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    Justifying, Selecting and Implementing Tube Bending Methods Author: GREG MILLER President/Owner Tubular Solutions, Inc. Medina, Ohio

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    I. Introduction Companies considering the purchase of tube bending equipment are faced with an extensive set of alternatives. It is important that a potential purchaser research his needs and the various equipment available. The manufacturer who gives special attention to details will gain a s...

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    Modern design concepts generally develop a bent tube shape by cartesian coordinates. These points in space, X, Y, and Z dimensions mean nothing to a tube bending machine. Even the most advanced CNC machines will do nothing more with this information than convert XYZ coordinates to bending data....

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    provided by the operator. The advantages of basic manual tube bending equipment are: a: Low initial investment b: Short lead times for machine and tooling c: Simple to operate (if part configuration is unsophisticated) d: Portable e: Relatively safe to operate The disadvantages of basic manua...

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    operator secures them to the desired distance between bend position. The trailing end of the tube contacts the stop and provides a way of repeating the distance between bend portion of the part configuration. Basic machines require that the operator rotate the part to the plane of bend positio...

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    More advanced semi-automatic benders are almost like "NC" controlled machines. Bender manufacturers are now offering several options to alleviate the drawbacks of the basic machines. Features available are: a: Digital input of part data and part number storage. Although actual machi...

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    Advantages of CNC tube bending: a: Maximum accuracy and repeatability b: Low labor input for production sequences c: High degree of control d: Quick change-over e: Versatility f: Complex part capability Disadvantages of CNC tube bending: a: Capital expenditure b: Requires operator computer fam...

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    Special application machines are generally either built "in-house" or by custom machine builders and engineering firms. It is important that a potential builder of this type equipment have tube fabricating expertise, as well as, the mechanical and design ability to make it a realit...

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    Disadvantages of special application benders a: Capital expenditure can be high for complex machines b: Minimum flexibility c: Difficult to find qualified long term suppliers d: Can be made obsolete by part design changes e: Delivery time can be long and increases with machine complexity f: Just...

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    APPROXIMATE PRICING ($1000) OD BASIC ADVANCED BASIC ADVANCED CAP. MANUAL MANUAL SEMI-AUTO SEMI-AUTO CNC .25" .01-.1 N.A. N.A. N.A. 50-70 .5" .05-.5 4-15 10-15 15-20 70-100 1" .1-1 15-40 10-30 35-50 100-150 2" 3-8 N.A. 14-40 ...

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    produce 1000 parts an hour with those hand benders and how many people"? The point is, measuring present methods is a variable that the manufacturer can find out for himself. Tubular components being purchased on the outside or produced in-house should be calculated and assigned an accurate...

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    The following table illustrates the labor savings between CNC and semi-auto bending. It is based on 1 years production, running 2 shifts 220 days/yr at a labor rate of $15/hr. SEMI-AUTO CNC LABOR PART #BENDS PARTS/YR PARTS/YR SAVINGS A 1 1,412,576 1,413,632 $39.47 B 3 424,864 5...

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    Parts that have numerous components or operations performed to them prior to bending can be very expensive to throw away. Fittings or brackets that are brazed onto the tube before bending can be very expensive. End forming operations represent significant labor input that can also be miscalcul...

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    may be additional benefits of controlling accuracy and repeatability of the tubular components. For example, an assembly operation with significant time spent "tweaking" the tubes so they will fit. This "tweeking" can also effect failure rates, especially in components for f...

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    (a) Rotation Standard bending machines can be built with the swing arm rotating either clockwise or counter-clockwise. The part configuration and machine interference zones will determine which is required. Give particular attention to the physical dimensions of a bender's interference zones. ...

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    (e) Servo drives Servo motors for controlling machine movements are generally "AC" or "DC". Early CNC machines utilized DC servo drives and they were the standard for many years. AC drives offer better speeds and accuracies, are less expensive, more compact and are easil...

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    The most widely accepted and time proven method is to use a gear, sprocket and chain link to supply force to the swing arm. Systems have been designed to allow independent swing arm and tool movement, shaft power transfer, belt drives, and rotary actuators, among others. Potential purchasers sh...

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    (c) Pressure die assist Pressure die assist should be a considered option for any machine over 3/4" capacity. The pressure die assist offers significant bend quality improvement and the definite likelihood that efforts to eliminate mandrels and/or wiper dies will be successful. There is n...

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    (1) Control system Most all powered tube bending machines use components such as relays, power supplies and switches common to many other electrically controlled devices. There should be a series of sensors and encoders throughout the machine to provide feedback to the computer of machine posit...

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    (c) Data storage Long term storage of data in the electronic memory of the CNC controller should be avoided because it does not provide "hard" copy of the program. In the event of controller failure the data could be lost. Permanent data storage is performed by either a tape, floppy ...

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    Intermediate pressure die positions allow the open position of the pressure die assembly to be selected during automatic cycling. This decreases machine movement, thus improving cycle time. Half-out position can also be indispensable when attempting to cycle tubes that are bowed or not straight...

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    Usually in chart form, the traditional PRB (position, rotation and bend) data can be input to create a bending machine program. The machine accepts the information similar to the following charts. PART NUMBER 1123B OD 1" MATERIAL STEEL WALL .065 BEND RADIUS 1 2" BEND RADI...

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    iv) Bending and wedging processes Most CNC benders allow input of 25 to 30 bends and 10 to 20 wedging movements per bend. Although this may seem excessive, there are many manufacturers that have requested optional increased capability to over 60 bends per part. v) Electronic memory storage Ma...

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    iii) Diagnostics Three areas of diagnostic functions should be standard equipment on CNC bending machines with output on the CRT and the printer. The first area identifies the present condition of normal functions, such as, "emergency stop activated", "automatic mode", &qu...

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    2. Purchase intangibles Purchase intangibles can be defined as factors separate from the immediate physical properties of the machine being considered. They should be held in high regard but should not dictate the selection process if possible. a) Delivery An area of concern in our fast paced...

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    procedure, production criteria and time tables associated with capital equipment purchases sometimes overshadow the importance of seeing the project to completion. Proper implementation of a tube bending machine into a company's manufacturing processes is critical for project success. Special a...

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    training process much more effective. It is also important if second and third shift personnel are to be trained that arrangements are made to assure their availability. It can be counterproductive for a company to train one shift completely and ignore others expected to operate the same machi...

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    a) Confirm shipment It goes without saying that it is important to confirm that everything expected is received. However, with extensive and complicated tooling and machine orders, it is easy to miss important items. Each item should be confirmed against the original order. This can prevent l...

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    The following chart is a general idea of time required for a CNC bender installation. Day 1 1 hour - utilities connection and technical check 2 hours - tube bending and tooling technique overviews 1 hour - explain and demonstrate of computer functions 1 hour - explain and demonstrate program ...

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