Top 10 problems and solutions that paints are most likely to produce

First, coating accumulation
cause:
1. The flow of coating is slow, because the coating is a denatured fluid, where there is a mesh structure and yield value, yield value and viscosity are the two main factors causing paint accumulation. Paint yield value is too high, stick too large, resulting in poor paint flow.
2. The flow marks produced by the coating in the flow process flow along the mould, and the groove is encountered to produce a build-up, resulting in the mould angle is not clear
china
.
3. The mould tilt angle is not suitable.
4. The flow rate is small, the paint flow can not be lowered resulting in accumulation.
5. The flow rate is slow due to insufficient pressure, resulting in accumulation.
to take measures:
 1. From the field operation to reduce the paint wave beauty, the practice has proved that when the flow coating paint wave beauty between 22-26 paint flow is the best. From the paint's own factors to reduce the paint yield value and viscosity.
2. Remove the flow marks by blowing the air pipe or diluent with a brush.
3. Mould placement angle requirements: the mould is hoisted above the coating groove with a horizontal angle of 75-90 degrees for flow coating.
4. Increase the cross-sectional area of the flow-coated rod head and hose, with the aim of increasing the flow flow, the general use of the flow-coated rod head and hose is 4 sub-tubes, if the increased cross-sectional area can be used 4 and 6 pipes respectively, or both can use 6-pipe.
5. To increase the flow rate of wind pressure, in order to obtain the appropriate coating thickness, the speed at which the coating flows out of the coating machine is appropriate at 100-200mm/s, and the wind pressure is generally between 0.4×105Pa-0.6×105Pa, which is prone to splashing if it is too large.
, the thickness of the coating is not
:
1. The coating does not form enough coating thickness to flow directly.
2. The coating all penetrates into the sand, resulting in insufficient coating thickness.
mold release agent on the mould surface, which reduces the permeability of the coating and directly affects the size of the coating thickness.
take
1
. to improve the viscosity of the coating (maximum not more than 7 s), thereby improving the coating, to avoid excessive flow of the coating
.2. Improve mould tightness, can effectively avoid excessive penetration of the coating, mould compaction between 45% to 55% is more appropriate.
3. The mold release agent on the surface of the mould can be fully dried before production, the mould locally contaminated with the release agent with fine sand paper to grind off and then flow coating.
4. Cast iron mould wet coating thickness requirements: thin-wall casting 0.15mm-0.30mm, medium casting 0.30mm-0.75mm, thick-wall casting 0.75mm-1.00mm, thick casting 1.00mm-2.00mm.
, the coating surface falls off
assembly process, the operator blows sand in the cavity with a wind pipe, the surface of the coating layer occasionally falls off.
reason:
1. The coating strength is low.
2. The coating layer and the layer are not fully integrated to form a whole.
to take measures:
1. A small amount of binder in the coating tends to cause the coating strength to be insufficient, so increase the proportion of binder in the coating.
2. The coating does not burn sufficiently to create a combination of the susceptible layer and the layer. For more than 3 tons castings easy to occur coating surface shedding phenomenon, as long as reasonable control ignition time can solve this problem, generally 3-5 seconds after the upper box flow ignition is appropriate, the lower box flow coating after 5-7 seconds ignition is best. Can also be baked by gas fire, but not too long, otherwise the coating will crack.
4. Casting sticky sand
reason:
coating fire resistance is not enough, coating or mould and high temperature metal liquid contact chemical reaction, so that the casting surface forms a very difficult to clean the material, often referred to as viscose sand, flow coating method will also produce sticky sand phenomenon.
to take measures:
1. Change the composition of paint composition, improve the refracessability of the paint to choose high bauxite powder, zircon powder and other refrainable fillers.
2. Increase the thickness of the coating, but the thickness can not exceed the maximum required thickness of the coating, too thick will produce casting defects such as coating skin.
3. Increase the flow coating wave beauty, up to a maximum of 28, otherwise the flow will be reduced.
4. Some castings are partially overheated, the flow coating is very easy to stick sand, before the flow coating in the hot section position to paint high fire resistance paint, can effectively prevent sticky sand.
5, the flow marks serious
reasons: poor paint mobility, high viscosity, paint flow down can not drop, resulting in serious flow marks;
to take measures:
1. When the flow coating uses a large flow from top to bottom rapid flow, do not stay on the mould surface for a long time.
2. Improve the fluid leveling of coatings and reduce viscosity.
3. It is appropriate to increase the distance between the flow rod head and the surface of the cavity, which is generally 18-25mm.
4. Use a fan-shaped flow-coated rod head.
, laminar
overlays are overlay textures that result from two or more flows from top to bottom or from left to right when coating the surface of the cavity.
: mainly because of the high mould temperature, large viscosity of the coating, small flow flow, multiple flow coating caused.
to take measures:
1. Sand mixer just finished the mould temperature is high do not immediately flow coating, according to the specific situation of air cooling.
2. Reduce paint wave beauty and improve fluidity.
3. Increase traffic and avoid multiple scribes. By making different specifications of the flow coating machine reasonable control flow, in the selection of pumps, its flue, flow selection should be slightly higher, the flow pressure is large, through the control switch and other drainage to achieve fluid flow control, to achieve the required application pressure and flow rate.
, paint splash
paint splash, is a smooth coating surface splash paint drops.
: This defect is mainly caused by too much pressure on the flow coating outlet.
to take measures:
1. Reduce the flow coating outlet pressure. The thickness, length, surface roughness, outflow position, etc. of the pipeline flowing of the coating will have a great impact on the pressure of the flow coating, and the outflow pressure P of the coating must not be less than 0.4×105Pa.
2. Do not apply vertically to the surface of the flow rod and cavity to avoid paint splashes.
8, mould surface pickpocketing sand
commonly known as "pulling hair", mold use time is long or unstable mould surface pickpocketing phenomenon often occurs, after the flow of mould surface plane is not enough, depression, to the appearance of the quality of a great impact.
to take measures:
1. The sand-type pickpocketing part with paint paste patched after the flow coating, the deficiency of this method is that after the flow coating needs to be placed for a longer period of time, otherwise the part patched with paint paste will foam.
2. After the flow of paint paste to repair the sand part, and then use thinner to brush the paint paste flat, and finally ignition. This method is widely used at present, saving manpower and making up for the deficiencies brought about by the workwear and pre-order operation.
, uneven coating
moulds are often prone to thin and thick coating. In the case of viscosity meter roil speed fixed, the surface viscosity of the coating with the increase in shear time and decrease, a long time can reach a constant value, if it is converted to a static state, its surface viscosity with the increase of the stationary time and gradually rebound, this is the tenacity of the coating. The tentacles of the coating are too strong, which is good for leveling, but it is easy to cause excessive flow, so that the coating appears thin and thick. The flow is not good, the tilt angle is small will also cause the coating thickness is not uniform phenomenon. For water-based Tannin powder coatings, the tentacle rate of M is 9%-12%.
10, and the substrate adhesion difference, paint
reason: coating in the coating spraying process, due to the substrate and paint between the layer adhesion difference, often appear paint problem, resulting in high product failure rate, serious damage to quality and production cycle.
To take measures: now the general practice is to use adhesion promoter, it is a special treatment agent that can enhance the adhesion between the coating and substrate, with special function groups, can be effectively combined with the polar group of the material surface, resulting in high adhesion between layers, play a good role in the bottom coating.