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Processing enterprises should be in the injection molding machine, injection mold under normal operation, test all kinds of injection mold performance, and finally measure forming parts size, through these information can determine the existing state of injection mold, find out the cavity, core, cooling system and parting surface damage, according to the information provided by the plastic, can judge the injection mold damage status and maintenance measures.
There are many factors to influence the injection mold cooling,such as the shape of plastic parts,and the parting surface design, the types, temperature and flow rate of cooling medium, geometry parameters and spatial arrangement of cooling pipe, mold material, melt temperature, eject and mold temperature that plastic parts requiring, thermal cycling interaction between plastic parts and molds,etc.
Four matters needing attention of maintenance of injection mould.
According to concerning sectional statistic, at present, China has been built and begun to take shape of the injection mold industrial park have nearly one hundred or so, there are some injection mold industrial park is under the construction planning. We believe that China will develop into the world injection mold manufacturing center in the future.
Most of my injection experience is in optical lens, so stress (optical birefringence) is visible and to be avoided. We molded opthalmic lenses and magnifiers so we had high aspect ratio parts. We measured part deformation with a Wyco. We also added dyes to the products, mixing in the injection molding extruder only.

To me the key is getting the resin into the injection mold quickly, slowing cooling to the Tg all the part and then cooling it slowly down to room temperature. If there was a way to injection a warm injection mold and then bring the temperature of the part down slowly and evenly at first and then speed it up this would be an asset. Naturally I have considered other ideas over the years. Air cooling could allow an on off approach to cooling, but I have set up a PET tape process with just air drying after the bath and the volume of high pressure air required to get significant cooling is costly.
It depends on several factors.
  1. You can work with the same mold, but you need to consider what happening with the cavity surface, due to a great friction inside if try a 50% of G.F., your mold must be have a surface treatments, or special finishing protection, also some time is better use special oil.
  2. If the sink marks is continuously you can try to improve some special test runs into the injection molding machine process, I recommend you try with 3-4 different profiles at the second pressure in order to led the flow front advance and fill the cavities more properly.
  3. The data of the material that you are using is around of: Linear mold shrink for PA66+30GF 0.2-0.6%
    Melt temperature 428-579 °F
    Mold temp. 104-140°F
    Linear mold shrink for PA66+50GF 0.09-0.11%
    Melt temperature 455-590 °F
    Mold temp. 104-140°F
It is bit unfortunate that the injection molding machines have made so many advances whilst the mold- where all the action happens remains in 17th century- apart from using CNC technology that makes it more accurate reproduction of CAD file. Cooling is by and large after thought, where can I put some cooling lines? Radiator in a car is not an option, car will not run without one and why our molds have an afterthought for radiator? How many tool specifications define no. of shots to tool stabilization? Uniformity of temperature over entire part (just take a simple thermal image of any part after injection molding and see how bad the variation is). Parts vary in quality and have warpage not so much because melt is having some variation in couple of degrees C, when tool has hot spots and delta T in excess of 60 Deg. C.
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It has been proven that electric injection molding machines are much better than hydraulics for many reasons such as, less power consumption, very quiet operation, no oil leaks, repeatability, independent drives (it is easy to achieve parallel movement of the injection molding machine), reliability, no linear transducers and ideal for clean rooms.

Most of the injection molding machine manufactures tend to use the same control panel for both hydraulics and electric but the way electrics control velocity to pressure and screw recovery are different to hydraulic injection molding machines, some machines have shown some issues due to this, also when using core pulls on electric injection molding machines it may be required to get a mobile hydraulic core pull unit as some tools have hydraulic core pulls.
We all know that the skin layer in a molded part with PP is less crystalline than the core in a PP injection molded component. Could you please explain the mechanism behind why it happens? Is it due to the rapid cooling during the cooling cycle during injection molding which prevents the formation of crystalline phases? If there is some literature on the internet which explains the same I would like the links to the same.

The crystalizing of the material takes time and usually progress better at temperatures a bit higher than the injection mold surface temperature (actually in some cases you might gain cycle time by increasing injection mold temperature when running crystalline materials). Some companies make inductive heaters for the injection mold to increase the surface temperature to get close to the melt temperature to avoid or reduce the frozen layer. Then they apply a rapid cooling system with optimized cooling channel design and in some cases using an expanding gas for cooling.
Not only injection mold temperature determines melt temperature as it moves quickly through the mold. The melt temperature itself as it starts its journey through the injection mold (self-evidently) is the reference point. Speed of injection, particularly in thin sections, is of huge influence, as it will determine the degree of shear heating. Fighting against this will be the loss of heat to the injection mold. Forget the idea of notional mold temperature. In other words, it is a fantasy to imagine that coolant (water usually) set temperature is what the material encounters at each point in its journey.

It is a cyclically fluctuating parameter with each injection cycle and will vary from point-to-point over the entire pair of injection mold surfaces. This is why mold-filling and cooling simulation is such a great tool and does give a fantastically useful insight into what actually happens throughout each cycle. Only by measuring at/near injection mold surfaces dynamically (thermocouple) can anyone know what the REAL (not SET) conditions are actually being encountered by the highly compressible fluid we know as plastic. It never ceases to fascinate me.
The reduction of wall section should always be a "given" in any half-decent designer's approach to designing a component. Sometimes, however, the thinnest wall section that can be contemplated to fulfill key requirements are still what most would call "thick." I'm dealing with components at the moment (not injection molded, but thermoplastic) that are needed to withstand 40 tones short-term loading. Some ABS injection moldings I was aware of in the '80s were around 25mm thick (spin-welded fishing net flotation spheres) and — I am told — some modern fighter jet cockpit canopies are injection molded in polycarbonate at around 65mm!
Moldflow has been around for a third of a century and even in its first decade, I commissioned its use, in the hands of an expert and highly experienced injection mold designer to solve a molding problem that had jeopardized the main assembly line of a world-renowned automotive supplier. The injection mold in question had indeed been designed by highly experienced specialists, but they got it spectacularly wrong. The problem was simulated, tool modifications proposed and re-simulated, with promising results. The injection mold was physically modified in line with the simulated changes and immediately ran with effectively zero defects. Previously, convoys of taxis had to be reserved to ferry parts a round trip of over 800 km, just to keep the main line supplied with reduced numbers, as there had been at least 30% reject levels pre-modification. Now, THAT really was some experience!
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