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Introducing a compounding extrusion line into your manufacturing operation is a complex undertaking that can pay great dividends. Choosing the right vendor with the right expertise is the difference between success and failure.

Depending on what ����ý need is driving your decision to purchase an extruder alone or components to build an entire extrusion line, a full analysis of your project — including the space, budget and personnel required— begins by selecting a knowledgeable partner.

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To be sure, if you already have in-house experience building and running a compounding extrusion line, that expertise is a significant advantage in installing another line. However, even experienced compounders will seek expert input. 

For example, if you’ve developed a new formulation and never produced pellets with it, starting that line carries significant risk. Creating pellets with biodegradable polymers containing PHA or PLA presents still more unique challenges, primarily in shear issues and ignition temperatures. Having additional outside experts on hand to ensure production kicks off smoothly is a worthwhile investment.

Producing pellets can create unique challenges. For instance, when compounding biodegradable polymers containing PHA or PLA, shear issues and ignition temperatures need to be considered. Having outside experts on hand to ensure production kicks off smoothly is a worthwhile investment. Source: ENTEK

Business Cases

Business cases for building a compounding extrusion line run the gamut from making small masterbatches to supplying a high volume of material for a new product. 

Depending on the material volume required and the level of in-house expertise, a manufacturer might simply buy an extruder and assemble the rest of the compounding line themselves. Another option is to purchase a turnkey system, including feeders, material handling equipment and more, from one source.

The complexity of the mixing process is a key determinant. For instance, the most basic line might be used to make pellets with a color concentrate on a simple mixing system in which five or six ingredients are mixed, taken to a single feeder and fed into an extruder. Compounded material then goes through a pelletizer to create the end product. A ����ý with five or six of these lines can easily duplicate them without having a lot of engineering support in-house.

Consider a vendor that has the necessary expertise to not only sell you a system but help you get the most out of it over time.

A more complex operation, with all compounding performed at the extruder instead of in a mixing room, requires multiple loss-in-weight feeders — up to eight or nine depending on the number of products requiring material. A compounding line of that size will require a mezzanine over the extruder and the appropriate material handling system to fill an array of feeders. Even operations with in-house engineering support might opt to choose an experienced vendor to assist in building such a complex system.

Choosing an Extruder

The extruder is of course the heart of your compounding line — and choosing the right screw size depends on the size of your production runs, the amount of material you’re making and the price of raw materials.

General guidelines: 

• An extruder with 27-mm screws is an ideal machine for lab use. 
• The most common extruders for compounding run from 33 mm to 53 mm. 
• Large-scale pelletizing applications (hundreds of thousands of pounds per year) might require a 73 mm — and occasionally a 103 mm — extruder.

Because there is always some waste material at startup, the smaller the extruder the less initial waste. That’s important when handling the costlier materials. Smaller extruders are also easier and faster to clean during job changeovers. 

Finding Space

Ceilings: The size of your compounding extruder line determines the space required to locate it. The key factor here is head height over the line. Standard ceilings can accommodate lines featuring 33- to 53-mm extruders. But 73 mm and larger which require bigger material handling equipment, will require more ceiling height.

Many factors need to be considered when adding a compounding extrusion line to your facility, including floor space, ceiling height, utilities and more, often requiring modifications to your plant’s infrastructure.

Utilities: Power and water requirements for compounding lines with extruders of 33- through 53-mm are relatively low and can often be accommodated with the existing infrastructure. The utility requirements for large extruders often require modifications to a facility’s infrastructure.  For instance, a 73-mm extruder can have a 600-hp motor, requiring more power than what is available. Bringing in a new transformer is a significant additional expense. That added expense might lead an operation sticking with a 53-mm extruder.

Planning and Executing the Installation

The number of players involved in planning the design and installation of a compounding extrusion line is another critical factor for a successful operation.

With enough in-house engineering experience, an operation might choose to buy components — the extruder, pelletizer(s) and material handling equipment —  individually from different vendors. But making components from different vendors work together seamlessly can be a challenge. 

The fewer players involved means less chance of having to troubleshoot complex equipment communication failures among disparate brands.

Choosing a Vendor

While you are planning to introduce a compounding extrusion line into your operation, you’ll want to carefully consider a vendor which has the necessary expertise to not only sell you a system but help you get the most out of it over time.

A qualified supplier should be positioned to lend its know-how on how to optimize your new compounding line, including the advantages of water baths, slides and underwater pelletizing.

The ideal vendor can demonstrate expertise with components throughout the compounding extrusion line — from the extruder itself to the feeders, pelletizers, controllers and more.

Questions to ask your vendor:

• Lab resources: Can you run preproduction material tests to screen for processing performance and inform equipment decisions?
• Pelletizing: Do you understand the advantages of underwater pelletizing, water slides or a water bath with a rotary cutter?
• Feeders: Can you advise on the benefits of volumetric vs. loss-in-weight options?
• Changeovers: Do you provide quick-change capabilities for replacing screws?

Feeder Know-How 

It’s worth noting that as soon as a second feeder is added to a compounding line, formulation consistency — and potential deviations — becomes a critical issue. For instance, if you’re selling pellet comprising 50% calcium carbonate and 50% polyolefin, a second feeder of the wrong type could introduce a variation that could veer off to as much as 40% of one and 60% of the other.

Additional considerations regarding feeders include: 

• Most compounding lines will use loss-in-weight feeders.
• Powder cannot typically be fed through a pellet feeder.
• Some powder feeders can feed pellets if the screen and/or tube is changed. While you don’t want to pay extra for the agitation capability that powder requires, the pellets of some materials stick together and therefore require that additional agitation. 

Side feeders, vacuum stuffers and other equipment can be used for better compounding quality, efficiency and safety.

Maintaining Barrels and Screws

The primary wear items on extruders are the barrels and screws. Improper alignment will shorten their lifespan because they are rubbing together — and making metal scrap instead of parts.

Wellness checks are an ideal way to ensure your barrels and screws function properly and enjoy long life. Even compounders who have extensive experience will call in external experts to assess the health of their equipment, as alignment and wear assessment require the utmost accuracy.

Questions to ask your vendor:

• Do you have the expertise and personnel to keep equipment running and support any level of in-house competency with compounding extrusion lines? 
• Do you include a built-in maintenance schedule to alert operators when it’s time to perform critical tasks such as changing gearbox oil or torquing the heaters?
• Do you provide services for monitoring and maintenance with laser-alignment tools and wear-assessment tools?

All considered, there are tremendous benefits to installing a compounding extrusion line in your operation. Choosing the right vendor with the proper range of expertise in all the equipment required is the first step toward successful compounding operations.

About the Author: Al Bailey is ENTEK’s sales engineer. In this role, he assists with mechanical and electrical quoting for turnkey projects, interviews contractors and prepares detailed schedules for entire projects from the engineering phase through equipment and plant build, installations, startup and training. A 1992 graduate of Eastern Washington University with a degree in mechanical engineering technology, Bailey has worked at ENTEK since 1995 when he joined the company as a controls engineer. Contact: abailey@entek.com; .