Mold design to end product dimensional control

Mold Design

Control of mold design aspects

1、First of all, we should fully understand the technical requirements of users in many aspects such as mold structure, material, hardness and precision, including whether the shrinkage rate of forming plastic material is correct and whether the 3D dimensional shape of the product is complete and reasonable for processing analysis.

2、To give full consideration to the appearance of the injection molded products such as shrinkage, flow marks, mold slope, fusion line and cracks.

3、On the premise of not hindering the function and pattern making of the injection molded parts, the processing method of the mold is simplified as much as possible.

4、the parting surface is selected appropriately, the mold processing, forming appearance and forming parts deburring should be carefully selected.

5、pushing the top of the way is appropriate, using the push rod, unloading plate, pushing the top of the casing and other ways or other ways, push rod and unloading plate position is appropriate.

6、the side core extraction mechanism is adopted whether the appropriate, flexible and reliable action, there should be no jamming phenomenon.

7、temperature control with what method is easy to plastic products more appropriate, temperature control oil, temperature control water, coolant, etc. with which structure circulation system, the size of the coolant hole, the number, location, etc. is appropriate.

8、The form of sprue, the size of channel and inlet, the location and size of sprue are appropriate.

9、all kinds of modules and mold core heat treatment deformation impact and the choice of standard parts is appropriate.

10、injection molding machinery injection volume, injection pressure and clamping force is sufficient, nozzle R, gate sleeve aperture and so on whether the match is appropriate.

These aspects, such as comprehensive analysis and preparation, should be strictly controlled from the initial stage of the product pieces.

Plastic injection Mold
Second, the process of manufacturing control

Although comprehensive and full consideration and arrangements are made in the design stage, there are still many problems and difficulties in actual production, and we have to conform to the original intention of the design in production as far as possible, and find out more effective and more economical and reasonable process means in actual processing.

1、Choose the economical and suitable machine tool equipment for 2D and 3D machining solutions.

2、can also consider the appropriate tooling fixtures for production of auxiliary preparations, the reasonable use of tools, to prevent the product pieces of deformation, to prevent the product pieces of shrinkage fluctuations, to prevent the product pieces of deformation, to improve the accuracy of mold manufacturing, reduce errors, to prevent changes in mold accuracy, etc., a series of production process requirements and solutions.

3、here mention about the British Plastics Council (BPF) formed parts dimensional errors generated by the causes and their proportion of the distribution of.

A: mold manufacturing error of about 1/3, B by the mold wear error of 1/6 C by the uneven shrinkage rate of formed parts generated by the error of about 1/3, D scheduled shrinkage rate and the actual shrinkage rate inconsistent error of about 1/6

The total error = A + B + C + D, so it can be seen that the mold manufacturing tolerance should be less than 1/3 of the dimensional tolerance of the formed part, otherwise it is difficult for the mold to ensure the geometry of the formed part.

Third, the usual production aspects of the control

Fluctuations in geometry after molding are a common problem and a frequent occurrence.

1、the material temperature, mold temperature control, different grades of plastic necessary for different temperature requirements, plastic material fluidity and the use of more than two kinds of mixed materials will have different situations

should be controlled in the best flow value range, these are usually easy to do, but the mold temperature control is more complex

different geometry, size, wall thickness ratio of different forming parts have certain requirements for the cooling system The mold temperature controls the cooling time to a large extent.

Therefore, try to keep the mold in the allowable low temperature state, in order to help shorten the injection cycle, improve production efficiency, mold temperature changes

then the shrinkage rate will also change, mold temperature remains stable, the dimensional accuracy is also stable, so as to prevent the deformation of the molded parts, bad gloss, cooling spot and other defects, so that the physical properties of plastic in the best state

of course, there is a debugging process, especially multi-cavity mold The molded parts are more complicated. Therefore, the mold temperature should not be changed during the production process

and the setting of the mold temperature should be within the recommended temperature range of the material.

2、Pressure and exhaust adjustment control.
Proper injection pressure, clamping force matching should be determined when commissioning the mold, the air in the mold cavity and core formed by the gap and the gas generated by the plastic must be discharged from the exhaust slot outside the mold, such as poor exhaust will be underfilled and produce fusion marks or burns.

These three kinds of forming defects sometimes appear in the same part of the intermittent, when the thin-walled part of the forming parts around the presence of thick walls, the mold temperature is too low

the mold temperature is too high, then there will be a burn phenomenon, usually in the burn site and at the same time there will be fusion marks, exhaust slot is often overlooked, generally in a small state

so usually as long as no hairy edge; exhaust shoulder depth As deep as possible, the back of the shoulder to open a larger size of the ventilation slot, so that the gas through the shoulder can be quickly discharged outside the mold

such as a special need to open the exhaust slot on the top bar, the reason is the same, one is not to appear flying edge, the second is out of the gas quickly can play a good effect on the line.

The depth of the exhaust shoulder is as deep as possible, and the back of the shoulder is opened with a larger size ventilation slot, so that the gas can be quickly discharged out of the mold through the shoulder

if there is a special need to open the exhaust slot on the top bar, the reason is the same, one is not to appear flying edge, the second is the gas can play a good effect on the fast.

3、injection molding size of the supplementary plastic control
Some plastic parts are different in shape and size, and after demolding, with the change of temperature and pressure loss, different deformation and warpage will occur, which can be adjusted by some auxiliary tooling fixtures, and remedial

measures can be taken promptly after the molded parts are released, and better correction and adjustment can be achieved after natural cooling and deformation. If we ensure strict management in the whole injection molding process, the size of the injection molded parts will be very ideal control.


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