How to Improve Efficiency & OEE in Mixing and Packing

Nutritional companies have been willing to spend significant capital installing the highest speed mixers and packing lines in order to achieve high efficiency and throughput. But time and time again these expensive machines are used at half the capacity or less due to changing operational circumstances, driven by customer demand. Or it can also be due to poor conceptual analysis of the needs and future requirements to begin with. The current trend to further diversify and increase the number of SKUs only makes matters worse.

It is therefore time to take a fresh look at what is really efficient and adds to the bottom line!

Bottlenecks in Batch Mixing – There are numerous different technologies available to pro¬duce a homogenous mixture of dry solids, with hundreds of suppliers providing high quality machines. Most technolo-gies provide a good mix within 5-15 minutes. When mov¬ing to very large batch sizes (>5m3), it typically takes a little longer.

On this basis, it should be possible to run (on average) around 4-6 batches per hour through the mixer. However, more often, the reality is that just one or two batches are processed per hour, resulting in a poor OEE (overall equipment effectiveness) rate. So why is this?

The reason stems from the time it takes to fill and empty the mixer, and not least, the time is takes to clean at each recipe change. These circumstances are often accepted as facts, instead of being challenged as the waste that they clearly represent.

Bottlenecks in Packing – There is an even greater diversity of different technologies available for industrial packing of powders. For the purposes of this article we are only considering the packing of consumer SKUs from single portion sachets to 5kg tubs.

Unlike with the mixers, one can’t generalise processing times with packing machines, it all depends on pack sizes/types and overall batch size. However, it is clear that the cost of the packing machine is in direct relation to its nominal speed (and accuracy) of filling, with a premium to pay for having hygienic and easy to clean machines.

Automated packing lines (including all marking and handling equipment) will typically start at €0.25M with €1-2M being more common. Investments like these clearly need to be justified by great productivity, but we often see OEE rates of less than 50%. Why?

Bottlenecks Upstream – There is usually a good flow analysis conducted on the post-packing stage – so no bottlenecks to consider there. The issue is more often upstream. On paper, the mixer typically has a far greater peak capacity than the packing line, but as noted earlier, mixers often run at very low OEE rates which results in an irregular amount of supply to the packing lines. There may also be general powder handling issues preventing a consistent feed to the packing line, including segregation or de-mixing of the blended material, caused by the conveying systems. This results in reduced output due to defects (notified by weight variances or worse still, resulting in a poor quality end product), which directly affects the nominal (good) production output of the plant.

Cleaning is the biggest problem – The most significant contributor to poor OEE for packing lines is related to recipe changes and the need for cleaning. The changeover time between recipes can vary from as little as half an hour for a dry clean between non-allergen recipes, up to taking a full 8-hour shift for a full wet clean and dry.

Longer campaigns are NOT the answer! – It is tempting to simply produce more than what is required of each recipe. Whilst this make sense from a productivity perspective (in terms of increased OEE which is good for the Production Manager who can report high utilisation rates) the business owners and share-holders will not accept increased working capital or exposure to the risk of inventory losses if a recipe loses its popularity, the expiry of a shelf-life or indeed the added warehousing cost.

What does the Lean text book say? – Many have invested heavily in using Lean Consultants to overcome these problems. The Consultants will promote “Flow processing” and “single-unit flow” – great in theory and relatively easy to apply to car manufacture, but not so obvious a solution with the variety and hygienic demands of food processing.

The ideas that can work are:

Protect the bottleneck – by employing simple and practical “Kanban” it’s possible to assure that the critical process (typically packing) is never starved; without the need for excessive WIP.

Value Stream Mapping (VSM) – by identifying where the value is truly created (and where it’s not!), one can attack the wasteful operations and work towards a more efficient flow pattern.

Takt Time – it should be possible to identify a suitable process rhythm (Takt Time) which enables parallel operations to work more effectively together. However, this is only applicable with robust processes which cannot suffer deficiencies, known as ‘quality by design’ in the Pharmaceutical Industry.

SMED (“Single minute exchange of dies”) – of all detailed initiatives originating from the car industry, this is probably the most relevant to transfer to the manufacture of nutritional products. This is about streamlining the time it takes to change from one recipe to another (not only focusing on peak capacity for individual processes).

Purpose-designed processing IS the answer – It is time to accept that “one size fits all” is not a viable way forward. The large batch mixers and the high speed packing lines which are designed to process 3-5 tonnes per hour are not ideal for producing low quantities of specialty recipes. The answer is to apply purpose built, flexible process solutions with all Lean considerations at the forefront.

Matcon’s IBC based mixing and transfer solutions are designed to be cleaned down and ready for a new recipe within minutes, not hours. A detailed and case by case analysis (Lean feasibility study) should preferably be conducted at the start of any transformation, but as a rule of thumb, any campaigns of less than 30 tonnes will be more efficient to process using IBCs and parallel processing.

When not in production of finished goods, the Matcon IBC system can be utilised for the production of Premixes which will be automatically fed to the large mixer. This further removes upstream bottlenecks.

What can be achieved? – By removing the short and special campaigns from the large coupled process lines, you will dramatically improve OEE.

Matcon are currently executing projects in the Infant Nutrition sector where OEEs had been around 50%, but by installing (or adding) a flexible IBC system, the end result is an improvement to 75-80% OEE. The subsequent throughput increase has generated additional millions in revenue per annum. The investment in Matcon’s expertise and technology is immediately rewarded by a 50% production increase!

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