It's fun working in a shop that does both welding & machining. On the surface they seem to go together hand in hand, but in reality they are two totally different processes and you end up with totally different results. When I say it's fun, I mean it can be a challenge, but at Craftco we're always up for a good challenge. In this case, the challenge is communicating through the details of what the end user really needs & what the finished product's purpose is. Then taking that information & communicating it with the crew that manufactures the product in an understandable & accurate fashion.
At Craftco, we hire professionals. Many of our team members have 10-20 years of experience, and almost all of the "inexperienced" team members have college degrees in their trade. Generally speaking our fabricators work to complete projects to tolerances within +-1/16" and our machinists typically aim to keep their work within +-.003". This is where the fun comes in as these are just general statements. To keep from always working towards these standards we try hard to ensure prints hit the shop floor that spell out these details, and show the correct tolerances for the project at hand. Our experienced crews know how to read these drawings, and the tolerances, and all goes well.
If its a welding project that tolerances increase on its generally not a tough to work through. For instance, explaining & showing that a tolerance of +-1/2'' on the length of a tent stake is acceptable is an easy one. When you go the other way and tighten the tolerances up on a welding project it's often nearly impossible to do. Looking at the picture above that was the case. We were looking to hold a parallel tolerance of .020" That's tough to do. Not impossible, but tough. We decided to weld first and then machine our surfaces to make sure we were spot on and could be confident we were delivering a quality project within the .020'' tolerance specified.
Here is a picture of another weldment that needs machined that is moving through our shop. This is a pedestal for a robotic arm & it has tolerances that vary greatly. The overall height can vary by 1/8'' while the top surface must be within .003" flatness, and there are 3 or 4 holes in the top with location tolerances of .001", and diameter tolerances of .0005". That's not an extra 0 in there, we are looking to keep the holes within 5 tenths. In situations where you are holding tolerances that tight your machining process needs to be perfect. Depending on how it's been welded, whether there has been stress relief done or not, and many other factors the entire weldment might "move" and affect your tolerances. Often it takes multiple rough cuts to relieve the stress before the final machining can be done & ensure it comes out right.
In some instances we will have a customer come in that truthfully doesn't understand these terms and tolerances. They just know what they need, where it goes, and how it functions. Here is another area where Craftco can help out. Our experienced crew can give advice on implementing realistic tolerances that help keep costs in line and maintain functionality of the end product. If you are in need of manufacturing assistance with any weldments, precision ones or not, let us know. We're always up for the challenge!
Share The Weldment Challenge