Using state-of the art 16 spindle slotting machines, our highly skilled technicians cut precision slots radial to the center of the pipe. At a high production rate, slotted pipe is milled under close tolerances, resulting in clean openings and consistent slot width throughout the entire pipe. Common pipesizes and slot configurations are shown, other sizes up to 48', SCH or SDR'S and slot patterns are available upon request. Slot spacing and slot length is nominal, small variances may occur due to ovality of pipe and the effects of temperature. 14 1/2' 11 3/4'.375' 9 1' 5 2' 3.5 3' 2 6'.
Roll slitting is a shearing operation that cuts a large roll of material into narrower rolls. There are two types of slitting: log slitting and rewind slitting. In log slitting the roll of material is treated as a whole (the 'log') and one or more slices are taken from it without an unrolling/re-reeling process. In rewind slitting the web is unwound and run through the machine, passing through knives or lasers, before being rewound on one or more shafts to form narrower rolls. The multiple narrower strips of material may be known as mults (short for multiple) or pancakes if their diameter is much more than their width.[1] For rewind slitting the machine used is called a slitter rewinder, a slitter or a slitting machine – these names are used interchangeably for the same machines. For particularly narrow and thin products, the pancakes become unstable, and then the rewind may be onto a bobbin-wound reel: the rewind bobbins are much wider than the slit width and the web oscillates across the reel as it is rewound. Apart from the stability benefit it is also then possible to put very long lengths, (frequently many tens of kilometres), onto one bobbin.
Process[edit]
Soft materials[edit]
Several methods are available for soft materials like plastic films, textiles, adhesive tapes, and paper. Razor blades, straight, or circular blades are being used. Some blades cut through the material while others crush the material against a hard roll. Those are similar to knives. The cutting blades can be set to a desired width. Some machines have many blades and can produce a number of output rolls at once. The slit material is rewound on paper, plastic or metal cores on the exit side of the machine.
The process is used because of its low cost and high precision for mass production. Some machines have a program that monitors the blades and sharpens the blades often to maintain the quality and precision of the cut. Depending on the industry and the product that is being slit these machine can run between 10m/min (special metal webs) and 5000 m/min (paper making process). The machines can also incorporate extensive automation to precisely control material tension, automatically position the slitting knives, automatically align the cores onto which the material is wound and to reduce manual handling of the rolls.
Examples of materials that can be cut this way are: adhesive tape, foam, rubber, paper products, foil, plastics (such as tarps and cling wrap), glass cloth, fabrics, release liner and film.
Hard materials[edit]
For harder materials, such as sheet metal, blades cannot be used. Instead, a modified form of shearing is used. Two cylindrical rolls with matching ribs and grooves are used to cut a large roll into multiple narrower rolls. This continuous production process is economical yet precise; usually more precise than most other cutting processes. However, the occurrence of rough edges known as burrs are commonplace on slit edges. Also, the geometry of these rolls is determined by specific tolerances in addition to the type of material and workpiece thickness.[2]
Machinery[edit]
For metal coils, the slitter consists of three main parts: an uncoiler, slitter, and recoiler.[3] The material is fed from the uncoiler, through the nip between the two circular cutting wheels (one on top and another underneath), and then re-wound in slit pieces on the recoiler.
When the term 'slitter rewinder' or 'slitting machine' is used to describe the machine, the three parts are referred to as the unwind, the slitting section and the rewind. Slitter rewinders are normally used to slit plastic films, paper and metal foils. The unwind stage holds the roll stably and allows it to spin; it is either braked or driven to maintain accurate tension in the material. Some machines have a driven unwind which reduces the effect of inertia when starting to unwind heavy rolls or when the material is very tension-sensitive.
The slitting section has three main options:
- Razor slitting, which is ideal for thin plastic films – the system is very simple and quick to set. Although the razor blades are of low cost, they need to be frequently changed to ensure a good quality slit edge.
- Rotary shear slitting. Male and female circular knives engage to give a scissor cutting effect. This system is used widely on paper, films and foils. Although the knives take longer to position, they stay sharp longer than razor blades. The setting time can be reduced by using an automatic knife-positioning system.
- Crush cut slitting. A male knife runs against an anvil. The system works well with certain materials including non-wovens and foams.
The rewind section also has options. The main type is centre winding using differential rewind shafts. These shafts are becoming universal on most slitting machines. The differential shafts ensure an even tension across the full width of the material. Closed-loop control of the winding tension using feedback from load cells provides the total tension-control system required for running tension-sensitive materials. Precise and accurate tension control is the key to good roll slitting. Modern machines use AC vector drives with closed-loop feedback from AC motors. When used with the correct control algorithms, they produce excellent results with the minimum of maintenance.
Industry usage[edit]
Roll slitting is a technique heavily used by Converters (industry). The converter industry normally refers to companies who print, coat and laminate materials. A typical converter is a company that produces flexible packaging material for packaging food. This may involve purchasing large rolls of plastic film such as biaxially orientated polypropylene (BOPP) which is then printed to the customer's design and coated with cold seal adhesive for use on high speed packaging machines. This material is printed and coated in wide, large diameter rolls for maximum efficiency. The rolls are then slit, using a slitting machine, into smaller rolls of the size to be used on the packaging machine.[4]
See also[edit]
References[edit]
- ^Todd, H. Robert; Allen, K. Dell; Alting, Leo (1994), Manufacturing Processes Reference Guide (1st ed.), Industrial Press Inc., pp. 131–132, ISBN0-8311-3049-0.
- ^Degarmo, E. Paul; Black, J T.; Kohser, Ronald A. (2003), Materials and Processes in Manufacturing (9th ed.), Wiley, p. 427, ISBN0-471-65653-4.
- ^Robert H. Todd, Dell K. Allen and Leo Alting manufacturing process recourse guide, Robert H. Todd, Dell K. Allen and Leo Alting pg. 131, ISBN0-8311-3049-0
- ^'Converting Industry Overview'(PDF). Kivitopoulous. Retrieved 2017-03-10.
External links[edit]
The Science of Slotted PVC/HDPE screen.
Hello, I need some slotted screen for my well. Can you help me? This is sometimes a common question and all the information we get to work with. The truth and science behind this scenario can be overwhelming, but by asking a few more questions we can offer the exact product for your specific job.
Lets start with the raw material. There are several plastics used throughout the world for water wells. The type of well you have has a lot to do with which material is used. In addition, the type of well installation may change your request for the raw material.
PVC, CPVC and HDPE are the most common materials used today. Whether you are sleaving an existing well, installing a new monitoring well or drilling a leachate collection system, one of these materials will surly be asked for.
There are 2 basic requirements for these products.
The casing. The casing is the pipe itself. It is available in a few basic configurations. The most widely available is belled end or solvent weld. One end of the pipe is extruded so that the belled end slips over the plain end and can be glued together with PVC cement. This works well for horizontal applications but is not very strong for deep vertical wells. The ASTM F-480 thread is another option. This is a flush joint thread which has a square thread machined directly on each end of the pipe utilizing the wall thickness of the pipe to accommodate the thread. The big advantage of this thread is that the joint is “flush”. There is no joint to catch on going down the hole or for tooling to snag while inside of the pipe. “NPT” of National Pipe thread is one more option, but requires a threaded coupler to join the pipe together.
The Screen. Slotting the raw PVC material is usually an easy task. Typically, a machine will have an arbor loaded with slitting saw blades and the machine will travel lengthwise along the pipe slotting as it goes. Farwest Special Products in Edgewood, WA has six of these machines, 2 of which are CNC controlled. “We are able to slot just about any configuration, in just about any size of pipe from ¼” through 24” diameters” says Dave Baca from Farwest. Dave has been with the company, formerly known as Aardvark Corporation for 17 years, and has seen just about every slotting configuration possible. The biggest concern when it comes to knowing what to order will be the amount of open area. Open area is calculated in the following manner.
Multiply the slot width x the slot length (inside of pipe) x number of slots /row/ft x number of rows around the diameter. The spacing of the slots and the slot width will determine the number of slots /row/ft. For example.
.020” slot width x 1.0” slot length x 42 slots/row/ft x 6 = 5.04 sq. In / ft of screen.
This dimension is based on 4” schedule 40 PVC pipe with a minimum I.D. slot length of 1.0 inches and ¼” spacing between the slots.
Using these numbers of open area, we can then multiply the amount of open area / ft to .3117 and have what is called intake velocity per foot of screen. The answer from the above formula, 5.04 x .3117 = 1.5709 G.P.M. per foot of screen. You can then take that out to a 10 foot length of pipe and so on. This information will be very helpful because of two major concerns. The first is the size of soils you are trying to keep out of the screen. In fine sands a slot width of .060” will allow that material smaller than .060” to come into the screen, eventually blocking the screen. The .020” wide slots will keep most of the fine sands out of the screen yet allowing the water to pass through the slots without bridging.
The second concern to look at is the production of the well. The “science” or better described; magic of determining the size of screen is combining the soil size and the well production to allow the most amount of water into the well and screening out the soil. A Hydrologist will perform most of this work if one is hired for the site work. If not, you will need to look at your drill cuttings while you are drilling and make that determination where you find the water.
Pvc Pipe Slotting Machine
The production of your well can be made adequate or diminished based on the size and type of screen used. These basic steps should help you choose the correct PVC screen for each job.
- Diameter of screen: You will know this when drilling the well.
- How many rows of slots around the pipe.
- The width of the slots.
- The spacing between each slot.
- What type of joint will you need?
Once this data is available the pipe can be slotted and threads machined on the pipe and shipped worldwide to your jobsite. As slotted PVC and HDPE have several market fields, many construction companies are also switching to slotted pipe versus perforated pipe for their drainage needs. Slotted screens have approximately 60 percent more open area per foot than conventional perforated pipe. There is also less chance for bridging, which can cut down the intake velocity.
What Is Pipe Slotting Machine For Sale
Joints: Joining the casing and screen will be another important issue to think about. After all, if you buy a screen made from 4” schedule 40 PVC with a belled end, how will you join that to the 4” schedule 40 ASTM F-480 PVC casing ?
Typically, when installing monitoring wells, there are 4 basic parts when talking about the pipe. Starting at the bottom, they are…
1.Bottom plug or End plug: This is usually a 6” long length of PVC pipe with a female flush joint thread on one end, and a cap machined on the other end.
2.The PVC screen, which also has the flush joint threads, would screw into the bottom plug. The screen length will be determined by the driller depending on where the water is.
3.Attached to the screen is the flush joint casing. The casing would then be installed to the surface.
4.The last part of the well is a locking well cap. These are made from steel or PVC and have a rubber gasket to seal any objects from entering the well as well as a locking device to prevent vandalism.
ASTM F-480: This is a standard in ASTM, which relates specifically to the threads on plastic pipe as well as metal pipe. First introduced to ASTM by Aardvark Corporation (now Farwest Special Products) in 1972 and was developed as a fast connecting yet strong thread for horizontal water well drilling. After several thousand dollars of testing, it was introduced to ASTM where they performed some of their own testing and made it a standard. Today, The F-480 thread is used world wide in a multitude of applications from monitoring wells, piezometers, edge drains and dewatering wells.
What Is Pipe Slotting Machinery
The biggest advantage of the F-480 threads is the fact that there is no ridge or lip when the joints are screwed together. The outside diameter and the inside diameters are flush with each other.
Another distinct advantage is the tensile strength of the thread. In a vertical application, such as a monitoring well, 2” schedule 40 PVC with ASTM F-480 threads will hang 1400 lbs. If you calculate the weight of the pipe itself at .689 lbs/ft, you are able to install 2000 feet of pipe with a .2 percent safety factor.
In a study by the United States Department of the Interior in July of 1989 publication (R-89-06) by Jay Swihart, the Applied Sciences Branch concluded the following summary.
“ The research results confirm that PVC casing and well screen are highly suitable for many well applications and that strengths of most components are adequate for deeper installations than originally considered. The results also show that the collapse strength of most components can be accurately predicted by simple stiffness tests; however, there are still concerns about collapse at elevated grouting temperatures that were not addressed. Shortcomings of PVC well components include low pressure ratings of flush threaded joints and low tensile strengths for some joint systems. These problems should be investigated further.”
These issues were investigated further and the result was the introduction of the o-ring seal at the base of the male thread. The afore mentioned study by the Department of the Interior went on to state “ASTM recently approved a threaded joint standard (ASTM: F-480) which requires an O-ring gasket. This standard along with computerized machining operations currently being perfected by the manufacturers should improve the watertightness of these threaded joints.”
The main reason for the ASTM Standard (ASTM F-480) is compatibility. How many of you have ordered flush joint pipe from two vendors and found that they do not match up or thread together. This is an issue that continues to haunt us even today. I have found that you should ask for ASTM F-480 threads if you need to have all of the joints mate up. Some manufacturers of threaded casing and screen are advertising, “flush joint pipe”, and that is exactly what you will receive. There is likely no testing or data provided for these joints. Do you really want to fish out 200 meters of pipe due to a faulty joint? ASTM and their standards are known world wide and used worldwide. The compatibility and versatility depends on your choice of the type of products you order. The correct choice will cause fewer headaches in your planning and scheduling.
Contributed by:
Dave Baca
Farwest Aircraft - Special Products Division
800-438-3808
dave-b@farwestair.com
www.farwestair.com/products