Oh boy. I’m sure I’ll get flak from someone for tackling this one, but here goes anyway.
Let’s talk about tolerances for welding. For this post, we’ll focus only on the weld joint and follow the common theme of customer-vendor interaction.
Customer: “What kind of gap range can you tolerate in a weld?”
Vendor: “What kind of weld? Process? How deep? How wide? Material? Filler?”
Customer: “That doesn’t matter yet, I just need to know how big of a gap you can weld and how much it can vary.”
One of the most dreaded phrases we can hear on the welding job shop side is “Just weld it.”
This is a trap, no matter the good intentions behind it. It's also a recipe for disappointment and hurt feelings. To avoid that disappointment and save some time, money, and aggravation on your welding project, let me explain.
We’ve touched on some pretty heady stuff in the past couple of blogs, so maybe something more straightforward is in order. Here goes:
Why use laser welding?
| Sandwiches don't mix well with welding. |
I mentioned in blog 4 that contamination is a topic in itself. Well, why not follow that train of thought?
Anything and everything that is not the “stuff” being welded is a potential contaminant. Whether it be oil from machining, paper fibers, soapy water from a wash cycle, a sliver of plastic from your expensive non-marring table top, or even brown mustard from that London broil sandwich you had for lunch, these are going to put something unexpected into your end product.
Alright, now that you’ve read the “Misconceptions About Welding” blogs, you want to know what else you might not know about welding, huh? So, let’s talk defects. In this blog we’ll discuss porosity.
I like to talk about porosity more than other weld defects because even though there are many contributing factors to it, at the end of the day it is always (did I use an absolute?) trapped gas in the solidifying weld.
To go along with the last post on welding myths and non-weldable materials, I also often get grudging calls from a designer who has been “forced” to add a weld to a design.
Customer: “How much do I have to overdesign this part for this weld?”
Me: “Why do you want to overdesign?”
Customer: “Well, the weld is going to weaken the part! I need to beef it up to compensate.”
This misconception about welding comes up far more often than I’d like. An engineer calls in a rush to get a prototype stainless steel part welded. To save time and cost, he had the parts made from free machining material. Frantic on the phone, the conversation generally goes something like this:
There are lots of misconceptions about welding that keep it off a designer’s list of preferred joining methods. Over a couple of blog posts, I’ll debunk a few of the most common myths and explain why they aren’t accurate.
I hear this one all the time: “Welding is going to distort my part so that it will be unusable!”
