Hot Searches: Stainless Steel 316LStainless Steel 17-4PHIron basedMIMGearsWatch parts

Current location: Home » News Center » Metal injection molding Short Shot defect analysis

Metal injection molding Short Shot defect analysis

Categories: ZCMIM NewsStars: 3StarsVisit: -Release time: 2019-04-17 08:22:00
Font size:【 Large Middle SmallSource: ZCMIMEditor:ZCMIM Author: ZCMIM

1. improper equipment selection

When using equipment, maximum injection volume of injection molding machine must be greater than total weight of molding parts and nozzle, and total weight of injection should not exceed 85% of plasticizing amount of injection molding machine.

2. Insufficient material supply

At present, commonly method for controlling feedstock is fixed volume feeding, whether feed amount and material particles uniform or not, and whether exist "bridge" phenomenon at bottom of feed inlet.

3. Poor material flow 

When fluidity of raw material is poor, structural parameters of mold are the main reasons for short shot. Therefore, it is necessary to improve the stagnation defect of mold casting system, such as proper placement of runner, expansion of gate, size of runner and injection gate, and use of larger nozzles.

4. Lubricant excess

If amount of lubricant in raw material formula is too large, when the wear gap between the ejector screw reverse ring and the cylinder is large, the reflux of molten material in the cylinder will lead to insufficient feed, resulting in short shot.

5. Cold material impurities block channel

? When impurities in melt block nozzle or cold material

? When filling gates and runners, nozzles should be folded down to clean or enlarge mold cold pockets and runner sections.

6. Unreasonable Pouring system design

In the case of one mold with multiple cavities, the appearance defects of plastic parts are often caused by unreasonable gate and runner balance design. When a large amount of residual gas in the mold due to poor exhaust is squeezed by the flow material, resulting in a high pressure greater than the injection pressure, it will hinder the molten material from filling the cavity and cause short shot.

7. Bad Mold Exhaust

When a large amount of gas remaining in mold due to poor exhaust gas is squeezed by flow material to generate a high pressure greater than injection pressure, melt is prevented from filling cavity and causing short shot.

8. Mold temperature is too low

After melt enters low temperature cavity, it will not be able to fill all corners of cavity due to cooling too fast. Therefore, mold must be preheated to temperature required by process before starting machine. When starting up, throughput of cooling water in mold should be properly controlled. If mold temperature does not rise, check design of mold cooling system is reasonable.

9. Melt temperature is too low

At beginning of machine, temperature of barrel is always lower than temperature indicated by meter of barrel heater. It should be noted that after barrel is heated to temperature of meter, it needs to be warmed for a while to start. If it is necessary to take a low-temperature injection in order to prevent melt from decomposing, injection cycle time can be appropriately extended to overcome deficiencies. For a screw type injection molding machine, the temperature of front section of barrel can be appropriately increased.

10. Nozzle temperature is too low

During injection process, nozzle is in contact with mold. Since mold temperature is generally lower than nozzle temperature and temperature difference is large, frequent contact between  two causes nozzle temperature to drop, causing melt to freeze at nozzle.

If nozzle temperature is low and does not rise, check nozzle heater for damage and try to increase nozzle temperature. Otherwise, pressure loss of material will cause too much.

11. Injection speed is too slow

Injection speed is directly related to filling speed. If injection speed is too slow, melt filling is slow, and low-speed flowing melt is easily cooled, causing flow property to further degrade.

Keywords in the article: Metal injection molding
Contact ZCMIM
  • ContactAllysha
  • Whatsapp+86-180-0258-2401
  • Skypeallysha-yuan
  • Phone0086-755-23020959
  • AddressNo.522 Zhen'An east Road, Chang'An Town, DongGuan City, Guangdong Province China