SNS - The Heart of Understanding and Applying Slitting

Transcription

1 SNS - The Heart of Understanding and Applying Slitting Dominique Gallou Product Manager Mario Cotta Cincinnati, OH ABSTRACT All slitting the Spatial Nip-Point. The location of this Nip-Point in a spatial frame of reference will affect slitting results. Spatial Nip-Point Stability (SNS) is the crux of all successful slitting, independently of material, slitting type (shear, crush and razor) or slitting challenges. KEY Words & Expressions Spatial Slitting Nip-Point Stability, Process Related Factors, Design Related Factors. 1. SNS Definition SNS is an acronym for Spatial Nip-Point Stability. All points on a blade are capable of slicing a web. Only ONE point in the Spatial Frame of Reference of the slitter winder, as originally designed, will act as both a Nip and Slitting Point. This is the Slitting-Nip-Point. We label it the Nip-Point for short, since there is only ONE Slitting Nip-Point. This point is a mathematical point, that is, without dimensions. a. Determining Spatial Nip-Point (SN) location The SN is located at the junction of the web, upper slitter blade and lower slitter band. The location of this point is an integral part of the original design of the slitting section. It cannot be changed or moved, unless one changes the design of the slitting section. b. Spatial Nip-Point Stability Since the Nip-Point s spatial coordinates cannot be changed, all slitting activity taking place at the designed Slitting Point must occur there. Any activity which does not occur at the designed point will cause ineffective results. SNS Dominique Gallou / Mario Cotta

2 c. The SNS rules are: 1. Keep the top blade slitting the Spatial Nip-Point 2. Keep the bottom blade slitting the Spatial Nip-Point 3. Make sure the web is advancing through the designed slitting Nip-Point at constant velocity, or controlled acceleration, while maintaining flatness. 4. Minimize the contact between top blade and web. This causes the outside edge of the web to move away from the slitting Nip-Point. d. SNS limitations A spatial point is an entity with a location in space but no extent (volume, area or length). In geometry, the point therefore captures the notion of location; no further information is captured. However, all slitting equipment has dimensions. The blade thickness is detrimental to SNS. Various blade designs, bevels and finishes have been put forward in order to alleviate this negative factor. The web caliper is also detrimental to SNS. The lower level of the web being supported by the bottom band is, in theory, exactly at the SN; the upper level of the blade is above. Thinner web will respond better to slitting than thicker webs of the same material. e. Effective results Effective results are defined as meeting customer s expectations, while maintaining process control guidelines within production budgets. 2. Factors affecting Spatial Nip-Point Instability (SNI) Many Factors contribute to SNI. Some are Process Related and some are Design Related. Process Related Factors (PRF) are Factors which can be eliminated without any modifications to the existing machine design. Operator training, slitting process troubleshooting can eliminate these negative factors. Design Related Factors (DRF) are those which require small to major machine modifications. First resolve PRF than, if the slitting process is still inadequate, tackle the DRF. A slitting expert can determine whether PRF solving is sufficient prior to resolving DRF. SNS Dominique Gallou / Mario Cotta

3 a. Process Related SNI Factors: 1. Effective Spatial Relationships 2. Blade Geometries b. Design Related SNI Factors: 3. Spatial Accuracy 1. Blade Guidance 2. Web Guidance* 4. Positioning Reliability * Tension can be process related. 3. Solutions to Insuring Spatial Nip-Point Stability Some of these solutions will be expanded further in the slide presentation 1. Effective Spatial Relationships (PRF) a. Tangential Geometry b. Overlap Geometry c. Shear Angle Geometry d. Run-Out Geometry 2. Blade Geometries (PRF) a. Bevel Design b. Finish c. Blade Diameter d. Regrinding / Refinishing e. Blade Design f. Metallurgy 3. Spatial Accuracy (DRF) a. Blade Guidance Factors (SNS): blade holder design factors i. Vertical Trueness; the vertical guidance of the blade must be true (90 degrees) to the web plane. ii. Horizontal Trueness; the horizontal guidance of the blade must parallel to the web plane. iii. Rotational Trueness; the rotational guidance of the blade must be free of axial and radial run out. iv. Side Load; the horizontal side load of the blade against the bottom band must be linear to the air pressure, linear to the distance traveled from blade to band and consistent from slitting unit to slitting unit. v. Cant Angle Stability; the cant angle cannot slip during slitting. It must be easily adjustable in small, discrete increments. It must be predictable. vi. Depth Adjustment; the depth adjustment must be easily adjustable. SNS Dominique Gallou / Mario Cotta

4 b. Web Guidance Factors: slitting section design factors. i. Draw. ii. Air Entrainment. iii. Alignment. c. Other Factors: i. Web Caliper ii. Web Formation. iii. Web Other Particularities; can bring in a number of adverse factors iv. Machine Vibration; causes run out; strikes against SNS. v. Dust Factors; causes unreliability in the mechanical components. 4. Positioning Reliability (DRF): positioning system design factors. a. Repeatability b. Reliability c. Accuracy d. Feedback Conclusion Understanding Effective Slitting is possible. Applying Effective Slitting can be limited by new factors deriving from new products and processes developments. Understanding Spatial Nip-Point Stability helps the slitting supervisor resolve process related instability factors (PRF) in real time, while discovering insidious design related instability factors. Spatial Nip-Point Stability expands our understanding of slitting, while challenging us to achieve it. SNS Dominique Gallou / Mario Cotta

5 Figure 1 Y Spatial Nip-Point X Z SNS Dominique Gallou / Mario Cotta

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