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77-438: In the case of vehicles, the term rolling chassis means the frame plus the "running gear " like engine , transmission , drive shaft , differential , and suspension . The "rolling chassis" description originated from assembly production when an integrated chassis "rolled on its own tires" just before truck bodies were bolted to the frames near the end of the line. An underbody (sometimes referred to as " coachwork "), which

154-578: A monocoque shell and more like a bowl. One thousand were produced. A key role in developing the unitary body was played by the American firm the Budd Company, now ThyssenKrupp Budd . Budd supplied pressed-steel bodywork, fitted to separate frames, to automakers Dodge , Ford , Buick , and the French company, Citroën . In 1930, Joseph Ledwinka , an engineer with Budd, designed an automobile prototype with

231-478: A "U" and may be either right-side-up or inverted, with the open area facing down. They are not commonly used due to weakness and a propensity to rust. However, they can be found on 1936–1954 Chevrolet cars and some Studebakers . Abandoned for a while, the hat frame regained popularity when companies started welding it to the bottom of unibody cars, effectively creating a boxed frame. Originally, boxed frames were made by welding two matching C-rails together to form

308-434: A "crash" occurs when the machine moves in such a way that is harmful to the machine, tools, or parts being machined, sometimes resulting in bending or breakage of cutting tools, accessory clamps, vises, and fixtures, or causing damage to the machine itself by bending guide rails, breaking drive screws, or causing structural components to crack or deform under strain. A mild crash may not damage the machine or tools but may damage

385-438: A common component of most hobby CNC tools. Instead, most hobby CNC tools simply rely on the assumed accuracy of stepper motors that rotate a specific number of degrees in response to magnetic field changes. It is often assumed the stepper is perfectly accurate and never missteps, so tool position monitoring simply involves counting the number of pulses sent to the stepper over time. An alternate means of stepper position monitoring

462-464: A cycle will involve a crash. Although such simulation is not new, its accuracy and market penetration are changing considerably because of computing advancements. Within the numerical systems of CNC programming, the code generator can assume that the controlled mechanism is always perfectly accurate, or that precision tolerances are identical for all cutting or movement directions. While the common use of ball screws on most modern NC machines eliminates

539-530: A full unitary construction. Citroën purchased this fully unitary body design for the Citroën Traction Avant . This high-volume, mass-production car was introduced in 1934 and sold 760,000 units over the next 23 years of production. This application was the first iteration of the modern structural integration of body and chassis, using spot welded deeply stamped steel sheets into a structural cage, including sills, pillars, and roof beams. In addition to

616-426: A good machine operator can have parts finished to a high standard whilst a CNC workflow is still in setup. In modern CNC systems, the design of a mechanical part and its manufacturing program are highly automated. The part's mechanical dimensions are defined using CAD software and then translated into manufacturing directives by CAM software. The resulting directives are transformed (by " post processor " software) into

693-467: A government agency like National Highway Traffic Safety Administration (NHTSA) in the U.S. defines the design standards of chassis and body conversions. An armoured fighting vehicle 's hull serves as the chassis and comprises the bottom part of the AFV that includes the tracks , engine, driver's seat, and crew compartment. This describes the lower hull, although common usage might include the upper hull to mean

770-470: A ladder frame, but the middle sections of the frame rails sit outboard of the front and rear rails, routed around the passenger footwells, inside the rocker and sill panels. This allowed the floor pan to be lowered, especially the passenger footwells, lowering the passengers' seating height and thereby reducing both the roof-line and overall vehicle height, as well as the center of gravity, thus improving handling and road-holding in passenger cars. This became

847-420: A ladder, the ladder frame is one of the oldest, simplest, and most frequently used under-body, separate chassis/frame designs. It consists of two symmetrical beams, rails, or channels, running the length of the vehicle, connected by several transverse cross-members. Initially seen on almost all vehicles, the ladder frame was gradually phased out on cars in favor of perimeter frames and unitized body construction. It

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924-707: A large box as a safety measure (with safety glass in the doors to permit the operator to monitor the machine's function), often with additional safety interlocks to ensure the operator is far enough from the working piece for safe operation. Most new CNC systems built today are 100% electronically controlled. CNC-like systems are used for any process that can be described as movements and operations. These include laser cutting , welding , friction stir welding , ultrasonic welding , flame and plasma cutting , bending , spinning, hole-punching, pinning, gluing, fabric cutting, sewing, tape and fiber placement, routing, picking and placing, and sawing. The first CNC machines were built in

1001-547: A lightweight, multi-tubular, triangulated frame over which an aerodynamic aluminum body was crafted. In 1994, the Audi A8 was the first mass-market car with an aluminium chassis, made feasible by integrating an aluminium space-frame into the bodywork. Audi A8 models have since used this construction method co-developed with Alcoa , and marketed as the Audi Space Frame . The Italian term Superleggera (meaning 'super-light')

1078-737: A more extensive pillar bedding, providing a metal-on-metal bearing surface that has reduced shifting potential under the stress of recoil . A barreled action bedded into a metal chassis would theoretically operate more consistently during repeated firing, resulting in better precision . With the increasing availability of CNC machining , chassis have become more affordable and sophisticated as well as gained increasing popularity as these types of chassis can be expanded to accommodate customizable "furniture" ( buttstock , pistol grip , etc.) and rail interface systems that provide mounting points for various accessories. Frame (vehicle) A vehicle frame , also historically known as its chassis ,

1155-467: A platform frame. The frame of the Citroën 2CV used a minimal interpretation of a platform chassis under its body. In a (tubular) spaceframe chassis, the suspension, engine, and body panels are attached to a three-dimensional skeletal frame of tubes, and the body panels have limited or no structural function. To maximize rigidity and minimize weight, the design frequently makes maximum use of triangles, and all

1232-437: A rectangular tube. Modern techniques, however, use a process similar to making C-rails in that a piece of steel is bent into four sides and then welded where both ends meet. In the 1960s, the boxed frames of conventional American cars were spot-welded in multiple places down the seam; when turned into NASCAR "stock car" racers, the box was continuously welded from end to end for extra strength. While appearing at first glance as

1309-404: A series of step-down gears. Open-loop control works as long as the forces are kept small enough and speeds are not too great. On commercial metalworking machines, closed-loop controls are standard and required to provide the accuracy, speed, and repeatability demanded. As the controller hardware evolved, the mills themselves also evolved. One change has been to enclose the entire mechanism in

1386-686: A simple form made of metal, frames encounter significant stress and are built accordingly. The first issue addressed is "beam height", or the height of the vertical side of a frame. The taller the frame, the better it can resist vertical flex when force is applied to the top of the frame. This is the reason semi-trucks have taller frame rails than other vehicles instead of just being thicker. As looks, ride quality, and handling became more important to consumers, new shapes were incorporated into frames. The most visible of these are arches and kick-ups. Instead of running straight over both axles , arched frames sit lower—roughly level with their axles—and curve up over

1463-453: A subframe). The unibody is now the preferred construction for mass-market automobiles. This design provides weight savings, improved space utilization, and ease of manufacture. Acceptance grew dramatically in the wake of the two energy crises of the 1970s and that of the 2000s in which compact SUVs using a truck platform (primarily the USA market) were subjected to CAFE standards after 2005 (by

1540-399: A three-dimensional Cartesian coordinate system . This system is a typical plane often seen in mathematics when graphing. This system is required to map out the machine tool paths and any other kind of actions that need to happen in a specific coordinate. Absolute coordinates are what are generally used more commonly for machines and represent the (0,0,0) point on the plane. This point is set on

1617-564: A unitary body with no separate frame, the Traction Avant also featured other innovations such as front-wheel drive . The result was a low-slung vehicle with an open, flat-floored interior. For the Chrysler Airflow (1934–1937), Budd supplied a variation – three main sections from the Airflow's body were welded into what Chrysler called a bridge-truss construction. Unfortunately, this method

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1694-529: A weaker-than-usual frame and body framework welded to the chassis to provide stiffness, in 1960, Chrysler moved from body-on-frame construction to a unit-body design for most of its cars. Most of the American-manufactured unibody automobiles used torque boxes in their vehicle design to reduce vibrations and chassis flex, except for the Chevy II , which had a bolt-on front apron (erroneously referred to as

1771-485: Is a motorized maneuverable tool and often a motorized maneuverable platform, which are both controlled by a computer, according to specific input instructions. Instructions are delivered to a CNC machine in the form of a sequential program of machine control instructions such as G-code and M-code, and then executed. The program can be written by a person or, far more often, generated by graphical computer-aided design (CAD) or computer-aided manufacturing (CAM) software. In

1848-404: Is now "considered standard in the industry". By 1960, the unitized body design was used by Detroit's Big Three on their compact cars ( Ford Falcon , Plymouth Valiant , and Chevrolet Corvair ). After Nash merged with Hudson Motors to form American Motors Corporation , its Rambler-badged automobiles continued exclusively building variations of the unibody. Although the 1934 Chrysler Airflow had

1925-408: Is now seen mainly on large trucks. This design offers good beam resistance because of its continuous rails from front to rear, but poor resistance to torsion or warping if simple, perpendicular cross-members are used. The vehicle's overall height will be greater due to the floor pan sitting above the frame instead of inside it. A backbone chassis is a type of automotive construction with chassis that

2002-407: Is similar to the body-on-frame design. Instead of a relatively flat, ladder-like structure with two longitudinal, parallel frame rails, it consists of a central, strong tubular backbone (usually rectangular in cross-section) that carries the power-train and connects the front and rear suspension attachment structures. Although the backbone is frequently drawn upward into, and mostly above the floor of

2079-497: Is sometimes also referred to as a monocoque structure, because the car's outer skin and panels are made load-bearing, there are still ribs, bulkheads, and box sections to reinforce the body, making the description semi-monocoque more appropriate. The first attempt to develop such a design technique was on the 1922 Lancia Lambda to provide structural stiffness and a lower body height for its torpedo car body. The Lambda had an open layout with unstressed roof, which made it less of

2156-498: Is still used in modern-day sport utility vehicles such as the Jeep Grand Cherokee and Land Rover Defender . This design is also used in large vans such as Ford Transit , VW Crafter and Mercedes Sprinter . A subframe is a distinct structural frame component, to reinforce or complement a particular section of a vehicle's structure. Typically attached to a unibody or a monocoque, the rigid subframe can handle great forces from

2233-418: Is the automated control of tools by means of a computer . It is used to operate tools such as drills , lathes , mills , grinders , routers and 3D printers . CNC transforms a piece of material ( metal , plastic , wood, ceramic, stone, or composite) into a specified shape by following coded programmed instructions and without a manual operator directly controlling the machining operation. A CNC machine

2310-462: Is the combination of AI , using a large number of sensors , with the goal of achieving flexible manufacturing . EDM can be broadly divided into "sinker" type processes, where the electrode is the positive shape of the resulting feature in the part, and the electric discharge erodes this feature into the part, resulting in the negative shape, and "wire" type processes. Sinker processes are rather slow as compared to conventional machining, averaging on

2387-417: Is the main supporting structure of a motor vehicle to which all other components are attached, comparable to the skeleton of an organism. Until the 1930s, virtually every car had a structural frame separate from its body. This construction design is known as body-on-frame . By the 1960s, unibody construction in passenger cars had become common, and the trend to unibody for passenger cars continued over

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2464-418: Is usually not available, so crash or slip detection is not possible. Commercial CNC metalworking machines use closed-loop feedback controls for axis movement. In a closed-loop system, the controller monitors the actual position of each axis with an absolute or incremental encoder . Proper control programming will reduce the possibility of a crash, but it is still up to the operator and programmer to ensure that

2541-680: Is usually not necessary for the integrity of the structure, is built on the chassis to complete the vehicle. For commercial vehicles , a rolling chassis consists of an assembly of all the essential parts of a truck without the body to be ready for operation on the road. A car chassis will be different from one for commercial vehicles because of the heavier loads and constant work use. Commercial vehicle manufacturers sell "chassis only", "cowl and chassis", as well as " chassis cab " versions that can be outfitted with specialized bodies. These include motor homes , fire engines , ambulances , box trucks , etc. In particular applications, such as school buses ,

2618-536: The Hornets and all-wheel-drive Eagles for a new type of frame called the "Uniframe [...] a robust stamped steel frame welded to a strong unit-body structure, giving the strength of a conventional heavy frame with the weight advantages of Unibody construction." This design was also used with the XJC concept developed by American Motors before its absorption by Chrysler, which later became the Jeep Grand Cherokee (ZJ) . The design

2695-445: The circuit boards and other electronics are mounted. In some designs, such as older ENIAC sets, the chassis is mounted inside a heavy, rigid cabinet, while in other designs such as modern computer cases , lightweight covers or panels are attached to the chassis. The combination of chassis and outer covering is sometimes called an enclosure . In firearms, the chassis is a bedding frame on long guns such as rifles to replace

2772-620: The part program . Positioning control is handled using either an open-loop or a closed-loop system. In an open-loop system, communication takes place in one direction only: from the controller to the motor. In a closed-loop system, feedback is provided to the controller so that it can correct for errors in position, velocity, and acceleration, which can arise due to variations in load or temperature. Open-loop systems are generally cheaper but less accurate. Stepper motors can be used in both types of systems, while servo motors can only be used in closed systems. The G & M code positions are all based on

2849-404: The rails or beams . These are ordinarily made of steel channel sections by folding, rolling, or pressing steel plate. There are three main designs for these. If the material is folded twice, an open-ended cross-section, either C-shaped or hat-shaped (U-shaped), results. "Boxed" frames contain closed chassis rails, either by welding them up or by using premanufactured metal tubing . By far

2926-464: The 1940s and 1950s, based on existing tools that were modified with motors that moved the tool or part to follow points fed into the system on punched tape . These early servomechanisms were rapidly augmented with analog and digital computers, creating the modern CNC machine tools that have revolutionized machining processes. Now the CNC in the processing manufacturing field has been very extensive, not only

3003-500: The 1967–1981 GM F platform , the numerous years and models built on the GM X platform (1962) , GM's M/L platform vans (Chevrolet Astro/GMC Safari, which included an all-wheel drive variant), and the unibody AMC Pacer that incorporated a front subframe to isolate the passenger compartment from the engine, suspension, and steering loads. CNC machining In machining , numerical control , also called computer numerical control ( CNC ),

3080-428: The AFV without the turret . The hull serves as a basis for platforms on tanks , armoured personnel carriers , combat engineering vehicles , etc. In the intermodal trucking industry, a chassis is a type of semi-trailer onto which a cargo container can be mounted for road transport. In an electronic device (such as a computer ), the chassis consists of a frame or other internal supporting structure on which

3157-457: The X-axis, and all future motions are now invalid, which may result in further collisions with clamps, vises, or the machine itself. This is common in open-loop stepper systems but is not possible in closed-loop systems unless mechanical slippage between the motor and drive mechanism has occurred. Instead, in a closed-loop system, the machine will continue to attempt to move against the load until either

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3234-455: The addition of a chassis. The terms "unibody" and "unit-body" are short for "unitized body", "unitary construction", or alternatively (fully) integrated body and frame/chassis. It is defined as: A type of body/frame construction in which the body of the vehicle, its floor plan and chassis form a single structure. Such a design is generally lighter and more rigid than a vehicle having a separate body and frame. Vehicle structure has shifted from

3311-431: The axles and then back down on the other side for bumper placement. Kick-ups do the same thing without curving down on the other side and are more common on the front ends. Another feature are the tapered rails that narrow vertically or horizontally in front of a vehicle's cabin. This is done mainly on trucks to save weight and slightly increase room for the engine since the front of the vehicle does not bear as much load as

3388-479: The back. Design developments include frames that use multiple shapes in the same frame rail. For example, some pickup trucks have a boxed frame in front of the cab, shorter, narrower rails underneath the cab, and regular C-rails under the bed. On perimeter frames, the areas where the rails connect from front to center and center to rear are weak compared to regular frames, so that section is boxed in, creating what are called "torque boxes". Named for its resemblance to

3465-583: The case of 3D printers, the part to be printed is "sliced" before the instructions (or the program) are generated. 3D printers also use G-Code. CNC offers greatly increased productivity over non-computerized machining for repetitive production, where the machine must be manually controlled (e.g. using devices such as hand wheels or levers) or mechanically controlled by pre-fabricated pattern guides (see pantograph mill ). However, these advantages come at significant cost in terms of both capital expenditure and job setup time. For some prototyping and small batch jobs,

3542-529: The component from machine to machine. In either case, the series of steps needed to produce any part is highly automated and produces a part that meets every specification in the original CAD drawing, where each specification includes a tolerance. Motion is controlling multiple axes, normally at least two (X and Y), and a tool spindle that moves in the Z (depth). The position of the tool is driven by direct-drive stepper motors or servo motors to provide highly accurate movements, or in older designs, motors through

3619-639: The components needs to be stamped with ridges and hollows to give it strength. Platform chassis were used on several successful European cars, most notably the Volkswagen Beetle , where it was called "body-on-pan" construction. Another German example are the Mercedes-Benz "Ponton" cars of the 1950s and 1960s, where it was called a "frame floor" in English-language advertisements. The French Renault 4 , of which over eight million were made, also used

3696-423: The drive motor goes into an overload condition or a servo motor fails to get to the desired position. Collision detection and avoidance are possible, through the use of absolute position sensors (optical encoder strips or disks) to verify that motion occurred, or torque sensors or power-draw sensors on the drive system to detect abnormal strain when the machine should just be moving and not cutting, but these are not

3773-418: The drive system is weaker than the machine's structural integrity, then the drive system simply pushes against the obstruction, and the drive motors "slip in place". The machine tool may not detect the collision or the slipping, so for example the tool should now be at 210mm on the X-axis, but is, in fact, at 32mm where it hit the obstruction and kept slipping. All of the next tool motions will be off by −178mm on

3850-435: The engine and drive train. It can transfer them evenly to a wide area of relatively thin sheet metal of a unitized body shell. Subframes are often found at the front or rear end of cars and are used to attach the suspension to the vehicle. A subframe may also contain the engine and transmission . It normally has pressed or box steel construction but may be tubular and/or other material. Examples of passenger car use include

3927-437: The ensuing decades. Nearly all trucks , buses, and most pickups continue to use a separate frame as their chassis. The main functions of a frame in a motor vehicle are: Typically, the material used to construct vehicle chassis and frames include carbon steel for strength or aluminum alloys to achieve a more lightweight construction. In the case of a separate chassis, the frame is made up of structural elements called

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4004-526: The forces in each strut are either tensile or compressive, never bending, so they can be kept as thin as possible. The first true spaceframe chassis were produced in the 1930s by Buckminster Fuller and William Bushnell Stout (the Dymaxion and the Stout Scarab ) who understood the theory of the true spaceframe from either architecture or aircraft design. The 1951 Jaguar C-Type racing sports car utilized

4081-410: The last line of the program. The format for a G-code is the letter G followed by two to three digits; for example G01. G-codes differ slightly between a mill and lathe application, for example: [Code Miscellaneous Functions (M-Code)] . M-codes are miscellaneous machine commands that do not command axis motion. The format for an M-code is the letter M followed by two to three digits; for example: Having

4158-553: The late 2000s truck-based compact SUVs were phased out and replaced with crossovers). An additional advantage of a strong-bodied car lies in the improved crash protection for its passengers. American Motors (with its partner Renault ) during the late 1970s incorporated unibody construction when designing the Jeep Cherokee (XJ) platform using the manufacturing principles (unisides, floorplan with integrated frame rails and crumple zones, and roof panel) used in its passenger cars, such as

4235-425: The machine is operated safely. However, during the 2000s and 2010s, the software for machining simulation has been maturing rapidly, and it is no longer uncommon for the entire machine tool envelope (including all axes, spindles, chucks, turrets, tool holders, tailstocks, fixtures, clamps, and stock) to be modeled accurately with 3D solid models , which allows the simulation software to predict fairly accurately whether

4312-455: The machining code provided and it is up to an operator to detect if a crash is either occurring or about to occur, and for the operator to manually abort the active process. Machines equipped with load sensors can stop axis or spindle movement in response to an overload condition, but this does not prevent a crash from occurring. It may only limit the damage resulting from the crash. Some crashes may not ever overload any axis or spindle drives. If

4389-538: The main body. It was so successful that the Soviet post-war mass produced GAZ-M20 Pobeda of 1946 copied unibody structure from the Opel Kapitän. Later Soviet limousine GAZ-12 ZIM of 1950 introduced unibody design to automobiles with a wheelbase as long as 3.2 m (126 in). The streamlined 1936 Lincoln-Zephyr with conventional front-engine, rear-wheel-drive layout utilized a unibody structure. By 1941, unit construction

4466-470: The mechanism, by tightly applying pressure against the reference and setting that as the zero references for all following CNC-encoded motions. This is similar to the manual machine tool method of clamping a micrometer onto a reference beam and adjusting the Vernier dial to zero using that object as the reference. In numerical control systems, the position of the tool is defined by a set of instructions called

4543-487: The most common, the C-channel rail has been used on nearly every type of vehicle at one time or another. It is made by taking a flat piece of steel (usually ranging in thickness from 1/8" to 3/16", but up to 1/2" or more in some heavy-duty trucks ) and rolling both sides over to form a C-shaped beam running the length of the vehicle. C-channel is typically more flexible than (fully) boxed of the same gauge. Hat frames resemble

4620-481: The order of 100mm /min, as compared to 8x10 mm /min for conventional machining, but it can generate features that conventional machining cannot. Wire EDM operates by using a thin conductive wire, typically brass, as the electrode, and discharging as it runs past the part being machined. This is useful for complex profiles with inside 90 degree corners that would be challenging to machine with conventional methods. Many other tools have CNC variants, including: In CNC,

4697-587: The overall height of the vehicles regardless of the increase in the size of the transmission and propeller shaft humps since each row had to cover frame rails as well. Several models had the differential located not by the customary bar between axle and frame, but by a ball joint atop the differential connected to a socket in a wishbone hinged onto a crossmember of the frame. The X-frame was claimed to improve on previous designs, but it lacked side rails and thus did not provide adequate side impact and collision protection. Perimeter frames replaced this design. Similar to

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4774-412: The part being machined so that it must be scrapped. Many CNC tools have no inherent sense of the absolute position of the table or tools when turned on. They must be manually "homed" or "zeroed" to have any reference to work from, and these limits are just for figuring out the location of the part to work with it and are no hard motion limit on the mechanism. It is often possible to drive the machine outside

4851-485: The physical bounds of its drive mechanism, resulting in a collision with itself or damage to the drive mechanism. Many machines implement control parameters limiting axis motion past a certain limit in addition to physical limit switches . However, these parameters can often be changed by the operator. Many CNC tools also do not know anything about their working environment. Machines may have load sensing systems on spindle and axis drives, but some do not. They blindly follow

4928-461: The precision of some operations involving axis movement reversals during cutting, such as the milling of a circle, where axis motion is sinusoidal. However, this can be compensated for if the amount of backlash is precisely known by linear encoders or manual measurement. The high backlash mechanism itself is not necessarily relied on to be repeatedly precise for the cutting process, but some other reference object or precision surface may be used to zero

5005-498: The prevalent design for body-on-frame cars in the United States, but not in the rest of the world, until the unibody gained popularity. For example, Hudson introduced this construction on their 3rd generation Commodore models in 1948. This frame type allowed for annual model changes , and lower cars, introduced in the 1950s to increase sales – without costly structural changes. The Ford Panther platform , discontinued in 2011,

5082-444: The specific commands necessary for a particular machine to produce the component and then are loaded into the CNC machine. Since any particular component might require the use of several different tools – drills , saws , touch probes etc. – modern machines often combine multiple tools into a single "cell". In other installations, several different machines are used with an external controller and human or robotic operators that move

5159-427: The stock material to give a starting point or "home position" before starting the actual machining. G-codes are used to command specific movements of the machine, such as machine moves or drilling functions. The majority of G-code programs start with a percent (%) symbol on the first line, then followed by an "O" with a numerical name for the program (i.e. "O0001") on the second line, then another percent (%) symbol on

5236-648: The traditional body-on-frame architecture to the lighter unitized/integrated body structure that is now used for most cars. Integral frame and body construction requires more than simply welding an unstressed body to a conventional frame. In a fully integrated body structure, the entire car is a load-carrying unit that handles all the loads experienced by the vehicle – forces from driving and cargo loads. Integral-type bodies for wheeled vehicles are typically manufactured by welding preformed metal panels and other components together, by forming or casting whole sections as one piece, or by combining these techniques. Although this

5313-456: The traditional milling and turning , other machines and equipment are also installed with the corresponding CNC, which makes the manufacturing industry in its support, greatly improving the quality and efficiency. Of course, the latest trend in CNC is to combine traditional subtractive manufacturing with additive manufacturing (3D printing) to create a new manufacturing method - hybrid additive subtractive manufacturing (HASM). Another trend

5390-460: The traditionally wooden stock , for the purpose of better accurizing the gun. The chassis is usually made from hard metallic material such as aluminium alloy (and less frequently stainless steel , titanium alloy or recently magnesium alloy ) due to metals having superior stiffness and compressive strength compared with wood or synthetic polymer , which are commonly used in conventional rifle stocks. The chassis essentially functions as

5467-453: The transition areas from front to center and center to rear reduce beam and torsional resistance and is used in combination with torque boxes and soft suspension settings. This is a modification of the perimeter frame, or of the backbone frame, in which the passenger compartment floor, and sometimes the luggage compartment floor, have been integrated into the frame as loadbearing parts for strength and rigidity. The sheet metal used to assemble

5544-476: The vast majority of backlash, it still must be taken into account. CNC tools with a large amount of mechanical backlash can still be highly precise if the drive or cutting mechanism is only driven to apply cutting force from one direction, and all driving systems are pressed tightly together in that one cutting direction. However, a CNC device with high backlash and a dull cutting tool can lead to cutter chatter and possible workpiece gouging. The backlash also affects

5621-433: The vehicle, the body is still placed on or over (sometimes straddling) this structure from above. This is the design used for the full-size American models of General Motors in the late 1950s and early 1960s in which the rails from alongside the engine seemed to cross in the passenger compartment, each continuing to the opposite end of the crossmember at the extreme rear of the vehicle. It was specifically chosen to decrease

5698-445: Was no longer a new idea for cars, "but it was unheard of in the [American] low-price field [and] Nash wanted a bigger share of that market." The single unit-body construction of the Nash 600 provided weight savings and Nash's Chairman and CEO, George W. Mason was convinced "that unibody was the wave of the future." Since then, more cars were redesigned to the unibody structure, which

5775-515: Was not ideal because the panel fits were poor. To convince a skeptical public of the strength of unibody, both Citroën and Chrysler created advertising films showing cars surviving after being pushed off a cliff. Opel was the second European and the first German car manufacturer to produce a car with a unibody structure – production of the compact Olympia started in 1935. A larger Kapitän went into production in 1938, although its front longitudinal beams were stamped separately and then attached to

5852-432: Was one of the last perimeter frame passenger car platforms in the United States. The fourth to seventh generation Chevrolet Corvette used a perimeter frame integrated with an internal skeleton that serves as a clamshell. In addition to a lowered roof, the perimeter frame allows lower seating positions when that is desirable, and offers better safety in the event of a side impact. However, the design lacks stiffness because

5929-508: Was trademarked by Carrozzeria Touring for lightweight sports-car body construction that only resembles a space-frame chassis. Using a three-dimensional frame that consists of a cage of narrow tubes that, besides being under the body, run up the fenders and over the radiator, cowl, and roof, and under the rear window, it resembles a geodesic structure . A skin is attached to the outside of the frame, often made of aluminum. This body construction is, however, not stress-bearing and still requires

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