Why are sheet metal components machined after welding?

Welding is often one of the final steps in the assembly of a sheet metal structure. Yet the component is not always completely finished once the welding is complete.

Within sheet metal working It is common for certain surfaces and holes to only reach their final dimensions after welding. This is because of the way the material reacts to heat.

The heat from the welding affects the material

During welding, the sheet metal is heated intensely in a small area. The material expands and then contracts as it cools.

This creates stresses in the structure. Even when robotic welding With fixed fixtures, the material moves a little.

Dimensions and surface areas are subject to change

When the tension is released, the part may warp slightly. A flat surface may become slightly warped, and holes may shift from their intended position.

It isn’t always visible to the naked eye. But when the part is to be fitted to other components, even small deviations can mean that it doesn’t fit.

Tasks that require precision are left until last

For this reason, the part is rarely machined in full before welding. A surface that has been machined to exact dimensions prior to welding may shift as the sheet metal heats up.

Parts with tight tolerances are instead machined afterwards. In this case, the machining is based on the actual shape of the part following welding.

Milling and turning – when the component takes on its final dimensions

Post-welding machining is often carried out using CNC machining. This might, for example, involve:

• mill flat contact surfaces
• drill and tap holes for fixings
• cut grooves and recesses
• turn round sections to the correct diameter

Which surfaces are machined is determined by the drawing and by how the component is to be used. Often, only a few surfaces are involved, but it is these that determine whether the component is suitable.

Post-welding machining ensures the finished component is the correct dimensions

Welding gives the structure its shape, and machining ensures it is the correct dimensions. When precision is the final step, it is the finished component that matches the drawing. This ensures a better fit and requires less adjustment during assembly.

Do you need help with CNC machining?

Here at Linde Maskiner, we carry out both welding and CNC machining under one roof. This means that components can be welded and finished in-house without having to be sent to another supplier. Do you have a drawing, or would you like to discuss a project? Contact us today, and we will help you further.