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Cold-sawing roundup.

A cold saw actually mills a workpiece, rather than sawing it. Although the rotational speed of the blade may appear slow (5 to 100 rpm for cutting steel), the metal-removal rate is high--similar to that of conventional milling. The workpiece remains relatively cool, but the chips are hot. They take the heat away from the cutting area. Some setups are coolant; others don't.

Cold saws cut ferrous and nonferrous materials such as tool steels, aircraft alloys, aluminum, copper, precious metals--and plastics. Workpieces include bar stock, I-beams, thin tubing, and huge billets.

The high-quality cut from a cold saw saves costs by eliminating secondary sizing operations. Cut-to-length accuracy is typically within 0.000" to 0.005", and surface finishes range from 40 to 125 microinches.

Top performance requires modern equipment such as the UKS and KKS models from Kaltenbach Inc. Here, blade movement is controlled by preloaded ball screws. The ball-screw servodrives need no adjustment, and their precision allows use of both HSS and carbide blades in the same machine. The ball screw also provides constant feed, said to be smoother than hydraulic or pneumatic feeds.

Typical steel-cutting speeds range from 25 to 100 sfm, but systems designed for light alloys and plastics, such as Kaltenbach's DKL and SKL models, can rotate the blades at 3000 rpm, achieving cutting sppeds up to 14,760 sfm. Machines for smaller blades may rotate at 3500 rpm or higher.

Machine characteristics

Most machines are downstroking, so chips and coolants are disposed of without danger of catching in the spindle drive or other components; however, Kaltenbach offers several upstroking models, too. These provide front access to the working area of the saw table. While the material is handled and set up, the saw blade remains safely below the level of the table. Wide sections are easily handled, clamped, and cut lying down, and the saw table and blade can be swiveled through 180 degrees.

The section being cut is clamped on both sides of the blade, and, for miter cuts, the cutter approaches the material at 90 degrees. Thus, there is no tendency for blade deflection. The upstroking design permits a compact machine and minimum approach distance for the saw blade. Also, downward chip flow is advantageous for cutting tubes and sections. Finally, the design allows a short power train for high rigidity. The saw arm pivots on a double preloaded trunnion bearing guaranteed free of a play for life.

State-of-the-art cold saws should have devices to prevent pinching of the saw blade. For example, in the Metalcut carbide circular cutoff saw from Centro-Metalcut Inc (CMI), independent clamping cylinders are used on each side of the cut. Mounted on the front of the machine, they required no manual setting for different workpiece sizes, and they can be set to avoid pinching. unclamping devices prevent bent bars from squeezing the saw blade between cut edges when the blade is breaking through the material. Furthermore, a simplified spreading mechanism in the measuring system eliminates tool rubbing when the blade retracts. Chips are directed downward, and a positive chip-removal system keeps chips from entering the cut.

CMI machines generally use carbide-tipped blades with tool life averaging 10,000 to 20,000 sq in per blade sharpenning. The machines cycle automatically and usually cut cold without coolant. Spindle drives use either AC motors with speed variators, or DC motors with infinite speed adjustment and constant torque.

CMI believes cold saws should have special covers over the blade and workpiece to keep noise low and protect the operator from chips. And possible pinch points should be protected with safety covers and switches. Conveyors should be designed to transport bulky hot chips, especially when working with carbide blades.

Danobat Machine Tool Co offers the Gairu G Series machines including Model MQ 810 with 32'-dia blade and MQ 1400 with a 55'-dia blade. These machines feature inserted-tooth cutters and have two-speed spindle motors and infinitely variable hydraulic blade-feed motors. Accessories include miter-cutting devices, automatic-feed systems, and vertical clamps. For straight cutting, Model MQ 1400 handles 19 1-4" bars and tubes, 17 3-8" squares, and U's and I's of 40" horizontal measurement.

Each machine features a 59" length gage with mechanical stop, complete coolant system, adjustable clamping pressure, hydraulic system for both blade feed and chucking, and standard international mounting-hole pattern for the blade.

Small but mighty

Bewo cold saws from Scotchman Industries represent the smaller machines with capacities up to 4 1-2" round tubing or rectangular shapes up to 5 1-2" x 4". (Larger automatic Bewo models are available from Kaltenbach.) The CPO 250 series hand-operated circular metal sawing machines with 10" blades have two cutting speeds: 60 rpm (150 sfm) for mild steel, and 120 rpm (300 sfm) for onferrous materials and thin-walled mild steel tubing. A 30-rpm model handles stainless steel, and a double self-centering vise ensures burr-free cuts. These machines use coolant, and Scotchman offers its own brand that helps prevent chip welding.

The saw can include an automatic air vise to speed clamping and unclamping. A handwheel preadjusts the vise stroke to save clamping time, and the vise automatically opens and closes when the workhead is pulled up and down. Also, automatic guards help protect the operator's hands.

Bewo Model CPO 315 HA is semiautomatic. At the touch of a button, the workpiece is clamped, the saw motor switches on, and the guard opens. Then the workhead moves down. When the material is cut, the head rapidly returns to its starting position, after which the guard closes and the vise opens. Combined with input and output roller tracks, the adjustable-feed saw is suitable for batch production.

Brouwer Industries, Santa Monica, CA, manufactures the Brobo metal-sawing machine and claims to have introduced cold sawing to the US in 1976. Their machines feature large table area for maximum support when clamping and unclamping installation of special clamping fixtures. The work is always perpendicular to the table and clamped against the back fence.

Quick-action vise jaws with large surface area provide firm clamping of the workpiece against an equally large back fence. Coolant oil is delivered through a nozzle in the guard.

For billet and slab

Going from smaller saws, let's look at some really big machines for nonferrous metals. Loma Machine offers huge billet and slab saws said to represent the latest in cold-sawing practive. For large aluminum-alloy sheet requiring close tolerances and smooth cut surfaces, the Model SL-72 is based on a hydraulically operated circular saw designed to cut ingots 91" wide x 24" thick, weighing up to 25 tons. The new machine accepts blades up to 72" dia, using either HSS segmental cutters or tungsten-carbide-tipped tools.

The machine's 200-hp two-speed drive motor combines with a four-speed gear-shift transmission to furnish sawing speeds up to 6500 sfm with HSS blades; up to 12,000 sfm with carbide. Feed rates are infinitely variable up to 98 ipm, with a return rate of 315 ipm. A saw-blade stabilizer helps prevent blade wobble as the cutter enters the ingot, and special cylinder-mounted pads guide the tool. Lubrication is by coolant spray.

There are two horizontal clamps on each of the blades, and clamping of the ingots occurs when hydraulic cylinders on the rear jaws work against the fixed front jaws. The front jaws have a disengaging stroke of 2" to allow for passage of bulged-end ingots.

An anti-pinch device counteracts the tendency for kerf to close in on the blade as cutting progresses. For this feature, both inboard and outboard clamp assemblies pivot on the machine base. Each clamp-assembly cradle is a weldment with the stiffness required to withstand clamping forces.

Chips go down into the housing base, where they are captured by an air stream, part of a pneumatic chip-removal system. A 50-hp induced-draft fan creates a suction that moves chips through ducts to a cyclone separator feeding the plant's chip boxes.

An automated ingot-handling system boosts productivity. It is comprised of a two-section entry conveyor, exit and runout conveyors, a gage for automatic measurement and cutting of ingots to preset lengths, an ingot-stamping device, and a scrap-discharge system to remove crop ends from the exit conveyor.

Loma's automated high-speed billet-sawing system can cut logs up to 14" dia x 300" long. It uses a 44"-dia HSS segmental blade driven by a 125-hp motor at 6000 sfm. In one user's plant, it cuts 6000 series aluminum longs 7" dia x 300" cast length into 24"-long extrusion billets at the rate of 25,000 lb/hr. The machine has a tilt arm, and the cut is effected by downward movement of the blade. This arrangement lets the rugged housing take the feed pressure to reduce chatter.

Automation components include a log-storage rack with escapement feed, powered-roller charging conveyor, length-gaging stop (which has an automatic stamping devide), powered-roller discharge conveyor, and billet-discharge unit.

When the operator pushes the escapement button, the most-advanced log leaves the storage table and enters the saw on the charging conveyor. In the meantime, the length stop has swung into position, ready to halt and stamp the advancing log. Next, a hydraulic clamp grips the log, the stop swings out of the way, and the saw cuts the stock.

After the cut, the clamps release and the cut billet travels down the discharge conveyor until it is hit by the billet stop and removed to an output conveyor feeding an automatic stacker. At the same time, the charging conveyor advances another log for the next cut, and the cycle repeats.

The entire sawing installation employs a soft-wire control system based on a Texas Instruments programmable controller. To cater to the growing number of extruders using hot-billet shears at the press and requiring cut-end logs rather than billets, a special long-billet discharge is provided to handle logs up to 18-ft long. The output conveyor feeds an Acme automatic billet stacker requiring operator assistance only to insert wood runners and apply strapping to the finished bundles.

Sawing centers

As can be seen from the billet-saw discussion, many firms offer more than a saw--in a word, complete sawing systems--and they can be on a smaller scale. For instance, Peddinghaus Corp. provides an automatic version of its miter-cutting cold saw, the VSA 16-5.5. It has a 6 1-2-ft infeed conveyor and provides indexing of material to preset lengths from 1-4" to 27 1-2", handling material up to 12" wide. The movable table swivels from 0 to 180 degrees and has preset stops at 45 degrees, left; 90 degrees; and 45 degrees, right.

An infinitely variable blade feed of 0 to 40 ipm combines with an adjustable vertical clamp and back gage to produce an efficient stroke that minimizes cutter travel. These and larger systems can be combined with automatic storage systems, drilling systems, and other major components to produce turnkey installations for processing structural steel products as well as standard rounds, squares, flats, channels, angle iron, and miscellaneous channel sections.

IBP Equipment Corp has introduced an automatic saw that executes high-rate cutting directed by a programmable controller. Called the IBP/Conni 3300TG, the cutting system features an oleodynamic (oil hydraucli) control in the machine bed. It can be programmed to automatically produce miter cuts ranging from +45 degrees to -45 degrees, and straight cuts, on most metals in round, square, rectangular, oval, or special sections. It can cut mild-steel tubes at rates from 250 to 1300 pcs/hr.

The cutoff saw is available with many options including additional controllers for extra cycles, slide or bundle loaders, and special discharge sections. Feed slides achieve speeds up to 32 ips, and self-centering main and feed vises clamp all workpieces on the central axis of the blade. A hydraulic motor with mechanical stops and safety end-limits automatically pivots the cutting head. Workpieces range up to several inches in diameter.

For automation of work up to 12" rounds, the Hill Acme tilt-arm steel sawing center with carbide-tipped blade is said to reduce rework and scrap costs. Its cut is square, smooth, and virtually burr free. Because there are no ragged billet ends, you can eliminate secondary machining while improving end product.

The center replaces trouble-prone hot-shearing equipment and its costly energy consumption. it also avoids shear cracks caused by cold shearing. The saw-blade wear pattern is so even that teeth can be reground up to nine times before they need retipping.

You can automate the center to match your needs now, and expand the automation in the future. It accepts magazine feed tables, infeed conveyors, discharge conveyors, and chip-disposal systems. Available devices include cross-chain feed tables and walking-beam unscramblers for round or square bars.

The high speed of the tilt-arm sawing center can minimize cost per cut. In a test setup, the carbide-tipped saw blade worked many times faster than HSS segmental saws cutting 9" cast rounds of AISI 1035 steel. The tilt-arm saw completed a cycle in 47 sec that took 228 sec with an HSS blade. Squareness was held within 0.002", and length to [plus - or - minus]0.010". Surface finish averaged less than 125 microinches.

The tilt-arm saw is about 14 times faster than a bandsaw, and 48 times faster than a hack saw. A variable-speed, constant-torque hydraulic motor drives a ball screw to control blade movement, and an infinitely variable DC drive motor provides speeds from 100 sfm to 700 sfm. Maximum blade size for the largest model with 75-hp motor is 36". Model TS-24 takes a 24" blade and offers 40 hp.

Full systems approach

Kaltenbach claims to be the world's largest manufacturer of circular cold saws, and it is not surprising that they are promoting automation of all aspects of the operation. They connect the saws with all sorts of storage, retrieval, and packaging systems, and they offer fabrication systems including drilling and other operations.

in one installation, a robot removes a billet from a cutoff saw, transfers it to a lathe, loads it, and later removes the finished workpiece. This, in effect, turns an ordinary CNC lathe into an automatic!

There are automatic feed units, automatic miter-indexing systems, sorting units, NC length-preselection devices, and modular systems for material handling. But the CNC unit alone can perform a lot of automation. Using the HDM 911/1311 saw for miter cuts, the operator simply enters the type of section to be cut, its width, desired cutoff length, and miter angle. A microcomputer in the control then determines the best position for the front clamp jaw and the offset-length stop setting. Such easy setups allow efficient use of cold saws for both small- and large-batch production.

Another electronic feature provides adaptive feed control to vary feed rate and cutting speed to suit section thickness when cutting workpieces such as I beams.

Kaltenbach automation carries over into their Bewo line of sawing machines, material-supply systems, and deburring machines. Bewo automatic circular metal-sawing machines can include components such as material stops, material vises, ejection and sorting devices, and supply magazines. They feature electronic controls, short setting times (3 to 4 min), and high production of tubes and profiles with small and medium wall thickness. They serve the steel-furniture and bicycle industries, installation companies, tube works, and producers of exhaust pipes and scaffolding.

For full automation, Kaltenbach offers the RK 82 storage and sawing system using a Sistema robot and Remmert storage and bar-handling facility. It is a single-bar storage system linked to a computer-controlled CNC saw.

Individual bars are brought out of storage in the desired sequence, loaded on the saw, then cut to length as ordered. Next, the cut pieces are sorted and ejected, while the bar end is returned to storage. A bar change takes about 15 sec.

The system can store 80 to 100 different bar sizes, which usually represent 80 percent of the bars cut. Bars used less frequently are sorted outside the system and loaded onto a trolley that brings them onto the saw conveyor.

Certain Kaltenbach output systems feature a transverse sorter or robot arm with an extra vertical axis for quieter operation. The mechanism carefully scoops up each bar in a broad, deep shovel. In addition to cutting noise, the scoop is less likely to nick the bars.

Get the right point

Selecting the right blade is important. It must be rigid enough to permit relatively high feed rates to realize efficient metal removal. Rohbi Corp recommends using solid HSS blades for free-machining, low-carbon, high-carbon, and medium-alloy steels. Their Super HSS blades handle high-alloy steels and aircraft alloys; and their solid-carbide blades cut nonferrous alloys, plastics, and precious metals. Finally, carbide-tipped blades also handle nonferrous metals.

Because cold-saw blades can be resharpened many times, it is possible to hold down tooling costs by keeping a minimum number of blades in stock.

Saws International Corp offers segmental circular saw blades from 10" dia to 118" dia, custom designed for use in both ferrous and nonferrous cutting. the advantage here is recyclability through resegmentation. Although the firm says the process must be done at the factory, you can expect to save 20 percent in tool costs over the blade's useful life. Quick repair of broken segments and replacement with new pieces can extend normal tool life.

The frim also sells high-speed solid circular saw blades for slitting and cut-off. The tools serve both ferrous and nonferrous cutting and can be customized by varying size, thickness, hardness, tooth configuration, and surface finish.

Simonds calls them inserted-tooth metal-cutting saws, and they are designed for all makes and models of cold-sawing machines. They begin with a hardened, tempered, and smoothly ground saw plate of extra-tough alloy steel said to be virtually indestructible. The plate has precision-milled pockets or gullets around the outer edge, each fitted with precision-machined HSS teeth locked in place by a wedge.

The teeth are alternately beveled and square. The beveled teeth cut a groove in the center, producing a single chip, while the slightly lower square teeth cut on both sides of the groove, producing two chips. This Tri-Viding or splitting the chip into three parts relieves the cutting strain on each tooth, prevents clogged gullets, and permits faster cutting.

Six styles of teeth are available in a range of saw diameters. The teeth are said to have an extra long life between sharpenings, even with greater feed, because they hold a sharp cutting edge at working temperatures. Carbide-tipped teeth are furnished for special-purpose cutting.

Simonds says you can sharpen the teeth on a saw or cutter grinder, and you can replace worn or damaged teeth right in your plant, adding to possible savings.

The firm also makes solid circular saws, and they come in such variety that it takes a detailed guide to tell what you need to know to order effectively. The Simonds Technical Manual for Solid Circular Metal Saws tells about major applications and points out special cobalt and M-2 differential-heat-treated types that are exclusive to the line. It gives cutting-speed ranges for different blade materials and different workpiece materials and types. Also, it tells how to determine the optimum number of teeth for a blade, indicates proper selection of tooth style and angles of fitting, and discusses feeds, speeds, and required horsepower. Finally, it covers lubrication and coolant, chip control, tool removal, and safety instructions. For a copy, circle E200.
COPYRIGHT 1985 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1985 Gale, Cengage Learning. All rights reserved.

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Title Annotation:cold saws cut
Author:Miller, Paul C.
Publication:Tooling & Production
Date:Apr 1, 1985
Words:3209
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