For a case study on one of our trackpad projects, click here. We regularly make trackpads which range from 1kg – 15kg each, and haul off pads which typically range from 500g – 5kg each.
Trackpads, also known as Tensioner pads, Track covers, Track Pads, Tank pads and Caterpillar Track Pads, are essentially rubber pads which are normally bonded to a backing plate during the moulding process. They are used to reduce damage to, and to increase grip on, the surface they are pushing against e.g. roads, pipes or cables. They are also closely related to Haul-Off pads, which are generally much smaller but with more complex rubber profiles.
When selecting a supplier for trackpads, the following important factors should be considered:
Not all rubbers are the same, even though they might look the same. This applies to rubber type (e.g. natural, EPDM, Neo etc), base compound quality, reinforcing and non-reinforcing fillers Trackpads can be subject to highly abrasive environments, and are often at sea. Understanding the environment they work in, forces subjected to, elasticity required, and required lifespan helps refine the detail of the rubber compound. We would recommend that moulding companies use a dedicated compounding function or supplier ensure this achieved and to support what is often an iterative and ‘fine tuning’ process.
Depending on how trackpads are moulded, it is very easy to overcure the outside of a product whilst leaving the core under-cured. There are a ways to overcome this, and a few options normally need to be employed simultaneously to achieve a consistent result. In addition, if the cure is not relatively even, backrinding can result which leads to rough and pre-torn areas of rubber in the product near the tool mating lines and the substrate interface. These tears can propagate quickly in use and are open to environmental attack.
At AVMR, we understand these factors and conduct destructive and non-destructive testing to ensure a relatively consistent cure.
There are a number of potential pitfalls when bonding rubber, but larger items, like trackpads, are subject to additional risks.
Bonding agents can attempt to bond to the rubber while the rubber is still flowing over the substrate surface. Before the agent has the opportunity to bond properly, the rubber has moved on and broken the partially made bonds. The result, is areas of the product with low-to-no bond integrity.
For some applications, this issue might be considered as an acceptable risk, but not in this case. The rubber should be anchored to the backing plate consistently across the whole surface. Trackpads are often subject to high lateral and compressive loads simultaneously, all of which are transmitted through the bonded area. A reduced bonded area increases stress in the surrounding areas which can also lead to reduced life expectancy of the product through internal abrasion, tearing and increased pressure on the remaining bond interface.
At AVMR, we understand these factors and conduct destructive and non-destructive testing to ensure a consistent bond.
Trackpads are usually fairly large, the ones we regularly make are 1 – 15kg each, and as a result tooling can be up to 500kg for these parts (some tooling is up to 800kg). To maintain an efficient cycle time, a level of machine assistance is required to separate the tool and eject the parts. We used to do this manually and, apart from being a H&S concern, it was also slow.
Manual machines are still common in the industry, these place an emphasis on operator skill and memory. Our new machines are CNC for consistency, and have automatic demoulding functionality, which helps keep cycle times down.