Problems and Solutions of Furan Resin Sand Casting Sand Mould Brushing Coatings2.0

6. Serious flow marks
reason:
The paint has poor fluidity and high viscosity, and the paint cannot drip when it flows down, resulting in serious flow marks. When the paint flows out, the pressure is too large, the distance between the flow coating rod head and the surface of the cavity is too close, and the paint liquid has an impact on the surface of the coating. There are uneven traces, the paint flow is small, the flow is unstable, and flow marks will be formed on the surface of the cavity.
solution:
6.11 When flow coating, use a large flow to quickly flow from top to bottom, and do not stay on the surface of the sand mold for a long time.
6.12 Improve the fluidity and leveling of the coating and reduce the viscosity.
6.13 Increase the distance between the flow coating rod head and the surface of the cavity, and the general distance is 18-25mm.
6.14 adopts fan-shaped flow coating rod head.

7. Laminate
Lamination is the superimposed texture produced when flow coating the cavity surface two or more times from top to bottom or left to right.
cause:
It is mainly caused by high sand mold temperature, high paint viscosity, small flow coating flow and multiple flow coating.
solution:
7.1 If the temperature of the sand mold that has just been flowed by the sand mixer is high, do not flow coating immediately, and air cooling according to the specific situation.
7.2 Reduce the Baume degree of the coating and improve the fluidity.
7.3 Increase the flow and avoid multiple flow coating. By making flow coaters of different specifications to reasonably control the flow, when selecting a pump, the lift and flow rate should be slightly higher, and the liquid flow pressure is large. The liquid flow can be controlled by the control switch, etc. Application pressure and flow rate.

8. Sand surface scouring
Commonly known as "pulling", the mold surface is often plucked if the mold is used for a long time or the mold is unstable.
solution:
8.1 After repairing the sanding part of the sand mold with paint paste, flow coating is carried out. The disadvantage of this method is that it needs to be placed for a longer time after flow coating, otherwise the repaired part with paint paste will foam.
8.2 After flow coating, use paint paste to repair the sanded parts, then use thinner to brush the paint paste, and finally ignite. This method is currently widely used, saves manpower, and makes up for the deficiencies caused by tooling and pre-sequence operations.

9. Uneven coating
When flow coating, the sand mold is often prone to the situation that the coating is thin on the top and thick on the bottom. When the rotational speed of the viscometer rotor is fixed, the apparent viscosity of the coating decreases with the increase of the shearing time, and can reach a constant value for a long time. and gradually pick up, this is the thixotropy of the coating. The thixotropy of the coating is too strong, which is conducive to leveling, but it is easy to cause excessive flow, which makes the coating appear thinner at the top and thicker at the bottom. Poor fluidity and small inclination angle will also cause uneven coating thickness. For water-based zircon powder coatings, the thixotropy rate M=9%-12% is better.

10. Summary
10.1 The efficiency of the flow coating process is nearly ten times higher than that of the original brush coating process, which is very suitable for the assembly line operation.
10.2 The casting mold after flow coating operation has smooth surface, uniform coating thickness, dense and clear outline. After casting, the surface of the casting is smooth, the surface roughness can reach Ra25um or more, and the dimensional accuracy of the casting is high, reaching the CT9 level or above in GB 6414-1999 "Casting Dimensional Tolerance and Machining Allowance".
10.3 Due to the uniform coating of the flow coating, the flowed down coating can be recycled. According to the on-site measurement, the use of the flow coating process can save about 25% of the paint compared to the original.
10.4 After many experiments, it was found that when the Baume degree of the flow coating coating is between 22-26, the fluidity of the coating is the best, the coating thickness is suitable, and the casting defects are the least.
10.5 Reduce the pollution of the working environment, and use flow coating to completely solve the air pollution caused by paint dust.

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