Tools and Devices

Note: TJWA Inc. does not represent or sell any of these products, unless noted. 

Pi Tapes ™

Check roller diameter and diameter variations to 30 microns or 1 mil.

Pi Tapes are used to measure wear of rubber roller covers, diameter ratio of speed-ratio controlled rollers, and roller-to-roller parallelism as an alternative to a tramming stick.

The ‘easy to read’ product is highly recommend and worth the slightly higher price. 

Vimeo on using outside diameter tape (metric)

Vimeo on using outside diameter tape (American)

How to read a Pi Tape ™.

Precision levels are required tool for aligning rollers and framework. Look for a level with several key features:

• V-groove bottom for sitting squarely on cylinders.
• Side level to indicate level is plumb atop roller.
• Calibrated graduations to read in 0.5mm/m or 5 mils/ft

The most popular level in US is Starrett #98 Machinist Level, usually 12-inch length. They do make a more precise level, 199Z Master Precision Level.

A more compact alternative is the precision levels from EDA.

A tramming stick is a useful tool for checking roller-to-roller parallelism. Strangely not readily available from any supplier, most tramming sticks are custom-made. Also called a wiki-stick, named for its quickness, a tramming stick is comprised of:

• An extending shaft (often a tripod leg)
• A reference roller end, usually an angle iron modified to hold the tripod leg perpendicular to the reference roller
• A dial indicator, measuring down to 25 micron increments over a 25mm range (or 1 mil over 1 inch)

The Nedo measuring stick is a compact and convenient tool similar to a tramming stick, measuring long lengths to small increments. One model measures down to 1 mm over a 0.5 to 2m range ( 40mil over a 20-80 inch range),

The Durometer is the international standard for the hardness measurement of rubber, plastic, and other non-metallic materials. Durometers are described in the American Society for Testing and Material specification ASTM D2240. The measurement is neither metric or American units, instead reads in units proportional to the penetration of a conic, spring-loaded probe where less penetration is considered ‘harder’ and scores a higher Shore value.

Shore A Durometer is used for most rubber covered rollers in web handling applications. Shore A Durometer measurements use a lower spring value and truncated cone probe. Typical Shore A values range from 20 (elastic band), 40 (pencil eraser), 70 (automobile tire),  to 90+ (shopping cart wheel).

A handheld force gauges are a tool any web handler should have. Forces are important in web processes (e.g., tension, nip forces), but many are not measured or directly controlled. A force gauge is vital to calibrate these mysteries. There are many levels of sophistication to force gauges, going from simple fish-weighing scales (see below), to mechanical push-pull gauges, to electronic load cells with digital output and recording. Look for a force gauge with a 25-50 kgf (50-100 lbs) range if you intend to use it by hand. Larger force gauges are useful for higher load measurement inline with a rope or cable (i.e., when not held by hand).

Shimpo Push Pull Force Gauge

Fish-Weighing Scale from Walmart

Footprint measurements quantify differential indentation of rubber rollers, showing changes in contact at a single crossweb (CD) position or the profile from several CD measurements.

These are two quick, easy, and incredibly inexpensive methods to measure nip footprint length and CD variations. Like most nip footprint measurement, these are static, single condition measurements (i.e., the nip opens and closes, but does NOT rotate).

Using tape, lightly place strips of tape down on the open nip roller, intentionally leaving bubbles in the tape-roller contact area. This works best with tape on a chrome roller. After applying the tape, close the nip to the desired setting, then open it and measure the MD distance that the bubbles are ironed out in the contact zone.

Using sticky notes (such as 3M Post-It® notes), first, close the nip at the desired settings, then insert the sticky notes in from either side of the nip footprint as far as they will go, one note from either side (upstream and downstream) and tack them down to the roller. Next, open the nip and measure the MD length of the gap between opposing the sticky note pairs.

Listed below are three sources for nip impression kits/paper. These systems are similar to carbon paper. One roll contains a paper coated with the ‘donor’ material and the other roll of paper is an engineered ‘receiver’ paper. The donor material is similar to blue waxy coating. The two layers are inserted in a pressure point, such as between two nipping rollers, and squeezed. The blue waxy coating transfers to the donor paper where there is sufficient pressure and shows some gradient of pressure with darker blue transfer indicating higher pressure contact. Where tape and sticky notes are strictly used in open-close stationary nips, nip impression paper can also be fed through a rotating nip (usually at slow speeds) to measure pressure variations vs nip MD position.

Three suppliers are listed below. The Valmet product has been previously sold as Beloit and Metso paper. You can sometimes find old stock of this product on eBay and similar sites.

Similar to the footprint pressure-sensing webs, Fuji Prescale Film is an engineered donor-receiver pressure-sensitive two-sheet system. One roll is the donor paper with a unique coating of dye encapsulated inside microscopic glass beads. The other roll of paper is an engineered ‘receiver’ paper. Based on the glass bead size, Prescale film is available from “ultra extreme low” to “super high” each designed to measure over pressure over a specific range of pressures. Prescale film can be used for simple open-close footprint length measurement or for rotating MD pressure contour mapping. Each pressure range of PreScale film includes a color chart of light to dark pink color density vs pressure. Software and scanners are also available to translate the pink density variations into pressure units.

Tekscan and Sensor Products are the two major US-based distributors of Fuji Prescale film (SPI renames it PressureX).

Color Density vs Pressure

Mapping Laminator Pressure

Footprint vs MD Pressure Mapping

Web bagginess is difficult to measure. Roll hardness profile often strongly correlates to bagginess. Hardness profile, alone or combined with thickness or basis weight profile, is the best predictor of web bagginess for roll suppliers and customers. Ranging from manual ‘billy club’ rebound vs width to highly sophisticated mechatronic units, some form of roll profiling will help understand your web quality and correlate it to runnability.

A manual roll hardness measurement that is very similar to a policeman’s billy club or a night man’s self defense stick. The club is swung and struck against the bilge of the wound roll. The operator listens for the pitch of the impact as an assessment of web profile and wound roll tightness. It works well with many stiff materials except foils, but may not work as well for soft materials such as tissue. The method is still in everyday use on almost every paper machine for detecting web profile problems and is still quite useful in web and wound roll diagnostics for other materials. In film, this may be done much more crudely and somewhen less commonly by swinging a tool at hand, such as a screwdriver or utility knife. (David Roisum – AIMCAL Knowledge Base)