Design advantages and guidance of MIM process products

Glue feeding gate: form and position

Just like plastic injection molding, MIM parts must also consider the type and location of the injection point. In any case, the opening of the glue injection point of the MIM must be larger, because a large proportion of the solid metal powder in the MIM is mixed with low molecular weight materials with high fluidity, which is much higher than that of pure plastic (it is easy to "run out" of the burr).

In most design schemes, the glue injection point is usually located on the parting line, so the consideration of the position of the glue injection point should try not to destroy or affect the function of the part, including the feasibility of manufacturing, function, dimensional accuracy and appearance. The glue injection point will leave some indentation, and it should not fall on the important size area or the important appearance position in design, which must be noted. Generally, it is suggested that the glue injection point should fall on the thicker area, so that the high-viscosity ejected material can flow from the thickest place, and at the same time, it should be considered that the mold cavity can be filled evenly. As shown in Figures 1 to 5, three different glue injection point designs and descriptions are often used.

•The characteristics of the side edge glue entry point are as follows:

• The sprue on the formed green billet must be cut manually by itself, so the possibility of high automation is very low, which is not suitable for mass production. In any case, the cost of manual removal will be included in the cost.

• Suitable for MIM parts with small output. (The mold structure is simple and the processing cost is low).

• The concave glue feeding point is recommended, but the appearance and function should be considered (see Figure 2).

• Normally set at the position of parting line.

 The characteristics of submersible glue feeding point are as follows:

• During the demoulding process, the material head falling into the glue point can be directly removed.

• MIM parts suitable for any production.

• Leaving small concave marks like leaves on the green surface. However, it should be noted that too small glue inlet may cause injection difficulties.

• The submersible glue feeding point can hide the smallest trace on a concave surface of the part.

• The processing cost of the submerged processing mold is higher than that of the edge rubber inlet.

The submersible glue feeding point (periscope type) designed on an extended column has the following characteristics:

• During the demoulding process, the material head falling into the glue point can be directly removed.

• The green billet such as the extended cylinder can be removed after being taken out of the mold, but

It cannot be removed automatically.

• The submerged glue injection point can be hidden on a concave surface of the part to form a hole mark, where the extended cylinder can be broken during mold opening.

• MIM parts suitable for any production.

• The position of extending the cylinder, exiting the dent or cavity mark cannot be placed on the appearance surface.

Unless the customer has not specified the treatment method for the glue inlet, you can keep the glue inlet trace. If it is necessary to polish the glue point, a certain polishing thickness is required after sintering to completely remove the trace. Adopt prominent glue feeding points and minimize polishing amount. Just like picture 5 as below.