What happens when your CAD is different than the real-life part? And the case for touch-ups...

Francis Robert, Application Engineer

We like to say that the CAD for parts is near-perfect, while the real world is far from perfect. There will almost always be discrepancies in CAD, but often the discrepancies are very minor – a millimeter here or there. Sometimes though, for a variety of reasons, the CAD will be way off, and may even be missing key components on the part."How should I handle discrepancies in my part CAD?"

With minor discrepancies, it’s actually quite simple – use a technology to compensate. For applications like welding, talk to your integrator about touch sensing, seam tracking, or a vision system. For applications like deburring, look at compliant tooling. These compensation technologies are critically important, and many of our customers use them with great success. We HIGHLY recommend the investment. But note, the technologies described are only useful for small discrepancies – for more on that, read our last OLRP Expert Series article here.

For large discrepancies, there are two potential solutions

1. Modify the geometry in your CAD software.
2. Add components in your OLRP software. In OCTOPUZ, you can use parametric components, such as block geometry, cylinder geometry, and planes, which can often be used to mimic whatever geometry is missing (e.g. a clamp).

For situations where parametric components cannot be used

We advise that you just make sure the tool isn't in collision with the part and/or jig, and then touch-up. We know we know, touch-ups are frowned upon by many, but it's simply the best solution in a lot of cases; here are some reasons why:

1. Once a program has been touched-up, barring any issues from part to part (for which we would need compensation technologies regardless), the program will have an optimized cycle time, as the robot is not spending time compensating (especially when using touch sensing).
2. Minimizing the use of compensation technologies will result in fewer potential errors. Sadly, even the most reliable systems will still fail time to time.
3. Fixing a program that is not using compensation technologies is very easy. Training is minimal, so operators can learn to simply jog and touch-up, and then the robot cell will be online and running. Even the most experienced people aren’t experts in touch sensing, seam tracking, etc., so diagnosing issues is always tricky.