By: Chris Rindels, Chief Engineer & Machine Designer; Steve Swanson, AMSAW Sales Manager; Adam Mazela, Electrical Controls Engineer
Modern manufacturing requires automation, continuous flow, and streamlined operations to reduce waste and improve quality and control. As manufacturing technology continues to evolve in the rail industry, automation for rail sawing and drilling processes is becoming more of a requirement to help businesses maintain a competitive edge.
Industry Trends for Rail Manufacturing
According to Jeff Stagl, Managing Editor of Progressive Railroading, the future of the rail industry looks promising as customer confidence and customer spending continue to rise. Many manufacturing businesses have undergone a major technology shift, adapting certain innovations that improve safety, service, and efficiency. Integrating an automotive system for rail sawing and drilling processes provides more throughput, increases factory floor space, decreases human error, and increases rail safety.
Rail Manufacturing Production Process
There are several steps involved in the manufacturing process for rail production to ensure durability and resistance to cracking, including:
- Pre-Treatment and Bloom Casting
Carbon, manganese, and other elements are melted together to create hard, wear-resisting rails -- the manganese makes the metal harder, and more difficult to cut. From there, the alloy runs down a ceramic tube and gets forced through an opening of a mold, which extrudes the steel like Play-Doh into rectangular blocks called blooms.
- Rolling the Steel
The blooms then pass through a walking-beam, heated-furnace before entering a rolling mill, which elongates them into thinner rails.
- Heating for Pre-Bending and Shaping
A shear slices the thinner, longer blooms into four pieces so they can go into another furnace to be prepped for pre-bending and shaping. Once the steel rails pass through the milling process, a friction saw is used to square off the ends.
- Straightening the Rail
The rails are cooled down to about 90℃ (194℉) before running through two sets of rollers that flex them vertically and horizontally. This flexing process straightens the rail, increases the yield, reduces the residue stress, and lengthens the service life of it.
- Inspection Processes for Rail Stability
Remote inspection devices, non-contact measurement technologies, and non-destructive material testing detect and identify both profile deviations and surface defects within the rail in one step.
Combined surface inspection & profile
measurement system bei NEXTSENSE
Rail Sawing and Drilling Processes
The final steps of the machining process involve the sawing and drilling processes of the rail. A circular carbide saw system is the most common machine to use for drilling and processing the rail head, especially for achieving high accuracy cuts at a high production rate.
To increase the level of productivity and efficiency at these stages, some companies have integrated a combination rail sawing and drilling system to automate the rail processing line.
There are several things to consider before selecting an automated sawing system, including:
- Sawing requirements
- Drilling requirements
- Material flow in an automated system
Sawing Requirements for Rail Processing
Length Requirements for Rail Sawing
The length of a rail varies depending on the stage of the machining process and where they are being produced. There are differences among countries, but generally, the most common rail standards are 43, 60, and 75 kg/m. The heavier the steel rail per pound, the greater the weight the rail can bear. Click here to view the various sizes in rail.
During the final stages of the machining process, the rail can be cut into varying lengths depending on its use, but standard lengths are around 82 ft (25 m). Rails used for frogs and switches vary in size at random lengths as small as 6 ft (1.8 m).
“The most common rail size we cut is the 132 or 141 AREMA to 175 lbs. ASTM, and it has already been head-hardened, so it’s pretty difficult to cut,” explains Chris Rindels, Chief Engineer for AMSAW at Advanced Machine & Engineering (AME). “Another element of the rail that makes it difficult to cut is the cross-section. We designed the saw so that the saw blade contacts the head and the foot of the rail at the same time. To make sure that we’re hitting the head of the rail and the foot of the rail at the same time with the saw blade, we make sure the blade is coming in at a 15° angle. This is done to stabilize the blade, prevent vibration, and increase blade life.”
Surface Finish after Saw Cut
Normally, the surface finish after the saw cut is around 125 to 250 microinches.
- The length tolerance from one end to the other has to be within 0.125 in.
- Squareness of the cut is within .0015 per inch.
If the end of the rail isn’t squared and doesn’t have a flat surface, then it won’t weld together which could cause derailments and other issues.
Drilling Requirements for Rail Processing
Rail sections are commonly joined together by butt welding or bolting. A bolted joint requires the addition of angled bars or fish plates and bolting hardware. They also require fastening holes. The minimum requirement is two hook-up holes, but rails can have up to 3 or 4 on each side of the cut. AMSAW offers single spindle, double spindle, and machines for sawing only, sawing and drilling, or drilling only.
The center locations and tolerances vary depending on the application and the purpose of the rails. So, automatic tool changers may be incorporated with any desired hole size. Hole center distances change with the rail type--the smaller the rail, the closer the hole sizes are together.
Drilling machines can be designed to either move along a fixed rail to programmed locations or with fixed spindles as the rail moves by conveyor or index to the drilling locations.
A multi-spindle drilling system can drill and chamfer several holes at once increasing throughput, but the distance that the drills are from each other needs to be controlled. With a single spindle option, the hole location can be programmed to drill the hole wherever it’s needed. With multiple spindles, the center distances need to be adjustable. Also, depending on the rail size, the height of the rail and the height location of the hole will change. To accommodate the different heights, the spindle centerline must also include height adjustments.
Material Flow in Automated Sawing and Drilling Systems
Measurement Methods on Sawing and Drilling System
There are several methods of measuring and controlling the cut length of the rail:
- Pinch Roller With an Encoder: The pinch roller clamps and rolls the material through the system. The encoder measures the length by recording the rotations of the roller.
- Friction Roller: A roller is pressed against the material—as the material moves, the encoder measures the rail by the number of rotations through a friction wheel as the roller comes down on top of the material.
- Laser Measurement: A non-contact option in which a laser senses movement of the material and records the length. This option is best for reducing human error.
- Exit Side Material Measuring: Involves a conveyor with a positive stop, so once the material reaches the stop, the rail is clamped and cut.
- Index Measuring: Material is clamped and moved by an index that measures the length. Used for smaller pieces of rail that can’t be measured with pinch rollers, like small frogs and switches.
Automation, Continuous Flow, and Synchronous Operations
Combination rail sawing and drilling machines with material handling streamlines rail processing, directly impacting the throughput, quality, and efficiency of the rails. A carbide rail saw and drill synchronizes clamping, drilling, and sawing with a high level of efficiency and productivity. Some applications use band saws to cut the rail then move the rail to a different location to drill the holes—adding time and cost to the production process.
There are carbide sawing systems that feature vertical and horizontal material clamping with indexable-coated carbide insert drills that operate at 6 inches per minute for a total drill time of 8 seconds per hole. These machines operate at a feed rate of 14 inches per minute producing a combined cycle time of drilling and sawing of eight 1.5-inch diameter holes of 2 minutes and 25 seconds. If a multiple spindle unit is used, all of the holes can be drilled in one shot.
There are manufacturers that custom design fully automated machines that include infeed, sawing, measuring, drilling, drill tool changer, and exit systems for rail sawing and drill processes. These automated systems provide rail manufacturers a chance to improve their competitive position within the industry.
To learn more about automated rail sawing and drilling processes for rail manufacturing, contact a sawing expert!
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