AirTec relies on impeccable quality! Quality that requires the best machines. That’s why, after a number of tests, comparisons and demonstrations of different machines, we chose the absolute world leader in the production of hydraulic presses, Uniflex Hydraulik GmbH.
A key point in repairing any air spring is pressing the new rubber to the top and bottom parts. What is this? The rubber sleeve must be hermetically connected to the hard parts of the air spring (usually these are aluminum, steel or plastic “heads”), that is, we must crimp the rubber to the other parts without letting air out anywhere. The air pressure in the rubber sleeve during work is about 5-10 bar and even higher (peak pressures). This requires an extremely strong and reliable connection between the rubber and the aluminum parts. This connection is achieved through steel rings that clip the rubber to the metal parts. The steel ring is pressed (crimped) on a special press (crimping machine), tightly pressing the rubber. Although this process seems quite simple, it is the most critical point in air spring repair! Improper pressing (crimping) is the most common cause of future problems and low quality of the service performed.
Possible errors during crimping:
1. Insufficient crimping – the steel crimping ring is not sufficiently pressed, in which case it does not press the rubber hard enough, as a result, the rubber slips out from under the ring at the first higher load (for example, the car goes over a bump at a higher speed).
2. Tearing of the rubber during crimping – The wall of the rubber sleeve, which bears the entire weight of the car, consists of rubber and several layers of special fabric cords. It is the layers of fabric that are the supporting element. When pressing, it is necessary to apply enormous force (in some cases over 100 tons!) along the entire perimeter of the ring with extreme precision and not to exceed the specified pressing diameter. If we apply too much force or squeeze the ring to too small a diameter, the layers of cord in the rubber are torn. A ring literally cuts the threads and the whole sleeve is left to hold only the remaining layer of rubber. We get a seemingly solid sleeve that will explode over the first hole. In order to avoid tearing the rubber, it is necessary to press it precisely, without exceeding a certain force, while at the same time the final pressing diameter is accurate to hundredths.
3. Damage to the metal parts to which rubber is crimped – To keep the weight of the car as low as possible, manufacturers use sufficiently strong, thin-walled metal (and in some cases plastic) parts. Since the crimping press is hydraulic with a capacity of over 280 tons, it is easy for it to literally crush the metal parts that we are crimping the steel ring to. In other cases, if the sleeve has already been made poorly once, it is possible that the metal part is deformed elliptically, has yielded a little (invisible to the eye, but enough to cause a problem) or else it is Chinese of low quality and it is impossible to be sure to crimp the rubber to it without yielding.
4. Crimping rings of poor quality – The requirements for steel rings are extremely high and specific. If they are too soft, they leak; they should not rust; if they are too elastic, they loosen slightly after crimping; if they are too hard, they crack when crimped. Some materials are well-crimped only with sufficiently controlled crimping speed (slow deformation) and good force control.
AirTec is committed to the quality and safety of its products. We can proudly boast that we have the most modern, safest and most precise computer-controlled hydraulic crimping machine in the world, of the absolute leader Uniflex Hydraulik GmbH.
Some of the more remarkable advantages (facilitating quality control) of Uniflex Hydraulik over other crimping machines on the market are:
1. Built-in electronic micrometer – the desired crimping diameter is set in the machine control. Through the built-in micrometer, the machine crimps automatically with an accuracy of one hundredth of a millimeter without exceeding the set value. There’s no danger of over-squeezing, crimping too hard, or accidentally crushing something.
2. Pressure Force Monitoring (PFM) – 
PFM is a real-time monitoring and control function of the pressure force. This extra feature is extremely useful in preventing operator errors. The idea of PFM is to set a frame of minimum and maximum crimping pressure (force) and any crimping process completed outside this range is regarded as an error.
(The data in the following example are purely theoretical and have been chosen at random to facilitate the reader’s understanding of the matter.)
Let’s take as an example the crimping of an airspring with a steel ring, with optimal crimping achieved at a pressure of 40 bar (pressure force = 40 bar). We know that at this force the rubber is crimped well enough without tearing the cords in it, without deforming the ring too much and at the same time the aluminum (metal) cup that we crimp the rubber to will not yield (crush) at this force. We set a pressure range with a lower limit of 38 bars and an upper limit of 42 bars.
Scenario №1 – The set crimping diameter is achieved at a pressure of 20 bar. The machine automatically stops the whole process and alerts the operator of an achieved crimping diameter with a pressure that is too low. Possible reasons in this case are: incorrectly set crimping diameter, because the operator will squeeze the ring too little by mistake (we register an operator error and prevent weak and poor quality crimping of the rubber), the steel ring is too soft (we register a problem with the quality of the steel ring and prevent the use of a substandard part), unexpected size of the metal head we are crimping the rubber to (we register a deformed or defective part), the head we are crimping to has yielded or crushed during the crimping process (we register a substandard part, usually Chinese junk that yields when crimping is attempted).
Scenario №2 – The set crimping diameter has not been achieved yet, but the pressure force has reached 42 bar. When the upper limit of the pressing force is reached (in this case 42 bars), the machine automatically stops and signals that the top force has been reached and the crimping diameter we wish to achieve has not yet been reached. Possible causes are: wrongly set pressing diameter, that is, the operator decided to squeeze the ring too much by mistake, because of which the machine needs to exert a much greater force (over 42 bars) to achieve the set diameter (we register operator error and prevent excessive squeezing and tearing of the rubber, crushing of the metal parts we crimp against or breaking of the steel ring), the ring used is too hard (we identify a change in the quality or elasticity of the steel ring), the steel ring is the wrong size (we record an operator error, because the ring used is too big and to achieve the desired crimping diameter, and it needs to be squeezed enough (greater force is needed), the metal head we are crimping against is larger than expected (we identify an unsuitable, poor quality or defective part)
The Pressure Force Monitoring greatly enhances the safety and quality of the repaired airspring, while automatically eliminating incipient errors. Another proof of the quality you deserve.
3. Pressure Force Control (PFC) –
PFC is a machine function allowing especially precise control of the crimping process. It is used when crimping extremely pressure-sensitive materials such as carbon, hard, low-elasticity plastic, etc. With such materials, an extremely complex and methodical crimping control is required in order not to crack the part to which we apply force. Although rarely used in the repair of car airsprings, PFC control is of great use when we crimp rubber to a plastic head (e.g. BMW X5 rear airsprings). In this case, we have to crimp the rubber sleeve to a plastic base, using a steel ring, hard enough so that the connection holds and weak enough so as not to crush the plastic.
At AirTec we are prepared to face any challenge so as to gain your trust.
4. Crimping speed – a seemingly simple yet important function is jaw speed control. The crimping machine allows us to determine the crimping speed in relation to a set diameter and applied force. Why do we need this? There are materials whose elasticity can play a bad joke during fast loads. For example, with a certain type of steel rings, if we crimp at high speed, the ring “relaxes” after opening the jaws. That is, with the crimping machine, we quickly squeeze the ring to the desired diameter, then when we open the jaws, the ring goes back a little. As a result, we get a poorly pressed rubber and a poorly repaired sleeve. With our crimping machine, we are able to determine the desired crimping speed and durability. We can slowly apply the desired force in a controlled way, then hold the ring in a compressed state. We prevent unwanted deformations, loosening, peak overloads, etc.
High quality equipment comes at a price! Do your own research as to how many air-suspension repair companies have such a machine, and you will be Unpleasantly surprised.
With our machines, we leave NOTHING to chance, because quality is not achieved by chance.
