Producing quality products at the best possible price remains a key deliverable for any foundry. Keeping input cost under control on the one hand and balancing it against the available market price is a critical business skill.
Grinding operations contribute heavily to the total cost of an end product and as in most foundries, grinding wheel costs can vary immensely per ton of castings poured. This figure may differ from one foundry to another depending on the metal or alloy, size of casting, number and size of gates and risers, and on the type of equipment used—swing frame, floor stand or portable. Part of the cost involves wheels that may be used to notch or cut off gates and risers.
The grinding wheel can affect the total grinding cost as well as production rates. One major contributing factor to high grinding costs may be the use of lower quality or specification grinding wheels. While this buying policy does offer the lowest wheel cost, it will ultimately result in higher yearly purchasing and labour costs. Furthermore, the lower cost wheel may also reflect inconsistent quality, which could result in a variation of grinding wheel performance from wheel to wheel and from order to order directly impacting the quality of the end product.
In order to extend longevity of the wheel with the main objective of lowering the wheel cost, often an incorrect specification is used resulting in a wheel that is actually too hard for the application at hand. The loss in the material removal rate and operator (in)efficiency therefore offsets the costs of the wheel savings, as many tests have proved conclusively.
Using a too soft wheel, on the other hand, while contributing to a happier operator, will most certainly increase the total wheel consumption. Management may now ask how all these factors should be evaluated.
Some foundries measure grinding wheel efficiency in terms of the amount of metal removed versus the amount of grinding wheel used. Others may measure the grinding wheel cost per kg of metal removed. Both these methods may result in a two-dimensional view where a three-dimensional view with contact grinding time added will in most instances provide a better analysis.
In some instances, foundries do not realise how important wheel selection can be, relying only on operator opinion for the best wheel to use, without measuring wheel consumption or metal removed. Although this may seem like a simple solution, it is not likely to result in determining the efficient grinding wheel, or the lowest grinding cost. Operators most likely will tend to prefer a soft fast cutting wheel.
The above-mentioned approaches will most likely provide a very high ratio of metal removed to wheel wear resulting in a low production rate, or high productivity but with a relatively high wheel consumption. The ultimate aim is to strike a happy medium between rate of metal removed and wheel consumption.
Labour and overhead costs in most cases contribute more than the wheel cost in determining the total grinding cost therefore it is crucial to include the missing third dimension of time in these approaches to accurately calculate wheel efficiency and grinding costs. Contact time rather than total elapsed time is important as it is not subject to operator effort. Accurate measurement of the contact grinding time per casting or per test run is of utmost importance.
With the above in mind, it remains crucial to select the correct grinding wheel or abrasive product for your application in order to achieve the benefits stated. Grinding Techniques have locally been manufacturing specialised abrasives since 1981. With our local Research and Development team, all products are continually tested and evaluated to ensure that optimum performance is achieved during application whilst adhering to all the international safety standards as set out by OSA and ISO.
Our foundry offer consists of the all-reliable Superflex range of cutting and grinding discs and the well-known Andor range of Vitrified and Resin-bonded mounted points, cups, cones and grinding wheels for fettling and finishing applications. A quality range of Coated Abrasive products and Tungsten Carbide Burrs complete the full one stop offering of products to the Foundry Industry.