grinding operations for investment casting: keeping an eye on costs.
Grinding operation of investment casting: when reviewing the main cost of investment casting, pay attention to the cost, what will be immediately thought? Metal? Power? Labor? Don\'t feel uncomfortable if you forget to tidy up. Finishing costs are often considered necessary evil and are rarely considered in cost analysis, although they are usually one of the five major expense categories for investing in a foundry. In fact, the cost of finishing can account for up to 60- 70% of the cost of non-melting production. Because the finishing cost is quite large, metal casters interested in making the most of his foundry must carefully study the efficiency of the finishing room, more specifically, the total cost of grinding. It is not difficult to review the grinding cost and the results may be surprising. The analysis may indicate the need to upgrade the grinding process to use a high performance grinding product or, conversely, it may indicate that the current grinding is fully sufficient. In any case, the foundry management has a better understanding of its operations and costs. The inspection of grinding costs for grinding options requires a basic understanding of the grinding product category, various grinding materials, investment casting and metals used in the finishing chamber program. The first of these product categories include: * bonded abrasive, consisting of an abrasive held by a ceramic, organic or metal bond in a particular structure (Usually a wheel). Bonded abrasive for investment casting includes cutting Departure wheel, thin wheel and decoration; * Coated with abrasive, glued to flexible or semi-flexible by adhesive Hard cloth backing. Coated abrasive found in investment casting includes narrow bands, discs, flakes and special items such as flap wheels, cartridge rolls, spiral points, pencils and straps; * Loose sand for blasting; * Non-woven nylon grinding- Dip wheels for polishing and polishing. Each of these product categories has a variety of grinding materials (see Table 1). The more common grinding materials are: * Alumina, which is used to grind black materials. It is the softest of the traditional grinding material, but relatively anti-impact; * Conventional abrasive material commonly used to grind non-ferrous materials-sic. It is the hardest of traditional grinding materials, but less impact-resistant than alumina; * Zirconium alumina, one of the high-quality abrasive materials invested in casting. For rough grinding of metal ( Especially Black Metal) , It has high impact resistance and works best under high pressure in high inventory removal applications; * SG[TM] Abrasive, a ceramic alumina developed by Norton under the patented seed gel process. SG abrasive is a durable product for grinding wheels and belts. It contains Micron The size of the broken cutting edge, instead of becoming dim, constantly exposes new cutting points. The physical properties of the metal to be processed determine the applicable grinding material. For the purpose of grinding, the metal used in investment casting is divided into two categories. The first one is hightensile, heat- High temperature alloy of stainless steel and nimonics (nickel-or cobalt-based alloys). These materials are very difficult to grind. The second group of metals is soft, sticky materials such as copper, aluminum, and magnesium. These metals are easier to grind than the first group, but tend to load the grinding product by filling the grinding holes. This reduces the inventory removal rate. Compared to many other types of metal processing, investment casting requires relatively few processing steps. This meets its goal of casting to minimize the number of traditional metal molding. For the hard metal group and soft metal group listed above, the required finishing steps are the same, although in some cases the actual finishing methods are different. After pouring and cooling the mold, a single casting must be removed from the cluster. Band saw or friction saw for softer metal and small cross sawSegmented gate. Grinding and cutting for hard metal Wheels need to be turned off. The cut- The function of the Off wheel is to saw and cut the workpiece instead of grinding the surface of the workpiece. Following cut- Closed, the casting removes any traces of the shell through caustic soda cleaning or sandblasting operations. Then sandblasting with loose grinding particles to remove discoloration. Blasting can also be used to give the casting a final mottled appearance. Wear-resistant coating narrow band (under 14 in. wide) Used to remove the stub or gate on the left side from the cut-off operation. After the stub or gate is removed, the casting may enter the rework area where surface problems can be corrected by repeating the above steps. Additional grinding steps may be required depending on the type of casting and the size and finish requirements. These steps may require other adhesive grinding products such as thin wheels and mounting, as well as coated grinding products such as finegrit belts, discs, paper or special items. Final mixing or polishing of casting surfaces is usually done with nylon grinding wheels or similar products. Because about 70- 80% of the cost of finishing a foundry is being cut. We will focus on these operations as we discuss how to calculate the total grinding cost and optimize the grinding operations. The total cost of grinding is a combination of grinding cost, labor cost and indirect cost. The grinding cost of each piece of grinding can be calculated using the following formula: the number of grinding products x the cost of grinding products/The number of grinding. The labor and overhead costs per piece can be calculated as follows: labor and overhead x grinding time/Number of grinding pieces. The combination of grinding cost and labor and indirect cost per piece will be equal to the total cost of grinding per piece. After determining the total grinding cost, compare it with the production cost of each job-piece. If the grinding cost is high (60- 70% of total production cost) The process and equipment of the room should be reviewed. One cost- Conscious New England foundry uses these methods to analyze cutting It has traditionally been closed using traditional alumina wheels. By comparing alumina wheels with high The foundry found that more expensive zirconium alumina products provide more cutting per wheel, thus reducing the change of wheels ( Reduce downtime) , While leaving a cleaner cut that requires less extra finishing. The cut- The shutdown of this Foundry is a push. This is a Labor by applying. For the operator, the work of intensive physical exertion. In addition to the benefits mentioned earlier, management found Cutting the zirconium alumina wheel reduces the fatigue of the operator and also reduces the concern of the wheel breaking. These cost analyses show that the use of zirconium alumina products can save the foundry 25- The cost of wheels and finishing is 30%. Like the foundry just described, optimizing the grinding system, the first step in cost analysis is to re-evaluate the grinding products currently in use. If grinding materials are purchased only according to the price, the productivity increase of advanced grinding materials such as SG grinding materials or zirconium alumina may be ignored. If the quality abrasive looks promising, the foundry must ensure that its equipment meets the horsepower (hp) The grinding force requirements required to take advantage of the performance advantages of these wear. Grinding products are tools for removing unwanted metals, their productivity (i. e. , It removes the speed of the metal) Directly related to available horsepower. The following are two rules of thumb for determining horsepower requirements for quality grinding materials: Cutting 1 horsepower per inch from wheel diameter; Coating products (e. g. , narrow belts) Belt width needs three to five horses per inch Manual grinding applications and 10- Pressure is 15 hp per inchAssist in grinding. The second key to optimizing the abrasive is the grinding force. The two options are human or mechanical equipment such as lever or hydraulic or pneumatic feed. A person has less force than a mechanical device, and, with the operator\'s tires, the manpower varies during the working day. Power auxiliary equipment can improve grinding productivity ( In terms of inventory removal) Ten times. Because finishing touches are expensive, ignoring their investment casters can jeopardize their profitability. A simple analysis of grinding costs helps to control grinding costs while maximizing productivity.