A new product launch can achieve so much more
at the Corin Group

“We were initially approached by the inspection team, who asked us to print 48 variations of a ‘machined’ stem component. After this success, word spread quickly, and we were able to use printed parts for many steps in the process. So, we printed a full-size femur from the CAD model of the casting using Onyx and used it to run an initial test machining program to test the toolpaths developed in our CAM software. This part could then be passed on to the next person in the process for their design, and so on, until we were finished. Although we knew the feed rates and speeds would vary, the machining on the Onyx worked well, giving us good stability and part geometry on which to base the remaining processes.”

“My colleague started laser marking the onyx parts with great success. Another colleague designed the jig and engineered a way to capture all the different shaft sizes. This reduced the number of jigs needed, and we were able to write all the programs! Matt and the team had compressed the entire design process by working on it simultaneously. When the raw metal finally arrived, many of the inspection and laser marking programs were ready to go from day one.”

“The machining programs for the CNC machines were created and tested on life-size plastic models.”

Testing the toolpaths for 24 programs is a time-consuming activity and also means that other steps in the process cannot begin until they are approved.

The machining programs were written and tested in the background, using solid onyx parts instead of castings. “Using Onyx was great,” says Matt. “It gave us confidence that the toolpaths were correct, and since the parts are made of plastic, if we had done something wrong, we wouldn't have damaged the tool or the machine—the plastic parts would have given way first.”

The design and creation of robust machining fixtures using carbon or Kevlar also became much faster and easier for Corin Group. Sometimes the changes were simple, such as the clearance for a tool, and sometimes they were a little more complicated, such as the geometry of the point where the part is fixed.

Before the 3D printers were on site, Corin Group had to machine the clamping fixtures on its own production machines or send them to a subcontractor, where changes were not easy and costs were high. “Our development of the clamping fixtures on the printers was much, much faster, and we even identified applications where we can continue to use Onyx printing as a production fixture,” says Matt.

One team member developed an interchangeable fastening system so that we could use it for any shaft size.

Keeping 48 variants of a shaft for laser marking is problematic, especially when you are simultaneously learning how to use a new laser marking machine.

“In a strange way, using a new laser marking machine was an advantage,” says Matt. “Since we had this new machine that could hold multiple parts for marking, we looked at it from a new perspective. The old method of using one clamping device per part was simply unacceptable, so we had to develop a completely different approach.”

Corin Group decided to manufacture a single base unit and developed a range of interchangeable holders. A member of the design team worked with Matt on the project, and both sought advice and input from the machine operator. This collaboration would simply not have been possible if the work had been outsourced.

It is now possible to load a tray with 15 parts and laser mark them in one go, whereas previously we had to do this individually and would have needed 48 different fixtures. Our new fixture system means we can also mix and match part sizes. Changing a fixture is so easy that assembly and setup can be completed in a matter of minutes. The fixtures have been so successful that they plan to roll out the multi-part fixtures to the rest of the Corin Group's product range.

“All of our inspection programs were written before we even saw a finished metal part.”

As we operate in the orthopedic healthcare sector, traceability must be guaranteed, meaning that “inspection” covers a wide range of things for Corin Group. There is the initial inspection of cast or forged components, the intermediate inspection of machined and polished surfaces, and, of course, the final inspection.

"We started with a simple ‘gauge’ for each shaft size, and we were very happy with how the printers met the tolerances we had to work with. The ability to simply slide a part into an Onyx fixture printed with default settings is a real advantage. Before 3D printing was implemented at Corin Group, we had to have these machined externally, which was very expensive and time-consuming. After we completed the design of the first part, we were so happy that we could simply modify the CAD model and print with confidence that it would meet the specification. Corin Group took the same approach to CMM and non-contact measurement programs that they had used when developing their CNC programs, working in parallel with the machining team. By printing the finished plastic part and handing it over to the inspection team, the automated routines required to operate their CMM machines could be created long before they saw a metal product.

“The plastic parts were stable enough to allow us to complete the inspection process, which includes writing the programs for the CMMs. The surface finish of the printed Onyx didn't cause us any problems,” Matt continues. “It was amazing how we compressed our process by using a printed 3D model before the real models arrived. 3D printing was certainly beneficial to Corin Group in this area, and we plan to adopt it as a step in standard development.”