Custom Processing Services Blog

4 Secrets to Evaluating Powder Blending Companies

Justin Klinger, Jun 4, 2020 7:00:00 AM


At a rate unseen in modern manufacturing history, consumers are demanding more and more variety from product manufacturers who, in turn, are responding by adding more and more versions, or “recipes,” to their portfolios.

Yet, the only way many manufacturers can keep multiple product development tracks running (while maintaining hygiene and production standards) is to lean on toll processors with expertise in blending.

Blending is how “ingredients” become “products.”

That transformation may sound simple, but blending (powder blending, specifically) is often the most complex and vital step in a product’s development. It’s not easy to create a uniform, or homogeneous, mix of materials, which is likely critical to a product’s success. “Well blended” isn’t enough; it must be done exactly right every single time.

Blending (or mixing) of powder ingredients is common throughout many industries: food and pharmaceuticals, metals and minerals, chemicals, and plastics. From the feasibility phase through production, precision powder blending expertise can cost-effectively solve many issues and fine-tune the manufacturing process. So, no surprise, there’s quite a demand for companies that can blend powder ingredients properly.

The tricky part is finding those companies, or toll processors, that specialize in powder blending. That’s why in this article we’re going to share some insights into separating high-end, worthy-of-your-business toll processors from the ordinary ones you want to avoid. 

Is There A Secret To Finding Powder Blending Expertise?

No, there are four! Let’s uncover what you really need to know and the questions you should be asking when evaluating a toll processor’s capabilities.

1. Characteristics Are King

Many products rely on the correct mixing of powder and/or granular materials. The perfect blend that meets required attributes is only possible when you understand the characteristics and properties of all materials involved AND how they’ll interact when blended.

For instance, particles of similar sizes mix easily, so you want to achieve uniformity, if possible. On the challenging side, some fine powders can become electrostatically charged, which you want to minimize. Other characteristics include powder density, moisture content, lubricity, and others.

Instead of addressing each characteristic individually, the following three groups segment them by features, which can help to properly evaluate a mixed product:

  • Flowability — This concerns the blending equipment used as much as the materials themselves because the powder has to flow freely and consistently from its storage container into the feed area of the processing equipment.

    Without us getting too far into interparticle forces (van der Waals, electrostatic, capillary, and others), just know that they strongly affect powder flow systems and a material’s flow behavior, especially a powder’s cohesive properties that force it to agglomerate. Even the smallest amount of moisture can make a free-flowing powder tough to handle, so humidity needs to be monitored closely.

  • Homogeneity — Remember how “well blended” isn’t enough? Consider the pharmaceutical industry, in which using micronized powders, less than 10 microns, is important because it means a quicker drug absorption rate. Here, blend homogeneity is of paramount importance. 

    The active pharmaceutical ingredient (API) must be distributed uniformly with excipients within the mix. When there’s a difference between the particle sizes of the API and the excipient ingredients, it can result in de-mixing of the ingredients. Similarly, excipients that are stickier than the active ingredient are more difficult to blend.

    A blend is homogeneous when the API is within specification, which requires obtaining a number of samples. That brings us to sampling.

  • Sampling — There’s only one way to evaluate a mix: take samples and analyze them. There are various sampling methods — thief sampling, stream sampling, etc. — which are all designed to give representative samples. Typically in powder blend samples, variations are due to particle size distribution. Generally, sampling problems will increase as the quality of the mix decreases.

Blending of powders requires a deep understanding of individual particle characteristics to ensure the mix’s quality standard is achieved. These are features the right toll processor should document for you.

2. Equipment Types And Sizes

Having specialized equipment available is critical to effective powder blending. 

Fixed-shell blenders (ribbon, paddle, screw mixers) have an internal rotating device that provides a continuous shearing force on the particles, breaking up agglomerated powder particles as they slowly and gently mix powders.

Within a ribbon blender, a double-helix agitator performs two tasks: the outer blade moves material to the center of a trough; the inner blades move material to the outside of a trough. Paddle blenders, a slightly different design, is best for small batches and friable materials.

Rotating-shell blenders (twin-shell or “V,” drum, double cone), generally gentler than fixed-shell blenders, rely on the free-flowing particles mixing as they slide and tumble together; think of a concrete mixer on a truck.

High shear blenders handle sticky, cohesive powders well, forcing particles to fold together. Proper management is required so particle degradation and heat build-up doesn’t occur in the mixture.

Plow-style blenders, a type of high shear mixer, are used when particle size reduction and granules are needed.

Determining the size of the blender needed is based largely on powder weight and flow characteristics. The weight helps estimate the working capacity required, and the flow characteristics determine what type of blender is needed to handle that product.

A too full or too empty blender isn’t effective for powders; 35-65% capacity is best. A blender’s working capacity is typically 50% of its total volume, and while a blender is usually sized by its volume, powders are usually measured by density (grams per cubic centimeter or pounds per cubic foot). Powders can be fluffy or dense, meaning two products of the same weight could have very different volumes.

A particle’s characteristics influence the selection of a blender. Achieving a uniform mix is affected by the blender’s speed, fill volume, flow rate, and mixing duration, and it’s not as simple as blending for an extended period of time (which can cause ingredient de-mixing in some cases). In fact, mixing time needs to be adjusted for each formulation to achieve blend uniformity.

3. Processing Techniques

When it comes to the batch size a toll processor can handle, don’t simply assume that biggest is best. The right blender size is one that has a working capacity within the range that achieves a uniform blend. Often, when the volume is large or the mixing time long, the results will not be a homogeneous mix.

What you’re really looking for in a powder blending company is the ability to process a range of batch sizes with a focus on minimizing downtime and meeting scheduling needs. That variable range means agility; the ability to change —  short runs or multiple batches — to outperform the competition. Can that toll processor scale up production without changing the blender?

That brings up manufacturing processes, specifically batch and continuous processing. In traditional batch processing, components of a product are brought together in a step-by-step process (perhaps with multiple pieces of equipment), with the current batch finishing before the next batch is processed.

In continuous processing, a product goes from base ingredients to final product without needing to stop production; so no equipment shut down and no downtime. It’s time-efficient, reduces energy use, increases productivity, reduces waste and, with less people involved, the risk of human error is reduced.

Both are great tools to have. Some products require batch processing because of their composition or formula, and some are best for continuous processing. The best powder blending toll processors are flexible enough to handle both techniques.

4. Cleaning & Cross Contamination 

Toll processors are obsessive about cleanliness. When evaluating different options, review quality assurance and control procedures, as well as their track record.

Powder blending is especially challenging, with equipment requiring extensive cleaning to prevent cross contamination between products. Cleaning protocols are in place to ensure contamination is prevented.

You may want to develop an audit that helps you review quality failures, compliance issues, and the toll processor’s strengths and weaknesses. Remember that any worthy toll processor considers it standard procedure to trace product from arrival time through departure time.

Don’t dismiss industry certifications, either. You know that when a powder blending company achieves multiple certifications that cleanliness and cross contamination are nearly nonexistent.

Still unsure if using a toll processor is right for you? We’ve outlined five reasons to use toll processing, depending on your product and needs.

Your powder blending partner is the final guard between your product and your customer. The four “secrets” here are a great starting point, but we’re ready to go deeper and discuss your needs. Contact CPS today, “The Architects Of What’s Possible,” or give us a call at 610-779-7001.

Learn more about material science and particle specifications, equipment, quality assurance and process controls, and even industry certifications when you download our Particle Technology Glossary. Armed with an understanding of some of the most important terms, you can communicate with confidence about your toll processing needs. Just click the link below to download your copy today.New call-to-action

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