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Optimizing Your Molding Cycle

By: Garrett MacKenzie 3. August 2016

It is possible for machines to run too fast—find the sweet spot where maximum output overlaps with good parts.

 

In today’s fast paced plastic injection industry, lean manufacturing is a primary driver of profitability. Without lean, organizations find their operations are sluggish and ineffective. This not only affects a company’s ability to successfully grow and prosper, but the capability of taking on new work also suffers because current systems have not been effectively streamlined. This article addresses cycle time optimization, outlining the different variables within the molding process that can be used to maximize profits.

 

One of the first points that needs to be made when addressing this topic is to acknowledge that it is possible for machines to run too fast. Every molding job is different, and the following conditions must be satisfied to properly assure that the optimization is successful:

 

  1. Quality is key to the integrity of every molding operation. Running too fast to provide adequate operator inspection defeats the purpose of effective production. Rework and scrap reduce productivity, so steps must be taken to assure that quality is not affected by optimization.

 

  1. Keep optimization tactics real and consider potential failures that could occur due to optimization. For instance, knocking 10 seconds off of a job molding nylon parts sounds fantastic, but if the lower cooling time increases shrinkage, it could potentially throw parts out of spec dimensionally.

 

  1. During the optimization process, be vigilant to make adjustments slowly. When changes are made to the process in clusters, make the adjustments and then allow ample time for changes to take effect. Then take sample parts for part layout and PUT THE SETTINGS BACK until the parts and process have been validated. Sample runs should always be run separately from production as a means to prevent suspect parts from getting to the customer.

 

Following the steps above helps to prevent costly errors that can occur with poorly planned optimization events. Optimization is a fantastic tool when properly applied to your molding operation, but only with the understanding that proper approach is crucial to the success of continuous improvement.

 

The following list outlines many of the parameters that can be considered when reducing the cycle time of a molding operation:

 

Cooling Time: Cooling time is one of the easiest avenues of optimizing your cycle. In most molding scenarios, cooling time is set 1.5 to 2 seconds longer than screw rotate time. It is important to point out that there are situations that may require a longer cooling cycle (such as dimensional requirements or parts sticking), but as a general rule screw rotate time establishes cooling time.

 

Hold Time: Hold Time is another major contributor to maximizing cycle time. The best method of accomplishing this is through a gate-seal study. Gate seal is the amount of required hold time needed to cool the runner tip into stasis. This prevents plastic from leaking back out of the runner, which leads to molding inconsistencies.

 

Performing a gate seal study is simple—once a decoupled process has been established, set the hold time well above what is generally common for the material and part size you are working with. While running, make reductions to the hold time and weigh each part as it relates to the change. Watch for a weight reduction, and when part weight drops, add 1 second back to the hold time and the test is complete.

 

Fill Time: Fill time is another parameter that affects cycle time. Injection speed controls how fast or slow the resulting fill time is. Of course, the type of material and mold complexity put constraints on fill time. Based on this, the goal of optimizing fill time is to shoot material as quickly as possible without affecting the aesthetics and functionality of the parts being produced.

 

Melt Temperature: When setting up a process, using minimal temperature helps reduce cooling time, which in turn, helps improve cycle time. It is important to note that every processing approach is different, so the higher viscosity of a lower melt temperature could lead to defects. Start your process at the lower end of the melt window, and as you make adjustments, raise temperatures until you achieve process stability.

 

Mold Temperature: Mold temperature also affects cooling time. When establishing mold temperature, start at the lower end of normal processing recommendations from the material manufacturer. Higher temperatures might be required to improve aesthetics, and even part removal. Mold temperature also affects dimensional properties, so this needs to be taken into consideration.

 

Back Pressure: Higher back pressure increases screw rotate time, which can affect minimum cooling time. Use enough back pressure to achieve melt consistency, but keep it as low as possible to reduce screw rotate time.

 

Mold Open/Mold Close: Maximize mold open and close speeds to reduce mold open time. Here it is important to note that mold breakaway and mold close speeds are affected by the complexity of slides, horn pins, etc. so make safe operations of your molds the first priority as you set them up. In addition, watch low pressure close—you want to keep it as low as possible for mold protection, but remember that with speed/pressure set too low, they can add to overall cycle time. Again: safety and mold protection take first priority over optimization.

 

Ejection: Improper ejection set up can adversely affect cycle time. During ejection set up, use only the amount of stroke you need to remove the part safely without the part sticking in the mold. Ejection speed and pressure are also important to faster ejection time, but it is important to note that when increasing speed/pressure set points, watch for pin push or cracking. Minimal pressure and maximum speed will generally produce the optimum result.

 

Robot: Robot function also affects cycle. There are two primary effects that can be optimized. First, the robot needs to get in and out of the mold quickly to prevent an increase of mold open time. Second: the robot must be in position waiting for the mold to open. When possible, establish the robot “wait ” position as low on the “Y” axis as possible to improve the extraction time.

 

Lean manufacturing requires continuous improvement and maximized efficiencies. When cycle optimization is complete, the resulting process will produce the highest yield, minimum to zero scrap, and greatly reduced down time. It is important to remember that the primary goal of optimization is to achieve full efficiency while still maintaining world-class quality parts. Through careful and meticulous approach, process optimization is an effective tool in the movement towards lean manufacturing.

 

Garrett MacKenzie is the owner and editor of  www.plastic411.com. Mackenzie started in plastics at the age of 19 as an operator, eventually moving up through the ranks to engineering and management over a 29-year timeframe. He currently works as a plastic injection consultant in engineering and training capacities. He can be contacted at garrett.mackenzie@mail.com.

 

Extrusion 2016 Conference Open For Business

By: Jim Callari 3. August 2016

Register now for the discounted rate and network with more 70 speakers and 50 exhibitors at the must-attend extrusion event of 2016.

 

Last year’s inaugural Extrusion Conference was a smashing success. At Extrusion 2015, more than 350 people attended the two-day event in Charlotte devoted to all things extrusion.

 

Our expectation is that Extrusion 2016 will be even better…and bigger.

 

The Extrusion 2016 Conference will be held Dec. 6-8 at Sheraton Charlotte Hotel in Charlotte, N.C. We added a half-day to the event—the afternoon of Tuesday, Dec. 6, in an effort to expand the program.

 

You can check out the full agenda here. You will be able to see who is speaking and on what topic in the General Extrusion sessions as well as the four concurrent sessions—Compounding, Film, Sheet and Pipe Profile and Tubing—that run on the afternoons of Wednesday and Thursday.

 

The afternoon of Tuesday and the mornings of Wednesday and Thursday will be devoted to General Extrusion. We call it that because there are many common elements in extrusion regardless of what comes out of your die: screw design, controls, key auxiliaries like gear pumps and screen changers, materials, drying and conveying…the list goes on. Then after lunch those days, you can hone in on your particular business by attending one of the track sessions. (Of course, you can also move from one track session to another if a particular presentation sounds intriguing to you.)

 

Conference registration fees can be found here. Register now and save $100. Group-registration packages are also available. Follow this link to begin the registration process. Unless you are a speaker or a sponsor select Full Conference Registration.

 

Click here to reserve your hotel room. Last year, rooms were gobbled up fast and the hotel sold out quickly.

 

I look forward to seeing you at Extrusion 2016. Email me at jcallari@ptonline.com with any questions.

 

Americhem, LPKF Collaborate on Delivery of Colorful Laser Plastic Welding Results

By: Lilli Manolis Sherman 2. August 2016

Technology allows weight, time and money savings while optimizing aesthetics.

 

Since the early 2000s, laser plastics welding has been coming into its own, starting with electronics and gaining in acceptance in other key industries such as automotive. One of three non-friction welding processes, laser welding is a gentle and clean joining process that enables welding of complex geometries and materials that are difficult to bond with other techniques.

 

Just within the first half of this year, we have reported on new laser welders from major players like Branson and Dukane, including clear-to-clear plastic welding and large format welding for complex geometry parts. Other news included Japan’s Panasonic Corp.’s Automotive Systems Company (U.S. office in Peachtree City, Ga.) announcing the development and start of mass production of PBT molding compounds for laser welding. The target: automotive switches and sensors, where these new compounds reportedly enhance design flexibility and long-term reliability.

 

Now, Americhem, Cuyahoga Falls, Ohio, and Germany’s LPKF Laser & Electronics (U.S. office in Tualatin, Ore.) have collaborated on a laser plastic welding technology that allows manufacturers to save weight, time and money vs. using traditional materials, while maintaining and optimizing part aesthetics.

 

Two plastics are joined together using laser radiation in the laser plastics welding process. The plastics being welded have a transmissive upper layer and an absorbing lower layer, allowing the laser to heat the materials in the lower layer and bond them to another compatible material.

 

The lower layer is often based on high-absorptive pigments such as carbon black. In their partnership of this technology, LPKF provides the production equipment and process solutions used in laser plastic welding while Americhem provides custom coloring technology for both the upper and lower layers.

 

In order to provide the ultimate in design aesthetics, Americhem says it can match colors in the transmissive upper layer that enable the laser to pass through this visible layer and create the laser weld using the absorbing lower layer.

 

This technology is gaining wide use in the automotive, medical and consumer products industries. Brett Conway, group director, plastics for Americhem gives this example of the technology’s advantage: a car taillight cover, where laser plastic welding helps ensure a tight seam. “With LPKF’s welding equipment and Americhem’s color, this seal along the top of the taillight is visible and was actually used as part of the taillight’s creative design.”

 

Adds LPKF President Stephen Schmidt, “Though laser plastic welding has existed over a decade, the demand has grown recently as automobile manufacturers sought better quality solutions, lightweighting, and robotic assembly in their manufacturing processes. Because of the ability to custom color most parts, the welds can match the other components in the interior or exterior of the vehicle.”

 

For more on Americhem color and additive concentrates and compounds, see PT’s additives and materials databases.

 

How Important is China to Your Materials Suppliers?

By: Lilli Manolis Sherman 1. August 2016

 

Look at what DuPont did.

 

Having a presence in China is not new for most major material suppliers—both resin makers and compounders such as BASF, Dow, ExxonMobil, PolyOne, and Teknor Apex to name a few.

 

DuPont, which is about to merge with Dow Chemical, has opened up its largest yet engineering plastics compounding plant in Shenzhen, China. Last month, my colleague Tony Deligio reported on the company’s “pre-announcement” of the new facility during the Chinaplas 2016 Media Day in late April.

 

Further expansion into China was a definite theme among materials suppliers at this year’s Chinaplas, according to Tony. “If they weren’t adding/expanding local production, they were adding/expanding local design/application engineering.”

In DuPont’s case, its journey in Shenzhen started 27 years ago. The old facility was shuttered and its production folded into the new state-of-the-art facility.

 

A variety of compounds are being produced at this facility based on Zytel nylon, Crastin PBT, Delrin acetal (POM), Fusabond resins, and Bynell adhesive resins, intended to serve the automotive, industrial, consumer, and packaging markets in China and the broader Asia Pacific region.

 

The facility boasts the latest compounding technologies and reportedly features a number of innovations to deliver high quality and increased productivity. For example, DuPont collaborated closely with its extrusion equipment supplier to create a production setup that is said to allow for faster transitions between different product families, resulting in greater asset flexibility to meet customer needs with shorter delivery cycles.

 

The largest extruders installed in the new facility, which is designed with further expansion in mind, are said to deliver a high volume output with increased efficiency. The Shenzhen facility also boasts a high level of automation—from silo to extruder, which further bolsters product uniformity and quality. Product packaging is also fully automated.

 

For more on DuPont engineering plastics, see PT’s materials database.

 

PolyOne Expands Into Thermoplastic Composites

By: Lilli Manolis Sherman 29. July 2016

Through acquisition of two key businesses, PolyOne positions itself for “next-generation” composites development.

 

Just last month, my colleague senior editor Heather Caliendo reported on how PolyOne, is part of a consortium of corporations which includes three processors that make up the Composite and Nanocomposite Advanced Manufacturing (CNAM) Center at the South Dakota School of Mines & Technology in Rapid City.

 

Heather quoted Joe Golba, lead scientist, reactive extrusion at PolyOne, who told her, “What is compelling about CNAM is the overall intent to bring composites more into the mainstream for applications like transportation, infrastructure and energy.”

 

So, it was not entirely surprising to hear this week that PolyOne has acquired two key Colorado-based specialty businesses from Gordon Holdings—Gordon Composites of Montrose, and Polystrand of Engelwood, which design and produce innovative, lightweight, high-performance solutions, utilizing advanced composite technology and state-of-the-art manufacturing capabilities. Here is what this important move does:

 

• It strengthens PolyOne’s existing portfolio of thermoset composites, with the acquisition of Gordon Composites, which develop high-strength profiles and laminates for use in vertical and crossbow archery, sports and recreation equipment, prosthetics, and office furniture systems.

 

•  The acquisition of Polystrand, which has been a pioneer of continuous thermoplastic composite technology that delivers the high strength and lightweight characteristics of composites along with the design flexibility to form more complex shapes, places PolyOne at the vanguard of this next-generation technology. Current applications include materials for the aerospace, transportation, outdoor and security and protection markets.

 

• The acquisition, which totaled $85.5 million and comprised all assets related to the businesses, including intellectual property, trademarks and production assets, will join PolyOne’s existing portfolio of complementary products in a comprehensive platform which will form the new PolyOne Advanced Composites group.

 

Back in 2012, PolyOne entered into a cooperation and supply agreement with Italy’s Xenia Srl Unipersonale, a specialist in development and production of high-end polymer solutions reinforced with carbon fibers.

 

Their agreement offers customers support to transition from metal or thermoset resins to thermoplastic composites in high-end applications. Both PolyOne, with its OnForce long-fiber reinforced materials, and Xenia, with its Xecarb carbon fiber reinforced materials, have had substantial experience helping customers make such transitions.

 

For more on PolyOne’s broad range of compounds and additive concentrates, see PT’s materials and additives databases.

Photo courtesy: CompositesWorld




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