Indesit Company is a company located in Fabriano, Ancona Province, Italy. It is a major manufacturer and distributor of major European home appliances (washing machines, dryers, dishwashers, refrigerators, freezers, cookers, hoods, ovens and stoves), undisputed leader in major markets such as Italy, UK and Russia. Product diagram of dishwasher housing is shown in Figure 1. Maximum size of product is 597.00 mm * 520.5 mm * 337.50 mm, average thickness of plastic part is 7.56 mm, plastic part material is PP+40%CaCO3, shrinkage rate is 1.013, and weight of plastic part is 1477.40 grams. Technical requirements of plastic parts are that there must be no defects such as peaks, underfilling of injection molding, flow lines, pores, warpage deformation, silver streaks, cold materials, jet lines, etc. In addition to dimensional tolerances of plastic parts, geometric tolerances must also be guaranteed to meet assembly requirements.

 

Product drawing of dishwasher housing is shown in Figure 1. Technical requirements of product drawing and plastic parts are as follows:
1. UNQUOTED RADII: R 0,5
2. UNQUOTED ANGLES: 0,5°
3. FOOT FIXING TORQUE: 2 Nm +/-0,15
4. TRANSVERSE-SCREW FIXING TORQUE: 1,7 Nm +/-0,15
5. BOTTOM HINGE-SCREW FIXING TORQUE: 4,6 Nm +/-0,15
6. MINIMUM THICKNESS RIBS: 0,6 (TOP)-1,4 (BOTTOM).
7. MINIMUM THICKNESS: 1,9 mm +/-0,1

 

Figure 1 Dishwasher housing product picture

 

 

8. HOUSE-FOOT SURFACE SHOULD BE FULL AND PERFECTLY FORMED.
9. FOOT SHOLUD NOT HIT THE BOTTOM PACKING IN ANY CASE.
10. BASE MOULDING SHOULD BE COOLED FOR 24h AT LEAST AFTER HAVING BEEN MOULDED.
11. MAX NUMBER OF OVERLAPPED BASE MOULDING SHOULD NOT BE MORE THAN 4.
12. DO NOT OVERLAP MORE THAN ONE PALLET.
13. BEFORE MOUNTING, KEEP BASE MOULDING AT A TEMPERATURE OF 20°C +/-8°C FOR 2h AT LEAST, IN CASE OF STORING AT A TEMPERATURE LOWER THAN 0°C FOR MORE THAN 2h.
14. USE ADHESIVE TAPE TO GUARANTEE FOAM-TIGHT BETWEEN BACK AND ITS BASE MOULDING HOUSE.
15. CONDENSE DUCT CLEANING SHOULD BE VERIFIED USING APPROPRIATE TOOL.
16. PERPENDICULAR VALUE AND TOLERANCE LIMITS OF CONDENSE DUCT INDICATED ON THE DRAWING SHOULD NOT CHANGE AFTER HANDLING OPERATIONS.

 

17. MOULD JUNCTION LINES AND INJECTION POINTS SHOULD PREVENTIVELY BE AGREED WITH DESIGNERS.
18. FOR ALL MISSING DIMENSIONS SEEING 3D MODEL.
19. ALL DIMENSIONS INDICATED WITH ARE CRITICAL DIMENSIONS.
20. ALL ITEMS AND COMPONENTS MUST NOT CONTAIN: Pb,Me,Cd,Es,Cr,PBB,PBDE. (Instruction 2002/95/CE of European Parlament and Council of january,23 2003).
Geometric tolerances of plastic parts are shown in Figure 6. Above plane A is reference, perpendicularity tolerance between condensation hole and reference is 1.5, 27゜ plane is an important installation plane, its flatness and perpendicularity are not more than 0.3 respectively. Front mold has two threaded holes, and thread is a trapezoidal thread. It is required to measure from two end faces of threaded hole to ensure that it meets requirements.
It can be seen from Figure 1 that structure of plastic part is a complex-shaped shell with a large height difference. Size of plastic part is relatively large, there are undercuts on two end faces, and there are two threaded holes on one end face, which needs to be automatically unthreaded. For plastic parts of this set of molds, choice of mold opening direction is also a difficult point. Only when mold opening direction is selected correctly, can parting surface design be performed correctly, and entire mold design can be completed completely.
Mold design cavity rank is 1 cavity. Because it is a large mold, there is no standard mold base with corresponding specifications, because of use of hot runners, mold base is a non-standard mold base 95105, positioning pins are added to both movable mold and fixed mold. For large molds, positioning mold blank is very important. Important thing for small molds is strength. Important thing for large molds is stiffness. Positioning pin of movable and fixed mold is an important factor to solve problem of mold stiffness. Another factor is interlocking of movable and fixed molds. Interlocking design of mold base is on four corners of mold, fixed mold is protruding, and movable mold is recessed to interlock. Core of movable mold is higher than parting surface and is completely locked with fixed mold plate.
Mold diagram of dishwasher shell is shown in Figure 2, and mold design specification is shown in Figure 4. Hot runner system is YUDO system, corresponding splitter plate is designed with 4 hot nozzles.
Inclined surface of sliding block is designed with a wear-resistant plate, and corresponding position of A plate is also designed with a wear-resistant plate. It is convenient to make adjustments when mold is flying, it also helps to extend life of mold. Large sliding blocks on both sides are all driven by oblique guide posts.

 

There is an essential difference between unthreading of large-scale casing plastic parts and unthreading of round plastic parts of bottle caps. Way of unthreading round plastic parts is often related to sequence of mold opening and complexity of mold structure. Way of unthreading of casing plastic parts is often relatively simple, most of them use oil cylinders or pneumatic components to unthread. Therefore, two unthreading of fixed mold all use oil cylinder to drive rack to drive gear to unthread. Principle of unthreading is shown in Figure 7. First, rack drives pinion to rotate, which drives coaxial large gear to rotate, thereby driving screw core to rotate. Thread core retreats into thread sleeve while rotating to realize thread demolding.
Ejection of plastic parts adopts European strong pulling method. Ejector components are thimble and cylinder.

 

 

Figure 2 Dishwasher shell mold diagram

 

Figure 3 3D mold water transportation diagram

 

Figure 4 Mold specification book

 

Figure 5 3D drawing of dynamic mold

 

 

Figure 6 Geometric tolerances of plastic parts

 

Figure 7 Unthreaded part