How Screw Design Can Boost Output of Single-Screw Extruders

Optimizing screw design for a lower discharge temperature has been shown to significantly increase output rate.

Troubleshooting Vent Flow Problems in Single-Screw Extruders

Troubleshooting Vent Flow Problems in Single-Screw Extruders

Vent flow can be a costly problem and a housekeeping nuisance. Here is some advice on how to eliminate it.  

The Right Way to Design Vents in Single-Screw Extruders

Designing vents for single-screw extruders requires understanding of polymer flow in the screw channels. Some designs are more effective than others. Here are some guidelines.

Extruder Alignment: Important, but Only Half the Equation

The other half? Aligning and supporting downstream equipment. Here are best practices.

How Much L/D Do You Really Need?

Just like selecting the extruder size and drive combination, the L/D should be carefully evaluated.

Take Proper Care in Feeding Your Extruder

Everything that happens in an extruder starts at the feed throat, so proper attention to that zone’s temperature pays off in quality and productivity.

Smaller Screws Impose Bigger Challenges

Very small extruder screws work just about like their larger cousins, but some critical differences make them harder to design and machine.

How to Estimate and Control Head Pressure

You rightfully worry about melt temperature, but don’t overlook head pressure, because the two are closely linked and will influence line performance.

Cooling the Feed Throat and Screw: How Much Water Do You Need?

It’s one of the biggest quandaries in extrusion, as there is little or nothing published to give operators some guidance. So let’s try to shed some light on this trial-and-error process.

Extruding PCR? Consider a Vented Extruder

You’ll need two-stage screws to extract volatiles that post-consumer reclaim will likely contain. Screw design can be a complex balancing act. Here’s what you need to know.

The Importance of Viscosity in Melting

The calculations required to determine the right melt temperature for each polymer are complicated. Knowing the power-law coefficient and the consistency index of the polymer you run might prove useful.  

Why Are There No 'Universal' Screws for All Polymers?

There’s a simple answer: Because all plastics are not the same. 

Understanding Melting in Single-Screw Extruders

You can better visualize the melting process by “flipping” the observation point so that the barrel appears to be turning clockwise around a stationary screw.

Minimize Sheet Gauge Variation by Roll Design

‘Hour-glass’ sheet gauge can be avoided through a reverse-bending roll design that is out of patent and freely available.

The Importance of Specific Heat in Screw and Extruder Design

If you ever have to size an extruder drive, knowing the specific heat of the polymer can help you to determine the capability of your equipment.  

Understanding the Influence of Screw Geometry on Melting Rate

They are not as closely connected as most processors think. Here’s why.

Understanding Roll Deflection in Sheet Processing

Because of roll deflection, sheet stacks made for PS don’t work nearly as well with PP. One solution is to try a top roll that bends in the opposite direction.

How to Select the Right Cooling Stack for Sheet

First, remember there is no universal cooling-roll stack. And be sure to take into account the specific heat of the polymer you are processing.  

Put Science into Glass-Fiber Compounding on Single Screws

There are still companies that compound glass fibers on single screws. The process is considered an “art,” but can be made more predictable with attention to screw design, speed and length, as well the choice of mixer.

Extrusion: Follow These Tips to Get Profile Die Design Just Right

Calculating polymer flow is fairly straightforward when designing a die for a simple round profile, but as the shapes get more complicated these calculations can get extremely challenging. Here’s what you need to consider.  

General-Purpose Screws on the Comeback?

They are being specified more often for recycling applications to increase flexibility. But there is still no such thing as a GP screw and recyclers need to consider other processing approaches.

The Three Causes of Screw Wear

You run the risk of wasting time and money by not understanding what’s causing your screws to wear.

Extrusion: Solving Surging in Two-Stage Screws

This usually crops up when the two stages are not matched in output. The best solution is to install a pressure-adjusting valve at the discharge end of the extruder.