Don’t panic, a weldment can be easy to detail if you just learn a few pointers and keep it simple.
Pointer 1 — Learn from the resources available to you for weld symbols.
First, know that there are plenty of resources available to learn. For example, you may not know a whole lot about welds and welding, but search the net and you will find all kinds of sites to help you for free. And there is always the Manufacturers Handbook.
For weld symbols, you can refer to this great web resource. This site shows the weld symbols and how they look. Understanding what weld symbols to put where takes time to learn.
In machine design, usually the weldments have Fillet Welds;
OR when one side is flat and one side is curved like welding a plate to the side of a square tube;
OR when both sides are curved, like welding two steel tubes together.
See how easy it is to learn from images and text on the net? Groovy!
Pointer 2 — For each part in the weldment, think about what is machined before it is welded, and what is done after it is welded together.
For example, when detailing a weldment, there might be items welded together with angled cuts, like on the end of a tube or a chamfer on a gusset. These cuts are made before it is welded. So, it will simplify the drawing if you detail those parts separately.
This makes it easier for the shop to read a complex weldment drawing and helps them create cuts on some parts before welding them together. Be sure to note on the main weldement drawing that there are more details and where to find them. (ie: next sheet, or separately)
Pointer 3 — Never locate a part in a weldment from a finished surface!
In the weldment drawing locate each part first. And remember, that finished surface isn’t there until AFTER they weld it together!
In this image the .50 dimension should be used, not the .12 dimension which refers to the finished surface. The finish doesn’t exist until after the parts are welded together. Then the finishes and holes are added.
Pointer 4 — Remember, only finished surfaces can have critical dimensions.
Notice, only the finished surface gets a 3-place dimension. It is not possible to weld a part to a 3-place dimension. So locating dimensions should be 2 place on an inch drawing (1 place on a metric drawing) . Check your company standards.
Pointer 5 — After you locate the parts, give the overall dimensions of the parts.
If you don’t have a separate detail of a part, you need to give it’s dimensions (Thickness, Height, Depth/ xyz).
Pointer 6 — Dimension the machining that is done after the parts are welded together.
The holes and other machining can now be dimensioned. If the weldment is large and complex, it is a good idea to start with new views of the weldment, possibly on a new sheet. These views will have just the dimensions for the machining done after the parts are welded together. This makes the weldment drawing easier to read and understand.
Now you are on your way to making great weldment drawings. The key is to just keep learning.
‘Til next time,