When a fabrication shop uses a saw, it’s often the first step of many for that piece of material. The next stop could be a welding cell, machine tool or direct to assembly, which means the material can’t be too long or too short. It also can’t be out of square or have burrs. Downstream, bad cuts will affect costs related to more than just the material itself.
Unfortunately, plenty of shops will focus on a speedy saw in hopes of improving throughput to only find their productivity goals dashed by bad cuts. Sure, they pumped out a high volume of parts, but how many of them are usable? While not every bad cut goes to the scrap pile, many require extra touchpoints, which means more labor and time that add to the final cost of the part.
Missing the cut
Rarely will an out-of-square cut meet the needs of fabricators as it changes the way surfaces meet. Burrs are probably one of the most common issues requiring costly rework, but other common problems include inaccurate miter cuts, which pose issues related to angle and length. A saw blade that bows or twists will cause a curved cross-section rather than a flat plane. Chatter marks plague some shops while others are hampered by work-hardened parts caused by the blade rubbing instead of cutting.
The definition of a bad cut differs per shop, but for most, the blanket definition is a cut that creates a part that doesn’t meet the needs for the next stop in the production line. Adding to the complexity is that expectations have changed. A 2018 Sawing Productivity article included input from a sawing expert who said when he began his career 40-plus years ago, cutting a 10-in. round to within 1/2-in. accuracy was considered “good.” Today’s fabricators, he noted, expect far better than that.
In the “file under minor problems” category are parts that are cut too long. Rather than being scrapped, the operator can run it through the saw again to make the correction, but that extra handling time adds up to more cost. A burr might also be classified similarly, requiring the operator to run it through a dedicated deburring machine or a grinder.
Defining value
Before calculating the cost of a bad cut, fabricators first have to determine what a good cut looks like. A shop that uses manual welding might have more variation allowance than a shop where the next step is robotic welding or an automated assembly operation where the slightest deviations cause headaches. Understanding downstream requirements helps define which saw fits best in the workflow.
Comparing machine specifications side by side doesn’t necessarily point a fabricator in the right direction. For example, machine weight, horsepower and other data have limited meaning unless they translate into value. A statement from a major saw manufacturer featured in a Sawing Productivity article from 2023 lays it out nicely, stating that a specification is nothing but a feature of the machine.
In the article, several questions are posed: “What is its function, and does it truly deliver any benefit to the end user?” The response? “Many of the specifications or features I see listed on competitors’ documents is, ‘so what?’ A true benefit is something that is measurable, such as cutting speed, extended blade life, cut quality, reliability and longevity.”
When a shop finds a saw that cuts to their application needs, value can still be lost if the blade doesn’t match the work. In an article titled “A Blade for the Occasion,” a saw blade manufacturer says that blade selection is a variable that affects everything from throughput to cut quality to cost per cut. For shops cutting the hardest alloys, carbide-tipped blades are often the go-to option. But not just any carbide-tipped product will work. Rather, reducing the cutting load also needs to be taken into consideration, which is why a blade that creates a rocking motion is the right choice as it more easily moves through hard materials.
Process control
When two big hurdles have been cleared – finding the right saw and correct blades – there are other factors to consider, most importantly being machine setup and maintenance.
A heavy-duty bandsaw can weigh a ton, yet something as lightweight as a blade guide can have a huge impact on the cost of a cut. For example, a broken or worn blade guide will cause the blade to ride improperly, creating grooves along the side of the blade that shorten blade life.
While the improper wear is a big concern, so, too, is the fact that it will cause crooked cuts that sends more material to the scrap bin. In some cases, moving the guide arm closer to the material offers the support required for better wear and improved cutting.
Clamping issues can also lead to improper cuts. When the clamp pressure is too low, the material will vibrate, which leads to crooked cuts and inconsistent lengths. Too much pressure, especially on thin-walled tube or pipe, will cause distortion. The sweet spot allows the material to sit square and remain supported throughout the cut.
When other aspects of setup are dialed in, like tracking and alignment, the blade is doing what it’s meant to do – make chips. But those chips can lead to problems if they are not properly cleared from the blade gullets.
When the chip brush is absent, improperly positioned or worn or if the coolant flow is incorrectly adjusted, chips can be carried back to the cutting zone. The result is increased resistance and heat. Again, blade wear accelerates and a wavy or out-of-square cut can make the part unusable.
True productivity
The good news is that fabricators don’t have to suffer through a trial-and-error period to begin making usable pieces. Saw and blade manufacturers are more than willing to help customers establish cost-per-cut scenarios that factor in cycle times and consumables.
Saw manufacturers featured in Sawing Productivity have documented on-site services where they not only recommend the right saw but also help with the floor plan to position it precisely in the workflow and even offer material handling recommendations for improved output.
As with most objectives, turning faster cutting into true productivity takes a comprehensive approach. And when that approach accounts for all the possible variables, the result is accurate, clean cuts.
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