Pipe Fitting Mould

Pipe fitting mould is a thermoplastic pipe processing methods which are mainly injection moulding. The volume of injection machine for plastic pipe fittings range from 125g to 2500g , single product weight theoretical weight for pipe fitting mould machine range from 50 % to 75% , injection moulding machine should choose to configure dual proportional valve models. Here are several aspects of processing for specific discussion .

1.1 Temperature control of the feed zone temperature : 180 ~ 200 ; Barrel middle temperature : 190 ~ 210 ; nozzle section temperature : 200 ~ 220 specific temperature settings should consider the following factors :

 ( 1 ) plastic material, the material should be based on vendor-supplied parameter interval to set the temperature .

 ( 2 ) single- moulded plastic parts total weight ( including runner ) and the actual quantity of the barrel deposit ratio: the proportion of smaller , each time resulting pre-plastic melt residence time in the barrel in the longer temperature setting value should be taken downwards ; contrary, should be taken on the side values.

 ( 3 ) single product projected area of ​​the pipe fitting mould : projected area, the temperature is set to be high; the contrary, should be low. Due to increase in temperature can increase the fluidity of molten plastic , which will help fill a multi-cavity moulds. But the high temperature will increase the temperature difference between the inside and outside of the mould products , increase the amount of deformation is not conducive to the stability of product size .

1.2 Pressure Control

Injection pressure and holding pressure is key factor to ensure crisp dense plastic pipe fittings  . According to the size of pipe specifications ( product wall thickness ) , injection holding pressure is generally controlled at 50 ~ 75kg/cm. Pressure is too small , the product will produce shrink wall deformation , radio inadequate material defects ; too much pressure will produce flash , resulting in stripping difficulties , increasing pipe fitting mould machine and mould losses.

( 1 ) Injection pressure: generally divided into three . As compared to other plastic pipe products, are thick-walled plastic products ( such as φ110 S2 pipe wall thickness up to 21.1 +2.4 mm), injection pressure was first low-high distribution , before and after class difference 3 ~ 8kg/cm.

 ( 2 ) Holding pressure : Due to thick-wall, plastic pipe fittings tend to  form a large contraction , the product can be maintained after the formation of the pipe fitting mould without deformation , pressure at the size and dwell time is critical. With the continuous plastic melt solidified volume reduction ( shrinkage ) , melt rely packing process to enrich products bore to compensate for volume reduction resulting uneven ; Due to continued curing in the pipe fitting mould cavity , the cavity in the supplementary melt becomes difficult, so also need to hold pressure progressively increases and holding pressure should be greater than the injection pressure .

 ( 3 ) pressure setting considerations : crossing the mould pouring effective size, area, may be appropriate to reduce the pressure ; contrary, need to increase the pressure . injection holding pressure setting does not appear to flash or no stripping difficulties ceiling , wall to no shrinkage , deformation of the lower limit , and considering the temperature and other factors .

1.3 the speed control proportional valve can be adjusted by a double flow and the speed ratio , the pressure can be set to zero in theory, but the speed is 100%. The actual operation , the primary speed control to the main injection , take 70% to 85% progressively reduced later .

1.4 cooling time control of plastic pipe and more for mass production , so it must be in the production process of the product and the mould is cooled . Large diameter tube after moulding defects such as easy to produce elliptical deformation of the mould product Soaking treatment is a relatively common and effective method.

The shape and density of the product have a greater impact level is hold time and cooling time , the longer dwell time , product deformation is smaller , higher density ; longer the cooling time , the product can be reduced both inside and outside the cavity temperature , can also reduce distortion and improve the quality of stripping . With increasing product thickness , pressure and cooling time required substantial extension . But time extension will reduce efficiency.

2 plastic pipe fitting mould manufacturing

like other thermoplastics injection mould , plastic pipe fitting mould consisit of the casting system , core cavity , mould release mechanism and other components . Next, talk about the main aspects of personal views .

2.1 Gating System

Gating system consists of the sprue bushing , sub- runner , the inlet composition . Sprue bushing has become standardised , nothing to  discuss , and the inlet of the runner and the design of the main considerations sectional shape and area in two ways. The shape of the runner mostly circular , semicircular , trapezoidal . Practice has proved that the following bottom semicircular inverted trapezoidal is the best, while the inlet trapezoidal and semicircular mostly feed inlet is too big or too small . Too much effect on product shape and trimming is inconvenient ; inlet is too small, the process will dwell in the product produced at the feed tidbits like, affect the appearance , and the need to increase the injection and holding pressure , increasing presses and die load. A multi-cavity mould , the inlet area should be consistent to ensure that products in the moulding pressure is evenly distributed.

2.2 core and cavity, existing plastic pipe products are made of matt exterior handle , so the cavity to be sandblasted or pulse -corrosion treatment , to ensure beautiful appearance. According  to practices , blasting formed on the surface due to the sharp concave and convex portions speed flow easily washed off, should not be used . Product melt parts corresponding to the core part should be smooth , the surface roughness is 0.05 or less , to ensure that the products can be uniformly melt . With the core and the cavity should be considered part of the integrity of the product rounded , as shown in Figure 2 .

2.3 ejection. plastic pipe fitting mould commonly used stripper plate , push the top of the board out of the stripping method is not recommended , this approach will result in product appearance defects. Plastic melt index is small ( typically < 0.4 ) , the product can easily remain in the fixed mould , so Hose products should adopt the fixed mould stripper plate automatic ejection ( ie fixed mould and the mould is opened when the core sync separator ) institutions to reduce the fixed mould resistance ; Further , the movable model of the core at the vehicle tank , in order to increase the resistance of the fixed mould products , taking demoulding release force , is a commonly used method. The former is used more often , which is relatively simple.

Exhaust and Cooling

Plastic pipe fitting mould venting is very important, bad venting , will increase the line mark degree of local integration , and because the gas easily wrapped formation of pores inside the product , will produce serious coke material . Unless specifically shaped tube, ordinary plastic pipe exhaust mould core and cavity can be of the gap to be guaranteed. According to the size of the core , the gap between the 0.03 ~ 0.1mm can not guarantee smooth burr exhaust case . Reasonable feed location and orientation can effectively solve the poor condition of the exhaust . Plastic pipe fitting mould core and cavity are required through cooling water, cooling to the main core , cavity as deputy. 2.5 material and heat treatment of plastic material melt index is small , sticky, the mould material has a certain friction losses, but no corrosion . So the core cavity is usually used 40Cr, P20 , etc. manganese chromium molybdenum materials , pre- hardened hardness of HRC28 ~ 38, the service life of 10 to 300,000 die ; such as the use SM1, SM2, PMS and other materials , the surface after heat treatment hardness of HRC40 ~ 45, the service life of up to 60 million to 1.2 million die . Mould materials are generally made ​​of high quality steel 45.

Pipe Fitting Mould Products