Drawer mold design seems simple, but it is really difficult to make

Time:2020-09-16 09:06:49 / Popularity: / Source:

Drawer mold design 
Part 1: Basic information of mold (customer type, rubber product and mold size, steel)
Part 2: Product description and requirements (difficulties in product molding and demoulding)
Part 3: Mold structure design (gating, parting, ejection, reset, cooling, mold action)
Part 4: Mold manufacturing and processing (NC,EDM,WC, polishing, assembly, etc.)
Part V: Injection molding process (baking material requirements, mold temperature, material temperature, injection cycle, clamping force, injection pressure)
Part VI: Summary

Basic information of mold

1. Customer requirements:

1. This product is a transparent plastic part, with high quality requirements for clamping and appearance.
2. Average wall thickness is only 2.3mm, and customer requires a plastic cycle of 70S.
3. Customer accepts that front mold inverted buckle adopts a spring front mold structure, and large side inverted buckle of drawer rear mold uses a large lifter to drive a small lifter structure.

2. Mould materials and accessories specifications:

1. Original A board is made of 2711 pre-hardened steel; material of B board is 1.2311.
2. Lower mold, slider and other forming parts are made of 2711 pre-hardened steel, in which lifter nitrided depth is 0.15 and hardness is HRC50-52.
3. Except for AB board, mold base is made of medium carbon steel 1050; standard mold parts adopt HASC0 equivalent specifications.
4. Hot runner adopts Mold-Master needle valve hot nozzle with two points of water inlet; junction box and power supply/electric couple socket adopt HARTING specifications.
5. Parker oil pump is used in big slider; quick-insertion nozzle adopts STAUBIL specification.
Mold structure design 

Product description and requirements:

This drawer product is a transparent part, welding line and structure clamping line are complicated. Multiple positions need to be tripped when mold is formed.
Mold structure design 

Mold structure design

1. Gating system (hot runner system):

Mold-Master needle valve hot nozzle is used to inlet at two points; water inlet position has been verified by MoldFlow analysis.
Mold structure design 

2. Forming structure:

1. Parting surface design: pull out from R corner of product, smooth transition at the corner, no stepped sharp corners.
2 Treatment of thin steel at insertion position: inserts in two insertion positions of front mold for easy maintenance.
Mold structure design 

3. Lateral parting and core pulling mechanism:

1. Combined lifter structure:
Lifter is designed into three sections, large lifter in the middle is ejected obliquely under ejection drive, small lifter and large lifter on both sides have an angle difference in ejection direction (angle of small lifter is smaller than large lifter); Large lifter uses horizontal structural angle between large and small lifters, small lifters on both sides are dragged by "T"-shaped strip to shrink and demold inward while being pushed out diagonally; structure is mature and reliable, which is of great promotion significance .
Mold structure design 
2. Slider lifter structure:
Large slider moves outward, and slider slope is blocked by stopper fixed on B board, so that it moves upward under action of slider chute to escape undercut; stopper is disengaged from lifter of slider, lifter of slider and large slider move outward together to complete demolding. Structure is mature and reliable, and has promotion significance.
Mold structure design 
3. Structure of bullet front mold: (front mold slider)
Inside of drawer front is inverted, front mold adopts structure of bullet front mold; front mold has a length of 670mm, so there are oblique guide posts on both sides to guide, and there are four sets of springs in the middle of slider for ejection of front mold; in addition, there are three sets of Sanda screws at both ends and middle of row.
Mold structure design 
4. Ejection and reset system:
Pushing and oblique ejection, ejection is safe and easy to take parts; because oil pump position has strict sequence requirements when opening and closing mold, oil pump position is equipped with a card to control sequence of actions.
Mold structure design 
5. Cooling system:
Original front mold makes mold cool quickly. Each slider of lifter and hot nozzle has separate water transportation, and overall cooling is sufficient.
Mold structure design 
6. Other structures:
Product has a large projection area, about 1755CM2, design of no gap between A and B plates makes bearing surface sufficient. Stool square is designed on all sides.
Mold structure design 

Mold manufacturing and processing

1. Mold processing technology

1.  Note for NC processing:
1. In view of large processing depth of lower die, principle of segmented roughening should be adopted, different tool lengths, machining allowances and cutting depths should be set to ensure safety and efficiency.
2. In view of characteristics that lower die pushes square slot and knife is easy to spring, at the corner of push square slot, an arc transition should be added to avoid sudden changes in processing direction. Side of plastic position of push square groove should be appropriately increased by margin or side of drawing surface should be protected by translation to prevent knife from being flicked.
2. EDM processing precautions:
1. Pusher of lower die circumference should be installed in lower die and be galvanically eroded to prevent wire clamping at pusher.
2. When lower mold is electro-eroded, it should be electro-eroded one by one in one direction to avoid processing starting.
3. Large margin part of lower die adopts carbon open thickness, uses a large spark level, and appropriately increases discharge margin.
3. Note for wire cutting:
After NC processing is completed, perform wire cutting process, and pay attention to correct number of strokes according to auxiliary reference provided by NC processing.

2. Mold assembly process (production process)

Injection molding process 

Injection molding process:

Baking conditions: 80ºC, 2~4 hours. Mold temperature is 40~80ºC. It is recommended to use a larger value for this product to reduce influence of weld line.
High-speed injection as much as possible for injection molding, reasonable pressure holding to reduce shrinkage. During mold trial, clamping force is 650 tons, injection pressure is 950kgf/cm2, injection holding pressure is 7 seconds, cooling time is 18 seconds, ejection stroke is 105mm, and product molding cycle is 53 seconds.

Summary and description:

1. Combined lifter structure: while large and small lifters are ejected obliquely, large lifters are pulled inward by "T"-shaped strip and small lifters on both sides are retracted and demolded. This structure is novel and creative.
2. Cooling system, gating system and ejection system are designed reasonably.
3. Overall structure is compact, structure is simple and integrated, action is safe and reliable.
4. Overall processing is reasonable (non-adhesive part has less EDM), assembly process is reasonable, and it is easy to replace(Two thin steel positions as inserts, easy to replace).

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