Optimization of lost foam casting process for half coupling

1. Brief introduction of castings

Two half couplings connect shafts in two different mechanisms so that the two shafts rotate together to transmit torque. The structure is simple and belongs to small castings, and the hole of the half coupling on site is not cast, and is processed by drilling machine, and the keyway is also machined, so the process is relatively simple, and the main problem is low production efficiency.

2. Casting process and original process flow

2.1 casting process

As 2.1 in the following figure, V-shaped inner gate is adopted to make molten iron cut in along the circumference, and two small risers are set at the upper part of the half coupling for feeding. A group of four half couplings, bonded to the four surfaces of the sprue, are divided into two layers of buried boxes. The pouring temperature shall not be lower than 1420 degrees, the negative pressure shall be -0.04MPa, the pressure shall be maintained for 8min after pouring, and the box shall be turned over and taken after keeping the temperature for two hours. The current process is mature and the cast is qualified.

2.2 original process flow

The original process flow is as follows:

① The half coupling adopts a molding machine to make a white mold, and the density of pre-developed beads is 19~22 g/ml;

② After the machine-beating white mold is dried for 8 hours, the manually cut and bonded inner gate and small riser are bonded to the half coupling white mold;

Then brush paint, brush paint twice, the first time drying 12 hours, the second time drying 8 hours;

④ After the white mold is dried, it is taken to the black area modeling station for modeling. On site, the box group type is adopted, and the lost foam casting rigid line is produced. The sand box is added with bottom sand and vibrated;

⑤ Then the workers enter the sand box, stand the sprue in the sand, cut off part of the paint on the inner gate and the sprue, and then bond the four half couplings on the sprue respectively, and the first layer ends;

⑥ Then push the sand box to the bottom of the sand storage hopper, cover the first layer with rain and sand, vibrate, then move the sand box to the bottom of the sand storage hopper, and continue to bond the second layer;

⑦ Workers enter the sand box, repeat the process ⑤, finish the second layer, push the sand box to the bottom of the sand storage bucket again, add sand in the rain, and vibrate;

⑧ Cover the film and install the gate cup;

⑨ Negative pressure pouring.

The above process flow is in the modeling link,,It takes a long time and is tedious. Workers need to push the box repeatedly, enter the sand box repeatedly to cut paint and bond. Workers have great grievances and extremely low efficiency.

3. Improvement program

According to the observation of the actual production process on site and the feedback of workers, the following improvement suggestions are put forward:

⑴ You can contact the mold manufacturer to modify the mold, make the inner gate directly on the mold, and directly machine it out with the half coupling, which can save the time of cutting the inner gate and bonding the inner gate;

⑵ The main improvement suggestions are in the modeling process, the original process flow, and the whole modeling process completely adopts the box-in-box type, which is complicated and inefficient. The following process is proposed.

The sprue of a model cluster is divided into two sections, and four half couplings are directly bonded to one section of sprue outside the box. As a group, the tooling is made as shown in Figure 3.1. The two sections are connected as a tray to hold up a group, which is convenient to move and prevent the bonding part from breaking during the moving process;

Put a group directly into the sand box with the tooling, take out the tooling, make the tooling into two parts for the convenience of taking out the tooling, add sand to the sprue, and vibrate;

③ Put the second group into the sand box with tooling, directly bond the direct runner of the two groups, add sand and vibrate.

★This tooling as the focus, the production of the tooling has two points need to pay attention:

① It is convenient to transfer the model cluster, and the bonding part of the model cluster bonded in advance cannot be broken during the transfer process;

After putting the model cluster into the sand box with this tooling, it is convenient to take out the tooling, and the model cluster cannot be damaged during the process of taking out the tooling.

The above suggestion is that the modeling adopts the combination of box-outside group type and box-inside group type and the auxiliary method of making tooling. The inner gate and sprue outside the box are bonded after the paint in the yellow area is dried, and the sprue inside the box is bonded. In this way, the modeling worker only needs to bond the two sprue sections. Compared with the two modeling processes, the improvement is not so cumbersome, and a job is separated in the yellow area and the black area respectively, with better division of labor and cooperation, optimizing the process flow and greatly improving the production efficiency. The improved modeling process is very suitable for mass production.

4. Summary

Small size, simple structure of the casting, often easy to pour success, but want to improve efficiency need to work hard. Therefore, it is necessary to combine the structural characteristics of castings, design reasonable tooling assistance, and plan reasonable process flow, so as to improve production efficiency.

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