Potential Problems
One problem encountered (but not necessarily limited to) machining is the collection of small particles in and around the outer seal ring of the Visiport or DiscAir disc. High speed machining under certain conditions will also produce small chips which may collect around the seal ring.
Cast iron machining applications also produce small chips and dust that can interfere with proper spin window function without adequate maintenance. Gradual buildup occurs whereby material is deposited between the seal ring and the base. If this buildup is not flushed away or deflected with adequate guarding, the resulting interference can cause noise, disc wobble, slowing of disc rotation, and ultimately stall the spin disc.
The Visiport 220.B5 models were designed with this problem in mind, and have a new and improved forward-facing seal labyrinth which minimizes the ability of small chips and swarf to enter between the spin disc and the base.
Maintenance & Cleaning
Extended operation without cleaning of a spin window with internal contamination from buildup of small chips and dust will lead to motor failure. All spin windows are designed to operate with adequate coolant and are not suited to dry or near-dry machining applications.
To remedy this situation, carefully remove the disc by following the installation instructions. Clean the seal ring and spin window base, reassemble and restart the spin window. To prevent significant chip buildup, planning and attention to adequate coolant delivery to the interface between the disc assembly and the base of the unit should be undertaken.
Though this problem affects only a small percentage of installations, T2K has worked to find mitigating solutions suitable to address these applications. In addition to evaluating an upgrade to one of the new Visiport 220.B5 models, the next section addresses several alternative solutions that T2K, distributors, and customers have used to overcome difficult chip applications.
Present Solutions
Addressing the problem of small sized chips entering the labyrinth seal requires evaluating the type of machine, type of coolant, amount of coolant, coolant pressure, intended location of spin window, type of material being machined, and whether small chips or particles might accumulate in the area designated for spin window installation due to the typical trajectory of chips leaving the work area.
The first option is to ensure that the spin window is mounted where it can do the operator the most good for viewing rather than where it might receive the highest chip volume. Sometimes spin windows have been mounted in an awkward location for the operator to see simply because the installer knew that location received the worst swarf on the window. Relocation of the window to where the operator could see porperly also bypassed the worst area of fluid and chip impact on the window.
Add additional coolant delivery nozzles as may be required to flush chips from the window and any other areas of the machine tool where chip buildup could lead to more serious maintenance issues for the spin window system.
Add guarding above the spin window to deflect the majority of chips from landing of the top 120 degrees of the circumference of the spin window. The distance of such auxiliary guarding should be close enough to prevent the majority of chips from being able to land on the top of the unit, but not so close as to cause a binding problem, especially if the application or machining operations undertaken can include stringy chips that may potentially become lodged between the spin window and the auxiliary guard.
Machining abrasive materials, such as ceramics, will cause the spin disc to take on a sandblasted appearance over time, impairing vision. The spin disc is made from chemically strengthened float glass, but this nor any other available treatment, including the DLC (diamond-like carbon) coating available for high speed aluminum maching, will prevent the effect of sandblasting the glass surface.
It should be noted however, that some customers have purchased the Visiport and DiscAir system precisely for the cost saving and vision maintainability over traditional machine tool windows. (One customer purchased 10 replacement discs together with his Visiport for just such a ceramic machining application.) The OEM-supplied window will become permanently sandblasted unless replaced, just as the Visiport spin disc.
The difference is that replacing the spin disc is an inexpensive operation requiring two minutes of down time. Replacement of the machine tool window is far more expensive and often requires many hours of down time to tear down and replace the machine tool window.
The customer is invited to decide the cost-benefit ratio for abrasive machining applications, and to contact T2K for more information and pricing.
Spin Windows are the way T2K refers to all devices designed to keep the window of a machine tool running coolant or metalworking fluids clear of fluid spray and chips by means of a rotating sight glass, or that use a rotating glass to provide the operator of the machine tool with a view into the machine tool.