How to calculate Shot Timing in Injection Moulding process?
Injection molding is a manufacturing process used to create products by injecting molten material into a mold. The process involves heating plastic material to a molten state and then injecting it under high pressure into a mold cavity. Once the plastic material cools and solidifies, it is ejected from the mold as a finished product. The timing of the injection process is critical to ensuring that the finished product is of high quality and meets the required specifications. In this blog, we will discuss the calculation of shot timing for injection molding machines.
The shot timing for an injection molding machine refers to the time it takes to inject the molten plastic into the mold cavity. The shot timing is a critical parameter that affects the quality and consistency of the finished product. The shot timing is calculated based on several factors, including the size and shape of the mold cavity, the type of plastic material being used, and the injection pressure.
To calculate the shot timing for an injection molding machine, the following steps should be taken:
Step 1: Determine the volume of the mold cavity
The first step in calculating the shot timing is to determine the volume of the mold cavity. The volume of the mold cavity is the amount of molten plastic that will be injected into the mold cavity. The formula for calculating the volume of the mold cavity is:
V = L x W x H
Where V is the volume of the mold cavity, L is the length of the mold cavity, W is the width of the mold cavity, and H is the height of the mold cavity.
Step 2: Determine the amount of plastic material required
The next step is to determine the amount of plastic material required to fill the mold cavity. The amount of plastic material required is equal to the volume of the mold cavity multiplied by the specific gravity of the plastic material being used. The formula for calculating the amount of plastic material required is:
M = V x SG
Where M is the mass of the plastic material required, V is the volume of the mold cavity, and SG is the specific gravity of the plastic material being used.
Step 3: Determine the injection pressure
The injection pressure is the pressure required to inject the molten plastic into the mold cavity. The injection pressure is determined by the type of plastic material being used and the size and shape of the mold cavity. The injection pressure is typically measured in pounds per square inch (PSI).
Step 4: Determine the injection time
The injection time is the time it takes to inject the molten plastic into the mold cavity. The injection time is calculated using the following formula:
t = (M x 0.283) / (P x A)
Where t is the injection time in seconds, M is the mass of the plastic material required, P is the injection pressure in PSI, and A is the cross-sectional area of the mold cavity.
The constant 0.283 is a conversion factor used to convert the mass of the plastic material from grams to ounces.
Step 5: Determine the screw recovery time
The screw recovery time is the time it takes for the injection molding machine to recover after the injection process is complete. The screw recovery time is calculated using the following formula:
t = (L x C) / (R x RPM)
Where t is the screw recovery time in seconds, L is the length of the screw, C is the clearance between the screw and the barrel, R is the radius of the screw, and RPM is the rotational speed of the screw.
Step 6: Calculate the total cycle time
The total cycle time is the time it takes to complete one injection molding cycle. The total cycle time is calculated by adding the injection time and the screw recovery time together:
Total cycle time = injection time + screw recovery time
