Mould Maintenance

Storage and Care of Injection Molds

 Injection molds have a limited service life as shown in table6-6. Appropriate measure can greatly extend this, however. Such measures can be classified on the basis of maintenance,storage,and care.

To be able to quickly fall back on ready-to-use molds,the following demand on storage and care must be fulfilled.

1.every mold must be stored along with with one molded part and a mold card in its own,easily accessible space in the mold store.

2.Only ready to use, complete, clean molds may be stored. The purpose of also storing a molded part(usually the last one from previous production) and a mold card bearing the article number and the mold number is to allow the mold to be uniquely identified.

The mold card should also bear all the information needed for setting up the mold and starting up the injection molding machine . Information in this category includes the following.

1).Mold design

2)Dimension of the mold and the molded part

3)Mold mounting equipment

4)Injection molding machine suitable for production

5)Shot weight(injection volume)

6)suitable plastic

7)Rules on material pretreatment

8)Mold temperature and heat control medium

9)Cycle time

10)Injection pressure, follow-up pressure, and dynamic pressure

11)Injection speed

12)Screw speed

13)Cylinder equipment

14)Maintenance intervals

15)Number of pieces produced

This list could be extended and thus matched to the special needs of a factory. Instead of on a mould card, much of this information, such as the settings for the injection molding machine, could be stored on external data storage media that could be read into the computer prior to production startup.

Mold changes can only be performed quickly if the molds are ready for use when they leave the stores and can go into production without the need for major assembly or cleaning work. Every mold must therefore be a self-contained unit,i.e., it must not be made of parts that are required for other molds. Parts or groups of parts that are loaded or borrowed often disappear or are needed elsewhere just when the mold is scheduled for use. The consequences are unnecessary, incalculable, and often time-consuming downtimes.

Cleaning work also delays the start of production. It should therefore be kept to a minimum. This means that special care has to be taken of the molds and imposes specific demands on the store, its cleanness and particularly the ambient conditions. Damp rooms promote corrosion. Once rust has begun to attack the plastic mould, maintenance becomes very time consuming and very expensive. Often it is impossible. The mold store should therefore be kept at a constant temperature where possible. The mold store should therefore be kept at a constant temperature where possible, and dehumidified. Not much equipment is required for this, and it soon pays for itself.

Important to the accessibility of the molds is also the size of the store. It is essentially determined by the vehicles available in the factory and the maneuvering space.

When a job is complete, the mold may only be returned to storage when tis suitability for future use has been che3cked. The last parts produced with it can provide an indication of its condition. They must be examined for dimensional stability and closely scrutinized. This will provide information about the state of the mold surface, the level of seal in the mold parting line(perhaps flash formation on the molded part) and the working order of the ejectors,etc. If no deficiencies are found, the maintenance work then takes the form of the general care measure described below.