So, we’ve talked about gaps a few times (here and here), and if you’re not sick of hearing about them, thanks for your patience. Yes, there are other weld tolerance concerns, so let’s talk about one of the other common tolerances that can wreak havoc on a qualified welding process.
Thickness. No, I’m not referring to anyone’s skull, rather the tolerance of the cross section of the material at the point of welding. Depending on the weld joint configuration (assume autogenous for today), there may be 2 or more tolerances to consider.
- The penetration tolerance – how deep the weld is and the +/- allowance. This will play a critical role in the strength, repeatability and achievability of the weld.
- First component thickness tolerance – typically you will be welding two or more components together. With a full penetration weld, if your tolerance band here is wider than your weld process can readily accommodate, you can have over- or under-penetration with a whole host of problems – as always, a topic for a future post.
- Second component thickness tolerance – if there is sufficient thickness tolerance on both first and second members, this can lead to significant mismatch between the components, again leading to a host of potential issues.
- Additional components – weld backups, nearby features, etc. The tolerances of these need to be considered. We spoke about compensating for weld shrinkage in an earlier blog post. If that isn’t taken into consideration, you risk all sorts of undesirable weld issues.
Now, if we’re looking at a partial penetration weld, we may not be as concerned about the overall thickness, but we will be much more interested in the mismatch between the components.
Hopefully you’ve gleaned just a bit of useful information from this. Please remember to consult with a welding expert every time you're designing a component for welding. It will reduce your stress in the design process and all subsequent operations.