Static friction over driven roll, slippage issue /paper machines/

AI Thread Summary
The discussion focuses on the slippage issues between the forming fabric and the forward drive roll (FDR) in paper machines. Static friction is crucial for energy transmission, but confusion exists regarding the dominance of static versus dynamic friction in this context. The impact of working angles on micro-slippage and power loss is noted, with specific angles mentioned. Factors influencing slippage risk include the number of fabric yarns and centrifugal forces, which may complicate calculations. Overall, achieving a balance between de-watering and effective drive is essential for optimal performance in paper production.
knas
Messages
1
Reaction score
0
Hello All,

on paper machine which I work we have such configurations as is showed on the sketch:
http://imageshack.us/photo/my-images/706/systemt.jpg/

a forming fabric (wire) is driven by two rolls, couch roll (with two suctions chamber) and so called FDR (forward drive roll). On the forming fabric the paper is formed and dewatered.

A pick up roll just picks up and transfers the web / paper to the press section.

the problem with understanding slippage phenomena I have on the FDR.
As far as I know we need a static friction between wire and FDR roll to transmit energy. When we get a motion between FDR and wire we got a slippage.
Based on some formulas I am able to calculate a power transmitability capability. In the formula, the roll diameter, static friction coefficient, speed, wire tension after roll, width of the fabric are involved.

The questions to You are:
- What is more dominating on such power transfer a static friction or dynamic ? (I get confusing explanations) must be static…
- I know that there are so called two working angles (alpha and beta), for this specific roll alpha is 70 degree and beta 55 degree. On the beta angle as far as I know we get a micro-slippage which gives power loss by ~2%, do you have any experience on this field ?
- In general friction forces are independent of the area of contact, but we know also that more yarns of the fabric on cross direction will give at the same time lower specific pressure between two surfaces so again increase risk of slippage ?
- What from your experience can increase slippage risk?
- Do you think a centrifugal force can have an impact ?

Some additional data:
- Materials involved: on the roll rubber, hardness ~18PJ and on the wire polyester, the friction coefficient is ~0,2 between them
- Speed of the wire is ~16 m/s
- The engine power is 900 kW, working in the range up to 70% load
- Roll diameter is around 1 m while a forming fabric is 1 mm…
- The tension of the wire after the FDR is around 8,5 kg/cm.

If you have any questions or need more data please let me know.


many thanks for any answer / comment.
reagrds,
knas
 
Engineering news on Phys.org
Calculating wire slippage is quite complicated. Depending on the thickness of the stock, and the amount of fines in the stock, even the limited wrap on a couch roll can be nearly negated by the vacuum pulling on the wire/stock. Once the sheet has been transferred from the wire to the press' pick-up roll, you need a good deal of wrap on subsequent driven rolls.

Even on paper machines specifically designed for a specific weight/grade of paper, it often takes a bit of face-time (hopefully no hollering) between the paper machine-builders' field engineers and the fabric vendors' field techs to strike a balance between the need for openness and de-watering and the need for proper drive, sheet-smoothness, etc. You could write entire books about this stuff, so it will be tough to give you concise answers.
 
How did you find PF?: Via Google search Hi, I have a vessel I 3D printed to investigate single bubble rise. The vessel has a 4 mm gap separated by acrylic panels. This is essentially my viewing chamber where I can record the bubble motion. The vessel is open to atmosphere. The bubble generation mechanism is composed of a syringe pump and glass capillary tube (Internal Diameter of 0.45 mm). I connect a 1/4” air line hose from the syringe to the capillary The bubble is formed at the tip...
Thread 'Physics of Stretch: What pressure does a band apply on a cylinder?'
Scenario 1 (figure 1) A continuous loop of elastic material is stretched around two metal bars. The top bar is attached to a load cell that reads force. The lower bar can be moved downwards to stretch the elastic material. The lower bar is moved downwards until the two bars are 1190mm apart, stretching the elastic material. The bars are 5mm thick, so the total internal loop length is 1200mm (1190mm + 5mm + 5mm). At this level of stretch, the load cell reads 45N tensile force. Key numbers...
I'd like to create a thread with links to 3-D Printer resources, including printers and software package suggestions. My motivations are selfish, as I have a 3-D printed project that I'm working on, and I'd like to buy a simple printer and use low cost software to make the first prototype. There are some previous threads about 3-D printing like this: https://www.physicsforums.com/threads/are-3d-printers-easy-to-use-yet.917489/ but none that address the overall topic (unless I've missed...
Back
Top