What is Low Pressure Die Casting (LPDC)?
Low pressure die casting, as the name tells, uses low pressure of 10 to 21 psi to force molten metal upward into a mold cavity through a riser tube. This molten metal fills the die cavity from below to guarantee smooth flow with very less turbulence. This process is perfect for making symmetrical parts such as wheels.
What is High Pressure Die Casting?
High pressure die casting (HPDC) uses very high pressures of 1,500 – 25,400 psi. The process starts by injecting molten metal into sealed steel mold cavities through hydraulic pressure. In these cavities, rapid hardening of the molten metal occurs and complicated parts with smooth finishes and tight tolerances come out.
10 Main Differences between LPDC and HPDC
So far we have learned how LPDC and HPDC work. Now we’ll see the differences between them. After knowing these differences, you will be able to easily choose the right casting method according to your needs.
1. Pressure Levels
Low pressure die casting works at low pressure of 10 to 21 psi. This moderate pressure controls the flow of metal and reduces turbulence.
Whereas in HPDC, the pressure is much higher which can range from 1500 to 25400 psi. This very high pressure allows for the creation of fine details and helps fill the cavities quicker.
2. Production Rates
HPDC stands out due to its outstanding production speed. Its cycle time is about four times longer than LPDC. This very high production speed makes HPDC an amazing choice for bulk manufacturing where quick turnaround is critical.
LPDC, on the other hand, operates at a very slow speed which reduces production efficiency. But this low speed allows you to better control the quality of part during casting process.
3. Part Complexity
LPDC specializes in making large parts with thick walls. And these walls can be as little as three millimeters thick.
Whereas HPDC can make more complex components. These components can even have half a millimeter thin walls. HPDC’s fast filling and high pressure capabilities make it ideal for manufacturing complicated parts of electronic and automotive industries.
4. Filling Speed
We see a great difference in the metal flow rate of the two processes. LPDC maintains a relatively slow speed of 150 mm/s. This balanced speed leads to smooth filling and helps reduce cavity erosion.
HPDCs, on the other hand, can achieve much higher speeds of about 60 to 120 meters per second. This speed speeds up the production process but it can also produce more variable flow patterns.
5. Material Versatility
Each casting method performs better with certain materials. HPDC can work successfully with many alloys. It works particularly well with copper, zinc and aluminum-based materials. And LPDC specializes in processing low melting-point alloys and it shows particularly good results with magnesium and aluminum.
Although HPDC can work with many materials, LPDC provides better control over material properties. This control makes LPDC valuable for special components that require distinct mechanical properties.
6. Structural Integrity
LPDC gives great structural integrity to its finished parts. This is because the LPDC’s filling process can be controlled. The flow of metal in LPDC is also slow and turbulence is very less which greatly reduces voids and defects. It also prevents the formation of slag and oxidation. This results in a stronger crystalline structure. These qualities make LPDC-made-parts ideal for high strength applications.
In contrast sharp cavity filling of HPDC can trap air inside the component and this entrapped air increases the empty spaces in the material. This can affect the overall strength of finished parts.
7. Post-Casting Machining Needs
High injection pressure in HPDC produces parts with precise dimensions and outstanding surface finishes. And these parts usually require very little post-processing. But if we look at the LPDC parts, additional secondary operations are usually required to achieve the finish we have desired.
However parts manufactured from LPDC generally exhibit better internal quality. This difference between the two casting techniques greatly affects both final cost and production time.
8. Operating and Tooling Costs
HPDC usually deals with very high pressures which require very strong tools. That’s why the initial investment and general maintenance costs for HPDCs are high. And these tools wear out very quickly due to pressure. But this process is generally cost effective for mass production.
LPDC, on the other side, uses less pressure which increases tool life and lowers tooling costs. In addition, maintenance costs are also greatly reduced. This makes LPDC really economical for small scale production.
9. Heat Treatment Capability
Components made of LPDC usually show fantastic performance in the heat treatment process. Their low porosity and low gas content prevent warping and blistering during treatment. This is why LPDC is preferred for parts that require specific mechanical properties through heat treatment.
In contrast conventional HPDC parts have difficulties in heat treatment due to internal voids and trapped gases. But new age technological advancements have greatly improved the heat treatment capabilities of HPDC.
10. Application Range
HPDC is broadly used in automotive manufacturing where it is used to make engine blocks, brake calipers and transmission housings. And in the electronics industry it makes things like connector shields, laptop housings and smartphone frames. In the aerospace industry too, HPDC is useful for making structural brackets and fuel system parts.
And if we look at the application of LPDC, it is very specialized in making cylindrical heads and intake manifolds and vehicle wheels. Medical industry also relies on LPDC to make things like X-ray machine frames, diagnostic tool housings and surgical equipment. LPDC is also used in the home appliance sector. Here it makes washing machine mixers, parts of vacuum cleaner and food processor bodies.
Pros and Cons of Low Pressure vs High Pressure Die Casting
Low Pressure Die Casting
Pros
Low-pressure die casting produces parts with extraordinary mechanical properties. The process also maintains the structural integrity of the part and guarantees outstanding surface finishing. The controlled flow of metal in this process significantly reduces voids. As a result, we can produce parts with better quality and higher material density. And users can expect better performance and better fatigue resistance from such parts.
This process also excels in material efficiency because the unused metal is returned directly to the crucible. And it also uses much less energy than high-pressure methods.
Cons
Slow production speed is a significant challenge in low-pressure die casting. This slow speed greatly affects efficiency in mass manufacturing. And the process cannot produce walls thinner than three millimeters, which limit its use in some designs.
High Pressure Die Casting
Pros
High-pressure dry casting can produce parts with walls as thin as one millimeter and these parts are produced with smooth surfaces and accurate measurements which greatly reduce the need for additive finishing. And its very fast production cycle makes this method very cost-effective for mass manufacturing.
Parts produced by this process have fine details and meet strict measurement requirements too. And the automated nature of HPDC makes sure of uniform quality during production and greatly reduces material wastage.
Cons
The initial setup costs of HPDC are much higher than other methods due to the complex mold requirements. And parts produced by this method may have lower strength due to material inclusions and potential voids. The process is also not amenable to the production of very large parts and post-casting heat treatment options are also limited in this process.
Which One Is Best? Low Pressure Die Casting or High Pressure Die Casting
Your specific manufacturing needs should guide the choice between these processes. LPDC is more suitable for large parts that need thick walls and simple designs. For these, this process provides much better material properties at lower cost. And HPDC is more suitable for making complex, small parts that need to be produced in large numbers and that have thin walls.
When making a decision, you should also particularly consider production volume, design complexity, material properties and component size. And you can also contact casting experts like Richconn for guidance on which casting method is best for your specific needs.
In Summary
Your specific manufacturing needs determine the choice between HPDC and LPDC processes. Each method is suitable for different needs. LPDC is great for making large parts with better mechanical properties. While HPDC specializes in manufacturing large numbers of thin-walled parts. Therefore your choice should depend on the complexity of design and the size of the part to be produced. And if you want to avail custom casting services, please contact Richconn.
Common Questions
How does LPDC work?
The LPDC process works with a furnace located below the mold which melts the metal. The system then pushes molten metal upward through feed tube with the help of compressed gas. There this metal fills the cavities of the mold in a controlled way to produce quality parts.
Can parts with different wall thicknesses be made by die casting?
Yes, die casting can produce parts with different wall thicknesses within certain limits.
How high pressure die casting works?
HPDC uses a piston mechanism that pushes the molten metal into the die cavity with high pressure. This high pressure ensures complete filling of complex molds to produce smooth and fine detailed parts.
How can we avoid porosity in high pressure die casting?
You can reduce porosity in HPDC by:
- Providing adequate ventilation.
- Optimizing mold’s configuration.
- Keeping uniform wall thickness.
- Precisely controlling injection speed.
In what way gating system’s design affects the quality of die-cast parts?
This design determines the pattern of metal flow, the pressure distribution in the mold and the filling rate which directly affects the quality of the finished components.