Investigation of the Large-Scale Pallet by Recycled Polypropylene and the Sequential Valve Gate System during the Injection Molding

Plastic pallets are essential devices for the transport of industrial products within containers and can be made from recycled plastics to be more environmentally friendly. However, numerous thin reinforcing ribs are required to mold such large-size pallets, thereby requiring a large-scale injection-molding machine. Many filling gates can reduce the welding lines to enhance the structural strength of the pallet to achieve injection molding using a lower locking force machine. This study simulated the production of recycled polypropylene plastic pellets using a 3500-ton super-large injection-molding machine and the Moldex3D package to derive the flow analysis of the moldability. The PTC Creo software is used to construct plastic pallets ( 1100 mm × 1100 mm × 140 mm ), filled by twelve gates using a baffle cooling system. During the four-stage filling of the sequential valve gate system, the flow front spreads from the central gate to the four corners of the pallet, decreasing the number of welding lines, with an average filling pressure of 19.23 MPa by a sequential valve gate scheme which is approximately 65% of the concurrent valve gate opening scheme. The maximum clamping force by this sequential valve gate opening scheme in the molding of plastic pallet is 874.6 tons, only half of the one by concurrent valve gate opening scheme. The average welding angle was 85.7° in the concurrent valve gate opening scheme, with smaller angles than that of the sequential gates controlled scheme. The maximum temperatures during the filling by the two schemes with the concurrent valve gates opened and the sequential gates controlled were 230.5 and 232.5°C, respectively. The sequential valve gate opening scheme’s warpages are smaller than the ones by the concurrent valve gate opening scheme. The warpages of the pallet by the sequential valve gate system are smaller than the ones by the concurrent valve gate system. A higher temperature of the cooling channel and a medium level of cooling time result in lower warpage of the pallet.

Structure and Fluid Dynamic Characteristics Analysis of Enclosed Nuclear Electric Valve

The electric valve, cutting off or connecting pipeline of nuclear equipment, is an essential component of nuclear facilities for safe operation. The structure of self-developed enclosed nuclear electric valve is introduced in the paper firstly, and dynamics analysis of steam fluid in valve is carried out to tackle typical problems including leakage in the rapid open-close process of valve for high-temperature and high-pressure steam fluid. It can be determined that dynamic characteristic of steam fluid will directly affect force suffered by valve in the rapid open-close process, greatly influencing movement and ultimate position accuracy of valve gate.

The Finite Element Analysis of the Large-Diameter Composite Slurry Valve Gate

In a long distance slurry pipeline transport system, pulp valve plays a vital role, which combined the pulp valve application is more, ram is one of the important components of composite slurry valve. This article mainly aims at gate has carried on the design and analysis, finite element modeling, and study the corresponding constraints, in the process of loading method, large diameter combination valve gate stress and strain distribution are obtained, combined with the optimization method and finite element analysis software for its structure optimization research, realize the lightweight of the gate. To reduces the manufacturing cost of the gate, as to provide theoretical basis for design.

The Application of the Sequential Valve Gate Control in Injection Molding

Compared to the common hot runner molding,the valve gate control sequential molding has the advantages in the control of (injection and packing)pressure and weld lines,etc.the method is very suitable for large sized thin wall parts. In this paper,the door-panel of a washing machine was taken for an example, the simulation of the both process above mentioned were carried out by computer-aided engineering. According to the results of the study,the main achievements are as follows:Although the equipment cost of the valve gate control sequential molding was increased,the part quality (especially the quantity of weld 1ines and air traps) is improved greatly,at the same time,the clamping force of the injection machine are dropped.

The Saphenofemoral Valve: Gate Keeper Turned into Rear Guard

Objective: Trendelenburg's theory was based on the concept of a descending valvular incompetence com mencing at the saphenofemoral junction (SFJ) with subsequent distal progression of reflux. The aim of this study was to evaluate the distribution of reflux in patients with superficial venous incompetence in order to assess validity of the above hypothesis. Procedures: The superficial and deep venous system of a consecutive series of 443 patients presenting with primary varicose veins was examined by one vascular technologist using colour flow ultrasonography. Results: Six hundred and eleven lower limbs in 443 patients were examined. The distribution of long saphenous vein (LSV) reflux was the following: Of the 611 limbs 454 showed LSV reflux, with 240 legs exhibiting total reflux (SFJ and LSV) and 214 legs exhibiting reflux in evolution (LSV reflux with competent saphenofemoral valve, isolated posterior arch reflux and lateral anterior thigh vein reflux with SFJ reflux). Conclusion: These results suggest that reflux starts distally and progresses proximally, thus throwing the Trendelenburg theory into dispute.