Developing an Effective Quality Control Stage

Whether it’s for prototyping or production, customers ordering 3D printed parts want one thing: high-quality parts, delivered quickly. This means that well-designed production processes must go hand-in-hand with systems for ensuring the quality of every part that leaves the factory. In today’s blog post, we will look at the key elements of an effective quality control process and how developments in best practice will be of long-term benefit to 3D printing specialists and their customers.

The first step: an infallible quality assurance process

For any manufacturing process, it is always far better to prevent mistakes than fix them. That’s why it’s important that you establish an effective quality assurance process, to guarantee the quality of all project data before production begins. As soon as a project specification and the associated 3D files have been received, there should be a clear system in place for checking this information, repairing any errors and engaging with the customer where necessary. This can take place manually, or be partially automated, but however you approach it, it must be a standard part of your workflows. This will minimise the chances of flawed project data creating costly and time-consuming mistakes during production and — in turn — make your quality control stage far more efficient.

Check the quality of each print prior to finishing

Once a part has been removed from the printing bed, each part must be checked thoroughly before any post-processing takes place. As the absolute minimum, we would recommend working through the following checklist:

• Dimensional accuracy. Check that the original file’s X, Y and Z axises have been accurately reflected in the printed part. While any file repair that has taken place should not affect the part dimensions, it is still important to check.
• Surface quality. All parts should be free of voids or warping, and all fine details should be captured accurately. Any polygon simplification that has been utilised should have minimal (or ideally, no) visible effect on the surface quality.
• Mechanical qualities. Tests should be in place for any parts where the mechanical qualities need to meet specific standards, i.e. functional prototypes or parts. Further tests of this sort may be required once finishing is complete (see below).
• Chemical qualities. This is important for any parts that will be used in medical applications, come into contact with food, or be exposed to any type of chemical. Your materials’ data sheets should offer guidance in this regard.

Ensuring the quality of the finish

Once post-processing and finishing has taken place, another check should take place to ensure the end result is consistent from part to part and free of any unsightly errors. In particular, consider the following:

• If you are printing with a powder-based technology, has all leftover material been removed?
• Have all support structures been cleanly removed, with no effect on the surface quality?
• Has the finish been applied evenly across the whole part?
• Have the colours been applied evenly? If multiple colours are being utilised,
• Is the part clean of dirt, oil and finger marks?
• Are the part dimensions still accurate (potentially an issue with thicker finishes), and all fine details still visible?
• For finishes such as metal plating, which are designed to grant parts specific mechanical qualities, further mechanical tests will be required.

Developing systems for high-volume orders

Given the number of elements that need to be considered, quality control becomes more challenging for high-volume orders, but this is something 3D printing specialists must consider if the technology is to be deployed in a production capacity. The good news is that technology is evolving to strategically automate this process, minimising the amount of manual checking that is necessary. For example, EOS currently offer a number of software tools to streamline the quality control process, using a mix of cameras and sensors to monitor printing beds. SigmaLabs offer a similar tools in their PrintRite3D® INSPECT™ software, which also offers tools for monitoring parts’ metallurgical qualities.

While such tools will require a financial investment, the time and resources they can free up for large-scale 3D printing means they warrant serious consideration. If you decide to take this route (as leading manufacturers like GE are already doing), it is essential that any new software tools are able to properly integrate with the existing platforms utilised across your project workflows.

Building customer confidence

If you wish to build on the elements discussed in this article, you should consider working towards ISO 9001 certification, the internationally-recognised quality management standard. While there is currently no specific quality standard for industrial 3D printing, this certification is recognised worldwide and will be a powerful symbol of your quality standards in the eyes of customers.

Effective quality control will do more than just establish consistent, repeatable manufacturing processes; it will help develop your customers’ confidence in 3D printing as a production technology, and encourage them to explore new applications for it.  The development of best practice in quality control across the whole 3D printing industry is therefore an essential part of its growth into a truly mature technology that can be utilised in a wide range of industries.