Products Finishing

APR 2016

Products Finishing magazine is the No. 1 industrial finishing publication in the world. We keep our readers informed about the latest news and trends in plating, painting, powder coating, anodizing, electrocoating, parts cleaning, and pretreatment.

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PFonline.com/experts P F o n l i n e . c o m / e x p e r t s MECHANICAL FINISHING C L I N I C PAT WENINO massfnishing@PFonline.com 42 APRIL 2016 — PFonline.com THE VOICE OF FINISHING 80 YEARS Multiple Grain Abrasives for Long Life and Consistent Finishing Q. We are using a 3-inch by 90-inch, X-weight cloth back, 120-grit aluminum oxide belt on our robotic polishing system. The excessive belt wear creates uneven finishes and productivity loss because of constant abrasive belt changes. What solution do you recommend? A. This happens often in high production robotic and auto- mated polishing. Increasing the belt length and long- lasting abrasive grains, such as zirconium or ceramics, will increase belt life. If the aluminum oxide or silicon carbide must be used because of its finishing capabilities, then a multiple-grain belt is the solution. A multiple-grain abrasive belt construction consists of layered abrasive grains with various thicknesses on cloth, polyester or film backing. These multiple layers can be randomly stacked, formed in a bubble or layered as a pyramid, depending on the coated abrasive manufacturer. The multiple layers appear to be coarser than the indi- vidual abrasive grain size they are comprised of, but they give the same finish as the individual grains themselves. We have had excellent success reducing robotic systems with daily belt changes to weekly belt changes. Consistent finish with extended life is the biggest advantage. Blast Finishing for Brightness Q. We are blasting our aluminum parts in a blast cabinet after machining for a uniform finish. Our current process is blasting with 80-grit aluminum oxide to eliminate machine lines. What media is recommended for a brighter finish? A. For brighter blast finishes, we recommend a No. 10 to 13 size glass bead or a 120-grit and finer ceramic media. Both media will produce a visually brighter and smoother roughness average (Ra) finish. The aluminum oxide you are currently using is an angular abrasive that produces a duller visual matte finish and a courser Ra surface finish. It is a great media for the removal of scale, rust and paint. Aluminum oxide produces an excellent pre-paint and coating adhesion surface and will hide a large tool mark on machined parts. The glass and ceramic beads are round abrasives that produce a brighter satin matte finish and a finer Ra surface finish. It can also remove light oxidation, rust, scale and paint, but at a much slower speed. Beads are generally used to produce a uniform, bright satin finish on machine and intricate parts. If the beads do not hide all of the tool marks that the current aluminum oxide hides, try the following recommendations: 1. Turn up the air pressure. 2. Try a larger size bead. 3. Blast first with the aluminum oxide and second with the beads. 4. Mass-finish to smooth the lines first and then blast with the fine beads. Mechanical Finishing with Bowl Vibratory Machine Q. We use a 3-cubic-foot tub vibratory machine in our finishing depart- ment. The tub has produced some good results for uniform finishing and deburring, but we want to invest in a better machine to produce more parts. We have heard a lot about other types of vibratory and high energy systems. What is your recommendation for the best machine? A. Your parts are machined and the tub vibratory machine is working, but you want to increase your production. For this specification, I would recommend a 10-cubic-foot vibra- tory bowl machine. We sell a lot of tubs for first-time inexpensive systems. Parts that need to run within a divided space and parts that are too large for bowls are good tub vibratory projects. There are many reasons to use bowl systems: • They can be built with systems that separate parts/ media and unload parts. • They can be fine-tuned for media aggression, roll and feed. • They do a good job of keeping parts separated without dividers. • Larger parts can be hand-unloaded as they run. Machine parts tend to be larger than 3 to 4 inches square, which can cause part-on-part damage with automatic unloading. These large parts can be easily hand-picked out of the non-unload bowls, as the part and media sweep by Bowl without an unload system.

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