Single screw extruder vs twin screw extruder

What’s the difference between single screw extruder & twin screw extruder? Sunpring will tell you the answer. For several years, engineers and food manufacturers have invested a lot of money in the development of affordable and efficient technology to produce high quality foods. Truthfully, these investments have yielded admirable results after several years of testing and reevaluation. One of the latest developments in the food extrusion industry is the invention of the twin screw extrusion system. Today, leading commercial food manufacturers are using this technology to produce their foodstuffs, thanks its ample benefits.

In general, extrusion equipment used currently to process foodstuff falls into two major categories: twin-screw extruders and single screw extruders. Here is a detailed explanation of each type of equipment:

Single screw extruder

The single screw extruder is simple. It is uses a rotating belt way and has a constant/fixed speed. In addition, solid conveying, pumping, melting as well as blending occur simultaneously and interdependently. More so, process control is difficult, thus leading to low efficiency and effectiveness.

In terms of production, the single screw extruder tends to have a lower productivity as compared to the same power twin screw extruder especially in high pressure conditions.

Characteristics of the single screw extruder include:

v Suitable for extrusion processing of less complex ingredients

v Small scale production

v Short life

v Higher heat production by friction

v Lower adaptability

Twin screw extruder 

Depending on the manufacturer, the twin screw extruder can be counter-rotating, co-rotating, intermeshing or non-intermeshing in relation to basic designs. Basically, the screw plan of the twin screw may affect the operating efficiency and capability of the device. Screw components in the feed division of the barrel may be solo, twofold or triple flight arrangements in some cases. 

In the meantime, beginners are often faced with difficulties when deciding whether to invest in the twin screw extruder or the single screw extruder system. Due the high amount of capital investment involved in each of these machines, it is vital to compare their benefits and shortcomings before making the final decision. For this reason, this article will focus on comparing twin screw extrusion versus single screw extrusion.

Characteristics of the twin screw extruder include:

v Long life

v Wide adaptability

v Higher shear rate

v Temperature-controlled

v Vacuum exhaust device

v Direct molding powder characteristics

v Ingredients easily broken down

v Suitable for production of complex ingredients

v Less heat produced by friction

v Materials/ingredients stay in the machine barrel, hence leading to better mixing

v Relatively stable and uniform transmission capacity 

Single screw extruder vs twin screw extruder

To come up with a design that has superior operating flexibility and with improved operational power, the twin screw extruders were designed. When investing in food extrusion processing, there are certain guidelines that should be considered. 

Below is a list of guidelines of most important processing advantages of the twin screw extrusion machinery:

1. Better levels of Flexibility in Production. 

Unlike the single screw extruder, the twin screw extruder is tailored with a throughput and screw speed independency, as well as the capacity to handle multiple processing functions such as mixing, cooking, cooling, melting, venting, and a lot more in a single screw extruder. On the other hand, the single screw speed and throughput are dependent, thus single screw extruders with multiple processing functions in series are limited. 

2. Improved Mixing Capability

To enhance mixing of ingredients, the twin screw extruder is modified with a broad diversity of specialized screw designs such as kneading blocks, reverse screw techniques, gear mixing elements and a lot more. With these features, the degree of mixing of ingredients can be adjusted accordingly, thus leading to better mixing intensity and quality. On the other hand, the mixing capacity of the single screw extruders is incredibly limited. Besides, the single screw extruder`s throughput tends to get depressed despite development of special screw designs and flow restrictions to enhance mixing. 

3. Higher Productivity

In terms of productivity, the twin screw extruder tends to have higher productivity than the single screw system. More particularly, the twin screw extruder has a better capacity to handle wider varieties of raw materials and complex formulations such as complex recipes. On the other hand, the performance of single screw extruders tends to decrease as screw wear increases. In twin screw extruders, wear and tear is compensated by high operational speed thus leading to higher process productivity. 

4. Improved Economic Opportunities and Business Potential

Compared to the single screw extruders, the double screw extruders have higher economical opportunities and business potential, thanks to their better productivity and higher flexibility. With higher process flexibility and productivity, the twin screw process can produce a wider range of products, convert materials, and handle product quality more consistently compared to the single screw extruders. More so, the twin extruders are also enabled to compensate the effect of screw wear and tear through screw speed adjustment. 

5. Enhanced Control of Process Parameters 

Unlike the single screw extruder, the twin screw extruder system is tailored with better regulatory mechanisms such as reduced dispersion of shear rates and strain, narrower residence time distribution, precise control of temperature profile, higher convective heat transfer; thus leading to enhanced control of shear-time-temperature histories in the extrusion process, increased range of mechanical power inputs as well as enhanced steadiness in product conversion and quality. In general, the twin screw extruder is much better in terms of control of process parameters as compared to the single screw extruder.

Twin screw extruder is better than single screw extruder

From above, it is clear that the choice of the type of extruder affects quality as well as the overall production efficiency. It is therefore important to consider the guidelines above when selecting the type of technology to invest in.

In conclusion, the single screw extruders are more affordable and economical to operate unlike the twin-screw extruders.

On the other hand, twin screw extruders are more productive; more advanced and have more extensive application than single screw machines. In a nutshell, the twin screw extruders have wider benefits which include higher levels of flexibility in production, higher productivity, higher mixing capabilities, improved control of process parameters, as well as improved economic opportunities and business potential. What’s more, the application of extrusion to the manufacture of foodstuffs will go on and will result in enhanced usage of the know-how in the future of the feed business.