T-slot ground rail

What is a cast iron ground rail? What are the technical requirements?
The process design of the cast iron ground rail pattern often exhibits the following errors: improper selection of the parting surface, resulting in an excessively high upper mold or the formation of deep cavities in the sand mold. Improper placement of the pattern on the mold plate makes it difficult to compact recessed areas, which may be due to the pattern being too close to the box wall or arranged too densely.
From the entire inspection process of the cast iron ground rail, the rail itself serves as the measurement reference surface and must be placed stably. When calibrating with an autocollimator, the instrument and the cast iron ground rail are not on the same rigid body. To address this, special sand molds, such as zircon sand or olivine sand, can be used in areas where heat is concentrated on the cast iron ground rail to improve its long-term heat resistance or its ability to withstand high-temperature radiation. The stability of the instrument support is particularly important. Therefore, the calibration specifications for cast iron ground rails require that the calibration site be solid and stable, and vibrations should be avoided at the calibration location.

The adhesive layer mixed mechanically with sand grains shows a metallic luster when the sand-adhering layer is scraped away. The mechanically adhered sand on the surface of the cast iron ground rail appears spongy and firmly adheres to the casting surface. It often occurs in areas where the sand core surface is strongly heated and the sand mold compactness is low, such as near the pouring gates of the cast iron ground rail, thick sections of the casting, internal corners, and recesses.
If the structure of the cast iron ground rail and the pattern causes the sand mold to have sharp corners, overhangs, or protruding shapes, or to have thin sand platforms or sand cores, this design can promote mechanical sand adhesion. This is because such structures cause localized heat concentration in the sand mold and sand core, compromising their normal properties. The surface of the sand mold and sand core disintegrates prematurely, allowing molten metal to penetrate and cause mechanical sand adhesion.
When the molten metal of the cast iron ground rail not only has high pressure but also an excessively high temperature, the problem becomes particularly severe. An improper cross-sectional ratio of the sprue, runner, and ingate causes the molten metal to oxidize continuously during pouring, increasing the amount of metal oxides and leading to issues with the mold. During pouring, the gating system should always be filled with molten metal; otherwise, oxidation can occur anywhere in the gating system of the cast iron ground rail.
When the pouring temperature of the cast iron ground rail is too high, it not only improves the fluidity of the molten metal but also accelerates its oxidation, thereby increasing the occurrence of oxidative mechanical sand adhesion. Raising the ladle too high, like having an excessively high upper mold, creates excessive metal pressure, promoting the penetration of metal or metal oxides into the pores of the sand mold.
The cast iron ground rail is an essential tool in the production of profiles. After the profiles leave the production line, the cast iron ground rail is used to inspect the parallelism and distortion of the profiles. It can also be customized according to customer requirements. The thickness does not need to be excessive and can be designed based on the length of the platform. Some customers mistakenly believe that the thicker the panel of the cast iron ground rail, the higher the accuracy of the platform. In reality, the stability of the platform mainly depends on the strength of the bottom reinforcement ribs and the thickness of the platform's outer edge.
Due to mold crowding, the cast iron ground rail may experience sand expansion. Even without obvious sand expansion, mechanical sand adhesion can occur. Since the root cause is the same, mechanical sand adhesion and sand expansion often appear together on the cast iron ground rail. Improper placement of the sprue, riser, and runner can create recessed areas that are difficult to compact, which is related to the layout of the gating system of the cast iron ground rail.
The density of the casting coating for the cast iron ground rail reflects the content of solid particles in the coating. If the density of the casting coating is too low, the thickness of the coating layer formed on the sand mold and sand core during each application will be insufficient, making it difficult to provide adequate protection. Therefore, generally speaking, a higher density of casting coating is preferable.
Weiyue Machinery, Ms. Xie 15350773479