PT Blog

Posted by: Stephen Levy 21. February 2017

Melt Delivery Systems: Going Against Tradition

A well designed part is only as good as the melt delivery system feeding it. The goal of a properly designed melt delivery system is to create uniform melt conditions to each gate while accommodating filling pressure limitations, minimizing shear, and providing for cavity packing. 

Traditionally, melt delivery systems are sized based on estimates, similar part geometry, or poor design guidelines. However, when sizing a runner, it is important to minimize any restrictions of the material flowing through the channel. The cross-sectional area (diameter) of the melt delivery system has the biggest impact on both pressure drop and shear rate through the channel.  At a constant flow rate, both pressure and shear rate will increase with decreasing runner diameter to a point. 

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Materials and Additives are examples of the broad focus of Plastics Technology’s Molding 2017 Conference & Exhibit.

The 27th annual presentation of this event for injection molders will take place April 4-6 in Charlotte, N.C. The event will also feature a separate at-the-press seminar with scientific molding guru, John Bozzelli, plus a tour of RocTool; presentations on how to establish a robust/repeatable injection molding process; discussions of Industry 4.0;  trends and technology in tooling; and much more.

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During Plastec West (Feb. 7-9; Anaheim, Calif.), Plastics Technology caught up with Bill Carteaux, President and CEO of the Plastics Industry Association prior to its West Region reception at the event. In the video, Carteaux discusses: his outlook for the industry in 2017, the Trump effect on trade agreements, an update on the progress of NPE 2018, the importance of the Western region for plastics and feedback on the association’s rebranding. (Image Courtesy Plastics Industry Assn.)

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But at last week’s MD&M West 2017 show in Anaheim, four suppliers teamed up to display a coextrusion line running a 1.4-mm diameter Teflon fluoropolymer (FEP) catheter tube throughout the exhibit. Check out the video below to see the line in action.

The main body of the catheter was an FEP delivered by the primary 3/4-in. Davis Standard extruder. A second 3/4-in. extruder pumped equally spaced embedded white FEP stripes filled with barium sulfate for x-ray opacity. The material streams were combined in a cross-head co-extrusion die supplied by Guill Tool & Engineering so that the barium-filled material forms four stripes that are embedded at 90° intervals around the circumference of the tube. Both the extruders and die package featured streamlined designs to minimize residence time, owing to FEP’s tendency to burn.

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A joint venture recently formed by Victrex (U.S. office in West Conshohoken, Penn.) and Tri-Mack Plastics Manufacturing Corp. of Bristol, R.I., aims to accelerate the commercial adoption of PAEK composites in aerospace applications.  This multi-million dollar investment, TxV Aero Composites, includes the establishment of a new U.S.-based, purpose-built polyketone composites center of excellence, due for completion in 2017, according to the partners.

This PAEK (polyaryetherketone) composite parts downstream manufacturing venture represents the second such move by Victrex, which in 2015 acquired polymer gears specialist Kleiss Gears, Grantsburg, Wisc., with particular expertise in molding PAEK.  

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