To meet increased demand for in-line moisture meters, suppliers are launching new products and improving existing ones to help makers of plastic parts ensure resins are adequately dried prior to molding.
While underdrying of hygroscopic resins can result in streaks or bubbles in finished parts, overdrying can result in the finished product being brittle.
Some companies, including medical equipment and auto manufacturers, increasingly want verification of proper drying. In-line moisture meters help manufacturers provide evidence that parts were manufactured within specifications during the entire run.
"It provides quality control or validation data they could not otherwise provide," said Mark Haynie, VP of Novatec's dryer technology.
In-line moisture meters, as opposed to off-line or lab moisture meters, provide continuous monitoring of resin moisture during the manufacturing process. With off-line measurement equipment, small samples are taken throughout a production run and analyzed in a laboratory. However, in the time it takes to get results, a manufacturer could be turning out bad parts.
Continuous, instant monitoring allows for a quicker reaction.
"If you start seeing bad material, you could make an instantaneous change and stop making bad parts at that point, correcting an issue going on in your plant and not have made 45 minutes' worth of bad parts that you have to grind up and throw away," Haynie said.
Novatec, Moretto, Piovan SpA and MoistTech are among equipment manufacturers with new developments involving in-line moisture meters.
Moretto
Moretto announced in 2013 that it was developing a pilot in-line moisture meter technology. At the K show in October, Moretto announced its Moisture Meter was available for purchase globally.
The Moisture Meter is a compact instrument that fits underneath a drying hopper that allows the operator to read the residual moisture in the resin after it is treated. The device provides customers with real-time control. It can certify resin was dried within specifications and it can reduce energy consumption by preventing overdrying.
No calibration is required. Operators only have to select the polymer to be treated from a material database. Moisture Meter performs sampling every 2 seconds. With the Moisture Meter, operators can specify acceptable moisture levels in parts per million (ppm).
"You're not overdrying; you're not underdrying; you're getting it just right," a Moretto spokesperson said.
The Moisture Meter, which measures the moisture level of resin after drying, can be installed with any dryer system. However, it performs most efficiently when integrated with a Moretto drying system.
The Moisture Meter features the company's patented Power Peak technology, which uses electromagnetic waves to detect the amount of moisture in a pellet. The Moisture Meter is suitable for applications up to 3,300 pounds per hour and is capable of measuring to a minimum of 15 ppm.
Novatec
Novatec introduced its in-line MoistureMaster three years ago, but unveiled a significant upgrade at the beginning of this year.
"The really nice thing is, we have a sensor now that instead of being able to go down to 200 parts per million, it's able to go down to 50 parts per million," Haynie said.
The improved sensitivity will benefit processors of all types of resin, he said.
"Usually, if you get above 200 parts per million, you're going to have bad parts," Haynie said. "In order to be sure you are less than 200, a lot of people want to be able to measure down to 50 to 100 parts per million. That's where they really want to be. They don't want to be at that borderline 200 where you can start making bad parts."
Using an in-line moisture meter is a more accurate indicator of resin moisture than relying on measuring dew points, which indicate the amount of moisture in the air but not in the resin, according to Haynie.
The MoistureMaster is mounted at the discharge point for the hopper and measures 100 percent of the material that is coming out. The system consists of an electronic package and individual sensors.
"The electronic package is good for up to four sensors," Haynie said. "Typically, somebody will buy a sensor and an electronic package for a hopper and then add other hoppers to it over a course of time."
The MoistureMaster is able to provide the moisture content of hygroscopic plastics in either percentages or parts per million, according to the company. It can be connected with remote personal computers to provide trend charts for verification or validation processes. An alarm warns users if moisture parameters are being exceeded, and there are control options for a slide gate or diverter valve to prevent out-of-tolerance resin from being processed.
MoistureMaster's technology is based on capacitance and dielectric constants of resins and water, according to the company.
Una-Dyn/Piovan
Piovan launched its Aquality in-line moisture meter in 2010 at the K show following a developmental program that lasted more than a decade. Last year, it announced several enhancements to the technology. The Aquality moisture meter is available in the U.S. from Universal Dynamics Inc., the U.S. arm of Piovan, which is based in Santa Maria di Sala, Italy.
"The initial prototype units, put into operation in the late '90s, had the ability to precisely measure moisture in plastic pellets," said Giorgio Santella, Piovan's CMO. "However, the control stability back then was not sufficient to produce a reliable output signal."
Last year, the company enhanced the performance of the Aquality by introducing new software, a proprietary microprocessor control and a new moisture-sensing probe.
The main benefits of the upgrades are:
* instant real-time measurement of moisture levels in plastic materials;
* increased accuracy;
* quick sampling time of 200 microseconds; and
* CE certification.
The Aquality is able to measure moisture in plastic pellets down to values of 5 ppm at temperatures of up to 400 degrees Fahrenheit. Measurements are accurate to less than 1 ppm. It's more accurate than conventional moisture meters, according to the company.
The technology also means no routine maintenance is necessary. "Aquality does not need any periodic maintenance as it doesn't have any moving or perishable components," Santella said.
The sensor can be connected to either a dedicated terminal to display the moisture value or to Winfactory 4.0, Piovan software that allows communication among machines, systems and automation devices and with computer management systems.
The moisture meter works by determining the dielectric value of resin pellets.
Aquality can be used with any plastic material and is particularly suited for engineering polymers, where residual moisture control and stability are especially important.
MoistTech
MoistTech has begun marketing its MoistTech IR-3000 in-line sensor to the plastics industry to measure the moisture content of resin pellets, flake or regrind.The IR-3000 moisture meter uses near-infrared technology for instant, noncontact measurement of moisture in nearly any raw material.
The company initially introduced moisture meters for use with wood products, food products and coal. In late 2015, it decided to begin marketing the meter for plastics industry use. Last June, the company began offering a filter variation for use when reading moisture levels in colored plastics.
"Insensitive to material variations such as particle size, material height and color, the IR-3000 online process moisture analyzer provides continuous, reliable readings," the company said in a statement.
The sensors can be used with any hopper, silo, material line, or bent or screw conveyor, and the moisture results, in either percentages or parts per million, are displayed on a color touch screen or transferred to a personal computer through an Ethernet connection.
Off-line moisture analyzers use a sample size that is too small to be a true representation for some applications, and they are ineffective at preventing bad parts because the part has already been produced by the time the test is done, according to the company.
Instead of relying on a 10-gram sample to represent an entire hopper full of resin, an in-line moisture analyzer allows an operator to know the moisture content of all the resin coming out of a hopper, going into a machine or even at the hopper inlet, according to the company. That information allows the operator to adjust drying times based on moisture content before drying takes place.
The result is improved quality and lower production costs through reductions in energy consumption and wasted material, the company said.
Bruce Geiselman, senior staff reporter
For more information
MoistTech Corp.,Sarasota, Fla., 941-351-7870,www.moisttech.com
Moretto USA LLC,Columbus, Ohio, 614-541-9696, www.moretto.com/en/
Novatec Inc.,Baltimore, 410-789-4811,www.novatec.com
Universal Dynamics Inc.,Woodbridge, Va., 703-490-7000,www.unadyn.com
Bruce Geiselman | Senior Staff Reporter
Senior Staff Reporter Bruce Geiselman covers extrusion, blow molding, additive manufacturing, automation and end markets including automotive and packaging. He also writes features, including In Other Words and Problem Solved, for Plastics Machinery & Manufacturing, Plastics Recycling and The Journal of Blow Molding. He has extensive experience in daily and magazine journalism.
