Aluminium gravity casting with existing molds

Old gravity casting molds are welcome

Aluminum gravity casting molds are considered as permanent molds which can always has a long service life. A typical aluminum gravity casting mold made by tooling steel say H13 can have a duration of 50,000 to 100,000 shots, if the molds were handled and maintained properly. So we may always meet such thing that one mold may have a old age but is still on service. For old molds, we may have to adapt them to the gravity casting machines' innovation except necessary maintenance. And for some other molds, some modification or replacement of some component is enough to get it work.

HH provides service of utility evaluation for used molds. We had already imported old molds form Holland , Italy and Japan for adaption to local casting machines. The old molds should be checked carefully for their status and function. For some gravity casting molds which was maintained good, it is really economical to use it continually with slight modification. But for some molds, it either has high modification cost, or its total clamping means and feeding and pouring system is odd for local casting machines. Considering the high transportation cost and custom duty, it is really not worthy to use it any more. Making a brand new one can be much more economical.

How to evaluate old gravity casting molds

To evaluate a used gravity casting molds, we normally has to check the following three aspects.

Its cavity and core status. The mold cavity and core is the molding features of a mold which is a the key component of a mold. To determine a used mold is still useful or not, first we have to make sure its molding features are still good and sturdy in dimensions, and without fatal damage or crack. A mold cavity and core made by bad tooling material is subject to deformation and crack. So if the dimension distortion and the material status can acceptable, the mold is still acceptable for use.

Its clamping and holding system. The gravity casting machines are very flexible in design so there are various kinds of gravity casting machines which have fancy clamping system. Normally we use flange screw and blots to fasten a mold to a gravity casting machines' T slots. So the distance between each slots with different size should be checked carefully to make sure the ready clamping system of a used mold can fit. Except clamping by bolts and T-slots, some simple gravity casting machines especially small casting machines use screw holes to clamp gravity casting molds direct. The diameter and thread type of the screw hole can be critical for molds' clamping system.

Its feeding and running system. Sometimes, it won't effect a lot. Currently we always use tilting gravity casting machines which is good at air releasing. For such machines, a feeding and running system is preferred to a so called gradually feeding system. For some simple gravity casting molds, a top feeding system is preferred which is also good for tilting casting machines. With a slight modification, a former gravity casting mold adapted to a tilting gravity casting machine that can improve the casting quality attractively

How to adapt old gravity casting molds

An old gravity casting mold always has deformed molding features like mold cavity and core. If their dimension distortion is beyond the allowed tolerance or they are damaged seriously affecting molding, we have to replace them decidedly. As common experience, a gravity casting mold is always an integrated mold. So changing mold cavity and core together is the same thing as making a brand new mold.

If a mold only has some clamping trouble, it can be very easy to changing a clamping system. Compared with mold cavity and core which are always made by expensive tooling steel, for the clamping system, common mild steel is good and enough. It is the most economical situation that a gravity casting mold can be used only with some modification of its clamping system.

The sprue and running system is key component of a gravity casting mold. A good and functional sprue and running system can avoid cold flow, shrinkage holes and gas releasing. Currently the most popular sprue and running system for a gravity casting mold is the means we called gradually feeding system. It usually cooperates with a tilting gravity casting machines to achieve gravity cast parts with better density. So some old molds are always adapted to tilting casting machines .