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Skills Required For An Rubber Extruder Operator: What No One Is Talking About

To a layman and HR Department of most organizations, an extruder operator is a person who operates and maintains this rubber machinery. Period!

Is that it?

Operator

An Image From Web

Depending upon your final product, rubber extrusion could be either a very important or the most critical manufacturing aspect of your operations. Thus the skills required for your extruder operator are paramount.

Extruded rubber products differ from those produced through moulding. In extrusion, parts are forced through a die of the required cross section under pressure of an rubber extruder. The extrusion process begins when you feed the unvulcanized rubber compound into the extruder. The rubber travels over the flutes of the revolving screw into the die, with the pressure and temperature increasing as the compound gets closer to the die. And when it reaches the die, the built up pressure forces the material through the die-opening, where it will consequently swell in various degrees based on your compound and hardness.

Most extruded products are unvulcanized before extrusion. This leaves the the rubber in a soft and pliable state post-extrusion. Hence they need to be vulcanized before they are they are rendered usable. During the vulcanization, the extruded rubber will swell or shrink in both its cross section and its length (again based on the type of rubber compound used).

Hence, the cost of errors or omissions could turn out to be very high when extruding rubber. You need a skilled operator.

Rubicon-Halle Extruder

Image of Rubicon-Halle Extruder

Here are the skills required for an rubber extruder operator.

Monitoring and Control Of Operations – The most important skill of your extruder operator should be to have a keen eye for watching gauges, dials, or other indicators in the control panel to make sure the extruder is working properly. Your extruder operator should be able to adjust screw speed, set water flow to the required rate, operate temperature control unit (TCU) or the metal detector in cold feed extruders, observe the extrusion parameters and ensure adherence to SOP (temperature or die swell). He has to ensure that the extruder, dies and its allied downstream equipment are kept clean, safety features are functional, and all accessories are ready.

Quality Control Analysis – Conducting tests and inspections of products, services, or processes to evaluate quality or performance is a desirable basic skill that your operator should have. This could be as critical as preventing wastage (from scorch of your rubber extrudate) to as trivial as sending the sample to lab for testing.

Critical Thinking, Judgement and Decision Making – Operating a rubber extruder requires critical thinking skills because your operator should use logic and reasoning to identify alternative solutions, conclusions or approaches to problems he faces while extruder is in operation. There could be many problems while extruding rubber like die-swell, melt fracture, or poor appearance amongst others. While all of them may not be extrusion related, your operator should be able to judge the gravity of the error and also decide what to do about it – whether to fine tune the extruder operating parameters, or escalate to supervisor or raise a service visit request of the manufacturer’s engineer.

Troubleshooting, Repairing & Maintenance – Your operator is the first point of contact with your extruder in operation. Hence, he should have the experience or knowledge on extruders to determine the causes of any operating errors when they occur. Performing routine maintenance and determining when and what kind of maintenance is needed is an important skill that your operator should posses. He should be able to use the required tools to both repair and assist repair of your extruders when needed in the most urgent manner.

Complex Problem Solving – As a addendum to the above skill, your operator should develop skills to identify and solve complex problems when they occur at site and support maintenance department effectively over a period of time. This will reduce the downtime of your extruder and ensure maximum availability at site.

Speaking – Your operator should be able to talk to you (or his supervisor) to convey information effectively be it to report data/problems/incidents as applicable in a timely manner.

Reading Comprehension – Extruders have an operating and maintenance manual supplied by the manufacturer. This is a crucial document that requires a reading by your operator for his safety, training as well as equipment safety. Again your extrusion process would have specific work related instructions or SOP. Your operator should be able to understand written sentences and paragraphs in these documents. Hence, reading skills is very important for a successful operator. It is not necessary (while it is preferred) that they read English, because you could translate these documents to your operator’s local language for ease of reading.

Active Learning – Your operator should display active learning skills.  This is because, the sophistication of the rubber extrusion machinery has risen over the years. Automation and new controls might get introduced or new parameters of extrusion could be introduced further too –  all of which he might have to learn or get trained in.

Summarizing, your rubber extruder operator needs high level of skills to give you maximum output. Hence, its wise that either you hire a skilled operator or train your operator to upgrade his skills. Your extruder operator must stay up-to-date on current and developing technologies and techniques. He must also have a solid understanding of safety techniques and practices.


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Here’s Why TCU Is An Irresistible Ancillary For Your Rubber Machinery And Worth Your Investment.

TCU or Temperature Control Units are ancillary equipment to your rubber machinery that control process temperatures during rubber processing. During rubber processing, you continually seek optimal temperatures for the best product quality.

A TCU achieves temperature control by circulating water or an oil based fluid through the process application (in a closed loop). This results in heating of the application and temperature control of the process.

Temperature control units service a single process at any one time. In rubber industry, water is most popular circulating media.

For example, you have Three-Zone Water TCU’s for your internal mixer where One Zone supplies water to the Rotors, Second Zone to Drilled Sides (or Mixing Chamber) and Third Zone to Discharge Drop Door (and Floating Weight, RE Plates as appropriate to the mixer model). Usage of TCU in an intensive internal mixer is found to improve carbon black dispersion, eliminate first-batch-effect, maintain batch-to-batch consistency of your rubber mix compound, increase productivity, and reduce machine stress (which in turn increases the life of your internal mixer).

Similarly, you have 4 or 5 Zone TCU’s for your Extruders, where each of the zones supply water to screw, forward and rear barrels, die head, feed roll, etc as is required for your rubber extrusion process. Or you may have Two-Zone TCU for open two-roll mixing mills where each zone supplies water to your peripherally drilled or cored rolls. Most Rubber Calenders also have TCU supplying water to the rolls to control the calendering process temperature.

TCU for a 3-Roll Calender

3-Zone TCU for a 3-Roll Vertical Calender – Image from Bainite Machines Website

A properly installed, operated, and maintained TCU system gives you years of reliable operation.

Each TCU is a self-contained system consisting of a centrifugal pump, electric heater, cool/vent solenoid valve, electrical control, including a PID microprocessor controller and thermocouple along with standard safety devices like a mechanical over temperature safety thermostat, a pressure relief valve, motor overload protection, a low pressure cut out switch, etc.

Temperature Control Units come both in portable and robust sizes (depending on the application) with a variety of different control instruments, heater sizes, and cooling vales.

A Compact TCU

Compact TCU – Image from AEC Website

And you are right when you imagine that the portable TCU’s are visually appealing and popular because of their compact size.

At your installation site, you need to provide adequate water (from portable or central chillers or towers) to these TCUs from your plant water supply source. Check your manufacturer’s operations manual to verify the recommended water pressure requirement. This is important because lower than recommended water pressure can cause pump cavitations while excess pressure can damage internal components.

The pump in your TCU is used for rapid circulation of a relatively small amount of water. This in turn ensures close and uniform temperature differences between the delivery and the return lines.

You use temperature control units, when you want to preheat a process to the desired operating temperature. The heater and  cooling valve works together to give fast and accurate response to bring the water up to desired temperature or to change the settings when needed. This controls your circulating water temperature.

Here is an animation, that I found on the website of Sentra Temperature Controllers. It is quite informative and I hope you too like it. (Click on the picture to start animation)

Advantage Make TCU

Upon reaching your desired operating temperature the TCU can continue to add heat or convert into a cooling device by exchanging a small amount of circulated water with cooling water from an external source. Modern TCU have the controls wherein cooling water is precisely metered into the system by the cooling valve.

Most TCU’s in rubber industry for your machinery has temperature control from 30° to 300°F and designed for easy maintenance.

Summarizing, rubber processing under optimal temperature conditions is a must for your final product quality. And the features of TCU makes it irresistible as an efficiency enhancing ancillary equipment, which control process temperatures on your rubber machinery. Thus worth your investment.

Do you agree?


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A Dummies Guide to Rubber Extruders

Rubber extruders have a varied field of application. So, when you come across a rubber profile, strip, hose, cable, wire, cord coating, tire tread, v-belt, tube, or blank remember that they are only a few handful of products manufactured using extrusion process. 

And your main goal of extrusion is to get the highest output at good quality of product.

Based on the convenience and usage history, you need to know of the two types of rubber extruders viz. Hot Feed Extruders (HFE) and Cold Feed Extruders (CFE).

And further, you have variants within Cold Feed Extruders viz. Plain Type, Pin Barrel Type and Vent Type Extruders. The recent most advanced adoption that you will come across is that of co-extrusion lines.

When you choose a rubber extruder, you should deliberate and discuss extensively upon few key things i.e the design, material technology and manufacturing accuracy of screw, barrel and die-head. While, I would cover more on them in a later post, I would like you to remember that very few manufacturers world-wide can guarantee you a well-designed and precisely manufactured rubber extruder.

Hot Feed Extruder (HFE)

Rubber industry only had Hot Feed Extruders until 1950’s. HFE’s extrude your rubber compounds at reduced temperatures.

Hot Feed Extruder with Dual Head

Bainite Machines Make Hot Feed Extruder

The screw depth of a HFE is relatively larger and you get a consistent output due to its short screw design. L/D ratio is mostly in the range of 4:1 to 6:1 which keeps your rubber compound dwell time and its temperature increase to a minimum.

Each HFE has an hopper and feed roller section with spiral undercut liner that allows your compound to enter the extruder easily. The feed roller on a hot feed extruder allows your compound to pass the scraper knife, directed around the roll and then fed back into the hopper. The feed roll bearings are placed in positions to prevent contamination. You can vary the output by changing the screw speed using variable speed drives.

Despite these advantages, the HFE’s are getting outdated in many applications.  Because the rubber that is fed into a Hot Feed Extruder needs to be pre-heated or warmed using two-roll mills to achieve the required degree of viscosity and temperature that facilitates smooth flow of rubber, its compaction and extrusion through the die.

And that made experts introduce Cold Feed Extruders.

Cold Feed Extruder (CFE)

Cold Feed Extruders are designed and manufactured with specially designed screws best suited for cold feeding of rubber. You can discuss with your manufacturer and avail various options of screws for a wide range of compound and extrusion applications.

While manufacturers offer L/D ratio up to 24:1, the most preferred by end-users is generally in the range 12:1 to 18:1.

Pin Type CFE

Pin Type CFE Image from Web

For feeding the cold rubber, it is recommended that you use a feeding conveyor with metal detector to remove metal particles. This avoids damage to the screw or barrel. In some plants, I find the sensitivity of the metal detector calibrated to a low value that it virtually renders the detector useless.

Every CFE comes with a Temperature Controller Unit (TCU) that controls the barrel temperature so that the shape and size of the extruded products are uniform.

Variants in cold feed extruders along with their uses are

  1. Plain Barrel Type Cold Feed Extruder – These CFE’s as the name suggests have a plan barrel and used in manufacturing of hoses, blanks, fluorocarbon rubber, butyl rubber, etc.
  2. Pin Barrel Type Cold Feed Extruder – These CFE’s have around 80-100 pins protruding out of the barrel towards the screw center. These pins enhance the mixing and dispersion of your rubber as it is kneaded between the barrel and screw. And the result is processed rubber with outstanding homogeneity and extrudate quality. This flexibility in Pin Type Cold Feed Extruders endears to all making it a universal extruder for many rubber compound formulations involving varied applications. Hard rubber compounds also can be processed because of high extruder torque.
  3. Vent Type Cold Feed Extruder – Vent type or vacuum type extruders were developed for production of non-porous profiles and hoses. These CFE’s have a custom-built screw, and a degassing barrel with a vacuum pump attached to vent bubbles out of extruded compounds.
Triplex Extruder

Nakata Make Triplex Extruder

Co-extrusion: Customer-specific customization and usage complexity demands led to the introduction of co-extrusion for manufacturing of various profiles. And so you today have Simplex, Multiplex (Duplex, Triplex, Quadruplex, and Quintuplex) and Roller Head technology. Multiplex lines of piggy-back type of 2,3,4, and 5 layers have a compact construction.

Roller-Head-Extruder

Berstoff Make Roller Head Extruder

Roller Head Technology involves a combination of extruder with preform head and two-roll calender. They offer twin advantages of – high uniformity of the material thickness over the entire sheet width with absence of air traps even at higher thicknesses (~ 20mm thick as against conventional calender lines that give max 3mm thick sheets with or without air traps) and excellent homogeneity of the material produced.

Both these characteristics are important for high-quality rubber products such as tire components, V-belts, conveyor belts, tank linings, cover sheets, blank sheets and roofing sheets, etc. For even thickness across the entire sheet width of the roller head, there are three options that can be used alone or in combination with one another – roll crowning, roll crossing or roll bending, that will compensate for the elastic deflection of rolls. (I will cover more on these in an another post)

In today’s world you will see that usages of these technologies are overlapped. For example, in tire industry, you can notice that
Tread & Sidewall are extruded using Simplex, Duplex, Triplex, Quadruplex Lines
Apex are extruded using through Simple & Duplex
Inner Liner are extruded using Simple, Duplex & Roller Head Technology

Rubber extrusion is in itself a vast subject, however if you know the above terms and types of rubber extruders, you have made a good beginning.


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Top 15 Skills Required For An Internal Mixer (or Kneader) Operator

Rubber Mixing is a capital and energy intensive operation. And mixing machinery are the mother equipment. This could be an Internal Mixer (Banbury or Intermix) or Rubber Dispersion Kneader depending on the size of your organization and/or products manufactured.

Hence, the cost of errors or omissions are very high when compounding a batch in a mixer. You need a skilled operator. Ever pondered on the skills that make a mixer operator successful?

Internal Mixer Operator

Here is the list of top 15 skills for an successful batch mixer (or kneader) operator. (Updated on 23rd Dec 2015: Flip through this post in our digital edition and download here)

  1. Control of Operations – Your mixer operator should be able to adjust ram pressure, control the mixing process, set parameters and ensure its completion as per SOP (temperature or time or energy as programmed/specified).
  2. Monitoring Operations – The most important skill of your operator should be to have a keen eye for watching gauges, dials, or other indicators in the control panel or HMI to make sure the mixer is working properly. He has to ensure that the mixer is kept clean, safety features are functional,  upstream and downstream equipment along with all accessories (like cooling water, hydraulic/pneumatic system, temperature control unit (TCU), lubrication system, etc) are ready
  3. Active Listening – Your operator should be a skilled listener. He should actively listen to the sounds of the mixer and its motor during a mixing cycle; pay full attention to what his supervisor (or you) or his colleagues on the mixing room safety are saying, take time to understand the points being made, and ask relevant questions.
  4. Speaking – Your operator should be able to talk to you (or his supervisor) to convey information effectively be it to report data/problems/incidents as applicable in a timely manner
  5. Reading Comprehension – An operating and maintenance manual is normally supplied together with the rubber mixer. This is a crucial document. Again your compounding process may involve specific work related instructions or SOP. Or there could be a training manual in some instances. Your operator should be able to understand written sentences and paragraphs in these documents. Hence, reading skills is very important for a successful operator. It is not necessary (while it is preferred) that they read English, because you could translate these documents to your operator’s local language for ease of reading.
  6. Troubleshooting, Judgment and Decision Making – Your operator is the first point of contact with your mixer in operation. Hence, he should have the experience or knowledge on mixers to determine/read the causes of any operating errors when they occur, judge the gravity of the error and also decide what to do about it – whether to reset the mixer, or escalate to supervisor or raise a service visit request of the manufacturer’s engineer.
  7. Critical Thinking – Operating a rubber mixer requires critical thinking skills because your operator should use logic and reasoning to identify alternative solutions, conclusions or approaches to problems he faces while mixer is in operation.
  8. Quality Control Analysis – Your operator should have basic skills on quality control with an outlook to meet your set mix quality parameters in every batch. This may involve need for appropriate fine tuning like helping you fix the batch weight, or sending the sample of specified compound/ batch in specified form to lab for testing.
  9. Social Perceptiveness – Emotions could run high in the rubber mixing room. Your operator should display “awareness” of others’ reactions and understanding of why they react as they do in a particular circumstance.
  10. Repairing – Your mixer operator should be able to use the required tools to both repair and assist repair of mixers when needed in the most urgent manner.
  11. Time Management – Your operator should manage his own time and display sensitivity to the time of other co-workers involved in the mixing room.
  12. Mixer Maintenance – Performing routine maintenance on mixer and determining when and what kind of maintenance is needed is an important skill that your operator should posses.
  13. Active Learning – Your operator should display active learning skills. This is because, mixers get upgraded, automation and new controls might get introduced or new methods of mixing could be introduced all of which he might have to learn or get trained in.
  14. Writing – If you could get an operator who could communicate effectively in writing to you (or his supervisor) or to other departments, then I would say you have a great asset.
  15. Complex Problem Solving – Your operator should develop skills to identify and solve complex problems when they occur at site and support maintenance department effectively over a period of time. This reduces the downtime of your mixer.

Do you agree the above listed 15 skills, required for an Internal Mixer or Kneader Operator, are comprehensive? Let us know.


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