Why Plastics Industry Feed Screws are Designed the Way They Are

Feed screw selection
Download the white paper here.

The selection of the proper screw for a given injection molding or extrusion application can be critical to its success.

Screw geometry — length-to-diameter ratio, profile, channel depth, compression ratio, helix angle and a host of special design features — has everything to do with how well the screw performs in a given application.

There are documented applications where customers have improved production rates or reduced cycle times by 30 or 40% simply by switching to an improved screw design. Similarly, reject rates have been lowered from more than 4-6% to less than 1% by incorporating a custom designed mixing screw.

And experience shows that the amount of color concentrate required to achieve optimum color mix can be typically reduced from 4% (of the total blend) to 2%, just by using an optimized screw design. When considering resin and concentrate costs, payback for an optimized screw and non-return valve design can be almost immediate.

This white paper, published by Glycon Corporation, provides an in-depth look into plastics industry feed screw design.

Vibration Control Systems from Crystal Instruments and AP Corp.

Crystal Instruments designs, produces, sells, and services hardware and software for machine vibration monitoring, dynamic measurement and environmental testing. The CoCo and Spider instruments have been widely used in machine condition monitoring and diagnostics by taking and analyzing the vibration signals. In the testing lab, professionals use Crystal Instruments products to conduct the measurement and control for vibration, shock, acoustic, pressure, temperature, humidity and other physical quantities.

AP Corp. applies, specifies, and supports the sales of Crystal Instruments products in Connecticut, Massachusetts, Vermont, Rhode Island, New Hampshire, and Maine.




AP Corp.
https://a-pcorp.com
(508) 351-6200

Occupational Health & Environmental Sound and Vibration Meter: The SVAN 977A


The SVAN 977A is a class-one sound and vibration level meter that offers unprecedented state-of-the-art technology designed for general acoustic, occupational health,  and building acoustic measurements of  vibration and environmental noise. The instrument comes equipped as standard with the SV7052E polarized half inch microphone, the SV12 microphone preamplifier, and the SA22 foam windscreen, as well as a large 16 gigabyte internal memory which can be easily upgraded by a micro SD card. The meter comes equipped with a standard quarter inch photographic thread. On the bottom panel you can locate the usb serial and I/O sockets. There is also a micro SD card slot under the bottom cover and spaces for the four double a batteries. The SVAN 977A is equipped with a super contrast led color display. The instrument's user interface makes both configuration and measurement easier than ever before. The user can easily operate the instrument by selecting the appropriate position from the selected menu lists.

The instrument has 2 general modes of operation: Configuration mode; and measurement performance and results preview mode. The SVAN 977A can be used in the meter mode to perform the real-time 11 octave or 1/3 octave analysis including calculations of statistical levels, and can also perform FFT analysis.  For building acoustic applications SVAN 977A offers reverberation time measurements RT60 and building acoustics assistant application for smartphones.

With a special microphone the meter provides measurement range of the ultrasounds up to 40 kilohertz. Measurement results can be viewed indifferent view modes, the set of which you can change and activate depending on the selected measurement function. If you disconnect the microphone preamplifier, you can use the instrument to take vibration measurements simply by connecting a cable and a vibration sensor.  SVAN 977A can be easily installed into the SM277 case and used as an outdoor monitoring station thanks to a dedicated modem station which enables connection to the SVAN NET, an advanced server solution supporting remote connection giving users full access to the measurement data via web browser or dedicated application.

For more information, contact AP Corp. by visiting https://a-pcorp.com or by calling (508) 351-6200.

US Power Grids, Oil and Gas Industries, and Risk of Hacking


A report released in June, from the security firm Dragos, describes a worrisome development by a hacker group named, “Xenotime” and at least two dangerous oil and gas intrusions and ongoing reconnaissance on United States power grids.

Multiple ICS (Industrial Control Sectors) sectors now face the XENOTIME threat; this means individual verticals – such as oil and gas, manufacturing, or electric – cannot ignore threats to other ICS entities because they are not specifically targeted.

The Dragos researchers have termed this threat proliferation as the world’s most dangerous cyberthreat since an event in 2017 where Xenotime had caused a serious operational outage at a crucial site in the Middle East. 

The fact that concerns cybersecurity experts the most is that this hacking attack was a malware that chose to target the facility safety processes (SIS – safety instrumentation system).

For example, when temperatures in a reactor increase to an unsafe level, an SIS will automatically start a cooling process or immediately close a valve to prevent a safety accident. The SIS safety stems are both hardware and software that combine to protect facilities from life threatening accidents.

At this point, no one is sure who is behind Xenotime. Russia has been connected to one of the critical infrastructure attacks in the Ukraine.  That attack was viewed to be the first hacker related power grid outage.

This is a “Cause for Concern” post that was published by Dragos on June 14, 2019

“While none of the electric utility targeting events has resulted in a known, successful intrusion into victim organizations to date, the persistent attempts, and expansion in scope is cause for definite concern. XENOTIME has successfully compromised several oil and gas environments which demonstrates its ability to do so in other verticals. Specifically, XENOTIME remains one of only four threats (along with ELECTRUM, Sandworm, and the entities responsible for Stuxnet) to execute a deliberate disruptive or destructive attack.

XENOTIME is the only known entity to specifically target safety instrumented systems (SIS) for disruptive or destructive purposes. Electric utility environments are significantly different from oil and gas operations in several aspects, but electric operations still have safety and protection equipment that could be targeted with similar tradecraft. XENOTIME expressing consistent, direct interest in electric utility operations is a cause for deep concern given this adversary’s willingness to compromise process safety – and thus integrity – to fulfill its mission.

XENOTIME’s expansion to another industry vertical is emblematic of an increasingly hostile industrial threat landscape. Most observed XENOTIME activity focuses on initial information gathering and access operations necessary for follow-on ICS intrusion operations. As seen in long-running state-sponsored intrusions into US, UK, and other electric infrastructure, entities are increasingly interested in the fundamentals of ICS operations and displaying all the hallmarks associated with information and access acquisition necessary to conduct future attacks. While Dragos sees no evidence at this time indicating that XENOTIME (or any other activity group, such as ELECTRUM or ALLANITE) is capable of executing a prolonged disruptive or destructive event on electric utility operations, observed activity strongly signals adversary interest in meeting the prerequisites for doing so.”

In-Line Color Measurement for Recycled Plastic

Recycled Plastic with Color
Photo 1 - Recycled Plastic with Color
INTRODUCTION 

Color measurement is a well-accepted technology to check the quality of the color values in the production process. Usually these measurements are performed "off-line".

The delay between sampling and obtaining the results from the laboratory can be time consuming. A significant disadvantage is that only a single measurement is generated in this time period and the quality of the color during, before and after the sampling point is unknown.

With the in-line color measurements taking place directly in the melt, not only is complete documentation possible, but when color variations occur, immediate intervention can take place.

Reflection probe
Photo 2 - Reflection probe in strand pelletizer.
When recycling plastic to convert to new uniform  colored pellets many challenges can take place. Recycled plastic is much more inconsistent than virgin material. Understand-ing this inconsistency will help on your color dosing to provide a more homogeneous final product. With the proper color measurement system you can know the color values of your extrudate in real time. This allows for closing the loop on your color by changing your dosing rates to meet your specifications.

INNOVATIVE NEW TECHNOLOGY

Photo 4 - Stainless Steel NEMA4 box with touch-screen.
Technology from Equitech, a manufacturer of in-line process instrumentation, deploys a probe directly in the molten polymer. Their Reflection Polymer Melt Probe (RPMP, Photo 2) is installed on the exit (adapter) of the extruder by using ½”-20 UNF thread (typically Dynisco®). The RPMP is screwed into position in the adapter between the extruder and the die. The RPMP consists of the threaded body and optical fibers. The sapphire lens on the tip of the probe is the observation window and is very well suited to the harsh conditions in the extruder (temperature, pressure, and friction through flowing material). The self-cleaning function of the sapphire is ensured by the shear force of the material flow. Ideal installation is directly into the melt stream in the adapter.

Off-line measurements are used more effectively by downloading them to the Equitech Inline Color Spectrophotometer. This can be done manually or through OPC communications. By having the laboratory target values displayed on the Equitech system the operator can view trends of L*, a*, b* and Delta E.

This method provides complete documentation of a particular extrusion run. It also matches the known laboratory measurements giving confidence that an extrusion run has maintained specifications throughout its entirety. When color variations occur, notification can take place via digital alarms. Intervention can take place via OPC or analog signals i.e. L* feedback for closed loop color control.

EquiColor Software
Photo 3 - Trend charts of EquiColor Software
COLOR MEASUREMENT 

Illumination of the polymer through the sapphire window is achieved by 6 circumferentially-positioned glass fibers which convey the light of a xenon flash lamp. The reflection from the illuminated surface is detected by one center-positioned optical fiber. This reflected light is then interpreted by the spectrophotometer. Color values such as L*, a*, b* C*, h are calculated from this spectral curve, and displayed as trend charts, (see Photo 3).

For a continuous process monitoring, 10 to 60 seconds is recommended as the measurement interval. Intervals as fast as 1 to 2 seconds are possible. The calibration of the spectrophotometer is designed specifically for the demands of the production process. Calibration can be done without interruption of the process.

USER BENEFITS
  • Real-time information about process stability & quality
  • Impact of speed changes on the quality of the extrusion
  • Controlled color changes: start phase, end of run  
  • Avoid off-specification batches & waste production
  • Detection of dosage elevations
  • Optimized recipe formulation & process design
  • Available feedback loop for L* closed loop control via feeder
  • Comprehensive quality audit trail customer documentation
For more information, contact AP Corp. by calling (508) 351-6200 or visiting https://a-pcorp.com.

Reprinted with permission from Equitech International Corporation.

The Three Most Common Types of Temperature Sensors

Temperature Sensors
Various types and styles of temperature sensors (Pyromation).

This post describes the three most popular temperature sensors, how they function, and where they are used.

THERMOCOUPLES


Thermocouples
Thermocouple illustration showing base metal designs
with various types of junctions (Pyromation).
Thermocouples are temperature sensing devices that operate on a phenomena called the Seebeck
effect. In the simplest terms, thermocouples produce a micro-voltage between two conductors - joined at each end and made of dissimilar metals - when one junction varies in temperature and the second junction (called the reference junction) is known and maintained at a constant temperature. The corresponding voltage produced at the sensing junction can be measured and directly correlated to the change in the sensing junction's temperature.

Thermocouples are popular and widely used in industrial and commercial temperate systems because they are:
  • Cost-effective.
  • Provide good accuracy.
  • Have a sufficiently linear temperature-to-signal output curve.
  • Are available in many different metal alloys for many different temperature ranges.
  • Are easily interchangeable.
Thermocouples require no external power source to work and can be used in continuous temperature measurement applications from -185 Deg. Celsius (Type T) up to 1700 Deg. Celsius (Type B).

Thermocouples are commonly found in many industrial processes. Examples are the plastics industry, primary metals, power generation, kilns, industrial boilers, HVAC, gas turbine exhaust systems and and diesel engines. And because they are affordable and easy to produce, thermocouples are also used in many consumer applications, such as residential and commercial cooking and heating equipment.

RTDs


Wirewound RTD
Wire wound RTD
(Image courtesy Wikipedia)
Resistance Temperature Detectors, referred to as RTD’s, are temperature sensing devices that determine temperature based on a relative change in resistance of the sensing element. The sensing element is a wire or etched circuit made from a metal with a well established resistance to temperature curve, most commonly platinum, nickel, or copper.  Platinum, nickel and copper are used because they produce a predictable and stable change in resistance as the temperature changes. Normally the wire is coiled around a bobbin (made of glass or ceramic), and inserted into a protective sheath. Alternatively, RTD's can also be manufactured as a thin-film, etched element with the pure metal deposited on a ceramic base, very similar to the way a printed circuit is made.

RTD’s are popular because:
  • They offer considerably higher accuracy and repeatability than thermocouples.
  • Can be used up to 600 Deg. Celsius.
  • Thin film RTD
    Thin-film RTD
    (Image courtesy of Wikipedia)
  • Can be integrated directly on the part to be monitored.
They are used where accuracy is important, such as in biomedical applications, semiconductor processing and temperature critical industrial applications. They tend to be higher priced than thermocouples because they are made of pure metals, and they do need an excitation voltage from an external source for the device to be read.


THERMISTORS


Thermistor
Another very common temperature sensing device is the thermistor. Thermistors are also a resistance measuring device similar to RTD’s. However, instead of using a pure metal as the resistance element, thermistors employ a very inexpensive polymer or ceramic resistance element. While these materials are very cost-effective, the downside is the resistance-to-temperature output curve. The change in resistance to a corresponding temperature change is very non-linear, and as such, make thermistors' use practical only within a narrow temperature range.

Thermistors are very inexpensive and have a very fast response making them very attractive in applications where a narrow sensing range exists and cost is important. Thermistors also come in two varieties, PTC, or positive temperature coefficient, and NTC, or  negative temperature coefficient. PTC's resistance increases with increasing temperature,  while NTC's resistance decreases with increasing temperature.

Thermistors are used widely in food processing in digital thermostats, and for on-board temperature monitoring of electronics and circuit boards. They are also used widely in many consumer appliances.

For more information on any temperature sensing application, contact AP Corp and discuss your requirement with one of their experienced application experts. They can be reached at (508) 351-6200 or visit them at https://a-pcorp.com.