Do you know main points of mold trial process?

Time:2020-05-18 09:17:12 / Popularity: / Source:

First. introduction

When we receive a new mold to be proofed, we are always eager to try out a result earlier, pray for a smooth process to avoid wasting man-hours and causing confusion.
But here we must remind two points:
First, mold designers and manufacturing technicians sometimes make mistakes. If we are not alert when we try molds, small mistakes may cause large damage.
Second, result of mold trial is to ensure smooth production in the future. If reasonable steps are not followed and proper records are made during mold trial process, it will not be able to guarantee smooth progress of mass production. We emphasize more that "if mold is used smoothly, profit recovery will increase rapidly, otherwise cost loss caused will be more than cost of mold itself."
mold trial 

Second, matters needing attention before mold trial

1. Understand relevant information of mold:
It is best to get design drawing of mold, analyze it in detail, and ask mold technician to participate in mold trial work.
2. First check mechanical cooperation on workbench:
Pay attention to whether there are scratches, missing parts, looseness, etc., whether movement of mold slide is correct, whether there are leaks in waterway, air pipe, and oil pipe joints. If mold opening process is restricted, it should also be marked on mold. If above actions can be done before hanging mold, you can avoid waste of man-hours that occur when problem is found during hanging of mold.
3. When it is determined that various parts of mold are properly operated, it is necessary to choose a suitable test mold injection machine, and pay attention to
(a) Injection capacity
(b) Guide width
(c) Maximum start
(d) Accessories
Whether it is complete and so on. After confirming that there are no problems, next step is to hang mold. When hanging, please pay attention not to lock all clamps before lifting mold. Do not remove fishing tools to prevent clamps from loosening or breaking and mold falling.
After mold is installed, you should carefully check mechanical actions of each part of mold, such as slide, thimble, retracting structure and limit switch. And pay attention to whether injection nozzle and feeding port are aligned. Next step is to pay attention to mold clamping action. At this time, mold closing pressure should be lowered. During manual and low-speed mold clamp, pay attention to see if there are any irregular motions and abnormal sounds.
4. Increase mold temperature:
According to performance of raw materials used in finished product and size of mold, an appropriate mold temperature control machine is used to increase mold temperature to temperature required for production.
After mold temperature is increased, movement of each part must be inspected again, because steel may cause mold clamp after thermal expansion, so you must pay attention to sliding of each part to avoid occurrence of strain and chatter.
5. If experimental plan rule is not implemented in factory, we recommend that only one condition be adjusted at a time when adjusting mold trial conditions in order to distinguish impact of a single condition change on finished product.
6. According to different raw materials, do a proper baking of original ravioli.
7. Trial mold and future mass production use same raw materials as much as possible.
8. Try to simulate actual production situation.
9. Internal stress and other problems often affect secondary processing. After mold is tested and finished product is stable, secondary processing mold should be added. After mold is closed at a slow speed, adjust mold closing pressure and move it several times to check whether mold clamping pressure is uneven, so as to avoid burrs and mold deformation in finished product.
After above steps are checked, lower mold closing speed and mold closing pressure, set safety buckle and ejection stroke, then adjust normal mold closing and mold closing speed. If limit switch of maximum stroke is involved, mold opening stroke should be adjusted slightly shorter, and high-speed mold opening action should be cut off before maximum stroke of mold opening. This is because during entire mold opening stroke and mold loading, high-speed action stroke is longer than low-speed stroke. On plastic machine, mechanical ejector must also be adjusted to act after mold is opened at full speed to prevent ejector plate or peeling plate from being deformed by force.

Please check following items before making the first shot:

(a) Whether feeding stroke is too long or insufficient.
(b) Whether pressure is too high or too low.
(c) Whether filling speed is too fast or too slow.
(d) Whether machining cycle is too long or too short.
To prevent short shots, fractures, deformation, burrs and even damage to mold.
If processing cycle is too short, ejector pin will push through finished product or peel ring to crush finished product. This kind of situation may make you spend two or three hours to take out finished product.
If processing cycle is too long, thin parts of mold core may be broken due to shrinkage of rubber.
Of course you can't anticipate all problems that may occur during mold trial process, but taking full consideration of timely measures in advance will help you avoid serious and expensive losses.
mold trial 

Third, main steps of mold trial

In order to avoid unnecessary waste of time and trouble during mass production, it is indeed necessary to pay patience to adjust and control various processing conditions, to find the best temperature and pressure conditions, and to develop standard mold test procedures, which can be used to establish daily working methods.
1. Check whether plastic material in barrel is correct and whether it is baked according to regulations. (If different raw materials are used for test mold and production, different results are likely to be obtained).
2. Cleaning of material tube must be thorough to prevent inferior dissolving materials or miscellaneous materials from being injected into mold, because inferior dissolving materials and miscellaneous materials may jam mold. Test whether temperature of material tube and mold temperature are suitable for raw materials processing.
3. Adjust pressure and injection amount to produce a finished product with a satisfactory appearance, but no burrs, especially when some finished products of cavity are not completely solidified, you should think about it before adjusting various control conditions, because a slight change in filling rate may cause a large change in filling.
4. Wait patiently until conditions of machine and mold have stabilized. Even medium-sized machines may have to wait more than 30 minutes. You can use this time to view possible problems with finished product.
5. Screw advance time should not be shorter than solidification time of gate plastic, otherwise weight of finished product will be reduced and performance of finished product will be impaired. And when mold is heated, screw advance time needs to be lengthened to compact finished product.
6. Reasonably adjust and reduce total processing cycle.
7. Run newly adjusted conditions for at least 30 minutes to stabilize, then continuously produce at least a dozen full mold samples, indicate date and quantity on container, place them separately according to mold cavity to test stability of actual operation. And derive reasonable control tolerances. (Especially valuable for multi-cavity molds).
8. Measure and record important dimensions of continuous sample (it should be measured when sample is cooled to room temperature).
9. Compare size of each mold sample. Pay attention to:
(a) Whether size is stable.
(b) Whether there is a tendency for certain dimensions to increase or decrease, indicating that machining conditions are still changing, such as poor temperature control or oil pressure control.
(c) Whether size change is within tolerance range.
10. If size of finished product does not change and processing conditions are normal, you need to observe whether quality of finished product of each cavity is acceptable and its size is within allowable tolerance. Write down number of cavities measured continuously larger or smaller than average to check whether size of mold is correct.
Record and analyze data as need to modify mold and production conditions, and reference basis for future mass production.
1. Make processing time longer to stabilize melt temperature and hydraulic oil temperature.
2. Adjust machine conditions according to oversized or undersized of all finished products. If shrinkage is too large and finished product appears to be insufficiently shot, you can also refer to increase gate size.
3. If size of each cavity is too large or too small, modify it. If cavity and door dimensions are still correct, then you should try to change machine conditions, such as filling rate, mold temperature, and pressure of each part, and check whether some of cavity is slow to fill.
4.According to matching situation of finished product of cavity or displacement of mold core, it should be corrected separately. It is also possible to adjust filling rate and mold temperature again to improve its uniformity.
5. Inspect and modify malfunction of injection machine. Defects such as oil pumps, oil valves, temperature controllers will cause changes in processing conditions. Even perfect molds cannot perform well in poorly maintained machines.
After reviewing all recorded values, keep a set of samples to check whether corrected samples have improved.
mold trial 

Fourth, important matters

Keep a proper record of all sample inspections during mold test, including various pressures in processing cycle, melt temperature and mold temperature, tube temperature, injection operation time, screw feeding period, etc. In short, all data that will help in future to successfully establish same processing conditions should be kept in order to obtain products that meet quality standards.
At present, mold temperature is often ignored in factory mold trial, and mold temperature is the easiest to grasp in short-term test and future mass production. Incorrect mold temperature is sufficient to affect sample size, brightness, shrinkage, flow, and missing materials. If mold temperature controller is not used to control future mass production, difficulties may occur.

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