The Great Scanner Debate: Move the Part or the Coil?
Induction scanning machines for vertical part orientation come in a wide variety of length ranges and weight capacities. Generally speaking, induction scanning machines either move the part or move the induction coil. This applies to horizontal as well as vertical scanning operations. There are certainly pros and cons to each method. This article addresses some of the major differences.
Induction scanners process many different parts in many different ways. The ability to scan the part may not even be required during the process. In some cases the scanning allows the part to be loaded and then moved into position, where it is heated with rotation but no scanning in a “single-shot” application.
In some cases the part indexes from one feature to another, such as a camshaft with a variety of heated locations on a single part. In other parts, such as an axle shaft, the flange area requires additional heating time in a static mode, and then the scanning operation begins to case harden the material for the strength and wear characteristics required by the manufacturer. The variety of parts can range from a small 1-inch-long pin weighing a few grams to an 8-foot-tall mill roll weighing over 1,000 pounds.
When a prospective user is evaluating the different scanners on the market, they need to know a number of process variables to help the equipment builder better understand what the full range of use will be on the system. This includes future requirements, as in the case of a commercial heat treater that may see virtually any possible application. The idea is to make the machine as versatile as possible without spending additional money on features that may never be used or that overly complicate it with extensive setup work to change production jobs.
While an equipment manufacturer can make a machine that will offer 1- to 100-inch part length and 0.01- to 1.00-inch case depth, this machine would be so expensive it would probably never be built. Once the user narrows down the scope of the project, the next step is to determine how the machine will be operated.
Will the machine have operators or be automatically operated with a pick-and-place mechanism (robot)? Will the machine be capable of making the production rate with a single spindle, or will multiple spindles need to be provided? The equipment builder will look at the production rate and make the determination on how to approach the entire scope and how to offer the machine that will perform to the process requirements.
There is one additional item that the end user may not understand is available, and that is the method that the process is done. That leads us to the discussion of moving the part or moving the induction coil. First, let’s look at how they are built.
Vertical Scanner Construction – Moving the Part
When moving the part, the induction scanner consists of several major components. The tower is a bench-made assembly, which incorporates the guide shafts, ball-screw assembly, upper and lower tooling, and mounting bracket to tie it into the machine. The tower is either mounted on a pedestal in the quench tank or hung from the wall of the tank. The tooling cantilevers over the tank, while the tower sits off to the side.
The part-rotation motors are part of the assembly as well as the motor and gearbox arrangement to drive the ball screw. The upper and lower tooling include the part nests/centers and are fairly self-contained. Depending on features, air-operated upper centers, monitoring devices or other mechanisms may be installed. Counterweights are used on higher-capacity machines to offset the weight of the part and tooling. The remaining components consist of the quench basin and circulation/filtration system, the induction power supply and load-matching components, an access door, the induction coil and the workpiece to be heated.
The scanner operates by loading a part (typically between centers), closing the door and initiating the start-cycle command. The tower then locates into position with the induction coil, begins the part rotation and the heating and quenching cycle as required to perform the required application.
Upon completion of the heating and quenching operations, a temper cycle may be run, or the part will return to the home positon for unloading and loading of a new part.
- It is less expensive to build with standard lower-cost components.
- It is good for smaller parts, lightweight parts or part families.
- It has a familiar design – what one typically thinks of when hearing the term “induction scanner.”
- It has an adjustable load height. It can be set up for different operators, but the machine must be reprogrammed.
- Ease of automation for robotics or other means. Auto doors, load-assist vee guides and air-operated centers allow robotic loading and unloading.
- The part weight range is narrow and too light; the scanner is over-counterweighted and too heavy. There is more wear and tear on components.
- The length range is narrow, and upper and lower tooling cut into heating space.
- It is less precise – the cantilevered design and up-and-down torqueing motion can wander over time.
- Tooling is exposed and subject to intense quenching action, scale and oils from parts. This leads to more maintenance and less service life. Polymer quenchants gummy coat the moving parts.
- It needs more time to set up. Since the lower tooling can be adjusted, each part setup requires calibrating the new datum point.
Vertical Scanner Construction – Moving the Coil
When moving the induction coil, the construction of the scanner is different since the part locator is stationary. This lower tooling is built into the machine base and sealed in a water-tight chamber. The moving portion is built against a rigid weldment outside of the quench tank. There are linear bearings attached to the carriage that mounts the remote heat station (matching transformer) and induction coil.
The carriage that the heat station sits on also has additional linear guide bearings for X-Y adjustment. This carriage is counterweighted and also raised and lowered by a ball screw and gearbox arrangement. This carriage assembly is shrouded from the quench tank by a rubber bellows, which prevents quench spray from leaving the quench tank.
The induction coil and the mounting face of the heat station are all that is exposed to the quench tank on the back side of the machine. Like the original scanner, the remaining components consist of the quench basin and circulation/filtration system, the induction power supply and load-matching components, an access door, the induction coil and the workpiece to be heated.
The scanner operates by loading a part (typically between centers), closing the door and initiating the start-cycle command. The carriage then locates into position with the induction coil, begins the part rotation and the heating and quenching cycle as required to perform the required application.
- The dedicated load height can be much lower to accommodate longer parts. Setup is easy because datum never changes.
- Longer parts can be easily accommodated.
- The part weight range is wider. Since there is very little variation in induction coil weight, the weight of the part has little effect on the moving carriage. Heavier parts are no problem with the robust non-moving lower tooling.
- The scanner maintains precision with linear bearing track to follow with precision ball-screw drive.
- There is minimal exposure to quench spray. Since the rotation motors are sealed in a chamber and the lifting/lowering mechanism is external to the tank, there is very little exposed to the quench water. Stainless steel tank and stainless lower tooling results in longer life for the equipment.
- It is easy to automate. Auto doors, load-assist vee guides and air-operated centers allow robotic loading and unloading.
- It is more expensive to build – more precision components add to the initial cost of the equipment.
- The bottom tooling is fixed, and the user would have to add a platform to change operator loading preferences.
- The equipment has a slightly larger footprint.
While both moving the part and moving the induction coil can offer the solution to the process requirements, the advantages as far as the life of the equipment, ease of setup and part range capabilities makes the moving-the-coil method very attractive to a lot of users. I hope you find some of the points in this article useful when considering your next induction scanner.
For more information: Contact Mike Rugg, product line manager, Interpower Induction, 3578 Van Dyke, Almont, MI 48003; tel: 810-798-9201 X 104; e-mail: firstname.lastname@example.org; web: www.interpowerinduction.com