How to Optimize Your Ribbon Mixer

Ribbon mixers in many industries are designed similarly from facility to facility with few variations. However, some design considerations can minimize the up front investment and maintenance, and maximize production and quality. The best way to get optimal efficiency from your ribbon mixer is to get the right design from the start. Depending on your materials, environment and overall mixing system, there may be more to consider than you think.

How to Optimize Your Ribbon Mixer

Compile Ingredients List

Your ingredient characteristics will play a role in several ribbon mixer design elements, and starting with this information will help your equipment manufacturer optimize the design. This way, you will have the size and features you need, without expensive extras. What characteristics you include will depend on whether your ingredients are solid, powder, liquid, or paste. For solids, it’s helpful to know any of the following that apply:

  • Number of ingredients
  • Names
  • Bulk density
  • Weight
  • Particle size variation
  • Adhesion
  • Friability
  • Shear sensitivity

Design the ideal system for your ingredients. Download the Engineer’s Guide to Weighing and Batching >

Record Facility Requirements

In some facilities, space may be a concern. This will impact the footprint and profile of your mixer, which in turn affects volume and production. If you require a large 8 or 10 ton ribbon mixer to meet production, be sure that this will not crowd out other equipment or create workplace hazards.

Calculate Total Production

How much you need to mix will help you determine the size and profile of the ribbon mixer design, or how many mixers you may need. This way, you aren’t investing in a larger mixer than you need, or one that doesn’t make sense with your total cycle time.

Determine Mixing Time

Your ingredients generally must move through the mixer completely three times to be adequately mixed. How long this takes depends on the ribbon mixer dimensions, as well as the ingredient characteristics. To be considered adequately mixed, you’ll need a coefficient of variation of 10 or less. Testing the mixer and the system with your ingredients beforehand will prevent excessive variation, while providing the ideal cycle time.

Record Weighing Time

Minimizing mixing time can yield efficiency gains, but not if the mixer sits idle while ingredients are measured. How long it takes to weigh and discharge ingredients will give you a guideline for the ideal mixing time. If your weighing time and mixing times are close to the same, you can minimize idle time for each process.

Accurate Agitator Profile Design

To get a good mix, you’ll need to fill the ribbon mixer to its swept volume. This means the agitator profile determines, in part, how much the machine can mix in one cycle. The mixer profile should not exceed 2.5 times the diameter of the agitator. The design of the agitator itself, including the ribbon thickness and shaft, may also be a factor, as a heavier agitator will require more energy to move and will have more shear. A simpler agitator design can reduce the initial investment if it’s suitable for the ingredients and facility.

Determine Ribbon Mixer Profile

With the previous information, you can determine the optimal ribbon mixer profile. Longer mixers will be able to mix more volume, but it will take longer, though this won’t be a problem if the cycle times aligns with the weighing time. For lower mixing time and more volume, you’ll need to scale up the ribbon mixer profile proportionately.

Number of Ribbon Mixers

In some cases, it may be more economical to use two ribbon mixers instead of one that is double the size. This way, a problem with one mixer will only reduce production instead of stopping it.

Liquid Coating Considerations

If your ingredients require a liquid coating, you may wish to apply it during the mixing stage. Keep in mind that some liquid coatings may not be evenly applied at this stage, or they liquid may not be suitable for spray nozzles. If the liquid coating can be applied during mixer, be sure to factor in any additional adhesion that may occur. If material stick to each other or to the mixer, extra maintenance may be required, which can eat into ROI.

Determine Shear

Ribbon mixers are generally gentle and impose little shear on ingredients, however it can be an important consideration with some shear sensitive materials. Consider any solid ingredients as well as liquid coatings; are they likely to break apart or separate? Do the ingredients require more shear to break up clumps? Most mixer manufacturers are happy to do testing in order to determine the best configuration for your product.

Accurate Horsepower

Most ribbon mixers operate at around 20 RPMs, though the horsepower it requires will depend on the size of the mixer and the characteristics of the ingredients. Make sure you don’t overestimate your motor and overspend, or underestimate your motor and reduce power to your ribbon mixer.

Install Proper Discharge Gate

The discharge gate on your ribbon mixer(s) will depend on your cycle time, downstream process and your materials. Drop bottom discharge gates will discharge quickly, but they can be harder to seal and allow powders to escape. This can be a challenge for very fine ingredients. Slide gates will discharge more slowly, but will seal more tightly. Multiple slide gates can provide a tight seal with faster discharge.

Reduce Maintenance

The type of gear reducer used in your ribbon mixer motor can impose unnecessary maintenance costs. A shaft reducer in lieu of a jack shaft or foot mount eliminates the need for an oil bath on the sprocket.

Some ribbon mixers are straightforward, and the mixer design varies little over time and throughout the industry. Others are more complex, and considering all the elements can help you improve the design. With the right ribbon mixer design from the start, your mixer will continue to work quietly in the background, with optimal efficiency and no problems.

Solving 5 Common Super Sack Unloader Problems

The right super sack unloader system allows you to measure and process materials quickly and cost-effectively, with very little waste, error or manpower required. Unloading materials may seem like a straightforward process, however the wrong bulk bag discharge system can cause product defects, ingredient loss, and pose workplace safety hazards. The ingredients you’re using as well as the design of your system and the volume processed will all play a role in choosing a safe, effective, durable super sack unloader.

5 Super Sack Unloader Problems and Solutions

1. Design for Space

The first thing to consider with your super sack unloader is the design, which will depend on how you transport the bulk bags, and the design of your facility. Your bulk bag unloader design may be any of the following:

  • Forklift: If you are transporting the bag from the top using a forklift, this will most likely be the easiest and simplest option. This allows a forklift operator to easily load the bag into the frame from the top, with no other steps required.
  • Dedicated Hoist: In some cases a clear path may not be available for a forklift. A dedicated hoist design allows you to secure the bag to support arms and lift, then push it into place. With this design, it is important to motorize the lifting and pushing mechanism to put the bag in place.
  • Bottom Lift: Facilities with low clearance, such as those retrofitting from individual bag unloading, may use a bottom lift mechanism. With this design, a forklift operator can move the super sack and support frame from the bottom and lift it into place with only about half the height needed.

Keep in mind that staff should never be below the bags at any point while loading the bag, as this presents a serious workplace hazard. Though bulk bag failures are uncommon, they do occur.

2. Preventing Bag Deformation

As the ingredients flow out of the bulk bag, it will begin to lose its shape and ingredients will flow slowly, or even stop. There are several ways to stop flow problems, and which you choose will depend on the ingredients you are using and the design of the super sack unloader.

  • Raise the Bag: With vertical clearance available, you can lift the bulk bag support arms as the bag unloads, increasing the flow angle.
  • Retractable Arms: If the arms supporting the super sack are spring-loaded, they will retract as the bag loses tension. This maintains the flow angle.
  • Paddles: Pneumatic paddles at the bottom of the bag can push the ingredients up as the bag discharges. For ingredients with low flow, or for sticky materials prone to clumping, paddles and other flow aid devices are useful.

3. Accounting for Material Characteristics

The characteristics of your materials are also important to consider when choosing your super sack unloader. Some materials are more susceptible to flow problems or segregation, which can cause other problems in the process. How the material flows, its moisture content, whether it is prone to static charge, clumping or flushing, and other characteristics will decide what type of special features your bag unloader may need to be effective.

  • Flushing: Dry, light, free-flowing materials may have a tendency to flush, continuing to flow after shut-off. Pay special attention to the valve or gate below the bag to prevent flushing.
  • Dust: Dry, light materials also tend to produce dust. A ventilation or vacuum system may be required around the bulk bag unloader to prevent dust build-up and workplace safety hazards. When the bag is empty, dust can be trapped inside, so it is also important to tie the empty bag before removing it.
  • Clumping: Adhesive materials may form clumps within the bag, or the bag may become solid if it is compressed. In some cases, a bag liner preventing moisture can stop clumping. Pneumatic rams can break up solid blocks, or paddles can break apart clumps.
  • Static: Very fine materials as well as some plastic resins can become statically charged as they flow, especially in dry conditions. This can cause materials to stick to the sides of the bag or feeder and decrease the feeder capacity. The static charge can also pose a risk to scales, load cells or system controls. Make sure the super sack unloader frame is grounded to prevent static build-up.
  • Moisture: Some materials may need protection against moisture to prevent spoiling or clumping. A bag liner can prevent this, but the bulk bag unloader frame should also secure the bag liner to prevent it from becoming lodged in the feeder.

4. The Right Discharge System

To accurately discharge ingredients, you’ll need to choose the right discharge system using either loss-in-weight or volumetric measurement. Which method you choose will depend on the level of accuracy you require.

  • Loss-in-weight: With load cells mounted underneath the bulk bag base or frame you can measure discharge through the weight of the bag. This is suitable for ingredients in large amounts, but more accurate scales will be required for ingredients discharged at 40 lbs or less with 1% accuracy, based on a one-ton bulk bag.
  • Gain-in-Weight: For more accurate measurements, gain-in-weight measurement may be preferred. In this case, the scale be sized for the actual amount being weighed, so the accuracy can be adjusted to your needs.

5. Meeting Sanitation Requirements

If your materials must meet food grade or other USDA or FDA standards, you’ll need to make sure the super sack unloader and the bag itself are suitable. A bag liner is useful here to protect the materials inside from moisture, damage or contamination. In this case, the frame around the bag should secure both the bag and the liner, or the liner may collapse and enter the feeder. The frame, as well as any surface the materials come into contact with should be made from stainless steel to allow for easy sanitation.

 

With the right bulk bag unloader system, you can process materials quickly, safely, and efficiently. The best way to make sure your system works effectively with your materials, as well as your downstream and upstream processes, is to design and test it properly. Your equipment supplier can help you address these issues and make each part of your system efficient.

Complete Ingredient Mixing Systems Design Checklist

ingredient mixing system design

There is no one-size-fits-all for ingredient mixing systems design, whether you are working in snack foods, animal feed, dry bulk solids or any other industry. Ingredient mixing system designs require careful consideration of all ingredients as well as production schedules, variation, storage and more. In this blog, we’ll provide a basic roadmap for automated ingredient mixing system design that business owners, facility managers, engineers and others can easily follow.

Automated Ingredient Mixing System Design Checklist

Planning System Design Requirements

Your ingredient mixing system design starts with needs and goals, including your ingredients, production volume and product variation. The accuracy of this initial information will determine the design of the rest of your system, so it’s important to be as clear and correct as possible at this stage.

You’ll need all of the following information

  • Ingredients: number, names, bulk density, weight, ingredient delivery schedule, special considerations (friability, viscosity, adhesion, particle size variation etc.)
  • Production: daily, weekly, monthly amounts
  • Environment: temperature, humidity, seasonal changes

This information will not only help you design your ingredient mixing systems for volume and production, but will also help you avoid any complications that could arise from system’s surrounding environment, or challenges with the materials or ingredients themselves, such as material segregation or flow control problems.

Get the secrets to automation systems design. Download the Engineer’s Guide to Weighing and Batching >

Storage Bins

Your production volume, number of ingredients, and ingredient delivery schedule will help you determine the size and number of storage bins you will need. Consider the minimum and maximum production levels of your facility, as well as the minimum and maximum ingredient volume delivery for each ingredient to determine the storage bin size you will need. Also, consider any safety requirements you will need when unloading ingredients, or any special considerations the ingredients may need during storage, such as temperature requirements or bin coatings for acidic or adhesive ingredients.

Consider these factors as you design your ingredient loading and storage area:

  • Storage bin size
  • Storage bin placement
  • Unloading area
  • Unloading safety requirements
  • Bin coating requirements

Feeder Design

Feeders are one of the most important parts of your ingredient mixing system design. Designing your feeder improperly can cause incorrect measurement and mixing, resulting in product defects, or slow-downs and downtime when ingredients don’t move through the feeder at the desired rate.

The maximum and minimum weight of each ingredient you determined in the planning stage can help you determine your feeder volume output. The feeder must be able to feed the smallest micro-ingredients as well as high-volume base ingredients, all within tolerances. This may mean installing multiple feeders or installing additional features on one feeder, such as speed controls. You’ll also need to determine your feeder drive mechanism, either hydraulic or electric, as well as a cut-off valve to prevent flushing.

To get the right feeder, consider the following:

  • Feeder volume output
  • Number of feeders or features
  • Feeder drive
  • Feed cut-off valve
  • Accuracy

Scales

To properly design and install scales for your ingredient mixing system, you’ll need to determine the maximum and minimum number and amount of ingredients you’ll be measuring, as well as how accurate the measurements must be. Remember that scales, like feeders, must be capable of meeting volume and accuracy requirements for micro- and macro-ingredients. This means they should be large enough to handle heavy volumes, but accurate enough to measure micro-ingredients without too much error. If there are large variations between your ingredients, using several scales or diluting ingredients can help you maintain accuracy.

The type of scale you choose will also have a dramatic impact on the system at large. The right type of scale can help you save time and eliminate extra processes, like a conveyor scale, make mixing easier and more uniform, like a conical scale hopper, or integrate with a variety of bins, like a roll-over tub. The best scale type will depend on your facility, ingredients, and product.

You’ll need to know the following:

  • Maximum scale weight
  • Maximum scale error
  • Number of scales
  • Scale inclusion rate
  • Scale display resolution
  • Scale type

Mixer

It’s important to choose a mixer that will properly mix all ingredients together, but will also give you an efficient cycle time. You’ll need to measure the cycle time of your mixer and compare it to the cycle time of your weighing and discharging system for maximum efficiency. This will allow you to run all processes simultaneously, instead of leaving your mixer or feeders idle. You’ll also need to consider any special requirements of your ingredients, such as adhesion, friability or heat and shear. Finally, remember that the mixer must be filled at least to swept volume to work properly, so all ingredient mixes, including the lowest possible volume, must fill the mixer at least to swept volume.

Consider all of the following for your mixer:

  • Mixer cycle time
  • Mixer footprint and profile
  • Mixer swept volume
  • Ingredient considerations

Controls

Without the right control system, even the best ingredient mixing systems designs won’t work. Your control system keeps you automated system running smoothly, and alerts you to any problems. You’ll need to choose a computer or PLC that integrates easily but completely with your system design. This means your controls must be able to work with all of your inputs and settings, including multiple feeder or mixing speeds, scales, sensors, and all upstream or downstream functions.

Keep in mind that your system, ingredients and recipe may change, and your controls may need to be reprogrammed at some point. The best control systems will adapt to your needs without the need for complex programming knowledge.

To get the right controls you’ll need to know:

  • Number of scales
  • Number of feeders
  • Number of mixers
  • Variable speed controls
  • Sensors and alarm conditions
  • Upstream or downstream processes
  • Reprogramming conditions

To complete your system, you’ll also need to consider upstream and downstream processes, which may vary depending on your ingredients, ingredient delivery system, and batching process. At each point in the process, your environmental conditions will also be a concern, as high temperatures or humidity can cause materials to separate, stick, or flow slowly. As you design and build your system, work closely with your equipment manufacturer to make sure your system is build for your ingredients and volume.

Solving Material Segregation in Batch Mixing Processes

material segregation in batch mixing processes

When solid materials mix, a degree of material segregation is inevitable. A variety of processes are used to achieve a predetermined level of uniformity in batch mixing processes, however other processes downstream can cause the materials to separate again. With proper design considerations and awareness of the material segregation physics at work, processes and products can be tested for separation, and product defects can be avoided.

Material Segregation Problems In Batch Mixing Processes

Sifting

How It Works

Scientifically known as granular convection and known in practice as the Brazil nut problem, sifting is one of the most common material segregation problems in batch mixing processes. Sifting occurs mainly through the relationship between the particles’ size and mass; particles significantly larger and more massive (like Brazil nuts) rise to the top of the mixture, and smaller, less massive particles (like cashews) fall between the spaces towards the bottom. It can occur without movement, but movement worsens the problem, since vibration or shaking causes smaller particles to relocate faster into empty spaces. The degree with which this material segregation problem occurs depends on the variation between the particles’ size and mass, and the amount of each.

What You’ll See

Sifting is a material segregation problem impacting many processes. A vibrating conveyor belt can cause sifting, as well as some stirring processes. Even shaking a completed package (like a jar of mixed nuts) can cause this separation.

Angle of Repose

How It Works

The angle of repose material segregation problem in batch mixing processes works similarly to sifting, but operates on a different principle. Instead of sinking to the bottom, smaller, finer particles form a hill when they are poured or dispensed. When thicker, coarser particles reach the hill, they tumble down towards the edges. The materials’ differing angle of repose—the angle at which it will be stable and not tumble down—causes this separation.

What You’ll See

This material segregation problem in batch mixing can be especially difficult. In silos and hoppers it’s often the cause of flow problems like ratholing and bridging. If the coarser particles stick to the sides of the hopper they can get rancid and contaminate the next batch. Since air flows through the coarse and fine materials at different levels when they are dispensed, it can create a pressure differential that can damage a holding unit, such as a silo. Most commonly in batch mixing, the material segregation causes different concentrations of ingredients when the mixture is dispensed from an improperly designed hopper.

Fluidization

How It Works

Fluidization occurs when a mixture is suspended in a gas or liquid. In batch mixing processes, this material segregation problem most commonly occurs in plain old air. When a mixture is aerated (which may occur simply through free falling), the finer, less dense particles retain air and move towards the top of the mixture, while the larger, denser particles which didn’t absorb air sink.

What You’ll See

This material segregation problem in batch mixing commonly occurs in powder ingredients. If the powder does not bind sufficiently to another material, it will separate through fluidization if aerated or allowed to free-fall. With all the powder at the top, the uniformity and product quality can be compromised. Fluidization, combined with the previous two material segregation problems, also poses workplace safety risks from powder explosions and respiratory hazards as large amounts of powders separate into the air.

Trajectory Segregation

How It Works

Unlike the previous three material segregation problems, trajectory segregation occurs through horizontal movement. This occurs by two different principles. In a fluid mixture, trajectory segregation occurs through a relationship between particle size, density, viscosity, and velocity. Particles with the same viscosity and velocity, but different size or density will travel at different rates. This causes the mixture to seperate.

In a solid mixture, trajectory segregation occurs through friction. Finer materials with more surface area and therefore more friction move slower and will deposit closer to the end of the horizontal path. Larger materials with less surface area and less friction move faster and deposit further.

What You’ll See

This material segregation problem in batch mixing processes commonly occurs in ribbon blenders and conveyors or chutes. In ribbon blenders, the particles in a fluid suspension separate in the blender due to their differing size or density. In chutes and conveyors, friction causes the materials to move at different rates, creating a pile of fine materials near the end of the chute and coarse materials further away.

Material Segregation Solutions In Batch Mixing Processes

Ingredient Testing

In order to solve material segregation problems in batch mixing processes, the materials and processes must be well understood. Knowing the particles’ density, size, mass and other properties can help you predict how the materials will segregate. While designing process automation equipment, ask your manufacturer if they will conduct ingredient testing for angle of repose, sifting capacity, and other issues. With this information, your manufacturer can design equipment to prevent material segregation problems in batch mixing processes.

Material Segregation Testing

When testing material segregation in existing batch mixing processes, make sure to test accurately. Remember that material segregation in the end product will also affect any tests on the end product. Use a sample thief or a riffler to get samples that accurately represent the whole, and see where and to what extent problems exist in the process chain. Remember to check the coefficient of variation at different points of the process, not just at the mixer, to see if your downstream process is causing segregation.

Feed Bin Design

Angle of repose problems are most commonly caused by an improperly designed feed bin and hopper. Using a mass flow hopper designed according to the materials’ angle of repose will prevent the mix from dispensing unevenly. In general, an angle of at least 70 degrees is recommended. Hopper inserts or low-traction coatings can also be used.

Mixing And Blending

Mixing and blending processes should be carefully selected and placed. The wrong mixer or blender can actually cause materials to separate through trajectory segregation. If the mixer is placed too early in the process, the materials may simply resegregate downstream. Placing a mixer immediately before dispensing can mitigate segregation effects.

Coating

Many material segregation problems only occur in free-flowing mixtures. Adding a binder can stop problems like sifting, though other problems like sticking and clogging should also be considered.

Agitation

Aeration or vibration can remix some materials, particularly if they are separated in a silo or hopper. With both of these methods, be careful not to introduce sifting or fluidization.

New Materials

More drastic differences between materials cause more drastic material segregation problems in batch mixing processes. If your materials are especially coarse, or a large variation between particle size and density exists, talk with your supplier about material quality. Or, consider additional processing to a diverse material; would adding another process for more material uniformity prevent material segregation problems? Would it be cost-effective?


Material segregation may occur in areas that operators never see. This means you might only see the results in low product quality or contamination. You might also experience repeated processing problems and machine errors due to clogging, flooding, low flow and other issues. If you’ve noticed these issues, assess your batch mixing processes and see where material segregation problems may occur. Once you identify the problem, a simple fix may increase product quality significantly.