THIẾT KẾ CHẾ TẠO KHUÔN MẪU ĐỦ 25 BÀI_SPKT-2-EN

BÁO CÁO CÔNG NGHỆ NHỰA ĐỦ 25 BÀI_SPKT

DEFECTS IN INJECTION MOLDING PRODUCTS

1) Products deviations size

- Shrinkage in molding If the thickness of the product increases, the shrinkage increases

- shrinkage after the product removed from the mold - Pressure:

+ Long retention time and maximum pressure higher, lower shrinkage

-Temperature:

+ If the temperature increases, the shrinkage increases in the process of injection

- Molecular orientation in injection molding:

+ The molecular orientation due to shear modulus and is retained by the combination with the process of cooling

2) Products warping

Reason The variables that influence Solution

- Shrinkage change across products - Thickness difference in product - Increased time and pressure

- Products take off too soon, therefore the product

is not shaped

- Influence of pressure + The material compression uneven

- Controlled the temperature on the surface of the mold

- Mold design inconsistent and thickness difference

in product

- Influence of temperature + High mold temperature would make that the product cool slowly => warping increases

- Test the structure of product and the accuracy of product

- Influence of Molecular orientation:

+ The orientation is not the same => very high risk of warping

- Avoid internal stress by choosing materials and shapes products

3) Focus Bubble

- The gas bubbles form the hole inside product or

make products that are not filled completely

- When products have the gas line focus, Air

is pushed into one place cause air bubbles

- The air is left in the product in the area product filled final cause air bubbles

- Design thickness of production in the appropriate positionĐổi vị trí cổng phun

- Reduce speed injection

- Optimized exhaust system

- Reduce the pressure lossy of the screw or reduced pressure by reducing the speed

- If there are air bubbles, you need to put them in areas that can exhaust or more the entrance to the exhaust sound

4) Products with the dimples.

- Material shrinkage

- Where the crust of hard enough to not be shrinkage, the product will form

a hollow inner part

- Change the parameters pressed (pressure, temperature, time)

- Changes plastic shrinkage coefficient smaller

5) The phenomenon of injection lack :

- Melting temperature, mold temperature and injection speed too low

- Plastics are not flexible

- Valve exhaust system mismatch: The air in the mold is not drained

- Product thickness too small or too long

- Lack of raw materials (installation screw itinerary insufficient)

- Low injection pressure

- The glossy surface of the mold should not hinder the flow

- Increased melting temperature or temperature mold and injection speed

- Increased volume injection (injection volume is too small, no buffer)

- Install matching between injection pressure and injection volume, increased

injection pressure

- Improved exhaust valve system, reducing mold clamping force

- Increased the size channel system (runner)

- If the temperature is low, increase the temperature mold

6) Products with burrs

- Moldmaking inaccuracies, errors between the two halves of the mold too

big or mold damage

- Mold clamping force is too low

- Melting temperature, cylinder temperature, injection speed or pressure in the

mold too high

- Mold does not close by: mold mounting unmatched, with channels (due to

dirt, corrosion)

- Repair mold and Correct damaged places

- Mold clamping forces higher or change larger machine

- Reduce the injection pressure, speed injection or pressure smaller

- Reduced melting temperature and mold temperature

- Check the correct surface fabrication closed mold

- Select the appropriate port position

7) Products have welded

- Similar to the product not filling the mold

- Design unreasonable gateway

- The air is trapped

- Influence of color, the position weldline usually affects the mechanical

properties

- Check the exhaust system of mold or adding gas drainage

- Can be designed to take the road to the location weldline unseen

- Use materials with lower viscosity

- Identification of specific areas by analyzing MOLDFLOW

8) Products with many wrinkles

- Surface product uneven

- Injection pressure is low Mold temperature is too high

- Gateway is size too small or high

- Reduced thickness

- Make multiple tendon

9) Surface peeling, scratch, uneven

- The surface is separated into sheets, flake

- Very difficult to identify because the surface is

not cracked

- The surface is damaged when using hard objects

scratch lightly

- High shear modulus layers formed

- The dirt incompatible with thermoplastic

- Increased temperature and decreased speed injection

10) Cracks

- The impact from the outside, appears as the power grab

- Due to residual stresses form Internal stress in the parameters by pressing

inappropriate

- Because of structural weaknesses products difficult to obtain products from

the mold or adhesive partial product in the mold

- Reduce the force on mold or using thermoplastic less susceptible to stress

- Review the design of products to improve the flow

- Increase the mold surface temperature and melting temperature of the plastic, reducing pressure maintenance, reset the time and injection speed accordingly

- - Reduce the injection pressure, reduced pressure compression

- Reduce mold temperature, check the temperature uniformity mold

11) Products with black burn marks

- High pressure injection

- The temperature of the plastic is too high

- Air is trapped in the mold

- Reduce injection pressure, injection speed

- Check the exhaust system