Metal Finishing Guide Book


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eat away at the rack material. Coating failure and damaged framework will cost more in the end due to early repair of the rack and replacement of the damaged framework. One should never purchase racks based upon cosmetics alone, as much can be hidden under the plastisol. Be sure that your supplier uses good quality material from the metals to the plastisol. Building a plating rack is not rocket science. For the most part, all rack suppliers use similar methods of manufacturing — that is, we cut, drill, punch, bend, rivet, bolt, and coat. The difference from a good supplier and an "adequate" supplier is quality of construction. The preferred method of constructing the rack frame is to bolt the pieces of the framework together. There are occasions when the customer requests that the framework be soldered at the joints. This does improve the integrity of the joint by fusing the two pieces together, but there is a question if it improves conductivity. Tips can be bolted or riveted in place on the rack. Either method works fine for smaller tips; larger tips will require bolts. Rivets do offer a tighter contact in overall pounds per square inch. One may twist the bolt head off trying to match the "psi" of a rivet. Racks do have a life expectancy. Over time, through use, tips will break, the plastisol will break down, or your machine will crash, making a pretzel out of your once-square rack. When one returns a rack to your supplier for rebuilding, one should expect more than just repairs. On a rack that has been used, resulting in the tips being broken from stress, the rack supplier should replace all of the existing contacts with new ones, thereby turning a repair into a rebuild. This normally costs a little more, but what good is it to have a few tips replaced only to have a few more break within a month after getting the rack back after repair? The first tips broke due to stress, and the rest of the tips are also stressed. Finishers should never have only the broken tips replaced. One method to save money is to consider replaceable tip racks. These are made to allow the broken or worn tips to be replaced by the customer without the expense of sending in the frame. Extra tips can be kept on hand for use as required. OPTIMIZED DESIGNS Your supplier would like to sell you as many racks as he can, but in most cases this is just not necessary. Competent and experienced rack suppliers will design the racks to carry as many different parts as possible on the same rack. By doing this you can minimize your inventory and initial costs. Unfortunately, you cannot always optimize the rack design. One must always plan for enough in the budget to supply all the process requirements. Money not used can be returned to the account, but anyone who has underestimated a capital request knows that it is next to impossible to receive extra funding above and beyond what was previously approved by management. There is always the human element that must be considered when designing racks, and ergonomics must always be considered. Excessive contact squeezing can cause repetitive motion injury such as Carpal Tunnel Syndrome. Gravity or push-on tips should be incorporated in contact design — when the process permits — and this will help with productivity and keep employees happy and content. It is always a good idea to rotate your people to avoid repetitive injury. SELECTING A SUPPLIER When selecting a supplier, one should not look for the cheapest, but rather one that offers the greatest value. In many cases you get what you pay for. After all, 720

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