When a manufacturing company begins production of a new material, it has a choice as to the manufacturing process it uses. The type of process depends on the facility, the staff, and the information systems available. Each process has its advantages and some are best at certain tasks, for example, large batches of finished goods, or small numbers of custom items. When the decision is being considered about which manufacturing process to use, there are a number of questions that should be asked; what are the volumes to be produced, what are the requirements to make the product, and does the company manufacture a similar product? There are a number of basic manufacturing processes that they can select from; production line, continuous flow, custom manufacturing, and fixed position manufacturing.
A production line is a traditional method which people associate with manufacturing. The production line is arranged so that the product is moved sequentially along the line and stops at work centers along the line where an operation is performed. The item may move along some kind of conveyor, or be moved manually by staff or forklift. For example, operations along the production line could include assembly, painting, drying, testing, and packaging. If needed, some parts can be removed from the production line and stored as semi-finished goods.
The production line manufacturing process is very suited to high volume manufacturing of a single product or product group. For example, a production line may be used to manufacture a range of vacuum cleaners, where the only difference between the models is the color of the plastic assembly and the attachments that are included in the final product.
There are disadvantages to using the production line manufacturing process. The fact that the production line manufactures a single product or similar products limits its ability to manufacture anything else. For example, if the company manufacturing vacuums wanted to make kitchen mops, it would not be able to use the same production line. The second issue with production lines is that there is a high cost involved in the initial setup of the production line and it requires a large volume of goods to be produced to justify the capital investment.
The continuous flow manufacturing process is similar to the production line, but the products that are manufactured cannot be removed from the production line and stored, but require to have been through each process. For example, materials that are suited to continuous flow include chemicals, pharmaceuticals, and plastics. The continuous flow process is more inflexible than a production line as it does not allow for other materials to be produced on the line without significant changes and the cost involved.
Magnetic separation takes advantage of differences in the magnetic properties of minerals. Minerals fall into one of three magnetic properties: ferromagnetic, paramagnetic and diamagnetic. Ferromagnetic minerals are themselves magnetic (i.e., magnetite and pyrrhotite) and can be easily separated from other minerals with a magnet since they will stick to the poles of the magnet. These minerals can be separated by wrapping the poles of a magnet in paper, passing the magnet over the mineral mixture. The ferromagnetic minerals will stick to the magnet and may be easily separated by removing the paper covering the magnet. Paramagnetic and diamagnetic minerals are not magnetic, but they differ in how they interact with a magnetic field. Paramagnetic minerals are weakly attracted into a magnetic field and diamagnetic minerals are weakly repelled by a magnetic field. Thus, if a mixture of paramagnetic and diamagnetic minerals is passed through a magnetic field, they will be pulled into the field (paramagnetic) or repelled from the field (diamagnetic) and may be separated. Furthermore, paramagnetic minerals with different degrees of paramagnetism can be separated from one another in the same way. The device used to separate minerals based on their magnetic properties is called a Frantz Isodynamic Magnetic Separator. The magnetic separator consists of a large electromagnet through which mineral mixtures can be passed on a metal trough which is divided near its exit end. Varying the strength of the magnetic field and/or slope of the separation trough is used to separate minerals.
All forms of mineral separation suffer from one difficulty. It is impossible to completely eliminate impurities. Depending on what the impurities are, that may or may not be a major problem. For example, if you were separating hornblende from a granite for Zr analysis, potential contamination by zircon inclusions in the hornblende might be a major problem. A typical hornblende crystal might have a Zr content of 50 ppm. A zircon crystal (ZrSiO4) has approximately 500,000 ppm Zr. Thus, if the hornblende separate contained only 0.01% Zr, the hornblende would contribute 4999.5 units of Zr and the zircon impurity would contribute 5000 units of Zr. The resulting concentration you would measure would be 100 ppm, which is twice the correct result. This is a major problem that cannot be eliminated when mineral separations are involved in the analysis.