Product category:
Materials processing and testing
News Release from: Twinshot Technologies | Subject: Twinshot Version II co-injection technology
Edited by the Engineeringtalk Editorial
Team on 15 January 2002
Co-injection moulding process improved
further
Twinshot Version II improves on the Twinshot process that permits co-injection moulding of multi-material, by only needing a single screw, with a 2-stage design similar to a vented extruder
Twinshot Technologies, pioneer of the process that permits co-injection moulding of multi-material using two concentric screws within one barrel, has now commercialized Twinshot Version II, patent-pending single-barrel co-injection technology that does not require two-separate screws Plasticizing of both components is achieved using a single screw with a 2-stage design similar to a vented extruder
The ratio of materials is controlled externally by starve feeding one or both of the screw stages.
Joel Thomson, inventor of Twinshot, describes the numerous advantages in performance, cost and ease-of-use.
"Recovery time is much quicker - even faster than an equivalent conventional screw - because both materials extrude simultaneously.
Independent heat control on the two melting zones is also possible.
Overall cost is reduced because one simple screw replaces two more complex ones." Other advancements include elimination of the hopper located behind the barrel, making Twinshot Version II retrofitable to all machines regardless of injection piston design.
No new pistons or castings are needed.
No clutch between the drive and the screw is required, thereby eliminating a potential wear component.
No signal or force from the machine is needed to run the process, so any software or control can be used, even old relay controls.
Twinshot Version II can be scaled down to much smaller screws, as low as 20g shot size, and can be installed or removed quickly just like any barrel and screw replacement.
Additionally, previously-established Twinshot Technologies advantages over conventional co-injection still apply.
Twinshot is retrofitable to existing presses and works with most conventional molds with no modifications - thereby overcoming the burdens of large capital expense and process complexity that have traditionally made co-injection prohibitive to custom molders.
A standard injection machine is used with no increase in footprint or power consumption.
There are no mixing manifold or hydraulic nozzle valves to maintain.
There is no pressure loss by directing melt through long distances and around corners resulting in faster clean-out and no dead spots.
The shot size never needs re-calculating when material ratio changes, now providing smooth and instantaneous switchover between materials during injection.
"Simplicity and low cost are the distinguishing attributes of the Twinshot system as compared to other commercial co-injection systems", according to co-injection veteran Joseph McRoskey.
Twinshot has been proven to reduce resin costs by 25% or more, dramatically cutting product material costs - the single greatest expense to custom molders.
Among the many benefits of Twinshot is the ability to encapsulate low-cost materials, including off-spec, regrind, or recycled material.
The system can also be used to produce soft-touch parts in a single molding operation, encapsulate foamed material to reduce sink, warp, and improve strength-to-weight ratio, and to encapsulate reinforced materials within a cosmetic surface.
(This was Engineeringtalk's Top Story on 14 January 2002).
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