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1、Closed Loop injection Machine Commissioning Hot Water, Chilled Water, Normal Water with appropriate connections. Closed loop Material Dryers slightly negative is ideal. If the error is greater than +5% error are not properly load compensated. Test at three different injection velocitiesslow, medium,
2、 and fast. If your machine passes this severe load-variation test, it will keep fill time constant during production.2.4. Velocity LinearityCaution: Before beginning this test, make sure short shots can be ejected easily. If shorts cannot be easily ejected you will have to use second-stage pressure
3、to finish filling the part.The purpose of this test is to compare a machines set velocity with what is actually achieved. To get good data, its recommended that the shot should be at least 60% of the barrel capacity. If you are using less than 40% of barrel capacity, do not use that mould for this v
4、elocity linearity test, as the results may be useless.In normal production mode using normal procedures to begin production making full parts. Lower the second-stage, or pack and hold, pressure as far as the machine will allow. At whatever velocity is currently set on the machines controller, this s
5、hould make a short shot. If not, adjust the position transfer to make a part that is short but at least 80% full.Make sure the machine is running under velocity control and you have an appropriate Delta P. Now increase the set injection velocity in reasonable (safe) increments until the machine is s
6、et to the fastest injection velocity allowable. As you increase the velocity, you may have to adjust the position transfer to ensure you are making short shots, and double check that you are still under velocity control with an appropriate Delta P. Once at the fastest allowable velocity, adjust the
7、position transfer to make a 99% full part.Once you are making 99% full parts under velocity control, you can start taking data. Note the actual “screw start position”dont go by the set shot size and decompression or suck back, if any. Then note the cut off or stroke transfer position and the fill ti
8、me (to within 0.01 sec). Without changing anything but injection velocity, reduce the set velocity from as fast as the machine can go to nearly as slow as the machine can go. Make sure you are transferring on position and not time; that is, make sure the overall injection timer has enough time on it
9、 to allow you to reach the transfer position. The parts may change in size but do not readjust shot size or position transfer during the test.Set up the data table to look like Table 1 and if you want, graph the data as shown in Fig. 1. To calculate the actual velocity, subtract the cut off or trans
10、fer position from the actual screw start position and divide by the fill time. Because this method includes the initial inertia to get the screw up to speed, expect the fastest actual velocities to be only 85% to 95% of the set velocities.ShotSet Velocity mm/sec.Fill Time sec.Actual Velocity mm/sec.
11、% of Set Velocity1 2 3 4 5 6 7 8 9 10 11 12Note: At high velocities actual being a bit slower then set is to be expected because of inertia. If the data shows actual velocities hitting a maximum and levelling out this test has failed.2.5. Switchover Response from First to Second StageSwitchover resp
12、onse is the phase of the cycle is the critical stage where the first stage of filling the part to 90+% full ends and the second stage (pack and hold) begins. Try, check two methods, 100 parts each method:5.1.1. Rapid TransferRapid transfer from first to second stage, very little plastic has to be de
13、livered to the cavity, the rapid drop of plastic pressure in the nozzle does not over pack or accentuate the rapid development of cavity pressure. If this method does produce consistent parts the performance of the screws check ring is suspect.5.1.2.Slow, Velocity Controlled PackRequires a three-sta
14、ge moulding process, the filling or first stage gets the part 90+% full. Second Stage, packing is velocity controlled to slow the cavity-pressure development and ends when the cavity pressure reaches a level previously found to produce an acceptable part. Once this cavity pressure is achieved, the m
15、achine transfers to holding (third stage) to keep all the plastic in the cavity and hold the part to specified dimensions. This method will compensate for viscosity variations and any leakage of the check ring.Data Recording:CycleTimeInjectionMax. inj.SwitchoverActual sw.DosageCycle numbertimepressurepressureover stroketimetime h:minsbarbarmmss
