Pro Tip: How to Properly Feed Your Multihead Weigher or Combination Scale

Written by Jason Schmidt, Senior OEM Accounts Manager

A multihead weigher’s performance is highly dependent on both upstream and downstream equipment. Let’s concentrate on the upstream equipment today. Specifically, feeding equipment.

A multihead weigher, also known as a combination scale, needs to have product on it in order to record any kind of weight. But how does the product get on the scale? Focusing on how to properly set up and use feed equipment will help you get the best speed and accuracy from your multihead weigher.

There are several different equipment options to consider when looking to feed product to a combination scale. Three of the main ways to feed product onto a multihead weigher include:

  1. A vibratory feeder – also known as a cross-feeder
  2. A bucket elevator
  3. Belt feeders

At Yamato Corporation, we typically recommend the use of a crosshead feeder, but no matter what type of feed equipment you choose to use, it is important to achieve the correct product flow. The key is to not starve or flood the scale. The goal is to achieve a waterfall-like flow of product onto the top of your scale. The recommendations below will help you accomplish this.

Avoid starving your multihead weigher with product.

Starving a scale is when the feed equipment is not delivering enough product to the scale, which can leave the top cone void of product, linear feed pans with little to no product, and feed/weigh buckets lacking adequate product levels. This will significantly hurt the performance of the combination scale.

A multihead weigher relies on a consistent level of product across all its components. When weigh buckets have limited levels of product inside them, finding a good combination of buckets to achieve the pre-programmed target weight will be hard to come by. On average, the scale is looking for four buckets in combination to reach the desired target weight. If the scale is being starved, then it will need to skip cycles as it looks for the best combination of buckets to choose from, reducing the speed of the scale and, in turn, slowing down the entire production line.

Avoid flooding your multihead weigher with product.

The flipside to starving a scale is when the scale is flooded with product. Flooding the scale is when the product level on the scale’s top cone, linear feed pans, and feed/weigh buckets is too high. Too much product in the weigh buckets will severely limit the number of buckets that can be used in a combination. Again, on average, the scale is looking for about four buckets to make a combination and the total target weight. Flooding weigh buckets will force the scale to potentially choose only one or two buckets in combination. This is not an efficient way to run a Yamato combination scale since each weigh head on a scale increases the accuracy.

A Yamato combination scale’s software contains the ability to force an overfilled bucket into combination after a settable number of cycles, but this is not the ideal way to run a multihead weigher. This should only be a last resort since your product giveaway may increase.

Let’s take it from the top (cone)…

The most successful feed equipment delivers product like a waterfall effect onto the top cone, not flooding or starving the scale. To help feed equipment know when to turn on and deliver more product to the scale, or turn off when enough has reached the scale, Yamato combination scales come equipped with a load cell below the top cone.

For each recipe/program set, the operator will adjust the high and low limits of this load cell under the top cone of the scale. The high limit refers to how much weight is allowed to be sitting on top of the scale’s top cone. When the load cell below the top cone reaches its set high limit of acceptable product on the scale, it will signal to the feed equipment to shut off and stop delivering product. The opposite of this is when the current level of product on the top cone begins to be drawn down. The load cell under the top cone will take a reading to determine if more product needs to be delivered to the top of the scale. Then, a signal will be sent by the scale to the feed equipment to turn on and deliver more product.

Determine the proper placement of your feed equipment.

When setting up your production line, it’s vital to optimize the placement of your feed equipment so it can deliver product to the most central point on the scale’s top cone. Typically, the top four to six inches of the top cone is where product should be directed towards. This allows the top cone to turn on, vibrating the product in a counterclockwise fashion evenly to each of the scale’s linear feed pans. If the feed equipment is not mounted directly above the top cone, there is a high likelihood of product undershooting or overshooting the top cone. This will not allow for the desired waterfall effect, preventing even distribution to each of the linear feed pans.

The mounting height of feed equipment above the top cone is also very important. Feed equipment should not be mounted too high or too low to the scale’s top cone. Mounting feed equipment too high above the top cone can cause several problems. The first being any fragile product dropping for an increased height can cause unnecessary damage to the product. Second, dropping product from too great of a height can cause the product to fall away from the upper most point of the scale’s top cone, defeating the purpose of the top cones ability to draw product evenly to each linear feed pan. The opposite of this is mounting feed equipment too close to the top cone, which restricts product, not allowing it to evenly reach all the linear feed pans. Also, having feed equipment too close to the top cone will restrict access during the removal of the top cone and linear feed pans on the scale for sanitation and maintenance. For handling delicate products like fruits and vegetables, poultry, and other meat products, this is especially crucial.

Keep the feed equipment isolated from the multihead weigher.

Lastly, Yamato Corporation highly recommends all feed equipment is isolated away from being on the same structure the Yamato combination scale is mounted to. It is important to minimize external vibrations to the scale as much as possible to reduce any potential vibration being transferred to the scale’s sensitive load cells. Isolating this equipment will help deliver the most accurate weighment possible, vital for cannabis as well as many other applications.

How can we help?

Regardless of the equipment you choose to feed your combination scale with, keep these key points in mind when setting up your product line to maximize performance. For more information on feeding equipment, troubleshooting, or to determine the best weighing solution for your next food packaging line, don’t hesitate to contact us. Also, do not forget to explore our range of multihead weighers (combination scales) or our many other automatic weighing and filling solutions, as well as our extensive parts and service offerings to maintain optimal performance.