Improve Auger Filler Accuracy: How to Maintain Consistent Fill Weight

Improve Auger Filler Accuracy: How to Maintain Consistent Fill Weight

Some of the information in this post may be well-known to those who are familiar with augers, bulk density, and fill weight. However, for those of you who may be new to the nuances of packaging with this type of filler, some of this basic information will be useful to you in packaging your product when using an auger filler.
We all want our powder or granular product to end up safely in its package. It would be great if it got there quickly and efficiently as well. The ideal scenario would be if it did all those things with a high level of consistency and accuracy.
We know having all these elements will improve weight accuracy which affects Overall Equipment Effectiveness (OEE).
If you’re not maintaining a consistent fill weight this could indicate issues with head pressure and bulk density.

BULK DENSITY AND HOW IT AFFECTS YOUR PRODUCT

First, let’s define bulk density. Bulk density is defined as the weight of the product per unit of volume.
How does bulk density affect your product?
Think of a cup of flour. If you scoop 1 cup of flour from its bag, that one cup of flour will weigh x amount of grams. When you tap that cup of flour on a table 3 or 4 times, the flour in the cup will pack down leaving space for more flour. The additional flour filling that space is just like the weight variation you see when there is inconsistent feed in the auger hopper.

WAYS TO MAINTAIN CONSISTENT HEAD PRESSURE AND FILL WEIGHT

1. HORIZONTAL FEED SCREW
   By far, one of the best methods in maintaining consistent head pressure in the hopper is to use a horizontal infeed screw. This method ensures the hopper maintains a uniform and controlled fill level required to achieve consistent head pressure in the hopper. The fill level is controlled from a level sensor in the auger hopper. When the fill level dips below the designated low limit, the feed screw turns on and fills the hopper as needed to maintain a consistent level.
2. HOPPER FILL LEVEL
   When your auger hopper doesn’t have consistent fill levels this will result in varying head pressures in the auger bowl. The auger tooling flights will then fill a different amount of product due to the changes in bulk density, causing your bags to be short-filled or over-filled.
   This wide variation with your weight control may lead to packages that don’t meet quality assurance and require more attention from the operator.
   Since the auger tooling is what actually feeds the product into the bag, it needs to deliver the same amount of product to the bag every time. As the volume of space between the auger flights is always the same, consistent bulk density plays an important role during the filling process.
3. SPEED OF AUGER
   The optimum rotation of the auger is about three to four turns to fill a bag. Keeping the fills in this window will maximize speed of filling the stand up pouch or pillow bag and provide accurate weight control. Auger tooling is an important factor in this area. If your auger is only rotating one to two times per bag and your weight control is off, your tooling may be too large for the application.
4. AGITATOR
   The agitator is designed for specific product applications such as non-free flowing powders. Determining the angle of repose and the bench test are two methods you can use to deduce if a product is free flowing or non-free flowing.
   Inside the auger hopper the agitator guides and pushes the product to the flights of the auger screw. It keeps the product from tunneling. You will want to make sure your agitator rotation is set for a speed that works with your product to achieve accurate fill weights.
   Agitator rotation speeds are user settable for optimal product performance.