At Proto-1 Manufacturing, one of our primary goals is to help educate those within the tube and pipe industry. Each month we will be releasing new content focused on educational topics within the tube and pipe industry. This month we will take a look at the different ways to cut-off tube after bend.
Tube cut-off is the process of cutting a tube to length in order to get a tube ready for another application or process. Tube cut-off after bend is a process that is a little more difficult to produce than cutting a more common straight tube. This process specifically involves the cut-off process after the tube has undergone a bending operation. Depending on the needed application, the cut-off point is sometimes close to the tangent of the bend, which can cause accurate cut-off challenges.
There are many ways to cut tube or pipe. Listed below are some of the more common solutions throughout the tube and pipe industry that are used for tube cut–off and tube cut–off after bend.
Common Equipment Used:
Band Saws are typically the most used equipment for cutting tubes after bending as they allow the user to get close to the tangent of the bend. Vertical band saws provide flexibility and are suited for larger diameters in comparison to a circular cold saw. Depending upon your production requirements, many band saws have bundle or layer cutting capabilities for increased production. Band saws are relatively inexpensive and cost effective. However, this process usually leaves burrs on the OD and ID of the tube. These burrs then require a deburring process. This is especially true if the tube requires any kind of tube end forming. Vertical band saws also leave shavings inside the inner diameter of the cut piece. Because of this, extra preparation must be completed prior to end forming to minimize the chance of forming issues. Band saw blade life expectancy depends on many variables, but if properly maintained they can withstand 10,000+ cuts when working with materials like mild steel. Blade replacement is inexpensive, and changeover is average at a time of around 15 minutes depending upon operator experience. Tubes are often clamped within saw to prevent the tube from spinning during the cut process. Most clamping processes only hold two points of contact during their cut operations. Tube cut-off may require vertical and horizontal clamping to prevent the tube from spinning. This clamping process on the outer diameter of the tube can result in a nonconcentric or out-of-round tube. This problem can be solved through the added use of fixtures that cradle the outer diameter rather than pressing 2 to 4 points of contact. The use of a fixture will also provide a better perpendicularity if the setup is correct.
Circular Cold Saw
Circular cold saws are also another option for tube cutoff after bend. This type of saw offers higher quality finishes but at the cost of longer cut times and smaller capacities. Because of the higher quality cuts, cold saws are well suited for projects that require an application, such as welding or end forming, after the tube is cut. Secondary operations are often eliminated when using a cold saw, however deburring may be required depending upon the end forming application and the tube material. Shavings from the tube material are left in the inner diameter and must be cleared out. Cold saws do provide a squarer cut than band saws, but additional fixturing and clamping may be required for tube cutoff after bend processes. While cold saws are initially inexpensive, blade cost is much more expensive in comparison to a band saw. Blade maintenance and resharpening is a high priority when using a cold saw. Blade change over for the cold saw is much quicker than a band saw.
Nick & Shear
Nick and shear is the process of cutting a nick in the tube with a scarf cut and then a guillotine like blade comes down to shear the tube. Clamps continuously feed material through to its desired cut length after each cut and the cycle repeats. This process is suited for high production volumes due to the quick cycle times of the process and very high initial costs. Tooling and consumable costs are high in comparison to the other saw options listed. While nick and shear solutions provide an efficient tube cutoff solution, many end forming applications are not viable after the cutting process due to the shearing process which compromises the material. The compromised and distorted end of the tube must be cutoff if any tube end forming is to be applied to the tube.
Proto-1 RFM-6 Tube Cut-off Technology:
At Proto-1 Manufacturing, not only do our machines specialize in tube end forming, but also in tube cut-off. Unlike other tube cut-off methods, our machines utilize rotary trim tooling that cuts from the inside out. Every tool that we make is custom designed and built in our facility. The tooling consists of inner segments that the tube goes over. Once the tube is clamped in place, the tooling is then spun. During the cutting (spinning) process, a drawbar that rides along the center of the inner segments is pushed forward, displacing the segments out towards the inner diameter of the tube. Mounted within each segment is a cut knife that cuts the material as it’s pushed through the inner diameter of the material. This process produces a clean, square cut with minimal burrs. Our cut-off technology eliminates the need for deburring after trimming for a large majority of our customers depending on their end use. Cycle times for this process average 5-7 seconds depending upon material type and thickness. Rotary tube cut-off is an ideal application for those who perform tube bending. With a Proto-1 rotary tube end forming machine next to a bender, the operator can do both bending and trimming within the cell, thus increasing efficiency. A wide variety of materials can be cut using our rotary tube cut-off tooling such as: copper, nickel-copper, titanium, Inconel, brass, mild steel, stainless steel, aluminized steel, and more. Proto-1’s line of rotary tube end forming machines are capable of tube cut-off after bend. End forming applications can also be added integrated into the tooling to produce both end forming and cut-off in the same process. For more information regarding our tube end forming and cut-off solutions, click the link here.
Proto-1 is an original equipment manufacturer of tube end forming and cutoff machines and custom tube end forming solutions based out of Winneconne, WI.