The more, the better

Over the years, advances in continuous mixing have been developed to improve ingredient metering, process controls and include specialized mixer designs and ultra-high capacity mixers. Compared to batch mixing, such technological developments make continuous mixing a better option than batch mixing, especially so for high-volume production.

+High throughput continuous mixers are becoming the best sellers in this equipment category, as the benefits that continuous mixing systems bring are amplified at higher production rates, compared with batch mixing.

Jim Warren, Vice President of Exact Mixing (Reading Bakery Systems), highlights the main reasons why the advantages of continuous mixing will amplify exponentially, with larger production volumes.

Cost-effectiveness

Beyond the initial investment considerations, for largecapacity production lines, continuous mixing is a more cost-effective process than batch mixing.

The key concept to understand is that when the throughput of a continuous mixing system increases, the cost of the system changes at a much lower ratio than with batch mixing. This is because the ingredient metering portion of the cost is nearly constant, no matter what the new throughput is. For example, at four times the throughput (from 500 kg/hr to 2,000 kg/hr), the continuous mixing system cost only increases by 50%. At 7.5 times the throughput (from 2,000 kg/hr to 15,000 kg/hr), the system cost would only double. When considering batch mixing, the cost of the model is quite different: doubling the throughput of a batch mixing system increases the equipment cost by 80-100%. Both the mixer and the downstream metering system must double in capacity. In short, when comparing the cost per pound of dough produced, continuous mixing is the more costeffective option.

Automation

Being a fully-automated process, continuous mixing requires significantly less labor in comparison with batch mixing. With batch mixing, the higher the volume, the more people are needed for every stage of the mixing process. A larger staff also implies more training is required, as the quality of the final products directly relies on the actions of the operators.

Alternatively, continuous systems provide controls over the entire system including bulk delivery, ingredient infeed and mixing via automated recipe control systems. With continuous mixing, no matter what the rate, only one operator is required and for only a small portion of the day.

Dough handling equipment

Continuous mixing requires less dough-handling equipment than batch mixing. In the case of continuous mixing, the resulting dough generally takes the form of a rope or log, which can be cut into chunks of the desired sizes. The dough pieces then fall onto a conveyor belt or directly into a hopper of the forming equipment. The process remains the same no matter the production capacity of the line. Batch mixers, on the other hand, produce a large mass of dough, which is discharged and must be resized for further processing – meaning, additional costs need to be considered for this dough handling equipment. Bigger volumes add to the batch-mixing challenges, as more equipment and operators will be needed.

“Anytime training becomes critical, retention is also critical. As the dough requirement increases with a batch system, the demands on the staff are multiplied. In the case of continuous mixing, no matter what the rate, only one operator is required and for only a small portion of the day.”

Warren,

Process efficiency

Continuous mixing is a more efficient process compared to batch mixing. There are no variations in the characteristics of the dough, which can occur between batches, which means less product waste. Additionally, if the manufacturing line needs to be stopped for an extended period, there is much more dough at risk when using the batch mixing method

– typically, around three mixer volumes. With continuous mixing, the only dough at risk is the small amount of dough inside the mixer.

Consistency

When using fully automated continuous mixing systems, consistency is guaranteed. The minor ingredients are blended with the use of loss-in-weight technology and a blender on load cells. All measurements are weighed automatically, and the data is saved in the system. Dry and liquid ingredients are carefully metered into the mixer, and automatically weighed and recorded. Metering rates are graphed in real time and saved for future reference. With batch mixing, as the mixer throughput increases, hand measuring creates a greater opportunity for errors, more employees are required to batch ingredients and the pressure to create blends quickly increases. Often in a batch system, the plan for correction is at the operator’s discretion. Forget to add something? The dough is too warm or too stiff? Not enough development? Wrong consistency? Downstream shutdown? When presented with these problems, if there is no plan to act quickly, product will often be inconsistent and out of spec, creating waste. With continuous mixing, the system anticipates potential concerns, determines proper corrective steps in advance and is programmed to take those steps automatically.

Conclusion

While continuous mixing technology has been around for over 30 years, only the last 10 years have brought the development of mixers with production rates in excess of 8,000 kilograms per hour. The benefit is that this increase has been made with no change to the process itself – the mixer’s operations remain unchanged, with no new requirements. Continuous mixers will cost less to operate over time than comparable batch mixing systems, which offsets the higher initial costs. Exact Mixing has developed a Continuous Mixing Calculator (exactmixing.com/calculator) that can show what savings can be achieved when using continuous mixing compared to batch mixing. +++