2 x 2 x 6-inch run part-on-part to remove heavy cut-off burrs. No doubt some experienced operators have run larger and heavier, parts without media. Yes, different parts will require different machine settings and this is where a fully adjustable, bowl style vibrator becomes the best choice. Some brands of bowl machines do not allow for easy changes of top and bottom weights, or lead angle settings. These machines are to be avoided if you plan much part-on-part processing. A smooth rolling action is essential to this method, and with the many changes of load weight and part configurations, you MUST be able to change all the parameters of energy distribution. Variable speed control is fun to play with, but is a poor substitute for fully adjustable weight and lead angle settings.
Bending, or breaking, of parts can occur. This can be caused by the weight of parts on top of each other, by tangling and twisting, or by thin wall sections of easily malleable metals. Typical steel stampings can take the process without problems unless they have configurations to catch and bend each other.
The maximum weight of the load is limited by machine design. Machines that can handle steel media (often these are called “burnishers”) can handle any weight of parts. The smaller the parts, the heavier the load will be. For example, steel ball media weighs about 300 pounds per cubic foot. A vibratory burnisher can roll over that much, or more, weight. Part-on-part loads of steel parts will weigh between 150 and 300 lbs/cu ft. You can see the value of selecting a vibrator that can handle the weight.
There are some downsides to part-on-part finishing with abrasive compounds. The effluent is loaded with solid particles and you don’t send it down the sanitary drain. The first rinse water—about one to two quarts per cubic foot of vibrator—should be diverted for separate disposal. Evaporating is a good method for this. Also, this process may reduce the bowl lining life by 30 to 50%.
Precision shot peening brings an entirely new concept to the field of microabrasive blasting, and it is complementary to its larger cousin. Using glass bead media, several companies have been shot peening for years with microabrasive blasting technology.
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