Hydroforming Process: The Complete Guide

Before starting you next hydroforming process, read this guide.

It has all information to guide you through basic and advanced stages of hydroforming processes.

Let’s dive right in.

What Is Hydroforming?

It is a process that involves forming a hollow part or thin sheet from a tube, a profile, or two blanks by application of internal pressure by use of an active fluid, mainly water-oil emulsion. The pressure depends on the material, thickness, and radius formed.

Tolerance And Finish In Hydroforming Process

The hydroforming process can give different parts very tight tolerances. These might include aircraft tolerance having a sheet tolerance of 0.76mm.  Removal of the initial pressing of a male and female die ago makes the hydroforming process have a smooth finish.

The hydroforming process eliminates the presence of springs back since it has been the area of research, especially in tube-making circles.  Tube deforms naturally difficult and does not show high degrees of elastic deformation when loaded.

Tolerance And Finish In Hydroforming Process
History Of Hydroforming Process

History Of Hydroforming Process

Due to the need for hydroforming processes in different solution guides, Frederick V Geiger and Fred Holz came up with the Cincinnati milling Machine Company back in 1889. In 1950, the first hydro machine was made in the company. Initially, due to unimproved technology, components of deep draw like reflectors in reflectors together with the covers of the gear case were the main products.

Traditional female dies were replaced by a rubber diaphragm supported with oil pressure. It was very economical due to its short production runs as it removed the use of costly matched die sets. In the 1970s, the company name changed to Milacron, describing its product as a deep drawing low initial investment cost. Later, the company focussed on improving the capability and speed of the machines as the initial company names changed.

Deep Draw Stamping Vs. Hydroforming Process

Deep Draw Stamping
Hydroforming Process

Developmental Costs

Since prototyping is the key making process, the material changes or thickness of the given wall characteristics can be maintained through the hydroforming process despite tooling. At the same time, deep draw stamping essentially requires a tooling process.

Tooling Process

The hydroforming process is half less expensive than the deep draw stamping. More punches are made from cast iron in hydroforming than deep draw stamping.  Tools in the hydroforming process are easily aligned and mounted, making it easy and efficient, while in deep draw stamping, the alignment is unclear.

Finishing Expenses

The hydroforming process gives an excellent and attractive finishing as the flexible diaphragm is utilized. Unlike the deep draw stamping in which the diaphragm is not used, giving a less attractive finishing.

Reduced Press Time

The hydroforming process has over 60% reduction presses, unlike the deep draw stamping with only 35-45% die presses.

Hydroforming Process Parameters

Hydroforming Process Parameters
Hydroforming Process Parameters

Internal Pressure

Internal pressure confirms the shape and the die contours. Pressure entails a hydraulic press having a specific die in a combination of water and a control system for high-pressure fluid.

Material Selection

It largely determines the force required to reform metal to develop automotive parts like hoods and roofing. In tube hydroforming, there are high and low-pressure applications.

Axial Feed

There are feasibility analysis methods in addition to windows and load path calculations. They are developed of simulations and experimentations. Additionally, they offer value ranges that command the press on the press in conjunction with path displacement following in the process.

Frictional Coefficient

Surfaces together with lubricants are critical in machine process workability. Reduced friction allows for material flow and prevents material thinning in critical areas.

Temperatures

Different temperature levels are exerted in the process based on the hydroforming process time involved in the formation process. High temperatures require high pressure, while low temperatures require low pressure.

Hydroforming Process Step-by-step Process

Hydroforming Process Step-by-step Process
Hydroforming Process Step-by-step Process

Step 1: A Blank Of Metal Is Put On The Ring Of Blank Holder

It works similarly to a female die. It has a chamber that is pressed and has oil, together with a rubber diaphragm and also a wear pad. The punch replaces the male die element. Hence, the punch is held on a hydraulic piston, then a ring that majorly encloses the punch.

Step 2: Exert Pressure On Fluid Chamber, While Lowering Top Of The Press

This step starts with a ring holding a metal blank. It follows by enclosing press brings the oil chamber down, topping blank.

While raising a punch through the ring while forming the chamber, presses oil together with the chamber. Pressure is exerted highly. Remember, having a female portion as rubber in the formation process, and blank formation occurs without the scratches due to stamping.

Step 3: Push The Punch Up; Thereby Forming Metal Blank Against Pressure Chamber

The diaphragm supports the blank surface.

Since the blank takes a punch shape, the diaphragm forms a blank around the rising punch. Pressure is released in the forming chamber after the hydroforming process is completed, a factor that results in the punch being retracted from the finished part.

Step 4: Raise Top Press, Then Release Pressure While Lowering The Punch

Since this is the last step for the product formation, the pressure being exerted is released for the punch to be lowered.

Sheet Hydroforming Process

Sheet Hydroforming Process
Sheet Hydroforming Process

The operational process of sheet hydroforming uses one tool, reducing the die cost regarding the other formation processes. Blanks are made of rolled sheet metal cut to a given size.

Its size and shape determine the parameters in the process that optimize the flow of the materials.  A punch does the process involving a hydroforming sheet or a cavity die. The process entailing hydroforming of punch is also referred to as hydro-mechanical deep drawing.

Geometrical complexity and deep draw depth decide the use of a punch or cavity. The complexity of the surface to work on will demand cavities like bulges, while cylindrical and smooth running surfaces use punches. Since punches have small beds, they can only work on simple surfaces.

Though the punches work on simple surfaces alone, they are suitable for working on deep draws and materials with less thinning. The parameters considered in the process are the temperatures, the pressure, and variations over time. During the process, blank is prevented from contacting fluid by using a flexible bladder.

Lubricants and working fluids are prevented from mixing by using the bladder, allowing other techniques in the formation process like circular intensifiers of pressure that aid in radius tightening.

Tube Hydroforming Process

Tube Hydroforming Process
Tube Hydroforming Process

It is used mainly in making plumbing parts.

Fluid pressure is applied inside the tube held with dies, closed on the tube with sealed ends, hence the hydraulic fluid being filled in the tube. The pressure forces the tube to conform to the dies.

End seals are exerted with axial force increasing internal pressure. It creates compressive stresses inside the axial, forcing a given tube to deform. A press intensifier controls the pressure.

Process parameters are axial pressure, fluid pressure, lubrication, and at some point, temperatures. Pre-forming processes are vital in helping the tube fit well in the hydroforming die as it flattens the tube in given areas. Pre-form also shapes the tube ends to match the sealing plug.

Normally, there are two scenarios:

High Pressure

Tube fully enclosed in the die before tube pressurization.  Usually, to prevent wrinkling or buckling, the tube circumference is slightly smaller than a die. Due to high internal pressure, a tube confirms a die shape through tube expansion inside the formation limits of materials used during the process.

Low Pressure

A tube is pressed as a die is closed. Hence a tube confirms the shape of a die as a die closes. The tube is first filled with pressurized fluid, after which the closing force of the press forms the tube due to pressure exertion.

Disadvantages Of Hydroforming Process

Delicate Balance Between High Fluid Pressure And Material Ductility
Delicate Balance Between High Fluid Pressure And Material Ductility

The fluid pressure must be higher enough to bend and stretch the workpiece through the radius of the curve. The material in use must be ductile to avoid rupture.

Temperature Differences
Temperature Differences

Maintaining temperatures in the isothermal conditions through the processes is difficult due to different environmental changes.

Longer Cycle Time
Longer Cycle Time

The cycle time, compared to the traditional one, is way longer, making the process more complicated and tedious.

Fluid Pressure And Punch Stroke Complexity
Fluid Pressure And Punch Stroke Complexity

The optimal path between the fluid pressure and the stroke complexity may be part specific.

Equipment Cost
Equipment Cost

The equipment used in the hydroforming process is costly, making the purchasing power very low.

Technical Skills
Technical Skills

The machine must be run by a technical expert who fully understands the processes required for quality products to be met.

Risks Of Operations
Risks Of Operations

The operator is constantly exposed to running machines which are risks. The devices cause wetness to the operator due to too many fluid spillages and pressure involvements.

Hydroforming Advantages

Higher Mechanical Strength
Higher Mechanical Strength

Products designed from the hydroforming process are more robust and durable.

Reduced Assembling Or Welding Connections
Reduced Assembling Or Welding Connections

High pressure forces different products to form a single product from their respective sources, an advantage to outdo welding and assembling needs.

Reduced Spring Back
Reduced Spring Back

Materials formed from the hydroforming process have les tendency to return to their original form or shape due to the high pressure exposed to them.

High Accuracy Level
High Accuracy Level

The hydroforming process puts high pressure on the products, eventually giving the required quality and design.

Durability
Durability

Ideally, high-pressure materials are more durable due to fewer risks or the ability to be affected by other surrounding materials. High pressure increases the stability of the material used.

Variety Designs For Complex Parts

During the process, the spaces and shapes of a given design are made based on the required form, size, and other quality components.

Hydroforming Process Applications

Aviation And Aerospace Industry
Aviation And Aerospace Industry

It shapes aluminum and its alloys into different parts like wing skins, seat spreaders, fuselage skins, backrests, and armrests. Also, jet engine components are made through stainless steel, alloys of nickel form nozzle parts, and titanium designs for portable water tanks.

Medical Equipment
Medical Equipment

It makes surgical trays, reflectors, and operation room light covers.

Automotive Industry
Automotive Industry

Hydroforming makes different components such as exhaust systems, chassis, and body parts. The parts include cross and side beams, roof frames, motor, and different pillars like the A-. B- and C-pillars.

Plumbing Industry
Plumbing Industry

It is used to make pipes and plumbing fixtures.

Heating Industry
Heating Industry

A metal tube is heated to a particular state, almost its melting point, then pressurized internally by gas to form tubes.

Household Appliances
Household Appliances

Stainless steel curtain holders are made from the hydroforming process.

Furniture Industry
Furniture Industry

Furniture products can be well finished or fixed using parts like hammocks, drawers, or other decorative arts used for symbolic or religious places like crosses.

Machine And Equipment Construction
Machine And Equipment Construction

Frame rails in cars and radiator supports are made from hydroforming processes.

People Also Ask:

Which Are The Two Types Of Hydroforming?

Hydroforming of Sheet and hydroforming of tube

Sheet hydroforming process

Ideally, it operates using a single sheet. A punch does the process involving sheet hydroforming or a cavity die.

Tube hydroforming process

Fluid pressure is applied inside the tube held with dies, closed on the tube with sealed ends, hence the hydraulic fluid being filled in the tube.

What Is Hydroforming Sheet Metal?

It is the process of exerting very high pressurized fluid force on a metal piece to change its shape. Besides, it results in structurally complex strong parts, which are a result of ductile metals. The pressure defines the shape of the workpiece.

What Are The Forms Of Sheet Hydroforming?

There are two types of sheet hydroforming processes;

  • Fluid cell hydroforming process
  • It is used to form shallow parts with open corners
  • Deep draw hydroforming process
  • It is used to make taller parts with closed corners up to 15 inches taller.
What Is The Purpose Of Hydroforming?

The hydroforming process replaces the older stamping process of two parts, welding them together to form a single material structure.

Also, hydroforming makes different parts more efficient by removing welding and creating complex shapes and contours. It reduces weight, wastes in the workpiece, and reduces tool costs.

Which Fluid Do You Use In Hydroforming?

Hydraulic fluid

It is a liquid that uses pressure below a rubber diaphragm that forces the workpiece to change its initial shape of the mold. Additionally, it helps in transferring the power to the hydraulic machinery. Commonly, the fluid is based on water or mineral oils.

Which Materials Are Suitable For Hydroforming?

Metals suitable for hydroforming include – Kovar metals, clad metals, Galvanized metals, Aluminum metals, Lead metals, Brass metals, Bronze metals, stainless steel metals, copper metals, titanium metals, high nickel alloys metals, cobalt metals, Inconel metals, and molybdenum metals.

More Resources:

Hydroforming

Sheet Metal Hydroforming

Hydroforming Stainless Steel

Titanium Hydroforming

Hydroforming Aluminum

Deep Draw Hydroforming

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