Die Casting Calculator
Estimate die casting shot volume, casting weight, runner and biscuit metal, fill time, clamp force, machine utilization, and molten alloy temperature factor.
Calculation Breakdown
| Alloy | Density | Target metal temp | Typical fill time | Common cavity pressure |
|---|---|---|---|---|
| A380 aluminum | 2.71 g/cm³ | 650-680°C / 1200-1255°F | 30-80 ms | 5000-8000 psi |
| A360 aluminum | 2.66 g/cm³ | 655-690°C / 1210-1275°F | 25-70 ms | 5500-8500 psi |
| A413 aluminum | 2.66 g/cm³ | 620-660°C / 1150-1220°F | 20-60 ms | 5000-8000 psi |
| Zamak 3 zinc | 6.60 g/cm³ | 400-430°C / 750-805°F | 40-100 ms | 3000-6000 psi |
| AZ91D magnesium | 1.81 g/cm³ | 630-670°C / 1165-1240°F | 20-60 ms | 4000-7000 psi |
| Die casting brass | 8.40 g/cm³ | 950-1010°C / 1740-1850°F | 35-80 ms | 7000-10000 psi |
| Machine preset | Best process | Clamp rating | Shot capacity | Typical use |
|---|---|---|---|---|
| 120 ton hot chamber | Zinc | 120 tons | 12 in³ | Small knobs, clips, fittings |
| 180 ton hot chamber | Zinc / ZA alloy | 180 tons | 18 in³ | Latches, handles, small plates |
| 350 ton cold chamber | Aluminum | 350 tons | 36 in³ | Covers and medium housings |
| 500 ton cold chamber | Aluminum / magnesium | 500 tons | 55 in³ | Heat sinks and wide covers |
| 800 ton cold chamber | Multi cavity aluminum | 800 tons | 95 in³ | Large or high projected area tools |
| Component | What to include | Typical share | Calculator input | Check point |
|---|---|---|---|---|
| Casting volume | All cavities after shrink settled | 40-75% | Net volume per cavity | Use CAD mass properties when possible |
| Runner and gate | Sprue runner, fan gates, cross runners | 10-35% | Runner and gate volume | Too high lowers yield |
| Biscuit | Cold chamber plunger discard | 5-25% | Biscuit volume | Needs enough solid metal to push cleanly |
| Overflow wells | Vent wells, wash tabs, purge pockets | 2-15% | Overflow volume | Needed for oxide and air capture |
| Trim allowance | Flash, ladle loss, process buffer | 2-10% | Trim allowance | Use higher values for trials |
When you choose between die casting machine, you must choose between different machine capacities. A smaller die casting machine will cost you less per hour. However, a smaller die casting machine may not provide enough force to the die to keep the die closed during the casting process.
If the machine dont provide enough force to keep the die closed, the molten metal will escape through the gaps in the die. The metal that escapes through the die is called flash. Flash requires that you remove the flash from every part that is produce by the die casting machine, which is extra work for the company, and it wastes metal.
How to Choose a Die Casting Machine
Die casting is the process of injecting molten metal into a die under extreme pressure. When you use a die casting calculator, you are performing calculation of the physics of the burst of molten metal. A person may make the mistake of only calculating the net volume of the casting, which is the volume of the part.
You must also account for the volume of the runners and the gates into which the molten metal must travels to fill the die casting with metal. Additionally, you must account for the volume of the biscuit, which is the portion of the metal that remains in the die after it is ejected from the die casting machine. If you do not calculate the volume of the runners, gates, and biscuit, the shot sleeve will run dry before the die casting cavity are filled.
When the shot sleeve runs dry, the metal will porosity within the die casting parts, which means they will be scrapped. Another calculation of importance in the die casting process is the clamp force that the machine’s press must provide to hold the dies closed. You should not calculate the area of the part that will be created.
Instead, calculate the projected area of the part at the parting line of the die. Additionally, multiply that area by the cavity pressure of the metal that will be use in the die casting process to determine the clamp force requirement for the die casting machine. Die casting calculators include a safety factor in the calculations because machines are not constructed to be perfectly rigid and dies is not constructed to be perfectly flat.
A safety factor of 1.20 is commonly used in the die casting process, but if the dies have not been seated into the press perfectly, a higher safety factor is required. It is always better to use a die casting machine with more clamp force than to have to remove flash from every die casting part. The third consideration of importance in the die casting process is the metal to be use in the die casting process.
Each metal alloy has a different density. Additionally, each metal has a different rate of heating to the target temperatures of the metal. For instance, aluminum A380 is a common metal alloy for die casting but Zamak 3 zinc metal alloy is another alloy that is denser than aluminum A380. Zinc metal alloys permit hot chamber casting die casting machines but aluminum metal alloys use cold chamber casting machines.
Different target temperatures for the metal have to be considered because if the metal is too hot it will solder to the dies but if the temperature of the metal is too low it will create cold shuts in the metal parts. Fill time for the die casting process is the amount of time that it takes for the molten metal to travel from the gates of the die to the furthest corner of the die casting cavity. Fill time must be calculated before the metal will begin to freeze during the die casting process.
Gate area and velocity determine the fill time. If the area of the gate is too small the velocity of the metal will be too high, which will create turbulence in the metal as it enters the casting cavity. Turbulence will carry air into the metal which will create bubbles in the die casting parts.
Additionally, if the area of the gate is too large the velocity of the metal will create a slow movement of the metal into the casting cavity which may lead to the metal freezing before it completely fills the cavity. The die casting calculator will tell the operator if the calculated fill time falls within the ideal time window for the metal that is to be used in the casting process. Another consideration for the part designer is the inclusion of a trim allowance in the casting process.
Because die casting use more metal than the weight of the final part calculations, a trim allowance must be added to account for the metal that will remain in the ladle when the casting is ejected from the die and the metal that will be lost to flash. If a trim allowance is not included in the volume calculations for the part, the shot capacity of the die casting machine may be too small to handle the total volume of metal. Using too small of a shot capacity of a die casting machine will require the metal jobs to be moved to a larger and more expensive die casting machine.
Finally, the use of these types of calculations will reduce the risk of the die casting process. By using these calculations, a person can find a die casting machine that is fast and small in size but produces perfect die casting parts. By calculating each of these variables, such as volume and pressure, it is possible to avoid using trial and error in the die casting process.
By avoiding trial and error the company will waste less aluminum metal and will have less machine downtime. Thus, when the clamp force required for the part is within the capabilities of the casting machine and the fill time for the metal is within the ideal time window for the metal that is to be used in the die casting machine, the die casting process will be a predictable and easy controlled engineering process.
