Maintenance Archives

Bonding failures have occasionally occurred where customers have used synthetic or semi-synthetic cutting fluids at extremely low pH levels. A known problem with such coolants is their tendency to become caustic if not maintained carefully, allowing them to attack the interface between the Visiport aluminum base and the bonding material.

After simulating such conditions with low pH metalworking fluids, it seems that bonding failures of this type are due more to the fact that the caustic metalworking fluid has eaten the aluminum away from underneath the seal junction than from a failure of the sealing material itself.

Naturally, caution should be exercised when using coolant susceptible to such pH balance problems. In addition to damaging the Visiport installed in such applications, it seems highly likely that significant and costly machine tool component failures would be an eventual outcome from this type of situation. Coolant types based on water soluble mineral or natural oils would seem to be preferable under these conditions, and are eminently compatible with Visiport installations.

The edge sealant provided with the system is intended to be applied during installation. This material is an oil-resistant silicone formulation that is used to protect the VHB bonding material at its interface with the substrate of the machine tool window from migration of the dyes used in most metalworking fluids. These dyes can leach into the VHB material over time, which presents an aesthetic rather than functional issue.

The edge sealant is not sufficient to prevent or protect against the effects of metalworking fluids that are not maintained to proper pH.

For more information, please contact T2K.

Avoiding Contact with the Spin Disc

Visiport spin window systems are rugged and safe. There have been no reports of accidents involving any spin window system we know in their 15 year history. As with any product, Spin Windows must be properly installed.

While we have no incidents on record where an operator has been injured due to contact with the spin disc, it is possible that some inadvertent contact may occur if the device is allowed to continue running while an operator or repair person enters the machine cabin during maintenance or repair of the machine tool. There are no sharp or protruding features on the spin disc that would injure anyone through contact.

T2K recommends that to avoid any possibility that hair or clothing could become entangled in a rotating spin disc, however, that the Visiport be switched off to avoid any such incidental contact.

All spin windows operate on the same basic concept, i.e., that a spinning disc catches the metalworking fluid and chips and spins them off to keep the viewing area clear at all times.

Wear Factors:
Depending on the type of material being machined, and the aggressiveness of the machining being done on a given piece of equipment, and the distance between the work are and the spin window, as well as a number of other factors, a glass spin disc will begin to lose it clarity and viewability over time.

This is due not only to the scratches and abrasion from chips, but also due to the surface interaction of evaporating metalworking fluids and the chemically-strengthened float glass itself. This is especially so in environments where calcium salts are used to prevent the foaming of coolant.

Finally, there are unintended influences such as tool breakage and projectiles such as inserts that will instantly degrade you viewing experience.

With such a large number of variables involved, there is no way for T2K to predict how long a spin disc will last in your particular application. Some aggressive applications, such a ceramic machining, will cause the spin disc to lose its clarity quickly, whereas other end customers have machined parts for nearly ten years and never replaced the disc assembly.

Replacement:
While we can make no prediction as to how long your disc assembly will last, T2K has designed the product to make the replacement of the disc assembly literally a two minute process, once you have acquired the appropriate replacement part. While we would recommend that all end user sites have at least one spare disc in stock to overcome broken discs due to tool failures, T2K tries to maintain stock of all models of Visiport and DiscAir spin windows available for same-day shipment. For details, contact T2K.

T2K has been informed by a number of customers that scratch resistant "siliconized" machine window are offered as a replacement option for machine windows surfaces which become badly damaged due to chip activity. Bonding Visiport or DiscAir spin window systems to such siliconized polycarbonate is not recommended for several reasons.

1) Material Compatability Issues
The 3M VHB+ material used on all mounting systems for Visiport and DiscAir products is based on an acrylic carrier closed-cell foam. A window material with a silicone-based coating is fundamentally compatible only with other silicone products. While the edge sealing material T2K supplied is compatible, the VHB+ material, being acrylic based, is not. As such, bonding is somewhat compromised in theory.

Based on our testing, however, any T2K spin window bonded according to the instructions laid out in the Installation documents will bond adequately well, as the area required for bonding is many times greater than that required to hold the unit onto the substrate. (Keep in mind that the secondary purpose of the bondset is as a gasket.) The installation instructions are available for download from each Visiport product page and supplied with the product.

2) Poor Cost-Benefit Ratio
As we hear it from the customers actually buying these products, the cost factor is much higher than for the simple, plain optical grade polycarbonate commonly used in the industry. If, however, the point is to increase the life of the window in a machine tool application, then this money is by and large wasted as the extra life provided by the siliconized surface is only marginally longer than for polycarbonate without it.

Truly, if you have a machining application that has sufficient chip activity that the ability to look through the polycarbonate window is destroyed, then you would be far better served either installing a Visiport and allowing the rest of the polycarbonate window's view area to degrade as before, or replacing the polycarbonate window with a safety window incorporating a glass surface on the inside of the machine to resist the chip activity of your application. The use of either window type, of course, does not impact your ability to bond the Visiport on, although a better bond is achieved in practice with glass due to the difference in surface energy this material provides.

3) Downtime and Availability
When the time comes to replace the window, either due to chip activity affecting visibility, metalworking fluid replacement guidelines (which at two years is no different than standard polycarbonate), cracking, or damage due to tool impact, a siliconized window may or may not be available from your OEM as quickly as standard polycarbonate. Certainly it will be more expensive.

T2K can provide you with either a new mounting plate or offer our factory rebonding service to replace the bondset from directly mounted spin windows. With our factory pre-mount service, we can send your Visiport clean, refurbished, and mounted so that you can minimize the downtime switching the old window for new.

For additional information, contact T2K.

Internal Visiport Venting
Visiport's patented design incorporates the ability to vent ambient or "clean" air from outside the machine cabin to prevent internal fogging of the Visiport. The most common method of providing this air flow is throught the use of flex conduit, which is a steel wire braid over a PTFE (teflon) tubing material. With the new B-type units, T2K also provides PUR (polyurethane) tubing as an alternative conduit material. [Shown as PUN on parts list and price sheets]

Venting and Air Flow
Improper installation of the flex conduit can block air flow to the unit. This can allow the Visiport spin window to fog up and can possibly lead to electrical and/or mechanical malfunctions.

Improper restriction of air flow can be caused by (a) over-tightening the fittings, (b) accidentally putting a crimp in the flex tubing, or (c) inappropriate placement of silicone sealant during installations. Please note that adequate air flow to the unit through installed flex conduit is necessary for the unit to function properly. The flex conduit protects the wiring harness between the Visiport unit and the external bulkhead assembly the on/off switch and/or motor electronics, but it is air flow that is the primary purpose behind the use of the flex conduit, PUN tubing, and STK-Steel Tubing Kit (for discontinued Visiport VP210, VP215 and VP220 models) sold with the product.

Custom OEM Wiring Harness / Tubing Designs
Customers incorporating their own tubing scheme to route the wiring harness between the Visiport and the external bulkhead assembly or the machine tool's electrical cabinet should note that it is extremely important to ensure adequate air flow is accommodated in their custom tubing designs.

If aesthetics or integration concerns demand a customized routing scheme, air flow considerations cannot be overemphasized. Due to the necessity to prevent fogging and internal moisture problems that may cause premature product failure, T2K can easily supply flex conduit for new or currently in service Visiport units. In addition, T2K is happy to provide technical support to customers who require custom installations. Contact T2K for details.