The need to accurately measure things is as old as civilization itself – the first such known tool, the Egyptian royal cubit, dates back to 3000 BC and was a granite rod setting the standard by which measurements were to be taken. But as we continue to evolve new methods to produce increasingly complex products, measurement tools also need to evolve.
In a recent Ask the Expert webinar, Guillaume Bull and John Immonen from Creaform discussed how to address the challenges of measuring large and complex parts in additive manufacturing with portable and fast 3D scanning technologies. The Levis, Que., headquartered company builds and sells portable and automated 3D measurement technologies.
A digital poll of the webinar participants revealed that the majority (35%) of them were still using manual measurements tools such as calipers and tapes while 25% were using either traditional or portable Coordinate Measurement Machines (CMMs). Only a quarter were using 3D scanners to measure while a surprising 15% reported using no measurement tools whatsoever.
Bull pointed out, however, that while CMMs remain widely used since being introduced in manufacturing back in the 60s, they have limits when it comes to measuring the increasingly complex parts produced by the additive manufacturing processes.
He outlined five key areas that present challenges for measurement tools:
SHAPE: We live in an era where product design is critically important. Companies differentiate themselves from competitors by leveraging unique design geometry and forms. Additive manufacturing aids this by allowing manufacturers to essentially reinvent their products with designs that are no longer constrained by traditional manufacturing techniques. These bold new designs, however, can prove a challenge to measure accurately.
SIZE: The part may be impossible to bring to the CMM for measurement because it’s too heavy to move or it’s fixed in place. It may also be too large for portable measuring equipment to handle.
MATERIAL: When products made with certain materials initially come out of the manufacturing process they can be too hard or soft or sticky to accurately measure.
SURFACE FINISH: Parts that are either too dark or too shiny can also be difficult to measure in certain situations.
TIME: The time required to measure parts could increase exponentially as the complexity of the part increases.
Another digital poll of the webinar participants found that the majority (40%) had issues with product shape/geometry when measuring, while 20% had issues with product size, 7% with the product material, 7% with the surface finish and 27% with the amount of time measuring was taking.
Bull made the case for how optical CMMs and 3D scanners can help tackle these challenges.
“3D scanners are obviously better suited to measuring non-geometrical shapes. There is no way you can take measurements of such shapes with standard manual tools and a traditional CMM would require a technician to program a thousand control points in order to get a good idea of complex shapes,” Bull said, adding that “a 3D scanner can scan every detail of a complex part and do it in no time. With 3D scanners it’s now possible to characterize the entire part instead of just measuring the surface with only a few control points.”
3D scanners can also be adjusted to different-sized parts with relative ease, Bull said but cautioned that it’s important to have a scanner that remains accurate under shop floor conditions, which can include vibration and temperature changes. Immonen, strategic account manager North America, Creaform USA, spoke about the example of 3D scanning use by American Magic, a premier sailboat racing team supported by the New York Yacht Club. American Magic uses 3D scanning to test some of yachting’s most innovative designs. “They are able to get into very small and confined areas with it. They can take a lot of concise information and remove the guess work. For example, they measure very small parts to see if they fit and mate inside the cavity they’re intended for,” Immonen said.
For parts that come out of the manufacturing process soft or sticky, obviously touch probing is not an option and 3D scanning becomes the obvious solution. “Since you don’t have to touch the part to be able to measure it, you can take measurements not just at the end of the manufacturing process but during different steps of the process,” Bull said.
Immonen added that 3D scanners can even be placed inside machines to check on any issues with the machine set up, such as shifting, so corrective action can be taken.
Surface finish is one area that could pose a problem for 3D scanners. Dark surfaces absorb the light and light surfaces reflect it, potentially making it difficult for scanners to capture the surface accurately. “Selecting a scanner capable of tackling those challenges is important as you don’t want to spend additional time prepping the part by modifying the surface with powder or paint so it can be measured,” Bull said.
3D scanners are also capable of taking well over one million measurements per second so it’s possible to scan large and complex parts in a fraction of the time it would take to do so with a traditional CMM, Bull added.
These abilities have led to a complete reversal in how 3D scanners have been used since they hit the market back in 1990s. Back then 3D scanning mainly supported reverse engineering applications, Immonen said. About 90% of the time that’s what 3D scanners were used for rather than for inspection purposes. But as their accuracy and reliability improved, they became formidable tools in inspecting parts. Today 3D scanners are purchased for the purpose of inspection about 90% of the time, the complete reversal of their use two decades ago.