How do you Press? 

Sometimes, an application has parts that conform to specifications in one dimension, but not another. A great example of this can be a simple dowel pin. Usually, a dowel pin has a tight tolerance on the diameter of the pin, but that’s not always the case in the length of the pin. It might be too expensive or time consuming to have them both manufactured with tight tolerances when only the diameter is critical to the function. Another way Promess handles this type of part is with what we call “Touch point positioning”. The software can be set up to “find” the top of the part, using the force sensor. From that point, we can measure how much we press in addition to how much force is exerted on the part. In an exaggerated example, if you have two pins exactly the same in every aspect except length, maybe one dowel is 1mm longer, we set a low target force (about 20lbs) to find this part in space as we travel down. We should reach the 20 pounds exactly 1mm before the shorter one. From there, the press can continue to press to either a target force or target position based on the starting point of that pin. This helps most often when there is a high amount of variability of a part. Instead of having to inspect each part before it’s assembled, you assemble each part the same based on its unique characteristics. 

There are other unique ways to assemble parts and solve complex applications using press fit techniques. One method is pressing to a specified rate of change, or derivative. Using external sensors, repeating movements, even measuring a part datum ahead of time to determine how much force or press distance is required to make that part perfect are all within the capability of the Promess EMAP system. Using the force and position measurement capabilities of the EMAP can be very powerful tools when the application requires a special touch.  This power, when paired with the knowledge of our expert application engineering team, makes for an unbeatable and cost-effective solution for a wide range of challenging assembly and manufacturing problems. 

There are many ways to assemble a part or product. Many items snap, click, push, slide, or can be put together with a “press fit.” In this context, a press fit is essentially two parts that have interfering tolerances, or an interference fit. How a part is put together influences how well it functions as an assembly. If a part has too little interference, it can easily come apart. Too much interference, and the part can be deformed or break when trying to assemble. What if you could assemble a part perfectly, every time, based off its interference characteristics, with an overall tolerance for what is “good?” Promess Inc. does that with a method of closed-loop force feedback.

A press that has feedback capability built into the system allows for a unique way to assemble parts. The Promess EMAP (Electro-mechanical-assembly-press) has a load cell incorporated into its design. There is also a positional encoder in the unit. The load cell can measure the actual load over the travel distance of the press. This allows us to complete some sophisticated movements in virtually any assembly process. The simplest of these movements is a “Move to Signal” step. In this type of program, the programming tells the press to move down until a certain force is reached. Since the load is being used to control the press as we reach the target force specified, the press regulates its own speed to not overshoot the target force value. This method is effective for seating bearings, seals, and other similar parts to shoulders or into housings. This critical interference fit ensures the part will maintain its hold throughout the life of the assembly. The signal also does not have to be from a load cell. There are applications that require pressing to different types of signals, such as temperature, flow, pressure, or even an external position transducer.