When looking for a good conveyor scale, you might not realize that the choice of construction materials and methods is one of the most important factors in your decision. A simple option for your structure material can make all the difference. When looking at materials for our conveyor scales, the materials we offer are aluminum and stainless steel. Let’s investigate why you should choose one versus the other.
Mild/ painted steel can fill a similar role as aluminum and stainless, but it doesn’t have the same versatility in various environments that they can boast. It doesn’t have the same resistance to rust and corrosion that stainless steel or aluminum does, depending on the environment. That is why mild steel has to be painted and repainted periodically to protect the metal’s surface from various elements.
When you compare stainless steel (in our case, Grade 304 or optionally Grade 316) and aluminum, there are some characteristic differences to account for. Stainless steel has an ultimate strength that is a good deal higher than that of aluminum, meaning that it will take much more to fracture. This means that stainless steel is also more durable to work with because stainless steel will yield enough when bending, but it won’t form cracks as quickly as aluminum will. At the same time, aluminum is quite a bit lighter than stainless steel which offers many advantages in itself..
Stainless steel can handle higher pH levels than aluminum can when it comes to corrosion resistance. For this reason and in addition to various food safety regulations, we designate stainless steel as our choice in direct food contact construction because it is able to stand up to the usage and cleaning practices used in the food industry.
Does this mean that aluminum is to be avoided with conveyor scales? Not necessarily. Aluminum conveyor scales are a lightweight and durable alternative to processes that require a different type of corrosion resistance. For example, a conveyor scale weighing small boxes or packages could easily be made out of aluminum because it wouldn’t require corrosive chemical cleaning. Aluminum is a little more affordable than stainless steel, so this would be a wise economic choice for many companies.
Neither material is inherently a bad choice, but you have to know the proper use for each to make the best decision. Getting a quality conveyor scale requires quality design decisions, and we are always willing to help with that.
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What are the differences between conveyor scales and checkweighers?
Let’s first describe a checkweigher; a checkweigher is a scale that allows you to set a target weight for a product often referred to as the “Accept range”. Other ranges can include “Over,” “Under,” “Accept Over” and “Accept Under.”
The accept range is generally a very small range where the target weight was almost perfectly hit. The accept over and accept under ranges refer to a product whose weight just slightly missed the target weight but is still acceptable enough to pass inspection. The over and under ranges are set to where a product is too far off of the target range to pass inspection at all, and will need to be reworked.
Checkweighers are available in two very different styles; the first is a “static” scale where an operator will have to place each individual product on a scale, the scales controller will then indicate to the scale operator what range the product fell into, often times with the use of a series of red, yellow, and green lights.
The second type is an “automatic checkweigher.” With an automatic checkweigher the products are conveyed across a series of conveyor belts and the weight is automatically collected with
An automatic checkweigher offers distinct advantages over the static checkweigher. Mainly it can be very cost effective, it also reduces the chance for unintentional human error, as well as removing the possibility of an operator having a bad day and letting their attitude enter into their decision making process.
Additionally, this type of automated system can also keep track of production data by keeping track of the total numbers of packages that fell into each of the ranges.
Now that you have a good understanding of what a checkweigher is we can look at what a conveyor scale is.
A conveyor scale is a component to be used in some sort of system, it’s essentially a scale with a conveyor mounted to it, and some sort of a controller to gather the weighing information.
The only thing the conveyor scale really does with this weight information is to send it to a controller that controls a larger system.
A checkweigher is a good example of one of these systems; another would be a sortation system where products need to be sorted according to weight so that a decision can be made as to how to process each particular product that goes across the scale based on its weight. A final example would be a box labeling system that would apply a net weight label.
A customer came to us needing to automatically weigh bagged product in a production line, but there was an unusual problem. As the product left the conveyor scale, it needed to immediately travel on an incline conveyor to get to an upper level. The frame for that incline conveyor needed to extend beneath the conveyor scale, leaving no room under the conveyor for the scale components.
We solved this problem by designing a suspended scale that we installed above the conveyor portion of the system. By placing the weighing platform above the conveyor, the customer was able to re-use his existing incline conveyor.
But, there was one other problem. This customer required three feet of clearance between the conveyor belt and the suspended scale. That kind of space meant that the scale would swing in one direction, let’s say north and south, and sway in the other direction, let’s call that east and west.
The solution to this challenge was the placing of bracing bars on the frame beneath the conveyor bed, perpendicular to the direction of belt travel, and to attach triangular gussets near the top of the frame structure.
Those measures completely stabilized the conveyor scale system and allowed those bagged products to be weighed in motion to a sensitivity of less than one ounce.
A heavy capacity suspended weighing platform conveyor scale with extraordinary clearance…another example of our customization that fits your needs, your speeds, and your space.
When you are in the market for conveyor scales, you may find it difficult to know exactly what to look for, and investing in a new conveyor scale can be a big deal. Fortunately, there are several areas that you can focus on when comparing your options.
Structural integrity is a prime consideration for conveyor scales. For example, stainless steel can hold up to almost any wear that you throw at it and can be made food grade, so it isn’t contaminating products. On the other hand, less resilient metals like aluminum can still live up to certain processes expectations and are more affordable. Just look at our Ecoline™ series of conveyor scales as an example.
Belting is something else to keep in mind. Do you handle food? There are specific types of conveyor belt for food grade.There are different belts for a variety of different products, so it is important that you know the whole spectrum of products that your conveyor is going to be working with.
Of course, you should also know the general weight range of the product as well. The scale’s weight capacity has to be able to handle your largest products. We offer NTEP-certified WeighMore® scales that vary from 10 to 200 lb capacities to fit any of your weighing needs.
Just as important as the capacity is the division size for the scale. The division size tells you a lot about the precision of your measurements. A scale with a smaller division size (more divisions) is more likely to have a precise weight reading than one with fewer divisions. The scales mentioned above have 2000 NTEP divisions.
Last, but not least, you need to consider throughput. Throughput is one of the most important factors for some plants, and you should always ensure that your conveyor speeds and belt selection can move product at the speeds you need. Our conveyor scales can run all the way up to 380 feet per minute.
It is always good to be informed when picking conveyor scales, but we recommend that you get in touch with us. We have a full product line which is guaranteed to have an answer to your conveyor scale necessities, and we also have a dedicated, qualified staff who is ready to work with you to make sure all of the pieces fall into place.
Although conveyor scales and checkweighers appear to be very similar, they are two entirely different entities. The ultimate difference between them is that one is a system and one is a component to be part of a system.
The in-motion checkweigher is defined as a system because it is formed of several components that form a single working unit. It is composed of an infeed conveyor, a conveyor scale, and an outfeed conveyor with some sort of diverting device, all as one unit.
The sole purpose of a checkweigher is to take a weight and check that against a user-specified range. If a product is inside this range, it passes through, down the conveyor. If not, the divert rejects the product onto another conveyor or container to be disposed of or reworked. This is all decided by software that is unique to the checkweigher.
Notice that a conveyor scale was just a single component of the checkweigher itself. A conveyor scale simply generates the weight of the product as it passes over. This makes it versatile.
A conveyor scale can be connected to a sortation system or an automatic labeler quite easily so that these systems can receive accurate weight information. Simply put a conveyor scale is just that – a scale that weighs products as it is conveyed over the scale’s live area, without stopping.
A checkweigher is more akin to a combo of conveyor scale and sortation system, except the sortation system only has two options: pass or fail.
As an example of how they differ in practice, let’s look at a producer that uses fixed weights and another that labels by weight (catch weight). For the former, a checkweigher is going to be far handier than just a conveyor scale because it can be programmed to reject any product that is below the minimum weight. Likewise, a conveyor scale is more valuable in the latter because it can link to a weigh price labeler and is capable of relaying individual weights to any number of systems.
The difference isn’t always obvious, but it is important to know the industry lingo when it comes to automatic systems.
It can save you a lot of trouble in the long run!
See our Checkweigher Conveyor Scales