What is Hydroforming – An Ultimate Guide for Beginners & Experts
What is the meaning of hydroforming? Hydroforming is a manufacturing technique used to manipulate malleable metals into various complex parts. In this article, we’ll dive deep into the intricacies of hydroforming process for your understanding.
What is Hydroforming?
Hydroforming mean also referred as fluid-forming is a modern manufacturing technique that uses high pressure fluid and molding die to fabricate flexible metals. Common metal materials with this technique include; aluminum, steel, brass, stainless steel, etc.
The metal tube or sheet is placed on a die and fluid pressure applied. This forces the metal to assumes the shape of the die cavity.
Hydroforming
How does hydroforming work? For sheet hydroforming process a metal sheet and only one die; the cavity or punch is used. Hydraulic pressured fluid presses against the metal sheet forcing it to adopt the contour of the cavity.
Whereas in tube fluid forming method, the tube metal is positioned between two dies and hydraulic pressure forced into the tube. This pressure pushes the tube outwards forcing it into the die cavity assuming its shape.
In both hydroforming technique, welding of parts is eliminated resulting into high-quality surface finishing of the parts.
Advantages of Hydroforming Process
There are benefits of using fluid forming process as your metal fabrication process and they include;
- Hydroforming is ideal for forming complex metal parts with irregular patterns and contours.
- It does not need welding of two halves like in old methods, this ensures the resulting shapes have smooth surface finishing. This maintains the quality of the metal material used.
- It eliminates chances of fabricated parts from springing back to original shape.
- Hydroforming is highly specific thus resulting into parts that equally bond seamlessly with other metal parts.
- Material thinning is reduced in hydroforming process due to its high precision in dimension and forming process.
- Metal parts formed through this method have their weight reduced and with improved metal strength.
- It is generally a cost saving technique in that it reduces cases of material wastage, additional stages and reduces labor cost.
Limitations of Hydroforming
Like any other metal forming technique, hydroforming also has its demerits although minimal.
- It requires high initial capital for purchasing the hydroforming equipment.
- The cycle time is slower in hydroforming process limiting the number of parts produced within a given period.
Tube Hydroforming vs Sheet Metal Hydroforming
Both tube and sheet metal hydroforming are a type of fabrication processes that are applied in different industries.
Tube Hydroforming
Tube hydroforming is also referred to as ’internal high-pressure forming or IHPF. This process of metal fabrication uses a metal tube as its raw material or blank placed between two dies.
Before the hydroforming process begins, metal tube is taken through a tube bending process. This pre-fabrication step ensures the raw metal is properly curved to enable it fit between the molds.
Tube Hydroforming
Once fitted between the dies and ends sealed, a high pressure hydraulic fluid is passed inside the tube. This forces the tube to bulge outwards into the mold cavity taking its shape.
Metal tube fabrication is commonly applied in aerospace, plumbing and automotive industries where lightweight tube parts are essential components.
Sheet Hydroforming
As the name implies, this type of fabrication uses metal sheet as its raw material or blank. It uses one die unlike tube hydroforming that requires two dies making it costly.
Sheet hydroforming places the sheet metal material on a hydroforming press and applies fluid pressure against it. This pressure forces the metal sheet to conform to die shape it presses upon.
Some of the areas where this process is applicable include; medical devices, defense, aerospace among others.
Sheet Hydroforming
Comparing Deep Draw Stamping and Hydroforming Process
Deep drawing stamping is a metal fabrication technique that uses compression force to form cavity, cylinder or cups from metal blank.
Hydroforming process on the other hand transform metal blanks into mold shape with the aid of hydraulic fluid pressure.
Hydroforming tools is made from cast iron while deep drawing tools are crafted from hardened steel. Steel is more expensive compared to cast iron.
Usually, hydroforming process is straightforward and produces high quality strong parts used preferably in automotive and aerospace industries.
Deep Draw Stamping
While hydroforming reduces material thinning, deep drawn stamping leads to material thinning.
Hydroforming is cheaper than deep draw stamping in terms of developmental cost because it does not need new tool every time. Instead, only material type and wall thickness dimensions can be changed to achieve new shape or parts.
Deep draw processing cost is only effective in large scale production due to expertise needed and the tooling costs. This is contrary with hydroforming process that is generally cheaper from initial tooling cost to processing cost.
Deep drawing method is rigid in design since it requires creation of new tools with every new design. Hydroforming process allows for an array of design changes making it more flexible than deep draw.
Hydroforming is highly precise leading to little or no material loss, deep draw stamping has higher material wastage.
Hydroforming process takes shorter cycle time in large scale production of complex patterns. Deep draw stamping takes longer production cycle times for complicated design configurations.
Hydroforming produces high quality smooth finishes compared to deep draw stamping that leaves scratches on product surfaces. This reduces costs for industries such as aerospace that demand polished finishing standards.
Factor to Consider in Hydroforming
Like any other fabrication process, there are factors that affect the process of hydroforming and its outcome. Some of the key variables to look into while considering hydroforming technique are:
Temperature
Temperature affects the amount of force to be applied during metal hydroforming process and the extent to which a blank is malleable. Some metal blanks lose their formidability beyond certain temperature levels.
Pressure
Hydroforming process applies fluid pressure to achieve part formation. The pressure applied is predetermined depending on the blank material tensile strength. The stronger the metal is the higher the pressure applied.
Additionally, different parts formation requires varying levels of pressure and pressure exposure time to form them.
Material
Choice of material is critical in hydroforming since it restricted to ductile materials and it also affects component part requirement characteristics.
Process Period and Load Path
Knowing process parameters such as hydraulic pressure values to engage and load path to follow are key for precise formation. These values can be determined by carrying out simulation process on the material type and parts design desired beforehand.
The values generated from experimental process and the load path determined will help in the actual hydroforming process.
Lubricants
Surface lubrication is important in this process as it minimize friction and encourage material flow which affects overall process performance. On the contrary, friction is also needed to act as material flow control to prevent level of material thinning.
Step-by-step Hydroforming Process
Step 1: Hydroforming process begins by tooling set up which consists of:
- Female or upper chamber that comprises of pressurized fluid chamber, rubber diaphragm and wear pad
- Lower die or male chamber can be interchanged with a ring and punch. The punch is connected hydraulic piston, blank holder or a ring
Step 2: The next step is to securely place the metal blank on the hydroforming chamber for the process to begin.
The chamber is the closed by lowering the hydraulic pressure system. Pressure is then applied by lifting the punch on the female die ring.
The blank conforms to the shape and patterns on the die elements forming the desired part.
Next, the pressure is withdrawn from the blank ending a hydroforming process cycle.
The final part has smooth surface due to the rubber diaphragm in the upper chamber which supports the blank metal.
Step 3: This is the final step of hydroforming process and is characterized by removal of both upper and lower chamber after depressurizing. The resulting part can be subjected to other stages like laser cutting depending on its application area.
Generally, material wastage is minimal in this process because it starts with a metal blank of required size.
Hydroforming Process
Factors Determining Cost of Hydroforming
Establishing the overall cost of hydroforming process can help you gauge its feasibility compared to other fabrication processes.
Hydroforming Tooling Cost
Hydroforming chamber comprises of female and male die chambers. The female chamber has pressurized fluid and rubber diaphragm responsible for approximately 50% process cost reduction as we’ll see later on.
Besides, hydroforming tools are made of cast iron which is less costly compared to hardened steel in deep draw stamping. Hydroforming tools are user friendly thus do not need expertise to install.
Process Cost
During this process of metal fabrication, design manipulation is simply achieved by change of material type and wall thickness dimension changes. The same is not applicable in deep draw stamping since a new tool must be created for a particular design. This reduces hydroforming process cost significantly.
Operational Cost
To form a particular part, deep draw stamping requires multiple press cycles. Hydroforming on the other hand conforms to die shape in a single press cycle. This leads reduced press time in hydroforming by about 65% compared to 40% in deep draw method.
Finishing Cost
The rubber diaphragm in female die ensures the metal part formed has a smooth finishing eliminating secondary processes like debossing. This cuts cost of hydroforming process. This is not possible in deep draw stamping that leaves scratches on surface that need further removing by additional processes.
As a result, hydroforming is preferred in aerospace parts production as well as in medical application.
Further cost reduction is realized in hydroforming process because of simple tooling structure, cost of material used, cheap installation labor cost, etc.
Materials Suitable for Hydroforming Process
Hydroforming process uses metals that are ductile such as aluminum, steel copper, brass, etc. In this section, we look closely why they are the preferred materials for hydroforming process.
Aluminum: Is a soft, lightweight and durable metal that is easy to conform into various mold shapes. This makes it one of the popular metal used across many industries.
Brass: Fabricating brass is easy sue to the fact that it is less problematic and easily takes mold shape with smooth finishing.
Copper: Copper is a malleable metal that is versatile due to its other characteristics such as electrical and heat conductivity, corrosion resistant, etc. Its tubes and sheets are widely used components across various industries.
Inconel: This is a special alloy known for its excellent tolerance to extreme conditions such as temperature, pressure or mechanical load. It is custom formed into parts that can be used for engine parts in aerospace crafts where temperatures are very high.
Stainless steel: This is a high grade metal that is popular in various industries due to its desirable properties. It is known for its strength, durability, rust free, among many others. Stainless steel material can be fabricated into complex parts without breaking or cracking.
Other materials that are used for specific purpose thus referred as specialty materials include:
Hastelloy: This superalloy is made from combining nickel-chromium-iron-molybdenum making it excellent for extremely corrosive conditions. It produces weldless parts suitable for use in chemical plants that are highly corrosive thus minimizing chances of part failure.
Waspaloy: This strong nickel superalloy is hard enough to be used in turbine construction, aerospace, etc.
Applications of Hydroforming Process
You can make many parts and components through hydroforming process. Virtually all industries have benefited from this sheet metal fabrication technique.
Here are some few examples:
| Industry | Examples of Parts |
| Automotive Industry | · Hoods
· Panels · Brake parts, · Engine shields · Gas Tanks · Sensor covers, etc. |
| Health Care Industry | · Dust bin lids
· Surgical equipment · Instrument sterilization trays, etc. |
| Food industry | · Trays
· Juicers · Clads, etc. |
| Defense industry | · Aircraft housing
· Engine covers · Protective gears, etc. |
| Lighting industry | · Light housing
· Electrical boxes |
Conclusion
In conclusion, hydroforming process is an advanced metal shaping method that can be used in various manufacturing industries. It is evidently cheaper and more efficient than traditional metal fabrication techniques.
At Tsinfa CNC Equipment, we manufacture a range of CNC machines designed for a range of applications – talk to us now for any inquiries.
