【Abstract】With increasing competition in the market, replacement of plastic products is getting faster and faster. Production of multiple varieties, small and medium batches, mixed-flow just-in-time production will become mainstream, role of quick-change injection molds will become prominent, especially in recent years. Combined with design of DC bracket, structure characteristics of Casket quick-change injection mold are described, realization methods of mold base and quick-change part are introduced in detail.

DC bracket is a smaller product among company’s main models. Size is 26*22.3*17mm, no sliding block, lifter and other structures, three-plate mold point gates, easy to automate production, similar to this smaller part or some products are still in experimental stage, demand for products is not particularly large. If these parts are produced with standard mold bases, they cannot meet delivery requirements and cost will be relatively high. In this case, a small number of multi-variety parts rapid molding technology has been spawned, "Casket" quick-change mold introduced in this article is one of them.

Quick-change mold: Without disassembling entire mold from forming machine, only by replacing main insert structure, plastic parts can be switched and mold can be adjusted, as shown in Figure 1.

Large mold base is fixed on machine tool, quick-change part is installed in installation area to control injection of mold, distance between molds and removal of gate waste. Large mold base is a one-time investment part, there is no need to design and process in the future, as shown in the figure 2 shown.

Quick-change part is equivalent to a reduced version of standard mold with a length, width and height of 150*120*165mm. It is mainly responsible for molding, cooling and ejection of plastic parts. Total weight is about 10kg, replacement operation is relatively easy to achieve, as shown in Figure 3.

Ejection system is similar to ordinary molds. Machine tool pushes ejector column and ejector plate to eject, as shown in Figure 4.

Cooling system adopts straight-through water inlet and outlet, as shown in Figure 5.

Switching process of mold is much simplified than that of ordinary mold, as shown in Figure 6.

 

Figure 1 Schematic diagram of overall structure of quick-change mold

 

Figure 2 Schematic diagram of large base structure

1. Quick-change part of installation area 2. Mold pull distance limit 3. Movable mold seat plate 4. Movable mold plate 5. Fixed mold plate 6. Small mold plate mounting plate 7. Unloading plate 8. Fixed mold plate seat plate

 

Figure 3 Schematic diagram of structure of quick change part
a — —Small mold base b — —Inlay block

1. Movable mold seat plate 2. Spacer 3. Reset lever 4. Return spring 5. Movable mold pad 6. Movable mold plate 7. Fixed mold plate 8. Fixed mold seat plate 9. Ejection limit post 10. Mandrel plate 11. Mandrel pad 12. Travel switch 13. Fixed mold insert 14. DC bracket parts 15. Movable mold insert 15. Ejector

 

Figure 4 Schematic diagram of ejection system structure
a — —clamping state b — — ejection state

1. Ejector 2. Ejection limit post 3. Ejector plate 4. Ejector backing plate 5. Top post

 

Figure 5 Schematic diagram of cooling system structure
a — —Moving mold side waterway b — —Fixed mold side waterway

 

Figure 6 Schematic diagram of mold switching process
a — —Remove operating side stopper and water pipes on both sides b — —Remove fixing screws
c — Use two threaded handles to pull out to remove small mold base
d — —Install small mold base to be produced e — —Install disassembled parts in turn
3 Value manifestation and results

(1) Time cost savings are shown in Table 1.

 

Mold switching cycle includes mold delivery time, mold installation time, mold heating time, material room cleaning time, mold cooling time, mold disassembly time, and mold return time.
Large mold base part only needs to be designed once, subsequent mold only needs to be designed for quick change part, which greatly shortens cycle of mold design and reduces difficulty of design.

(2) Cost savings of mold bases and standard parts are shown in Table 2.

 

Mold base model used for standard molds is 2025, and mold base model used for quick-change molds is 1215.
(3) Widespread use of quick-change molds.
This mold structure can be widely used in the production of multiple models, small batches, and fast switching products. For plastic parts with same size and same gate form, quick response capability of quick-change mold has certain competitiveness. Whether it is company's internal or external parts, size, length, width and height are within 60*30*18mm. Almost all those without sliders, lifters and other complex structures can use this mold structure to realize quick change, only replace some parts of quick change, which can save cost of mold base and related standard parts, shorten time of mold design.