Automotive bumpers are safety devices that absorb and mitigate external impact forces before and after Auto is protected. In the 1980s and 1990s, Automotive bumpers basically used metallic materials as raw materials. After more than 20 years of development, the front and rear bumpers of Hyundai Motor use plastic as raw material, which not only maintains the protection function, but also coordinates with the body shape. It is characterized by good uniformity, light weight and low fuel consumption. The plastic bumper not only has good strength and rigidity, but also has decorative properties. From a safety point of view, the plastic bumper can act as a bumper to protect the front and rear body when Auto collides; from the appearance, a carefully sprayed bumper can naturally be combined with the car, which is really beautiful. Therefore, it has become an important part of automotive exterior decoration, and the design of automotive bumper has become the key to the design of automotive parts. Due to the important role of plastic bumpers, major auto companies around the world are working on the shape of automotive plastic bumpers.
Bumper structure
The plastic front bumper consists of three parts: the outer plate, the cushioning material and the beam. The outer plate and the shock absorbing material are all plastic. The beam is a u-shaped groove punched by a cold-rolled plate, and the thickness of the cold-rolled plate is about 1.5 mm. Plastic buffers mainly use two materials: polyester and polypropylene, and the molding process is generally injection molding automotive mold technology.
Automotive bumper design principle:
When designing the shape of Auto bumper, the designer should clearly define the principles of active safety, passive safety, harmony, and convenient installation and maintenance when designing and developing Auto bumper.
(1) Active safety – On the basis of maximally satisfying the function of use, the design of the bumper should comply with the regulations of the car protrusions, and the design should implement a safe, reliable and reasonable design concept.
(2) Passive safety – When Auto collides with the outside world, the bumper acts as a safety device for protecting the front and rear body, and has good energy absorption characteristics.
(3) Harmony – Whether it is appearance, color or quality perception, we can not only pursue the characteristics of a single bumper, but also maintain coordination with the overall shape of the vehicle and integrate with the whole vehicle.
(4) Easy installation and maintenance – the bumper and its adjacent components can not interfere with each other, the clearance should be reasonable, and the installation point should be set according to ergonomics.
Bumper selection principles:
General plastic materials must meet the following requirements: good performance requirements, process performance requirements, and reasonable cost requirements. Although the raw materials for plastic buffers are generally polyester and polypropylene, there are still some differences in the molecular structure of these raw materials. These differences can lead to differences in plastic properties, so designers must master the selection principles.
Material selection principles:
First of all, to fully understand the application of plastic buffers in automotive mold technology, the understanding should include: what performance (and performance indicators) should be provided when the buffer works normally; buffer working environment, environmental indicators including temperature, humidity, medium Wait.
Master the performance characteristics of plastic raw materials. Based on a comprehensive understanding of material properties, the classification lists the excellent properties of various materials and facilitates the selection of materials. Modified polypropylene is generally used as the material for the plastic buffer. Modified polypropylene is a thermoplastic used for injection molding and its properties must be well known. When using modified polypropylene material, the following four basic characteristics should be satisfied: first, good heat resistance, in the range of 80-100 degrees; second, impact strength is controlled in the range of 0.3-4 J·cm2; The third is tensile strength range is 29 ~ 39 MPa; the fourth is good weather resistance and weather resistance.
Automotive bumper structure design
Follow the design principles, determine the shape and overall layout of the vehicle, carry out system layout and design, and design the plastic bumper. The first step in the design is to design and match adjacent components.
Automotive plastic bumpers are both safety components and decorative components. Its structural design is not only related to the safety of the whole vehicle, but also affects the quality perception of the whole vehicle. With the development of society, cars play an increasingly intimate role in the lives of modern people. The shape of automobile bumpers will also embark on the road of innovation, integrating automotive plastic shapes into beautiful, energy-absorbing, lightweight, low-cost, high Performance and fuel consumption.
The blog on automotive bumper design highlights how modern bumpers blend safety, aesthetics, and functionality. It’s fascinating to see the innovation in materials and engineering that enhance both vehicle protection and style. Great insights!
The bumper is one of the most easily damaged auto parts. Customers often face the following problems: if more than one percent of a bumper is damaged in a scratch or collision, the whole bumper must be scrapped; once the OEM label is torn off the bumper, the bumper can not be put back; and it takes time and money to reinstall a new bumper.
Many car lovers also like to customize bumpers to make their cars more personalized. Due to the sharp drop in the price of 3D printing and easier access to this technology, it has been widely used to replace bumpers with 3D printing.
After we have successfully produced some bumpers, we summarize the following design tips that are crucial for your reference.
Determine the wall thickness of the partTo top
The wall thickness should be appropriate and as uniform as possible. There should be no sudden change, and the thickness should be gradually transitioned.
A lot of plastics have a certain range of suitable wall thickness, generally 0.5-4mm. When the wall thickness is more than 4mm, it will cause too long cooling time and problems such as sink marks. Consideration should be given to changing the product structure, and minimize wall thickness when meeting requirements.
Uneven wall thickness can cause surface shrinkage. It’s more obvious when you apply PP, POM, PE, PA, etc. The wall thickness of automobile exterior parts is generally 2.5 ± 0.25mm, and of large parts such as bumpers are 3 ± 0.25mm to 3.5 ± 0.25mm.
Design of StiffenerTo top
The rational application of the stiffeners can increase the stiffness of the product and reduce deformation.
The thickness of the stiffener is generally not greater than 1/3 of the wall thickness of the product. Under special conditions (such as meeting the strength requirements), it must be less than 1/2 of the wall thickness of the product, otherwise, it will cause surface sink marks.
The slope of the stiffener on one side should be greater than 1.5 degrees to avoid cracking. The multiple stiffeners should be staggered and properly arranged, and the distance between them is greater than 4t (t is the wall thickness of the plastic part).
The height of the ribs is less than 3t, it should not be too large, otherwise, the ribs will be damaged by force.
Design of Support SurfaceTo top
If the entire surface is used as the support surface of the part, slight deformation will affect the fit with the vehicle body. Therefore, in practice, convex edges or partially convex supporting angles are often used as the supporting structure.
Design of HoleTo top
The various holes in the bumper must be provided at locations that do not weaken the mechanical strength of the product, and their shapes must also be convenient for mold manufacturing.
There should be a certain distance between the hole and the wall, and the minimum hole to the boundary is at least 1.5 times the hole diameter.
Material requirements for bumpersTo top
High toughness: In low-speed collisions, the material should decrease pedestrian injury and vehicle damage should be prevented.
Appearance: It should allow for free design, no thermal deformation, insensitive to the environment, scratch resistance, no cracks, shrinkage, easy to spray.
License Installation LocationTo top
When the radius of the curvature of the bumper where you install the license is less than 6,000 mm, an uneven surface or a license plate mount should be made at the installation position.
Arrangement of hook coverTo top
The hook cannot be installed in the middle. It should be installed on the longitudinal beam of the frame and on both sides of the longitudinal beam. The longitudinal beams are much stronger than the transverse beams and can avoid frame deformation. The hooks must be placed on the same stringer before and after, so that the front and rear forces are on a line to prevent the frame from deforming.
The bracket hook should be placed on the right side. Because the vehicle is driving on the right side, due to the friction of the vehicle, the amount of sinking on the right side of the vehicle is greater than the left side. Another reason is that when moving, the traction can move to the left so that the front and rear drivers can observe each other.
Requirements for energy-absorption blocksTo top
Arrangement method of energy-absorbing block: Determine its spatial position according to the impact point of the impactor in GB17354-1998 (at half load, the impact point is on the horizontal plane of the impactor’s reference line, and the reference height is 445mm above the ground). During the collision, it is also necessary to meet the protection of the lower leg in pedestrian protection (the contact height between the front protection and the lower leg is 115mm). The specific size of the buffer block is determined based on the vehicle and CAE inspection.
Buffer block material: Generally, a solid EPP foam structure is used. The material density is 46.5 kg / m², the compressive strength is 0.21 mPa, and the tensile strength is 0.66 mPa
A car bumper needs to be sturdy. Depending upon the regulations of the country in question, the degree of sturdiness and impact resilience will vary.
Bumpers need to be fairly lightweight. Added weight means more fuel to burn and higher manufacturing cost. Because of this, Styrofoam and plastics are common. Some (this is rare) will have aluminum foam cores.
Lightweight, but high energy absorption are important considerations.
When considering a vehicle such as a 1-ton payload pickup truck, the bumper needs to be much more sturdy because of the increased mass. Metals are far more common here.
A bumper serves a few purposes. Not only does it absorb the energy of an impact, but it also must deflect as well. In the case of small cars, pedestrian impact safety comes into play a lot. Hitting a pedestrian likely isn’t going to hurt the car, but it sure will the person! Because of this, newer designs take into consideration how best to minimize injury. This can include deflecting an impact onto-and-across the hood to try to slow the impact and prevent running someone over.
In the case of larger trucks, they must attempt to keep from riding over a smaller vehicle in an impact.
Most bumpers really only deflect damage below 5mph, meaning elastic deformation happens at the lower speeds. They can spring back. Above this, plastic deformation (no pun intended) occurs and the materials of the bumper actually absorb energy as they are permanently deformed.
The first bumpers that we know of were installed in 1897 by the Czech manufacturer Nesselsdorfer Wagenbarr-Fabrïksgesellschaft, and solely for aesthetic purposes.
In 1901, the British engineer Frederick Richard Simms was the first to consider auto bumpers as playing a certain role in improvement of safety. In 1905, he filed a patent application for the buffer, claiming that its goal was to “prevent damage to reflectors, mirrors, radiator and other parts of the vehicle, which should be the last to collide with an obstacle, as well as for the purpose of protecting people or vehicles on the road”. He also explained that the “buffer” should be manufactured “similarly to pneumatic tires or made from solid rubber or filled leather”.
The first plastic bumpers were installed by General Motors in the Pontiac GTO model from 1968. This component was made from an elastomer called Endura, in the color of the car body, and was designed to absorb shocks at low speeds without permanent deformation. Similar bumpers were also installed in the Barracuda model from Plymouth (1970-71). Other companies installed rubber bumpers on metal rods to absorb shocks.
In 1973, the Federal Motor Vehicle Safety Standards entered into force. This was a breakthrough for the automotive industry in North America and for all brands exporting their vehicles to the United States.
A bumper is a structure attached to or integrated with the front and rear ends of a motor vehicle, to absorb impact in a minor collision, ideally minimizing repair costs.Stiff metal bumpers appeared on automobiles as early as 1904 that had a mainly ornamental function.Numerous developments, improvements in materials and technologies, as well as greater focus on functionality for protecting vehicle components and improving safety have changed bumpers over the years. Bumpers ideally minimize height mismatches between vehicles and protect pedestrians from injury. Regulatory measures have been enacted to reduce vehicle repair costs and, more recently, impact on pedestrians.
Most of the plastic parts in automotive are injection molded.
Bumpers
Trims
Covers , enclosures,
Mounting brackets
Everything else which doesnot take load
Learning the Ins and outs of Injection moulding part design would give a fairly good idea.
A good hold on CAD is required as these part get really complex especially trims parts.
OEMs follow a certain guideline when designing features in plastics. Certain thumb rules and methodologies which are standardized . Highly confidential though.
Having discussed with a few colleagues in those areas , it mostly comes down to wall thickness, ribs and fins for stiffness and feasibility of smooth flow of plastic to not cause any defects.