Basic knowledge of die casting mold trial production

New product development is often encountered in die-casting production, and the finished die-casting mold requires trial production.

One, must confirm before installing the mold

Machine model; injection position; injection chamber diameter; injection chamber diameter and protrusion height.

2. Check the clearance between the injection chamber, the sprue sleeve and the plunger head

In the die-casting site, a simple and practical inspection method is usually adopted, that is, the protruding flange of the injection chamber is placed flat in the vertical sprue sleeve, and the clearance between the protruding flange and the sprue sleeve (generally 0.03mm), and then apply a little oil to the plunger head of the corresponding outer diameter, and insert it from the mouth of the injection chamber. If the plunger head can slide slowly and uniformly to the bottom of the sprue sleeve (note that the plunger head is overpressured) Whether there is any abnormality in the connection between the shooting chamber and the sprue sleeve), it can be basically concluded that the fit clearance is reasonable. If you use an integral injection chamber, you only need to check the clearance between the plunger head and the injection chamber.

3. Before hoisting the mold, the depth of the thread of the ring hole must be checked, and it must be enough to make the ring plane to tighten the mold base to ensure safety.

When hoisting the mold into the pillar, it is best to set the mounting bracket according to the eccentric position of the injection chamber of the mold design to ensure the injection concentricity. If the bracket is temporarily not in place, a plunger head of the corresponding outer diameter can be placed in the injection chamber for positioning. The plunger head generally exposes half the length of the plunger head from the flange of the injection chamber, which is convenient for positioning. After the introduction, the mold balance must be calibrated before the fixed mold is fixed to facilitate the force balance and pre-reset connection installation. At the same time, use the crane to slowly raise the height slightly to relieve the mold from being affected by gravity, the center moves down and moves, the fixed mold guide post, and the guide sleeve deviate.

After fixing the mold, you must check the height of the pre-reset rod above the middle plate of the die casting machine. The height must be less than the height of the limit block after the push plate (usually about 0.50mm) to avoid damage to the mold and die casting machine. The pre-recovery rod must be tightened to the flat surface of the push plate to avoid looseness during production.

When the moving mold is fixed at a slow speed, it is necessary to observe whether there is any friction between the through hole of the push plate and the pre-reset rod after the middle plate of the die-casting machine to avoid damaging the external thread used for the rear fixing of the die-casting machine and the pre-reset rod .

After the middle plate is close to the movable mold foot of the mold, the movable mold must be fixed first, and then the pre-reset rod must be fixed to avoid the failure of the pre-reset rod to be completely tightened, which will affect the ejection position and damage the mold.

It is recommended that when the mold is fixed to the head and middle plate, use the U-shaped groove with the mold foot corresponding to the T-shaped groove of the die-casting machine on the mold base, and directly add the spacer block through the T-bolt (usually used by the die-casting machine below 400 tons). The thickness of the cushion block is greater than 20mm, and the thickness of the cushion block used by the die casting machine of 500 tons or more is greater than 30mm). This is not only easy to install, but also fast to install.

At the same time, it is recommended that all die-casting molds use a pre-reset lever, so that after the ejector pin is pulled back, the die-casting operator can find the broken or bent ejector pin in time to avoid batch scrapping of castings and damage to the mold cavity.

Four. After the mold is installed, open the mold slowly to the end

At this time, it is necessary to confirm the mold opening limit or the electronic ruler mold opening position to avoid affecting the mold opening stroke if the lower slide block is too long, and disturbing the oil tank and base of the machine tool. Manually move the plunger head slowly, stop the movement every 50mm or so, and rotate the injection link to check the concentricity of the injection, until the plunger head passes the sprue sleeve and exposes about 20mm (if the model is thick, the plunger head can be omitted. The pouring spout is exposed, but the condition when the tracking is in place must be checked). At this time, the tracking distance can be set according to the thickness of the fixed model and the height of the shunt cone. Under normal circumstances, the tracking distance should be as short as possible from the distance in the parameter table set by the machine by about 5mm to avoid damage caused by prolonged collision of the injection cylinder.

Fifth, adjust the ejection distance, pressure and flow according to the characteristics of the adjustment casting

When the casting can be ejected, the smaller the better. When ejecting, do not make the ejector plate touch the mold ejection limit post. If there is a hydraulic core-pulling program for the movable mold. Before the program is confirmed and the tubing is not connected, it is strictly forbidden to eject it to avoid damage to the mold due to misoperation.

According to the characteristics of the casting to determine the nature of the core-pulling and the pressure and flow rate. When the lower sliding block on the parting surface is hydraulically cored, the limit switch should be a waterproof switch as much as possible, or the cover of an ordinary limit switch should be opened regularly to drain water in time. Avoid short circuit of the limit contact, causing the input signal error, ejecting malfunction, and damaging the mold cavity.

Timely adjust the various limits of the mold and the machine to set the parameters reasonably.

Six. According to theoretical values, preset various programs and parameters, fix the oil pipes, wires and cooling water pipes used by the mold, to avoid friction or talk about the parting surface.

If the inspection is correct, you can choose to insert cotton yarn into the injection chamber for full slow injection, with an empty cycle. Sometimes the operator must observe the situation on the spot, and place one hand on the emergency stop button. Once an abnormality occurs Shut down in time.

Seven. Before die casting, the mold must be preheated

If you have conditions, you can use a mold temperature heating and cooling machine. If you preheat to 200～250℃ unconditionally, you can use the gas spray gun to preheat the medium fire. Under these conditions, the outer flame must be controlled to contact the mold, and the spray gun must be moved slowly in time to keep the heat balance as much as possible. When preheating to about 100℃, you can continue to preheat after applying solder-resistant wax where needed in the cavity, and it is better to reach 150-180℃. During the pressure test, the cooling water must be turned on in a small flow in time to avoid the rapid cold and hot mold and reduce the life of the mold. According to the characteristics and needs of the casting, adjust the cooling water flow at each location reasonably.

8. When setting the parameters in trial production, only the castings can be qualified and meet the technical requirements of the drawings.

The lower the parameters such as the temperature of the molten aluminum, the injection speed of each level, and the pressure of each level, the better to protect the mold and the machine.