To understand procurement costs better, we need to look more closely at how a price is actually calculated. You start with the material costs, which are necessary for feeder production, and add the labor costs incurred to build the feeder. Together with the overhead costs, this results in the manufacturing costs. The overhead costs include administration as well as research and development. Companies with their own research and development departments, which actively research new technologies and thereby achieve technological leadership, are more burdened on the cost side. Depending on the location, an equipment manufacturer may have a price advantage based on local labor costs, but, nevertheless, the material used is a major part of the manufacturing cost. In order to achieve a lower price, savings can be made by considering different material grades and quality but this would likely have an impact on the equipment’s operating costs and service life. In the last step, margin is added to the cost. From the customer’s point of view, it may seem that manufacturers can obtain high margins. Ultimately, however, demand is always closely related to price, and a company that tries to achieve excessive margins, as opposed to companies with realistic margins, will hardly have any demand and not be able to survive as a result.
What does all this information mean in our case? Screw feeders are available in many design standards in different qualities and prices. For the sake of this comparison, we’ll assume that a new generic single screw feeder, with a throughput of about 1,000 kg/h, will have an average procurement market price of $17,000. In contrast to this, the new Coperion K-Tron K3 vibratory feeder with similar throughput, with the advancements mentioned earlier, is about 50 percent more expensive at around $27,000. The transport costs of $1,000 and the commissioning costs of $2,000 will be similar for the two feeders. As a result, with a $10,000 difference in procurement costs, the screw feeder is definitely in the lead in terms of lowest cost at this point.
Assuming both machines run fully automatically, the LIW feeder’s operating costs include spare parts, maintenance, cleaning, and energy costs.
Spare parts costs. Users often look for savings in lower prices during procurement, but lower prices often mean lower quality materials, which generally result in a shorter service life. Therefore, we can safely assume that a lower investment cost can lead to an increased requirement for spare parts later on. Screw feeders have a number of wear parts – such as ball bearings, motor brushes, shaft seals, or even the screws themselves – that need to be replaced at regular intervals. For a screw feeder in the intermediate price range, experience shows that spare parts costing $1,500 are required annually. Calculated over a 15-year service life, spare parts costs for a LIW screw feeder amount to about $22,500, which is probably still a conservative estimate.
Because a vibratory feeder has no rotating parts, operators can save money by not having to purchase and replace wear parts, which is unlike the experience with a screw feeder. In addition, LIW vibratory feeders are developed in such a way that all force is directed into the bulk material, eliminating the need for mechanical spare parts, such as those required for the screw feeder. But, of course, the vibratory feeder’s electronics – the vibratory drive itself or its measurement technology – may fail or become outdated over the course of 15 years. Such a failure should be planned for during a vibratory feeder’s service life and would result in replacement or repair costs of about $7,000.
Maintenance costs. Let's move on to the maintenance work, which, in this example, will be carried out by an in-house expert. Assuming an hourly rate of $50, maintenance work is normally carried out twice a year, during summer and winter holidays. For the screw feeder, this maintenance includes a scale check or calibration as well as a change of seals, ball bearings, and other wear parts. An accurate scale check takes about 30 minutes and the replacement of wear parts takes about 1 hour, which totals $150 for 3 hours of maintenance per year. And for 15 years of operation, that’s about $2,250 in total maintenance costs for a screw feeder. In comparison, since the vibratory feeder doesn’t require the replacement of wear parts, maintenance is limited mainly to a scale check or calibration. This corresponds to 1 hour of work per year or $50, and over 15 years of operation, that’s about $750 for maintenance costs for a vibratory feeder.
Cleaning costs. The next item on the list is the cleaning costs. The disadvantage of screw feeders is that cleaning always requires mechanical work, such as removing the feeding screws and agitator, cleaning the screw shaft, and changing seals. Often, the many edges and corners in a screw feeder make cleaning difficult. A specialist can disassemble, clean, and reassemble a screw feeder in about 30 minutes, which doesn’t seem like a long time. However, when we look at the vibratory feeder, we see that the feeder can be easily cleaned with a cloth if the tray is the open type or has a quick-release cover that can be removed without tools. Since there are no rotating parts with seals that must be removed in a time-consuming and costly manner, vibratory feeder cleaning is uncomplicated and can be carried out quickly within a maximum of 15 minutes.
If we assume that either feeder type is cleaned at least once a week, we can calculate the amount of time spent cleaning each feeder for the whole year. A screw feeder takes 0.5 hours to be cleaned each week and assuming the feeder will be cleaned 50 weeks out of the year, that’s 25 cleaning hours per year. Whereas a vibratory feeder takes 0.25 hours to be cleaned each week and cleaning the feeder 50 weeks in a year amounts to 12.5 cleaning hours per year. Already we can see that the vibratory feeder takes half the time to clean than a screw feeder. Factoring in an hourly cost of $30 for a cleaner, the annual cleaning costs for a screw feeder amount to around $750 and $375 for the vibratory feeder. And extrapolated to an assumed service life of 15 years, the cleaning costs for the life of a screw feeder amount to $11,250 compared to just $5,625 for the life of a vibratory feeder.