Posted on 17 Mar, 2016 by Neil Sharp
We’ve written blogs discussing the challenges facing OEMs in PCB assembly and the common problems that occur during box build assembly, and we’ve explored why documentation is vital to cabinet build assembly. So it seems only fitting that we turn our attention to electro-mechanical assembly – arguably the most complex of the four.
Electro-mechanical assemblies are complicated and demand high levels of skill, precision, accuracy and consistency. They contain moving parts, which need to be able to operate at high and low tolerances and work alongside the stationary parts in the product.
These assemblies also tend to feature bespoke metal work. Therefore, you need to have in place a broad and robust supply chain that can deliver you high-quality parts, as and when you need them.
However, there are a number of electro-mechanical assembly techniques you can implement to ensure the whole process runs smoothly and that confusion doesn’t arise.
1. Organise your purchasing team into clear commodity groups
Organising your purchasing team such that they focus on different commodities enables each buyer to clearly focus their skills and effort on their particular area. So, for example, you may have a single person purchasing sheet metal while another is responsible for all of the machined parts.
This approach encourages excellence, as each individual develops deep expertise in their area. They also acquire knowledge of the market, which enables them to understand, anticipate and deal with fluctuations in price and availability.
Having specialist buyers in place can also make a difference when searching for new sources, as they will be able to quickly identify a number of potential suppliers and then draw up a shortlist of candidates based on their experience. They will also be better placed to manage your existing supply base; and put in place objective measures relating to quality, delivery, cost, and other factors, in order to monitor and improve performance.
2. Set up an inspection room
It is vital that you provide clear drawings to your suppliers when ordering bespoke parts. One of the main challenges facing OEMs is the potential for tolerances to build up against multiple parts. Each drawn item will have its own manufacturing tolerance. However, when several drawn items come together OEMs can find they start to conflict with each other. For example, a roller may not spin freely when attached to a back plate; two gears may struggle to engage; or the wire and cabling inside an energy chain may begin to get trapped.
Therefore, once you have the parts, you need to ensure that they are as specified. To do this, your require an inspection room – and employees that have the correct training for inspecting the large number of drawn items electro-mechanical builds contain. At a minimum, your inspection room should include equipment such as height and surface measuring instruments, digital caliper and mechanical micrometers and high magnification microscopes.
Often, issues won’t be found until the physical build takes place as, individually, the parts produced will pass initial quality and goods receipt checks. However, problems such as wrong dimensions, missing cut outs to metalwork, incorrect paint or anodizing finishes, scratches to front panels etc. can, and should be, picked up beforehand.
Any issues that are found either at material level or during build should be fed back to the purchasing and engineering teams so that the corrective actions can be implemented. A common mistake OEMs can make is having a complicated process or restricting it to those with access to computers. Unfortunately, this can limit the number of operatives that are then able to input into process improvement. Simple methods, such as hand-written, colour-coded cards that flag up issues to line managers or senior staff, can work a treat.
3. Invest in 3D CAD modelling packages
It is well worth investing in a 3D computer aided design (CAD) modelling package. This software not only reduces the time it takes to design a product - it also helps to improve quality and delivery during the build process. Many of the software packages available today allow you to simulate "real world" scenarios, which bring your design to life. This process can help to identify if there will be tolerance issues during electro-mechanical build, enabling you to prevent them before you get to work.
Of course, the software has limitations. Issues such as panels not fitting together correctly or the PCBs getting crushed can be identified, but the software won’t always be able to determine the knock-on effect of several closely fitted parts clashing due to them all being produced on the outer limits of their tolerances, for example.
4. Implement a robust test strategy
Testing ought to be at the heart of everything you do as an OEM. After all, if your product doesn’t work as it should, the entire manufacturing process is rendered useless. Test is especially important when it comes to electro-mechanical assembly as the addition of moving parts introduces an extra layer of complexity.
For example, wires within energy chains can become trapped if they are not securely fitted or become loose. Likewise, a sliding arm moving across a metal plate could cause a system to jam if it has been fitted a couple of millimeters out. The ramifications of large metal plates and moving arms colliding into each other, or worse an operator or end user, can be huge. A robust test strategy is therefore required to ensure the product is functionally tested in order to meet the end user’s requirements.
Electro-mechanical assembly is a complicated process and, therefore, it's vital to implement techniques that will ensure success. The combination of moving parts and bespoke metal work mean that there is a lot to take into account. For more helpful information, why not download our eBook below.