注塑工艺参数优化

培训课程 2 工艺参数的优化受训者手册德马格注塑机工艺参数优化的步骤指导成型周期分析采用下面表格估计注塑过程中的每一阶段对周期的影响. 然后去机床看正在运行的模具, 写下实际的时间并计算出百分比.哪一阶段在整个周期中占最多的时间?那里可以是最有效的缩短成型周期?模具 1模具 2工艺参数优化目标:•一步步改进工艺过程稳定性.•评估各个参数的更改对工艺过程稳定性的影响•to demonstrate the cumulative improvemnt in the process and product consistency方法:At each stage, after the process has been given sufficient time to stabilise, a run of sixteen consecutive mouldings is to be made. These mouldings will be assessed for consistency by weight (a dimension, a physical property or some other attribute could equally well be used, weight is simply the most widely applicable).稳定性通过计算重量的标准偏差来衡量. 同时打印出机床IBED上的过程统计数据.1. 找出转压点2. 找出浇口冷却时间3. 优化注射速度4. 采用正确的螺杆转速5. 优化多级预塑曲线6. 优化松推7. 优化多级保压曲线8. 优化锁模力9. 设定注射压力限定步骤 1找出转压点在没有保压压力和保压时间的基础上填满产品95% -98%, 然后设定一定的保压和保压时间生产16模.初始设置时的指导称12 模产品的重量, 计算标准偏差打印:页面 20 工艺参数优化页面 50 工艺过程统计步骤 1 结果输入实际值步骤 2找出浇口冷凝时间设定保压压力为步骤1 上找出的注射压力峰值的50% 左右.设定保压时间为 1 s .生产数模产品使过程稳定后连续取5模产品称出每模重量和平均值增加保压时间至2 s, 生产数模产品使过程稳定后连续取5模产品称出每模重量. 在保压时间3s, 4s 5s . . . 时重复上述过程直到产品重量不再增加作出产品重量和保压时间的关系图.记录Record the TCU setting and the actual mould temperature.打印:页面 30 温度XL Spreadsheet graph为什么记录模具温度很重要?还有什么因素会影响浇口冷凝时间?步骤 2 结果输入实际值步骤 3优化注射速度采用多级注射曲线, 使注射行程最后的10-20% 采用逐步降低的注射速度.每次更改注射速度, 必须重新建立转压点. (注意每次保压和保压时间都设定为0.) 连续取16模, 计算出标准偏差.打印:页面 24 MWE 使用和没使用多级保压时的曲线页面 26 多级注射页面50 工艺过程统计为什么转压点要更改?注射压力发生了什么?为什么在数社的末端采用逐步降低的注射速度是有用的?步骤 3 结果输入实际值步骤 4采用正确的螺杆转速Select the correct, optimum screw speed for the material being processed (see T.01 notes, Section 5 ). Use this single speed for the whole plasticising strokeSet a back pressure of 5 to 10 bar (hydraulic).Readjust dosing stroke to achieve 95-98% fillTake sixteeen consecutive mouldings and determine the standard deviation of the weights.Print out:Page 50 Process StatisticsWhy is it important to use the manufacturer’s recommended screw speed?STEP FOUR RESULTS Insert actual values in the relevant boxesSTEP FIVEOptimise screw speed and back-pressure profileUse the Dosing Profile page to slow down the screw rotation speed for the last 10% of the metering stroke.Readjust dosing stroke to achieve 95-98% fillTake sixteeen consecutive mouldings and determine the standard deviation of the weights.Print out:Page 21 Dosing ProfilesPage 50 Process StatisticsWhat has happened to the Dosing Stop position?STEP FIVE RESULTS Insert actual values in the relevant boxesSTEP SIXOptimise decompressionFind the decompression speed which gives best screw stroke and melt cushion consistency. Set a decompression stroke of 5mm.Check that you still achieve 95-98% fill.Take sixteeen consecutive mouldings and determine the standard deviation of the weights.Print out:Page 21 Dosing ProfilesPage 50 Process StatisticsWhat has happened to the screw stop position?What is happening to the check ring?STEP SIX RESULTS Insert actual values in the relevant boxesSTEP SEVENOptimise holding pressure profileUse the Holding Profile page to set a holding pressure profile which ensures a smooth transition from injection to the holding pressure phase and use a high enough pressure to pack the part properly.Add a step which reduces holding pressure gradually to zero.Take sixteeen consecutive mouldings and determine the standard deviation of the weights.Print out:Page 24 MWEPage 27 Holding ProfilePage 50 Process StatisticsWhy do you need a smooth transition from injection to holding pressure?Why bother to reduce the pressure gradually if the gate has already frozen?STEP SEVEN RESULTS Insert actual values in the relevant boxesTABULATED RESULTSInsert actual values in the relevant boxesThe range value, R, is the maximum minus the minumum, taken from the seven steps.Can you see a trend?Which step had the greatest effect on the consistency of the moulding?Optimising the clamp forceReduce the clamp force by steps of 50 kN (100 kN for machines over 100 tonnes) using the settings far optimised in the seven steps above.Allow the process to stabilise each time and then weigh five mouldings.Tabulate your results below and plot a graph of tonnage against part weight.Does the mould require the expected clamp force?What are the advantages of running at reduced tonnage?STEP EIGHT RESULTSInsert actual values in the relevant boxesSet injection pressureUntil now the injection pressure has been set to the machine’s maximum value. From the Process Statistcs page it can be seen that the machine does not need all that pressure to fill the mould.Gradually decrease the set injection pressure until the injection time starts to increase. Increase the pressure again until the previous injection time is established with a consistency of 0.08 s or better – preferably 0.02 to 0.03 s variation.What is the purpose of limiting the injection pressure?STEP NINE RESULTSAppendix 1TYPICAL PROCESS TOLERANCESShot-weight deviation 0.05% 0.1% 0.2% 0.4%Plasticising time ± 0.04s ± 0.06s 0.08s 0.13s Injection time ± 0.02s ± 0.02s ± 0.04s ± 0.06s Cycle time ± 0.5% ± 0.5% ± 1% ± 1% Screw position, dosing stop ± 0.1mm ± 0.1mm ± 0.2mm ± 0.3mm Melt cushion ± 0.1mm ± 0.1mm ± 0.2mm ± 0.3mm Melt temperature ± 2°C ± 2°C ± 3°C ± 5°C Mould temperature ± 1°C ± 1°C ± 2°C ± 4°C Barrel temperature ± 1°C ± 1°C ± 2°C ± 4°C Feed zone temperature ± 1°C ± 2°C ± 3°C ± 4°C Hot runner temperature ± 1°C ± 2°C ± 3°C ± 4°C Hydraulic oil temperature ± 1°C ± 1°C ± 2°C ± 2°C Room temperature ± 2°C ± 2°C ± 3°C ± 4°C Mould cavity pressure ± 3 bar ± 4 bar ± 6 bar ± 8 bar Pressure integral ± 200 ± 300 ± 600 ± 900 Injection filling pressure ± 1 bar ± 2 bar ± 3 bar ± 4 bar Holding pressure ± 1 bar ± 1 bar ± 1.5 bar ± 2 bar Back pressure ± 0.5 bar ± 0.5 bar ± 1 bar ± 1 bar Filling differences (Balance of fill foreach cavity) on multi-cavity tools± 1% ± 1% ± 2% ± 5% Mould breathe 0.01mm 0.01mm 0.02mm 0.04mm Change over pressure (Pn Value) ± 1 bar ± 2 bar ± 3 bar ± 4 bar Screw surface speed ± 10mms-1± 15mms-1± 20mms-1± 30mms-1 Melt temperature peak value ± 0.3ºC ± 0.4ºC ± 0.5ºC ± 0.6ºC Melt temperature value atchangeover± 0.3ºC ± 0.4ºC ± 0.5ºC ± 0.6ºCThe achievable part quality is much influenced by the condition of the material processed.It is important that moisture content, proportion of regrind and proportion of colour (masterbatch) are constant.Acceptable tolerances of principal injection moulding processingparameters Bichler:Abt 9601- May 88 Updated Feb 01Appendix 2Standard deviationStandard deviation is a measure of the spread or scatter in a process and for a sample is given by the equation below:1)(12--=∑==n x x ni i iσwherevalues of number the mean valuethevalue individual the sdifference the of sum the deviationstandard =====∑n x x i σThe spread of a process may be estimated from the range, R . The maximum value minus the minimum. The smaller the range, the less spread in the process.A more sophisticated way of estimating scatter, which is widely used for statistical process control is standard deviation , σ, which not only provides a measure of theprecision of the process, but also predicts how many parts in a population will be out of tolerance.For what is known as a normal distribution, 68.3% of the population will lie within one standard deviation above and below the mean, ±1σ ; 95.4% lie within ±2σ, 99.7% within ±3σ and 99.994 within ±4σ.盛年不重来，一日难再晨。