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  • Injection mold failure

Injection mold failure

1. Preparation before assembling

Understand the product, check the workpiece, receive all the auxiliary materials and purchase spare parts.

 1) Firstly, we should understand the product drawing, check all the specifications and related technical standards of the assembly, then integrate the assembly drawing to master the structure, compare the materials on the assembly drawing to understand the geographical location of the raw materials on the assembly drawing and integrate the workpieces to get all the auxiliary parts such as dowels.

 2) Check and clean the workpieces against the workpiece serial numbers on the workpiece details, check if the parts processing is thorough against the parts diagram, and ensure timely feedback if there is a lack (the person responsible for the assembly should put the workpiece details in the product picture together).

 3) After accepting the auxiliary materials incoming order, compare the details within 24 hours of the order to receive all the auxiliary parts. If the auxiliary materials do not arrive in time for feedback and spacing 8 hours to track the feedback once (until the details of all auxiliary materials to receive all can be terminated tracking).

 4) All of the auxiliary materials received in the workpiece with which the workpiece also arrives, to check whether it can be applied or is not compatible, to prevent mis-subscription, mis-subscription, if there are abnormalities immediately to the process engineer.

 5) For the workpiece with the bullet yellow, we have to check whether the bullet yellow hole has sufficient narrowing stroke arrangement before cooperating.

 6) For the oblique guide pillar of hard mold, assemble the line position once before assembling. 2.

2. The processing sequence before assembly

(1) cool water in and out marking, mold embryo commodity number, test for cool water, test for ejector hole and over the hole

 1) After the template arrives at the template storage area, within 8 hours, the person responsible for the assembly should compare the product picture and assembly diagram to get the cool water in/out mark and the mold embryo product number.

 2) Clean up the dirt inside each workpiece, slide, screw hole, and cool water hole to prevent damage caused in the assembly.

 3) A, B board should be in the first time before the mold to carry out the first cool water test work.

 4) After the first assembly of the ejector pin in the workpiece, immediately after the ejector pin is not smooth and the pad is not smooth. (including flat ejector pin, syringe pin, oblique guide pillar, and its unique pressure injection equipment)

 5) Verify that the ejector plate countersink depth, gap, precise positioning is consistent with the auxiliary materials.

 6) Verify the bullet yellow hole, support column hole, and thimble fixed immovable plate, the bottom version of all over the hole.

(2) A, B board gap, locator installation, review the thimble height to width ratio specifications.

 1) compare the die kernel, die frame height to width ratio and relativity deep check A, B board with each other is not a moderate gap.

 2) A and B plates should be installed with a good positioning instrument before they fit each other to ensure the precision of mutual fit.

3)After the installation of the moving template, review the ejector pin isometric aspect ratio specifications compared to the ejector pin diagram. And make the new item specifications in the ejector production process sheet. Ship together with the ejector pin production process sheet.

3. The whole process of assembling

1) When assembling, the workpiece bears the force evenly, and the gong top angle is twisted tightly to ensure the standard level of the workpiece after installation, and its workpiece and the middle of the workpiece meet.

2) In the subject activity position filled with grease, to ensure that the mold with each other in the whole process of smooth.

3) Mutual fit touching through position, inserting through position more workpieces, the first mutual fit amplitude is moderate, to prevent the incorrect damage to the mold caused by the previous process, and endanger the progress and quality of the mold.

4) For the hole spacing and slot edges on the mold embryo that does not endanger the assembly and application, rounding should be done. (Except for the ejector hole and countersunk hole)

5) oblique guide pillar in the assembly, the word code serial number to be unified, from the mold kernel to oblique guide double cocking plate, ejector plate, ejector plate combination bearing the same group to use a word code.

6) The mold guide slider, steel cutting, clamping block, oblique guide column, syringe pin, and similar workpieces should be made to identify the number.

7) When the top of the syringe pin is thick, it should ensure a certain height to width ratio under the condition of commodity tolerance to prevent the shrinkage of the surface of the commodity.

4. Standard of assembly

(1) The standard of assembly of moving and fixed die.

 1)Check whether the standard side of the moving template and fixed template is consistent with the engineering drawings.

 2)Check the size specification of the back and front mold cores.

3) After putting the moving and fixed die cores into the template, the plug gauge checks whether the moving and fixed die cores are close to the standard side.

(2) The assembly standard of the insert.

According to the engineering drawings, the inserts are removed more than the standard another side. 5.

5. With mold red Dan regulations

(1) the face of the shell bile surface regulations proportional, the push side of the red Dan slightly black (that is, the bile surface than push side need to touch a little tight); speaker network regulations proportional, but can not be too tight; small touch broken hole, insert through the bit, red Dan proportional on.

2) cell phone back cover: depending on the state of its glue, general: the top surface of the network teeth and the back of the terminal board power plug at the touch through the bit of red Dan regulations than the push side of a little tight, both sides of the network teeth proportionate on. All pressure-resistant block thickness should be slightly higher than the push side (0.03MM ∽ 0.005MM).

6. Assembly is completed

1) Fill out the mold assembly sheet before the assembly is completed, and immediately submit the relevant undertaking (change the mold as well)

2) Re-check whether the ejector plate is smooth, the line position, the oblique guide column is smooth (the same as the alteration mold)

3) Check the mold fitness movement position including hot runner system movement system (the same as changing mold)

4) Do the commodity word code and concave die distinction code on the die kernel as required (hard die is sent to EDM for production and processing, and the outer single is produced and processed according to the processing technology label). The distinction code of concave mold is in English, and the distinction code of the mold of the same product is in digital code. Special cases must be approved by the process engineer.

5) Check if there is a burr at the place of cooperation, and the mold should be repaired at the turning point of the buried glue inlet.

6) Check if the line position is smooth after tightening the steel cutting.

7) The first assembly of the mold is to be cleared within 1 hour after the full set of workpiece drawings, assembly drawings, product pictures. Engineering drawings are folded up neatly according to the size of "A4" paper. The front mold engineering drawings are made as a stack, the back mold engineering drawings are made as a stack, and the assembly drawings and product pictures are made as a stack. Change the mold project drawings to the current change of all materials stacked together.

8) The workpieces that cannot be installed before the trial part due to special conditions, after the approval of the person responsible for repairing and touching group, make the moderate solution, and those that should be saved should be packed with workpiece cans and put in the storage area of repairing mold workpieces to be installed next time.

Injection molding processing mold structure form and production processing quality immediately endanger the plastic parts product quality and productivity. Mold processing process a variety of common failures is very much, the following are a few types of common solutions to common failures.

Feeding the mouth of the material is difficult.

In the whole process of injection molding processing, the inlet glue mouth is stuck in the inlet glue mouth sleeve, and it is not easy to slip off. When it comes out of the mold, the product appears to be damaged by cracks. In addition, the operator must use the top of the copper rod to hit the nozzle to make it loose before exiting the mold, which is more serious to jeopardize the productivity. The key reason for this kind of common failure is the poor smoothness of the conical hole of the glue inlet and the knife pattern on the orientation of the inner thread circle.

There is also the raw material is too soft, the application of a period after the cone hole small end deformation or damage, and its nozzle surface tilt is very small, resulting in the inlet glue mouth material here caused by riveting head. Into the cone hole of the glue mouth set is difficult to produce processing, should be used as far as possible standard parts, if the independent production and processing, should also be self-made or purchase special type reamer. The tapered hole should be lapped to Ra0.4 or less. In addition, be sure to set the inlet pulling rod or the inlet pressure injection organization.

Positioning pin damage.

Positioning pins are crucial in the injection molding process to ensure that the molding surfaces of the core and concave mold collide with each other under all conditions. In the following types of conditions, when injecting the dynamic, front mold will cause great lateral deflection force: (1) plastic parts wall thickness regulations are not proportional, the material goods flow through the thick wall tube at the speed, where it causes a lot of working pressure; (2) plastic parts side is not the same, such as trapezoidal analysis of the surface of the mold, the opposite of the two sides of the face of the anti-working pressure is not the same.

Dynamic, front mold offset.

Large and medium-sized molds, due to the different speed of charging in all directions, and its hazard of the mold's weight when loading the mold, resulting in dynamic and front mold deviation. In these conditions, the lateral deflection force will be added into the positioning pin when injecting, and the positioning pin surface will be calendered and damaged when leaving the mold, and the positioning pin will be bent or disconnected when it is more serious, and it is even impossible to leave the mold. To better deal with the above problem, the mold analysis surface with high toughness and precise positioning key on each side, the most simple and reasonable are to use the cylindrical key. The flatness of the positioning pinhole and the parting surface is especially important. In the production processing is the choice of dynamic, the front die pointing part after clamping, in the milling machine once boring, that can ensure the coaxiality of the dynamic, fixed die hole, and make the flatness error value at least. In addition, the positioning pin and guide column heat treatment process strength as far as possible to achieve the design program.

Dynamic template bending.

Injection processing mold in the injection, the mold core melting plastic caused by the great anti-working pressure, generally in 600 ~ 1000KG / cm 2. Mold makers sometimes do not pay great attention to this problem, usually change the original design specifications, or the dynamic template with low compressive strength thick steel plate instead, and then top bar top material in the mold, because of the large span of the two sides of the seat, resulting in injection when the template bend. Therefore, the moving template must use a high-quality stainless steel plate, to have sufficient thin thickness, do not use A3 and other low compressive strength thick steel plate, when necessary, should be set in the moving template directly below the support point column or support point block, to reduce the thin thickness of the template to enhance the bearing capacity.

The top bar is bent, cracked, or overflowing.

Self-made top bar quality is good, is too high production costs, now generally use standard parts, general quality. If the gap between the top bar and the hole is large, the material will be overflowed, but if the gap is small, the top bar will be stuck because of the high mold temperature when injecting.

The riskier is that sometimes the top bar is jacked out of the general pitch on the top did not move and break, the result in the next time the mold lock this section of the exposed top bar can not be calibrated and touch the bad cavity. To better deal with this problem, the top bar again sharpens, in the front end of the top bar development to save 10 ~ 15mm with each other, the middle part of the grinding small 0.2mm. all the top bar in the assembly, it is necessary to strictly check the gap with each other, generally in 0.05 ~ 0.08mm, to ensure that all pressure injection organizations can be in and out of the degree.

Poor refrigeration or water seepage.

The actual effect of the cooling of the injection molding process mold immediately jeopardizes the quality and productivity of the product, such as poor cooling, the product collects large, or collects unevenly and appears warped surface deformation and other shortcomings. On the other hand, the mold overall or part of the over-temperature, so that the mold can not all normal forming and stop, the situation is serious so that the top bar and other subject moving parts thermal expansion stuck and destroyed. Refrigeration system design program, production, and processing to commodity appearance do not have to be due to the mold structure are cumbersome or difficult production and processing and omit this system software, especially small and large molds must take into account the refrigeration problems.

Lock touch taut tissue failure.

Pendulum hook, press the button this kind of locking touch taut organization generally used in the former mold core or some secondary out of the mold, because this kind of organization in the mold of the two sides of the face set in pairs, its posture regulations must be the same step, that is, close the mold, in addition, to press the button, out of the mold to a certain part in addition to hook.

Once the loss of the same step, is bound to lead to be pulled mold template tilt and destruction, the parts of this organization to have a high bending stiffness and wear resistance, adjustment is also very difficult, organization life is short, minimize the application, can be changed to other organizations. In the case of small pumping energy can be used in the way of bullet yellow release before the mold, in the case of large pumping force can be used after the mold backward core dragging, first core posture and then the structure of the mold, in large and medium-sized mold can be used hydraulic cylinder pumping.

Slant pin guide slider type core extraction organization destruction.

Most of the problems that occur more often in this type of organization are not timely production and processing and its material is very small, the key has the following 2 difficulties: the tilt angle A of the slanted pin is large, the advantage is to be able to cause a larger core extraction distance in the shorter out of the mold stroke arrangement. However, if the tilt angle A is too large when the extraction force F is a certain value, the bending force P=F/COSA suffered by the tilt pin during the whole process of core extraction is also larger, and the tilt pin is easily deformed and the tilting hole is worn out.

In addition, the tilt pin to the guide slider caused by the upward torque N = FTGA is also larger, this force makes the guide slider to the guide groove body guiding surface of the positive pressure expand, and then enhance the dragging of the guide slider friction. Easy to lead to dragging unsatisfactory, guide groove wear bad. According to work experience, the tilt angle A should not exceed 25 °.

The length of the guide slot is very small.

Some molds are limited by the total area of the template, the length of the guide slot is very small, the guide slider is exposed outside the guide slot at the end of the core draw posture, so that after the core draw link and die calibration at the beginning of the link are very easy to lead to the guide slider skew, especially in the lock mold, the guide slider calibration is not satisfactory, so that the guide slider damage, and even bending and destruction. According to work experience, the guide slider for core posture stays to the slide inside the length of not less than 2/3 of the total length of the guide slot.

In the design scheme, production and manufacturing mold should be based on the provisions of the quality of plastic parts, the size of large quantities, the provisions of the production and manufacturing deadline, and other details, both can consider the product provisions, in the mold structure and the most simple and reliable, easy to produce and process, so that the project cost is low, which is considered the most extreme mold.

7. Standard in the whole process of work

1) During the whole process of assembling molds, workpieces should be packed in workpiece cans and placed neatly on the table.

2) Workpieces and engineering drawings are transferred together according to the production process and make a good work handover.

3) Maintain a clean and tidy cabinet surface during the whole process of work. Timely removal of waste caused during the whole process of work.

4) After the work is carried out, clear the operating table and work area promptly, and reimburse the auxiliary software promptly.
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