Technology Showcase (February 01, 2005)

INJECTION MOLDING

Large IMM equipped for efficiency and flexibility

CK Technologies has extended its capability for injection molding large components for the trucking industry with the installation of a second Cincinnati Milacron two-platen Maxima 3900 injection molding machine at its plant in Montpelier, OH.

The 4400-ton Maxima has a 3099 x 2700 mm platen size and 4200 mm maximum daylight, yet delivers fast cycle times with 762 mm/sec. clamp speed and 0.98 sec. tonnage build. To further enhance processing speed and productivity, CKT ordered its Maxima with an electric injection drive, which reduces cycle time by allowing overlap of screw and clamp functions, and also reduces energy costs.

The Maxima two-platen design also provides exceptional application flexibility, says Bob Houston, CKT facilities manager. “With the two-platen technology, we can make custom design changes on minimum and maximum daylight specifications to accommodate a large variety of tools.”

The large IMM is also equipped with electro-magnetic quick mold change, and a quick-change, lift-out barrel and screw. Both will contribute to faster product changeovers.

Cincinnati Milacron 888-254-1919

Assembly included

Usually, multi-component injection molding is used to bond individual components so that they are inseparable, but it can be used in another way: to make components that are attached to one another, but can move freely.

Termed assembly injection molding by Arburg, the process relies on the use of incompatible materials, as well as the different shrinkage properties of the materials. This process can be used to integrate joints into a part, for example.

One use of this technique is the production of a planetary preliminary stage for a micro gear. The central “sun-wheel” of the planetary gear is injected in a mold set up on a two-component machine. In a second station of the mold, the two planet wheels are injected, using a plastic that cannot adhere to the sun-wheel. Internal movements in the mold then push the planet wheels onto the sun wheel and set them down in the required position.

In the third step, the joined wheels are encapsulated with the cover plates and axes. The geometry and shrinkage properties of the last components ensure that the wheels are able to move on the axes.

When ejected, the planetary gear is assembled and ready to use.

Hamilton Avtec Inc. 800-590-5546

AUTOMATION

Shelf-mounted robot has greater downward capacity

Kuka Robotics’ KR 16KS six-axis robot has a low profile design suitable for platen mounting on injection molding machines. The shelf-mount design offers a greater downward working envelope compared with standard floor-mounted six-axis robots.

“The KS Series is ideal for optimizing space while increasing accessibility to the workcell,” explains Joe Campbell, director of strategic alliances.

The KS Series is available for payloads up to 60 kg and has vertical reach for part removal of 1800 mm. The robots are suitable for part unloading, insert loading, de-gating and other post-mold processes.

Kuka Robotics Corp. 866-873-5852

Robust in-mold labeling systems

In-mold labeling work cells designed by Automated Assemblies use the company’s Raptor side-entry robots with dual-function EOAT to minimize cycle times. Label placement and parts retrieval occur concurrently to save time.

For stack molds, a dual arm configuration with independent servo arm control is available.

The work cells also include label feeding by a precision turntable with servo tooling to ensure single label separation. Post molding manipulation is specific to each product, but can include closing of hinged lids and covers, repositioning and orienting of parts, and vision inspection of label presence.

As well, a six-axis robot can be incorporated for packing directly into a shipping carton.

Automated Assemblies Corp. 978-368-8914

BLOWN FILM

Air boards and rollers, together

A unique collapsing frame for blown film from Battenfeld Gloucester combines non-contact air boards with composite rollers. The result is consistent quality and higher line speeds for a diverse range of films.

The RollAir collapser is said to work equally well with thin films, transparent films, coextruded films, stretch films and tacky films. The system uses two air flotation sections below a set of composite rollers. The air flotation takes place in the lower section, the area where bubble contact may not have turned traditional rollers, which could have caused scratches.

The bubble then runs through the rollers, which give the bubble slight traction in the machine direction as it advances to the nip.

According to Battenfeld Gloucester, with this system the film moves in a much straighter direction to the nip than with full air board collapsing systems.

Battenfeld Gloucester 978-282-9268

AUXILIARIES

Large-part shredder has heavy-duty construction

Designed for the reduction of large parts and purgings, Economizer’s ESS Series shredders feature a self-aligning gearbox that is able to transmit the heavy shock loads encountered while shredding heavy material.

The unit’s rotor is fitted with either staggered-style square knives positioned in dual rows or a hybrid style suitable for film and fibre. Both are mounted on heavy-duty outboard style bearings. A “swoop” style ram uses gravity and pressure, allowing the material a better approach angle to the rotor without sitting on top of the ram.

The shredder has a slow rotation speed that provides uniform shredding, eliminates longs and operates with minimal noise and energy.

Economizer 508-399-3019

Air-cooled, hot-oil TCUs

Advantage has introduced hot-oil temperature control units that are air-cooled, meaning they can be installed without any water plumbing. The Regal temperature control units provide heat transfer fluid up to 500F for molding applications.

Both heating-only and heating and cooling models are available. Models equipped with the cooling feature are equipped with a high-temperature air-cooled heat exchanger to provide process cooling. When required, a valve opens to introduce cooled fluid into the process while the fan exhausts the heat to the environment.

According to Advantage, the air cooled units provide longer heat exchange life because there is no thermal shock, which can occur with water cooled units. As well, these units require less pump maintenance and less heat exchanger maintenance because scaling is eliminated.

Chillers Inc. 905-895-9667

Homogenous blend for extrusion processes

Sterling’s SPB Series Blender for continuous extrusion applications offers a more homogeneous blend compared with the common batch-type blenders or mixers. Materials such as PVC, wood flour and additives are effectively blended by the SPB unit. Twin-screw feeders can also be provided for non-free-flowing materials.

The control system automatically adjusts individual ingredient feeders to match the extruder rate at the exact ratio required. Color and additives can be metered down to the lowest tolerance level without affecting end product quality. This results in minimal usage of color or additives and a direct saving in overall production costs. Accuracy up to 0.1% can be achieved, even at very low throughputs.

The SPB Series Blender also features a flexible, modular design for up to eight ingredients and up to 16,500 lb. per hour (7500 kg/hr).

CNSmith Plastics Machinery Sales Inc. 416-917-3737

Inner cooling for gas injection molding

A cost-efficient and effective process to reduce the cooling time for gas-assist injection molded parts has been developed by Linde. Gas inner cooling is said to reduce cycle time by
30%. It is best suited to molded components with a pipe-shaped gas channel.

After the normal gas injection shot, the feed of nitrogen to the primary injector is interrupted, and the gas flow is reversed by moving nitrogen through a second injector at the opposite end of the gas channel. The primary gas injector is now the gas outlet. The high-pressure nitrogen flowing through the product cools the inner side of the gas channel.

Linde Gas LLC 216-642-6600

MATERIALS

PC/ABS pairs with X-Melt for thin walls

The X-Melt expansion injection molding process developed by machinery manufacturer Engel opens up new possibilities for manufacturing ultra-thin walled components. Bayer MaterialScience has developed a customized blend of polycarbonate and acrylonitrile-butadiene-styrene copolymer (PC/ABS) specifically for this process. Cell phone covers are being made with this material using X-Melt, at a wall thickness of less than 0.18 mm.

“Up until now, this type of PC/ABS cover could not be made so thin,” says Hans-Joerg Dahmen, an expert with Bayer. He sees considerable potential for applications in cell phone components, including battery covers and casings, and cell phone casings. The material could also find usage in micro-precision components.

In the X-Melt process, the screw exerts pressure up to 3000 bar on the plastic melt, compressing the melt by about 10% of its original volume. When the melt is allowed into the mold, it fills the cavity very quickly.

The Bayblend PC/ABS is highly compressible, and has the processing stability to withstand long periods in the heated screw. As well, it has good flow to permit the production of thin walls, and it reproduces fine detail in the mold surface very well.

Bayer MaterialScience 800-668-2554

Vinyl elastomers have better performance than flexible PVC

Flexalloy PVC-based elastomers from Teknor Apex have two key benefits for designers: they provide better performance than conventional flexible PVC, and they have cost advantages over more widely used styrenic and olefin-based thermoplastic elastomers (TPE).

“Besides exhibiting the look, feel, and elasticity of the more widely known TPEs, Flexalloy products surpass them in tear and tensile strength and resistance to flexural fatigue,” says Philip R. Morin, Teknor Apex industry manager.

Flexalloy compounds can be produced at hardness levels ranging from 30 to 80 Shore A.

Teknor Apex 800-554-9892

Good conformity, optics for shrink labels

A new grade of K-Resin styrene butadiene copolymer from Chevron Phillips provides low temperature shrinkage control and conformity for shrink labels, while maintaining a high degree of clarity, gloss and stiffness.

K-Resin RK54 SBC also provides economic advantages because it is has lower density, and thus higher yield, than other shrink label materials.

“We found that K-Resin RK54 SBC has the gentle shrink curve that provides the packager with excellent low temperature conformity for full or partial body labels in virtually any shape, while maintaining spectacular visuals,” says Andy Singer, styrenics global sales manager for Chevron Phillips.

With the proper surface treatment, films made with K-Resin SBC are well suited to printing with solvent-based inks on both flexographic and rotogravure printing presses. Notable progress has been made regarding UV printing on K-Resin as well.

Chevron Phillips Chemical Co.

905-478-1213

Irradiated PE grades move into production phase

Four grades of Raprex irradiated polyethylene resins are now available in production quantities, following a testing period which began in 2003. Using the Raprex process, long-chain branching, controlled cross-linking and controlled oxidation of polyethylene can be achieved. According to the manufacturer Sterigenics, these modifications result in the improvement of certain mechanical properties and allow the resins to be used in more demanding applications.

“We’ve received numerous inquiries regarding the Raprex resin line and processing, and have received very favorable feedback from customers about the improvements compared with the base polymer,” says George Forczek, product manager for Raprex products.

Sterigenics International Inc.

856-241-8880

Silicone additives promise easier compounding

Wacker-Chemie has developed an additive for thermoplastics which combines a universal carrier matrix with ultrahigh-molecular-weight silicone. Genioplast Pellet S is a high-viscosity silicone gum in pellet form. The main advantage of Genioplast compared with conventional silicone masterbatches, according to Wacker, is that it can be processed with any thermoplastic material, thus simplifying logistics. Compounders benefit from the high silicone concentration, and from the product’s enhanced flow characteristics.

Wacker -Chemie GmbH 49 89 6279-1601