2019年1月21日星期一
Technical Problem 8 from Fiberglass Compression Molding--Sink Marks
Description:The depressed deformation on the surface,ribs,raised part and/or the back side(shiny or dark).
Condition:uneven shrinkage during molding.Solution:
1).use low or no shrinkage resin in formulation for sheet molding compound(SMC).2).Increase the temperature of Cavity or Core and to bring the temperature difference between Cavity and Core to 5--6℃.
3).increase the pressure and shorten the length of glass fiber.4).improve the mold design,change the feed position.
5).narrow the gap between core and cavity of fiberglass mold.
Condition:uneven shrinkage during molding.Solution:
1).use low or no shrinkage resin in formulation for sheet molding compound(SMC).2).Increase the temperature of Cavity or Core and to bring the temperature difference between Cavity and Core to 5--6℃.
3).increase the pressure and shorten the length of glass fiber.4).improve the mold design,change the feed position.
5).narrow the gap between core and cavity of fiberglass mold.
2019年1月7日星期一
Analysis of reasons for Warpage of Plastic Injection Molding Products-2
1)Design of the gating system,the gate location, form and number of gates of the injection mold will affect the filling state of the plastic raw material in the mold cavity and then result in deformation of the plastic part. The longer the flow distance, the greater the internal stress caused by the flow and the filling between the frozen layer and the central flow layer.Conversely, the shorter the flow distance, the shorter the flow time from the gate to the flow end of the plastic injection parts, and the freezing during filling.The thickness of the layer is reduced, the internal stress is lowered, and the warpage deformation is also greatly reduced.
For a large flat plastic part, if only one center gate or one side gate is used, since the shrinkage rate in the diameter direction is larger than the shrinkage ratio in the circumferential direction, the molded plastic part will be distorted.Point gates or film gates can effectively prevent warpage. When molding by spot casting, the position and the number of gates have a great influence on the degree of deformation of the plastic part due to the anisotropy of shrinkage of the plastic.
Since 30% glass fiber reinforced PA6 is used, a large injection molded part with a weight of 4.95 kg is obtained, so that a plurality of reinforcing ribs are provided along the flow direction of the surrounding wall, so that a sufficient balance can be obtained for each gate. In addition, the use of multiple gates can also shorten the flow ratio (L/t) of the plastic, thereby making the density of the material in the cavity more uniform and shrinking more uniform. At the same time, the entire plastic part can be filled with a small injection pressure. The smaller injection pressure can reduce the molecular orientation tendency of the plastic and reduce the internal stress, thereby reducing the deformation of the plastic part.
For a large flat plastic part, if only one center gate or one side gate is used, since the shrinkage rate in the diameter direction is larger than the shrinkage ratio in the circumferential direction, the molded plastic part will be distorted.Point gates or film gates can effectively prevent warpage. When molding by spot casting, the position and the number of gates have a great influence on the degree of deformation of the plastic part due to the anisotropy of shrinkage of the plastic.
Since 30% glass fiber reinforced PA6 is used, a large injection molded part with a weight of 4.95 kg is obtained, so that a plurality of reinforcing ribs are provided along the flow direction of the surrounding wall, so that a sufficient balance can be obtained for each gate. In addition, the use of multiple gates can also shorten the flow ratio (L/t) of the plastic, thereby making the density of the material in the cavity more uniform and shrinking more uniform. At the same time, the entire plastic part can be filled with a small injection pressure. The smaller injection pressure can reduce the molecular orientation tendency of the plastic and reduce the internal stress, thereby reducing the deformation of the plastic part.
Technical Problem 8 from Fiberglass Compression Molding- Surface Ripple
Technical Problem 8 from Fiberglass Compression Molding- Surface Ripple
Description:Ripple on the long,vertical and thin surface of fiberglass parts,which is at right angles to the direction of flowing.Also due to other adverse flow conditions (wall thickness difference) may result in Irregular surface ripple.
Condition:Complex design of the product prevents uniform material flowing.
Solution:In most cases it cannot be completely eliminated, but can be improved in the following ways: Increase pressure, change the feeding position,to use low shrinkage or no shrinkage resin.
2018年12月26日星期三
Analysis of reasons for Warpage of Plastic Injection Molding Products-1
With the development of the plastics injection molding industry, people have higher and higher requirements on the appearance and performance of plastic injected parts. The degree of warpage deformation is one of the important indicators for evaluating product quality, and it is more and more concerned and valued by mold designers. Mold designers hope to predict the possible warpage of plastic parts during the design phase in order to optimize the design and then they can improve the efficiency and quality of injection molding, shorten the mold design cycle and reduce costs. I take this change to analyze the factors affecting the warpage of injection molded products during the design process of plastic injection molds.
1. Effect of the mold structure on the warpage of plastic injection products:In terms of mold design, themain factors affecting the deformation of plastic parts are pouring system, cooling system and ejection system.
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Technical Problem 7 from Fiberglass Compression Molding-- Warpage
Technical Problem 7 from Fiberglass Compression Molding-- Warpage
Description 1:The Fiberglass Compression Molding part is slightly warped.
Condition 1:Warpage due to shrinkage during hardening and cooling.
Solution:To cool fiberglass molding parts in fixture.To use low or no shrinkage resin.
Solution:To cool fiberglass molding parts in fixture.To use low or no shrinkage resin.
Condition 2：The temperature of half mold is higher than other half.
Solution:Reduce mold temperature difference.
Solution:Reduce mold temperature difference.
Description 2:The Fiberglass Compression Molding part is seriously warped.
Condition:Particularly long process cause fiberglass orientation and then result in warpage.Solution:To increase the feeding area,shorten the process and use low shrinkage or shrink free resin.
Condition:Particularly long process cause fiberglass orientation and then result in warpage.Solution:To increase the feeding area,shorten the process and use low shrinkage or shrink free resin.
2018年12月11日星期二
Technical Problem 6 from Fiberglass Compression Molding--Mucosa
Technical Problem 6 from Fiberglass Compression Molding--Mucosa
Description 1:The Fiberglass Molding part is difficult to remove from the mold, and the fiberglass sheet sticks to the mold in some areas.
Condition 1:Mold temperature is too low.
Solution:Increase the mold temperature.
Condition 2:Solidifying time is too short.
Solution:Extend solidifying time.
Solution:Extend solidifying time.
Condition 3:It is too long to open the outer packaging of Fiberglass sheet.
Solution:Always keep the Fiberglass sheet sealing before using them.
Solution:Always keep the Fiberglass sheet sealing before using them.
Condition 4:Without special treatment before using new molds or long-term unused molds.
Solution:To use release agent to help demoulding for first several cyclings.
Condition 5:The mold surface is too rough.Solution:better surface polishing.
Description2:It is difficult to demould the solidified fiberglass molding parts.In some areas
the fiberglass raw material sticks to the mold, and the surface of the final parts has some
the fiberglass raw material sticks to the mold, and the surface of the final parts has some
microholes and scars.
Condition:The feeding area is too large, the air can not be discharged, and the air impedes solidifying.
Solution:Reduce the feeding area and add small sheet at the top of the large sheet.
Solution:Reduce the feeding area and add small sheet at the top of the large sheet.
2018年12月3日星期一
Technical Problem 5 from Fiberglass Compression Molding--Swell.
Technical Problem 5 from Fiberglass Compression Molding--Swell.
Description:a semicircular swell on the surface of solidified fiberglass compression molding part.
Condition 1:Entrapped air between fiberglass sheets.Solution:Remove the interlayer air by pre-pressing method and reduce the feeding area to facilitate the discharge of air.
Condition 2:The tooling temperature is too high (evaporation of monomer).Solution:low tooling temperature.
Condition 3:Solidifying period is too short (evaporation of monomer).Solution:Extend solidifying period.
Condition 4:There is dry fiber.Solution:Reduce the viscosity of the resin.Install more work rolls in the impregnation area, and heat the dip rollers.Replace the glass fiber.
Condition 5:There are burrs in the cavity of fiberglass compression tooling.Solution:Carefully remove the burrs in cavity of tooling.
Condition 6:Fiberglass sheet is too soft.Solution:Increase the thickening of fiberglass SMC raw material or increase the content of thickener.
2018年11月26日星期一
Technical Problem 4 from Fiberglass Compression Molding--Many small surface holes.
Technical Problem 4 from Fiberglass Compression Molding--Many small surface holes.
Description:if there are too many small holes in the surface it will be difficult to release the fiberglass molding products.
Condition 1:The feeding area is too large, and the surface air is not discharged due to the short process.
Solution:Reduce the feeding area and add small material sheet at the top of the large sheet.
Solution:Reduce the feeding area and add small material sheet at the top of the large sheet.
Condition 2:The clipping edges are too large. Solution:Repair clipping edges.
Condition 3:There is dry fiber.The initial viscosity of the resin paste is too high. The glass fiber is not fully saturated.
Solution:Reduce the initial viscosity of the resin paste, increase the work roll in the impregnation area, and replace the glass fiber.
Solution:Reduce the initial viscosity of the resin paste, increase the work roll in the impregnation area, and replace the glass fiber.
Condition 4:Pre-gelled area on the fiberglass molding part. Solution:Reduce mold temperature and add inhibitor to resin paste.
Condition 5:SMC material dry.
Solution:When using the anti-seepage film to wrap the SMC material, the quantity of zinc stearate can not be prepared too much.
Solution:When using the anti-seepage film to wrap the SMC material, the quantity of zinc stearate can not be prepared too much.
Condition 6:Fiberglass SMC material too soft.
Solution:Increase thickening time or increase thickening temperature to increase thickening viscosity level.
Solution:Increase thickening time or increase thickening temperature to increase thickening viscosity level.
2018年11月19日星期一
Technical Problem 3 from Fiberglass Compression Molding-Internal cracking
Description:Due to excessive shrinkage stress in individual layers of thick-walled products, bosses or ribs.
Solution:Reduce the feeding area so that the fibers are better interwoven between the layers and reduce
the molding temperature.
2018年11月12日星期一
Chapter 2--Gas assistance system for Pressure Reduction technology in Plastic Injection Molding
Principle:
In fact, pressure must be generated in the production of molded plastic parts. In general, the pressure in the cavity is caused by a slight shrinkage, and its effect is cumulative, and this cumulative effect will eventually lead to the defective plastic injection parts. Typically, when the part is removed from the mold for the first time, it can resist the effect of the in-mold pressure on the structure of injected plastic parts. Plastic parts can cause slight deformation or cracking only at high temperature. In practical applications, all the mold parameters can cause a slight deformation, resulting in in-mold pressure. When these forces act together on the same part, a large amount of extra stress is generated. The forces acting on the part result in the generation of pressure. When the pressure is very small, it will not have a significant impact. However, if the pressure is high enough, the in-mold pressure becomes a factor that must be considered because the combined action with the external force will exceed the maximum value that the plastic injected partscan withstand.The most serious result is part’s fracture.
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