The welding process involves combining different pieces of metal to make a whole. The materials used in welding have to be cut and resized to bring the engineering drawings and fabrications to life. Because kerf is a common theme among the different methods of cutting welding metals, it is important to know about it.
Kerf or kerf width in welding refers to the width of material removed by a cutting process. Although some people apply kerf to the angle on the edge of the cut part, it should only refer to the actual width of the cut width.
This article delves into how to adjust kerf offset and what kerf is in welding. I will also discuss how you can prepare metal for welding and what kerf is in laser cutting.
How to Adjust Kerf Offset?
The machine operator at the Computer Numerical Control (CNC) traditionally adjusts the kerf offset. CNC machining is a process in manufacturing in which a pre-programmed computer software dictates the movement of factory machinery and tools.
Ranging from grinders to CNC routers and mills, this process controls a range of complex machinery. A single set of prompts via CNC machining can accomplish three-dimensional cutting tasks.
Before running the program, the machine operator must enter the kerf width for the CNC to calculate the actual tool path needed to cut according to the proper dimensions. Modern waterjet machine and thermal cutting controls enable the value of the kerf width to be added in the part program.
This kerf width value can also be pulled up from a process database stored in the CNC; hence, the machine operators don’t have to look up the values for each type of material and their thickness. The operators only select the material type and thickness, and the CNC does the rest.
What Is Kerf in Welding?
Kerf is a measure of the amount of material removed, and it once describes how much wood a saw removed. The kerf differs for every process because each one removes a different amount of material. Methods that remove a smaller amount of kerf, like laser and waterjet, are more precise.
For example, here are the typical kerf widths for ½ inch thick C. S, from different cutting processes:
- Laser – 0.025 inches
- Oxy-Fuel – 0.045 inches
- Plasma—0.150 inches
- Waterjet—0.035 inches
Calculating or measuring the kerf width is relatively straightforward: make a part with a known dimension and then carefully measure the actual width. If your two-inch square is actually 1.96 inches, your kerf is 0.4 inches.
Kerf is vital because you need accurate cut parts with final dimensions that are as close as possible to the programmed shape, especially when cutting parts on a CNC laser or plasma machine.
Apart from the cutting processes that lead to variation in kerf widths, other factors affect it, and they include:
- Cutting speed
- As the cutting speed increases, the kerf width will decrease.
- The thickness of the material
- Thicker materials increase the width of the kerf.
- Power setting
- The kerf width will increase if you set it too low or too high.
- Orifice diameter and standoff distance
- A smaller nozzle orifice leads to a smaller kerf, and the closer the work is to the nozzle tip of the torch, the narrower the kerf will be.
In summary, kerf widths increase with increasing material thickness because it takes more power to cut through the material. For oxyfuel cutting, more oxygen requires a larger nozzle, oxygen stream, and greater oxygen flow rates, resulting in a wider kerf.
How Do You Prepare a Metal for Welding?
Welding is one manufacturing process that uses various tools to ensure precision. Preparing metals for welding is essential before welding starts, and cleaner metals produce the best welds. How you clean or prepare the metal depends on the type of welding you want to do.
Tungsten Inert Gas (TIG) welding requires properly cleaned metal parts, whereas Metal Inert Gas (MIG) needs metal sheets that aren’t cleaned thoroughly. Follow these easy tips for cleaning metals for welding:
- Remove thick impurities with a wire brush
- Use a flap disc and angle grinder to remove any coating on a thick sheet of metal.
- You can use a plasma cutter to cut thick metals.
- If the metal sheet is rusty, you can use abrasive blasting. It helps remove impurities, and you should clean the metal with acetone after blasting. Acetone will remove the leftover contaminants.
Abrasive blasting may trap pieces of metal, which may initiate corrosion of the metal part later. You should avoid cleaning aluminum with this method because it is sensitive to any contaminants that may remain on the metal sheet even after wiping it with acetone.
What Is Kerf in Laser Cutting?
When you cut through a material with a laser, it burns off a portion of the material. The part it burns off is the laser kerf, and it ranges from 0.08mm to 1mm.
The type of material and its properties, the pressure of compressed air, the thickness of the material, and the lens’ focal length are factors contributing to the laser kerf.
If your design has areas narrower than 1mm, the material can warp easily while cutting. It would be best if your minimum width is not smaller than the material’s corresponding thickness.
There are some applications of laser cutting that require you to account for the kerf within your drawing. You can do this by adding or subtracting the kerf width from the dimensions of your components.
Below, I summarize the average kerf widths of some common cut materials and their corresponding thickness:
- Acrylic of 1mm to 3mm thickness has an average kerf of 0.18mm
- Acrylic of 10mm to 15mm thickness has an average kerf of 0.30mm
- Birch plywood of 1.5mm thickness has an average kerf of 0.16mm
- Paper of 90 to 350gsm thickness has an average kerf of 0.08mm
These measurements are only guidelines, and you should only use them as a guideline while you prototype a portion of your design, taking the kerf into account.
