02-february-2023
3 steps to prepare a part for welding
Preparing a metal part for welding is a process that has to be done in a thoughtful and planned way, otherwise it is not possible to get a quality weld.
Welding, by definition, is a process of joining metals through fusion, with or without the addition of material. That is, it consists of joining two or more metal parts by "melting" the point of contact between them.
For welding to be done effectively, it is important to geometry the parts, that is, to ensure that they are in the correct position relative to the engineering drawing for which their union was designed. Otherwise, the weld may be of poor quality (it may contain porosity, imperfections, etc.) and the resulting part itself may not meet the specifications of the drawing under which it was designed.
Therefore, proper part preparation is critical to produce high-quality results, maintain consistent levels of productivity, and minimize costs, especially costs related to rework and downtime.
Below are some steps you can't ignore every time you prepare a weld.
Cutting the workpiece is essential
Making the initial cut without burrs, guaranteeing the dimensional tolerances of the part and taking into account the characteristics of the metal for welding, is the first step to guarantee quality results.
The care and preparation that goes into initial cutting reduces the amount of parts that may need to be reworked.
Some of the main cutting tools or techniques used are guillotines, plasma cutting, oxyfuel, laser cutting, and waterjet.
Ensuring a clean, straight cut of the parts to be welded is essential for a stronger weld with less filler metal, reducing costs and saving time on subsequent deburring and sanding tasks if needed.
After cutting is done, other important operations may be required such as beveling (cutting the edges of the metal piece to more easily accommodate the welding process), bending (bending sheet metal using a punch and die), and bridging (joining two metals with a small bead of weld, ensuring they stay put). These processes will be made taking into account some specifics of the type of welding we want to use, such as the penetration point, size of the desired bead, plate thickness, etc..
Surface treatment and welding joint preparation
When the cut is finished, the part may be left with a burr, which is a hindrance to continuing welding. When this residue forms, if it has not been removed, it interferes with the quality of the weld because it creates a physical barrier that makes the surfaces of the parts as close together as possible.
If we do nothing and proceed to weld, we will get a poorly made, low quality weld that does not meet the quality requirements of a good weld (good penetration, no porosity, complete fusion, etc.).
However, we can treat these imperfections and leave the piece in good condition by deburring and sanding, with a brush or other type of abrasive, leaving the surface smooth and flat.
After treating the surface and leaving the welding joints prepared, we can geometry the piece.
Shaping the part (geometrizing it)
At this stage, the goal is to put these different shaped pieces together to form a puzzle. There are two ways to ensure that the pieces are correctly joined: by dotting or by using jigs.
Bridging is nothing more or less than joining the two pieces together with a small bead of solder. It is the most commonly used process when we use manual welding.
Jigs, on the other hand, are devices used to assemble and fix parts for welding, according to the position in which we want to weld them and always according to the drawing or other specifications.
Are any of these the best fixing method?
That depends on how we are welding and what we will be welding.
When we are manually welding parts with low tolerance requirements, we may opt for dotting, for practicality's sake.
However, if the part has high tolerance requirements, we have to use jigs as a method of fixturing. We also use jigs in case we opt for automated welding, a type of welding that is "blind" and does not adapt like a human to the possible imperfections that may exist in the part.
In Motofil, we produce robotized welding solutions and we also develop our jigs, a practical, efficient and high precision fixation solution, always taking into account the type of pieces that our clients' cells will weld.
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