January 25, 2016 / best practices, blade failure, blade life, blade selection, bottlenecks, cost per cut, operator training, preventative maintenance, productivity, quality, root cause analysis, workflow process
For any metal-cutting operation, blade life is critical. Premature blade failure not only results in increased tooling costs, it can also increase downtime, rework, and scrap—all of which eat into the bottom line.
For forges that cut and process metal, however, blade life is even more crucial. The scale that forms on forged metal pieces can quickly deteriorate blade life, which makes blade selection extremely important. In most cases, forges require aggressive bandsaw blades with varied tooth geometries that can get underneath any scale buildup (i.e., carbide-tipped blades).
While choosing the right blade is a good start, blade life also relies on a variety of other variables, including proper cutting speeds, feed rates, blade tension, lubrication, and break-in procedures. As an article form Fabricating & Metalworking explains, “Saws are very much like the people who use them: they don’t react well to heat, shock, abrasion, stress, and tension.” Far too often, managers and operators ignore these critical factors and, as a result, experience premature blade failure and end up going through far more blades than necessary.
To help forges extend the life of their band saw blades, below are a few troubleshooting tips from the reference guide, “User Error or Machine Error?”, from the LENOX Institute of Technology. By understanding some common blade issues and their root causes, operators can reduce and, hopefully, eliminate premature blade failure.
Issue #1: Heavy Even Wear On Tips and Corners Of Teeth
The wear on teeth is smooth across the tips and the corners of set teeth have become rounded.
- Improper break-in procedure
- Excessive band speed for the type of material being cut. This generates a high tooth tip temperature resulting in accelerated tooth wear.
- Low feed rate causes teeth to rub instead of penetrate. This is most common on work hardened materials such as stainless and tool steels.
- Hard materials being cut such as “Flame Cut Edge” or abrasive materials such as ” Fiber Reinforced Composites”
- Insufficient sawing fluid due to inadequate supply, improper ratio, and/or improper application
Issue #2: Wear On Both Sides Of Teeth
The side of teeth on both sides of band have heavy wear markings.
- Broken, worn or missing back-up guides allowing teeth to contact side guides
- Improper side guides for band width
- Backing the band out of an incomplete cut
Issue #3: Wear On One Side Of Teeth
Only one side of teeth has heavy wear markings.
- Worn wheel flange, allowing side of teeth to contact wheel surface or improper tracking on flangeless wheel
- Loose or improperly positioned side guides
- Blade not perpendicular to cut
- Blade rubbing against cut surface on return stroke of machine head
- The teeth rubbing against a part of the machine such as chip brush assembly, guards, etc.
Issue #4: Chipped Or Broken Teeth
A scattered type of tooth breakage on tips and corners of the teeth.
- Improper break-in procedure
- Improper blade selection for application
- Handling damage due to improper opening of folded band
- Improper positioning or clamping of material
- Excessive feed rate or feed pressure
- Hitting hard spots or hard scale in material
Issue #5: Body Breakage Or Cracks From Back Edge
The fracture originates from the back edge of band. The origin of the fracture is indicated by a flat area on the fracture surface.
- Excessive back-up guide “preload” will cause back edge to work harden which results in cracking
- Excessive feed rate
- Improper band tracking – back edge rubbing heavy on wheel flange
- Worn or defective back-up guides
- Improper band tension
- Notches in back edge from handling damage