機械模具外文翻譯---注射模具中熱量控制評估（英文）

1、Evaluation of heat management in injection mould toolsB. A. McCalla1, P. S. Allan*1 and P. R. Hornsby2The control and management of heat in injection mould tools is a vital requirement for obtainingoptimum production pro

2、cessing conditions. This paper describes an investigation that comparedconventional mould cooling methods with a relatively new technique called ‘pulse coolingtechnology’ (PCT). The principle of PCT is the use of an inte

3、rmittent flow of the cooling medium inthe mould tool with accurate control of the mould cavity surface temperature during the injectionmoulding cycle.A mould tool instrumented for cavity pressure, cavity surface temperat

4、ure and mould backgroundtemperature measurements was constructed for the study. Results showing the effectiveness ofPCT compared with conventional cooling are presented for polypropylene (PP), polycarbonate andfilled PP

5、with talc and aluminium powders. A reduction of up to 22% of the conventionally cooledmoulding cycle time for unfilled PP has been recorded when pulsed mould cooling was used.Keywords: Injection moulding, Mould cooling,

6、Pulsed cooling, Mould temperature controlIntroductionThe objective of the temperature control system in an injection mould tool is to maintain a consistent cavity surface temperature cycle that is essential for part repr

7、oducibility in injection moulding. Changes in the cavity surface temperature cycle can result in a variation in properties, such as shrinkage, internal stress, warpage and the surface quality of mouldings. The efficiency

8、 of the cooling system is a major factor that will affect the overall cycle time, as it is the time to cool the moulding from its injection temperature to a temperature at which it can be ejected from the mould tool that

9、 typically forms the largest portion of the moulding cycle time. The thermal properties of the mould material, the design of the cooling channels, the part section thickness, the properties of the pro- cessed material an

10、d the temperature of the cooling medium will all contribute to the efficiency of the tool.1Numerous commercial products have been designed to improve the efficiency of the removal of the heat from a thermoplastics inject

11、ion mould tool. Examples of some of these are as follows: (i) alloys with high thermal conductivities based on beryllium and copper have been used for the production of mould inserts (ii) conformal cooling channels have

12、been used to achieve uniform heat removal from complex moulded sections(iii) cooling probes and special designs to create turbulent flow in the cooling agent. All of these features can offer significant benefits to the e

13、fficiency of the cooling of the mould tool, but they do not provide for the management of the heat extraction in the mould tool. The conventional method of cooling that is used in the industry involves a temperature cont

14、rol unit that supplies a cooling fluid to the mould tool at a set temperature. The sensor used to control the temperature of the coolant can be situated in the mould tool or in the control unit. The main feature of this

15、method of cooling is that the coolant is constantly flowing and that typically only one controlling sensor is used on a mould tool. Over the last 15 years, a mould cooling process that claims to effectively manage the he

16、at transfer in injection mould tools has been developed.2,3 The process known as ‘pulsed cooling technology’ or ‘PCT’ operates with controlled pulses of the coolant to separate cooling zones in the mould tool. It also us

17、es the heat supplied by the injected resin melt to maintain the temperature of the tool so that only the excess heat from that source is extracted from the mould.2,3 A brief description of the operation of PCT is as foll

18、ows: (i) the mould is initially heated by the polymer that is moulded during the set-up procedure for the tool. Alternatively the tool can be initially primed by using an auxiliary heating system (ii) when the mould reac

19、hes the set temperature the pulsed cooling control takes over. The mould surface temperature in each of the zones of the tool is used to control the demand for coolant (iii) The PCT control is programmed to supply pulses

20、 of the cooling fluid only when the mould surface sensors demand it1Wolfson Centre for Materials Processing, Brunel University Uxbridge UB8 3PH, UK 2School of Mechanical and Aerospace Engineering, Queens University Belfa

21、st, Belfast BT9 5AH, UK*Corresponding author, email peter.allan@brunel.ac.uk26? 2007 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute Received 27 February 2006; accepted 25 Octobe

22、r 2006 DOI 10.1179/174328907X174593 Plastics, Rubber and Composites 2007 VOL 36 NO 1The talc filled PP compounds were made by blending PP powder (ground from pellets), with the dried talc powder in a V-blender and then c

23、ompounding the mix in a corotating twin screw extruder (a Betol TS40). The moulding trials for both conventional cooling and pulsed cooling were carried out with injection gates 1 and 3 on the ends of the tensile bar cav

24、ities (Fig. 2). When the basic moulding conditions had been estab- lished for a moulding run, the cycle was finally optimised by the use of cavity pressure monitoring to set the stroke position at which injection pressur

25、e was switched to holding pressure. The injection–moulding machine was set to operate in the fully automatic mode and was allowed to stabilise before any readings were recorded on the data acquisi- tion system. After the

26、 moulding conditions had been set for a particular resin compound, the same conditionswere used for both conventional cooling and PCT. This meant that any difference in the cycle time between the two sets of mouldings co

27、uld be directly related to the mould cooling method used. Typical mould cavity pressure and temperature traces are shown in Fig. 4a and b respectively. The mould cooling time is taken from the point when the cavity is vo

28、lumetrically full, (at the change over from injection pressure to holding pressure) to the point when the cavity pressure dropped to atmospheric. The cycle time was established from the temperature sensor profiles, as in

29、dicated in Fig. 4b. The mouldings were produced using both direct cooling and pulsed cooling at various set mould temperatures. For the pulsed cooling experiments, the coolant temperature was set at 11uC. The mould for t

30、he trials was set up according to the principles of pulsed cooling32 Component drawing showing runner, gates and locations of four cavity pressure–temperature transducersMcCalla et al. Evaluation of heat management in in