- October 17, 2011, By Timothy J. Walker, Contributing Editor
What is the ideal laminator design?
Someone asked me a couple years ago, after auditing their lamination process, "What is the ideal laminator design?" I always love these simple questions that open up a giant can of worms. There are many things I like and do not like in laminator design. To see where your laminator ranks relative to my ideals, take the following quiz.
For each Yes answer, award your laminator the points for that question.
1. Is your nip guarded and accident free? Yes = 20 pts.
2. Is your nip entry point well-lit and easily viewable? 3 pts.
3. Do you control pre-laminating tensions of input webs to match elastic strains? 10 pts.
4. Do you control downstream tension to a set point nearly equal to the sum of the input tensions (allowing you to run low nip loads without slipping)? 4 pts.
5. (a) If your nip is controlled by supply pressure (either pneumatic or hydraulic), do you know the relationship of pressure to nip load force? or (b) If your nip is controlled by open or overlap gapping, do you have a procedure to measure the gap and set it repeatedly? 10 pts.
6. If you have a rubber roller in your nip system, do you know the maximum indentation of the rubber at your typical process condition? 5 pts.
7. Do you avoid large wraps on rubber nip rollers? 3 pts.
8. When your product is in the nip, do you know if there is contact between the rollers outside the width of your product? 3 pts.
9. Have you measured cross nip footprint length or pressure to check for nip uniformity at typical process loads? 3 pts.
10. Do you know if either of your nip rollers is crowned and, if so, by how much and what profile? 3 pts.
11. Have you ever estimated nip footprint pressure by dividing total load force by effective area (width x footprint)? 5 pts.
12. Does your nip close in a pivoting motion (as opposed to a linear motion), and do you know if your moving nip roller is self-aligning to the non-moving roller or holds its own alignment? 3 pts.
13. If your nip is pressure loaded, do you use flow control to limit the nip closing speed, and does it open during long stop times? 3 pts.
14. Do you consider thermal and hygroscopic expansion coefficients in your laminating process, and do you know the Poisson’s ratios of your laminated materials? 3 pts.
15. Does your web exit the nip tangentially, not wrapping either of the nipping rollers after the nip point? 3 pts.
16. (a) Is your laminator driven, and if there is one steel and one rubber covered roller, is the steel roller the driven one? and (b) If you drive both rollers, is one driven in torque mode? 3 pts.
17. If your product is wrinkle-sensitive, is the last roller prior to the nip point: (a) a spreader roller, (b) does it form a short pre-nip span, and (c) does it create a small wrap angle on the nip roller? 5 pts.
18. Have you measured or estimated nipping roller deflection from end loading and avoid entering the nipped roller with 90-deg wrap angles (avoiding deflection-induced wrinkles)? 5 pts.
19. Do you set pre-laminate tension high enough to pull out product bagginess? 3 pts.
20. For cambered or skewed webs, do you have an adjustable roller upstream of the nip point to tighten one side or the other, and does this roller have a trammed or zero position indicator? 3 pts.
0-50 points = Ummm, what’s the opposite of ideal?
50-70 points = You are making the grade, but maybe summer school would help you.
70-90 points = Your laminator is close to greatness.
90-100 points = Wow! I’m impressed.
If you have any questions about why I like any of these questions answered "Yes," please contact me. Maybe there is another column to focus on some key issue listed here.
Web handling expert Tim Walker, president if TJWalker+Assoc., has 25 years of experience in web processes, education, development, and production problem solving. Contact him at 651-686-5400; email@example.com; www.webhandling.com.