Common defects and prevention methods of foaming mold used in EPC casting

In order to obtain high quality castings in EPC, it is necessary to have high quality EPC. The causes and prevention methods of common defects in foaming patterns are introduced.

1. The appearance is not complete and the outline is not clear

Causes:

(1) Insufficient bead quantity, incomplete filling of mold cavity or uneven bead filling;(2) the particle size of the foamed particles is inappropriate and uneven;(3) the mold cavity

Unsuitable fabric and structure;(4) Incoming particles are not standardized during operation.

Prevention method:

(1) bead size should match the wall thickness, thin wall appearance, the application of small bead;(2) Adjust the structure in the mold cavity and the arrangement, size and number of air holes;

(3) when filling granules by hand, appropriate vibration or manual help packing;When using compressed air spray gun packing, the pressure should be properly increased and the feeding direction should be adjusted.

2. The appearance of bad fusion, loose combination

Causes:

(1) steam heat, temperature is not enough, curing time is too long;(2) the particle size is too small, the foaming or foaming agent content is too small;(3) Uneven bead filling or the model is not filled.

Prevention method:

(1) Control the density of pre-foaming particles and control the ripening;(2) increase the temperature, time and pressure of ventilation;(3) Change the bead with smaller particle size.

3. The appearance is normal, and the interior is granular without melting

Causes:

(1) The steam pressure is insufficient and fails to enter the center of the model or the cold air is filled with the cavity;(2) The molding heating time is short, the molding temperature is low, and the mold does not reach a certain temperature degree;(3) the ripening time of pre-emitted particles is too long and the content of foaming agent is too small;(4) Particle expiration metamorphism.

Prevention method:

(1) improve the preheating temperature of the mold and make it uniform as a whole;(2) improve the steam pressure, prolong the molding time;(3) control the ripening time and development of particles the amount of foaming agent;(4) the use of plasmids.

4. The appearance of melting, softening

Causes:

(1) the molding temperature is too high, exceeding the particle process specification;(2) forming foam time is too long;(3) Too many and too big air holes in the model.

Prevention method:

(1) Reduce the forming foaming temperature and pressure;(2) shorten the time;(3) Adjust the size, quantity and distribution of mold cavity vents;

5. The appearance is enlarged and deformed by expansion

Causes:

(1) The mold is not sufficiently cooled and the temperature is too high;(2) appearance stripping too early, too fast;

Prevention method:

(1) Cooling the mold is not hot;(2) Control demoulding time.

6. The appearance of large plane contraction

Causes:

(1) the cooling rate is too fast and the cooling time is too short;(2) the molding time is too long, so that the appearance of a large area of overheating;(3) the mold is overheated.

Prevention method:

(1) Control the cooling rate and cooling time;(2) Reduce molding time;(3) put the shape into the oven (50~60℃) for post-treatment, promote its uniformity, do not make to overshrink and sag.

7. Local contraction of appearance

Causes:

(1) Uneven feeding;(2) uneven cooling;(3) The mold structure is unreasonable or the mold is not properly placed in the steam cylinder, and the part is directly facing the hot area at the steam inlet.

Prevention method:

(1) Control the uniformity of feeding;(2) Adjust the wall thickness of the mold and the size, number and distribution of the vent holes, so as to control the cooling rate and make the mold cooling uniform;(3) Change the position of the mold in the steam cylinder to avoid overheating in local places opposite the inlet.

8. Protrusive surface particle interface

Causes:

(1) forming foam time is too long;(2) the mold cooling rate is too fast.

Prevention method:

(1) shorten the time of forming foaming;(2) reduce the cooling rate of the mold or put it in the air for slow cooling;(3) to ensure the mass of the particle.

9. The surface particle interface is sunken and rough

Causes:

(1) forming foam time is too short;(2) Violation of pre-foaming and ripening norms;(3) the amount of foaming agent is too small;(4) The size, quantity and distribution of air holes are unreasonable.

Prevention method:

(1) prolong the molding foaming time;(2) shorten the pre-foaming time, reduce the molding heating temperature, and extend the curing time of particles;(3) Use dry particles or phases should be qualified beads;(4) The size, quantity and distribution of mold cavity vents should be reasonable.

10. Appearance peeling (peeling) micropore exposure

Cause: appearance and mold cavity surface adhesion.

Prevention method: add appropriate release agent or lubricant.

11. Deformation and damage

Causes:

(1) The working surface of the mold is not lubricated or even rough;(2) the mold structure is not reasonable or the shape is not appropriate;(3) Insufficient cooling time.

Prevention method:

(1) Add lubricating oil in time to ensure the smooth working surface of the mold;(2) modify the mold structure, the slope of the mold, take the shape of the process;(3) prolong the cooling time of the mold.

12. Flashes, burrs

Cause: the mold is not properly matched at the parting surface or the mold lock is not closed during operation.

Prevention method:

(1) the parting surface of the mold must be closely matched;(2) the flaps can be cut off with a beatknife or polished with sand paper.

13. The appearance contains condensed water

Causes:

(1) Incomplete particle bonding;(2) the water pressure is too high and the cooling time is too long;(3) the foaming particles are coarse and break and hole when forming and heating.

Prevention method:

(1) steam pressure should be appropriate when forming and heating;(2) adjust the cooling water pressure and time;(3) the appearance is placed at 50~60℃, oven or drying room hot air in the drying process.

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Post time: May-13-2021