Burrs caused by plastic pet dog toy products ( Batch of feng) The reason?
looks be like complex, in fact, all burrs caused by molding parameter setting, can be attributed to the pressure, when the injection pressure is beyond the equipment of the clamping force or die local bear strength, production capacity will flash. Around the gate, parting surface, insufficient strength of broken hole, burrs is likely to come in.
( 1) V/P switch too late.
are generally in shoot all good just ran full product structure, the pressure is the most ideal switch, switch late, a sharp rise in the cavity pressure, the excess pressure is prone to flash, even will cause the product deformation, size slants big, stick model, a series of problems such as head injury.
( 2) Shoot glue too fast.
shoot glue process by the same set of lock, speed setting generally should follow '- slow Fast - Slow 'principle, especially at the end of the shot speed, fast speed, making quick peak cavity pressure, die clearance under the condition of excessive or insufficient clamping force, flash will result.
( 3) The holding pressure or pressure too fast.
excessive pressure stress or pressure maintaining speed too fast, will be in the heart of the pressure maintaining process plastic quickly packed into cavity, resulting in steep cavity pressure, the excess pressure around the gate and even whole burrs, analysis of the interaction between the more serious can cause bilge mode. Product structure allows cases, in the first period of set a small pressure maintaining pressure ( Less than 10%) And a short holding time ( 1. More than 5 mm thickness of the product, can be set 0. 5 seconds or so) , which is used to buffer the transition of V/P switch, can have very good prevention effect of burrs.
the holding pressure Settings should follow the principle of a commonly: cavity in the plastic melt temperature is low, the location of the first full satisfied after the location of the high temperature. The position of the low temperature, general distribution in the end of the filling, the position of the adhesive thickness thinner, parting surface, so often in the holding pressure should not be set too high, as far as possible in the back of the holding pressure is used to solve the problem of local shrink or size problems.
the machine, pressure setting, increase gradually from low to high, suggested each cycle can increase 5% 10% of the way, until you find the reasonable pressure value, the plastic melt temperature too high can also cause product burrs, after the plastic melt temperature is too high, its viscosity will gradually decline, good liquidity, need of clamping force per unit area will also along with the increase, mould clamping force or large local clearance is insufficient, can appear the burrs. The causes of plastic melt the actual temperature rise is various, feed tube temperature setting is too high, melt metering is too large, the screw is too thick, cycle is too long, back pressure is too big, speed too fast, will lead to raise the temperature of plastic or directly led to the decrease of the viscosity. When the product appear burrs, these parameters to check in a timely manner.
in addition to the above problems, the different characteristics of the plastic itself determine their liquidity, the plastic mold parts assembly clearance requirements and the requirements of the machine clamping force is not the same. Need to be at the early stage of the plastic mold cavity assessment and fully evaluate the product distribution of the gate, into the possible in the lowest injection pressure to make qualified products. At the same time ensure that the product can stability of normal production, and achieve the ideal life, need to fully assess the mold structure and intensity of each part. Often the mold cost savings in manufacturing cost is taken into account in design, in subsequent not stable in the production of injection molding, mold more damage, even tinkering, will only cause a vicious cycle.