Workholding for Multi-Axis CNC Machines 219

“Workholding for Multi-Axis CNC Machines” provides an overview of common workholding devices and adapters for multi-axis CNC machines. Multi-axis machines have a greater range of motion and more cutting capabilities than conventional CNC mills and lathes. As a result, they require specially designed workholding setups to optimize cutting and reduce tool interference. Ideal workholding setups vary based on factors like part size, workpiece material, and machine configuration.

Workholding devices for multi-axis machines ensure that advanced machining centers can be used to the fullest extent of their capabilities. After completing this class, users will have a greater understanding of major types of multi-axis workholding devices, as well as considerations for selecting workholders.

Class Details

Class Name:
Workholding for Multi-Axis CNC Machines 219
Difficulty:
Intermediate
Number of Lessons:
13

Class Outline

  • Multi-Axis Workholding
  • Benefits of Multi-Axis Workholding
  • Workholding and Machine Programming
  • Considerations for Workholding
  • Review: Introduction to Workholding
  • Dovetail Fixtures
  • Hard Jaws
  • Pallets
  • Review: Common Workholding Devices
  • Workholding Adapters
  • Multi-Part Workholding
  • Alternative Workholding Options
  • Review: Additional Workholding Options

Objectives

  • Describe workholding for multi-axis CNC machines.
  • Describe benefits of multi-axis workholding devices.
  • Describe how workholding devices affect machine programming.
  • Describe considerations for selecting workholding devices.
  • Describe multi-axis dovetail fixtures.
  • Describe multi-axis hard jaws.
  • Describe multi-axis pallets.
  • Describe common adapters for workholding devices.
  • Describe workholding for multi-part setups.
  • Describe alternative workholding devices.

Job Roles

Certifications

Glossary

Vocabulary Term Definition
adapters A device that is used in combination with other multi-axis workholders. Adapters add support or clearance to provide better access for the cutting tool.
adhesives A non-metallic substance used to bond two or more materials together. Adhesives are sometimes used as workholding for non-metallic, delicate, and irregularly shaped workpieces.
axis configuration The number and location of all of the axes on a multi-axis machine. Axis configuration can affect how workholding interacts with machine movement, cutting tool access, and clearance during cutting.
ball lock pins A self-locking quick-release pin that uses a button and internal spring to control one or more balls at the end of the pin. A ball lock pin's balls retract for installation and return to their original position to hold the pin in place.
batch machining The process of creating multiple identical parts as part of a single production cycle. Batch machining with multi-axis machines often involves using pallet systems.
bond An attraction between two surfaces using glues, epoxies, or other adhesive agents. Bonds form when adhesive substances are exposed to heat or light.
ceramic A hard, brittle material that can withstand high temperatures and resist corrosion. Ceramic parts can be created through hybrid machining operations on multi-axis machines.
changeover The process of switching a machine from one part setup or process to another. Changeover time can be greatly reduced by using workholding designed to facilitate quick loading and unloading and reconfiguration.
chips An unwanted piece of metal that is removed from a workpiece. Chips can accumulate inside a workholding device and obstruct cutting tool access to the part.
clamping force The compressive force that holds a workpiece in place. Clamping forces resist machining forces.
clamping surfaces A section of a workholding device that grips workpieces or supports other workholding devices. Multi-axis workholding devices can have one or more clamping surfaces.
clearance An intentional amount of space left between two components. The clearance provided by multi-axis workholding devices improves cutting tool access and reduces the risk of tool interference.
collets A slitted multi-axis workholding adapter that is stacked beneath the ball lock pins on pallet systems or under irregular part features to provide added support and clearance. Specially designed collets can be used as stand-alone workholding devices for cylindrical multi-axis parts.
computer-aided manufacturing CAM. The use of a computer to assist in part manufacturing. Computer-aided manufacturing generates instructions for machining a part.
coolants A cutting fluid used to decrease the temperature of the tool and the workpiece. Coolant can consist of oils, water, or synthetics.
cutting speed The rate at which a workpiece and cutting tool move past one another at their point of contact. Cutting speed determines how quickly unwanted material is removed from the workpiece.
deformations A change or distortion in shape. Deformations caused by workholding devices can damage parts or require additional post-processing to remove.
depth of cut The distance that a cutting tool penetrates the surface of a workpiece. Depth of cut determines the amount of material removed with each cutting pass.
dovetail A raised, angled surface pre-machined into the bottom of a workpiece to be mounted on a dovetail fixture. Dovetails slide securely into a slot in the dovetail fixture that matches the angle and size of the dovetail.
dovetail cutter A mill cutter used to cut a dovetail angle into a workpiece. Dovetail cutters can produce raised surfaces that fit into angled slots on dovetail fixtures.
dovetail fixtures A multi-axis workholding device with an angled slot, dowel pin, and screws that clamp the workpiece in place. Dovetail fixtures create the most downward force to keep a part still during cutting.
dowel pin A cylindrical, semi-permanent pin that has one chamfered end and one radius end. Dowel pins are mainly used to locate machine parts in fixed positions or to maintain alignment.
electromagnets A magnet that gains an attractive force only when current passes through it. Electromagnets are typically formed by wrapping wire windings around an iron core.
environmental factors A condition that exists in the area around a multi-axis machine. Environmental factors such as friction, heat, and flying chips can impact machine behavior and affect workholding selection.
features A defining characteristic on a component or part that influences both design and machining. Features include holes, threads, text, and walls.
feed rate The rate at which the cutting tool and the workpiece move in relation to one another. Feed rate typically measures a linear movement.
ferrous Containing iron, generally as a primary ingredient in metals. Ferrous metals are usually magnetic.
fixtures A customized workholding device that is designed to effectively support, locate, and hold a specific type of workpiece. Workpieces with multiple complex dimensions often require dedicated fixtures.
flanged platforms A multi-axis riser with a projecting rim or edge at its base. Flanged platforms are wider at the bottom to increase clearance and improve stability.
friction A force that resists motion between components that are in contact with one another. Friction generates heat that can cause damage if it gets too high.
hard jaws A multi-axis workholding device that has vise jaws made of a material, usually hardened steel, that resists penetration, indentation, or scratching. Multi-axis hard jaws provide rigid support for workpieces and usually have serrations for added gripping strength.
hardness A material's ability to resist indentation or scratching. Increasing hardness generally lowers the machinability of a metal.
hybrid manufacturing A process that uses both traditional and additive manufacturing (AM) to create a finished part. Hybrid manufacturing can involve either using a traditional manufacturing process on a mostly additively manufactured part or vice versa.
hydraulic Powered by the controlled movement of pressurized liquid, usually oil. Hydraulic systems are sometimes used to provide extra clamping power to a workholding device.
interference An undesirable operating condition for a multi-axis CNC machine that occurs when parts of the spindle or cutting tool come into contact with other machine components or undesired parts of the workpiece. Interference can damage the workpiece or misalign the spindle.
jaw A component on a vise that grips and holds the workpiece in place. Jaws can be movable or stationary.
knob-and-receiver systems A type of pallet system that uses ball lock pins and cylindrical receivers to secure workpieces or workholding devices. Knob-and-receiver systems are highly accurate and disengage easily to allow attached components to be removed from the table.
lathes A machine tool commonly used to create cylindrical forms. A lathe holds a cylindrical workpiece on one or both ends while the cutting tool is gradually passed along the surface of the rotating part.
lights-out manufacturing Fully automated manufacturing that can operate independently in a facility without any employees on site. Lights-out manufacturing allows facilities to operate for extended hours while reducing labor costs.
lubricants A substance used to reduce friction between components that contact each other. Lubricants include oil, grease, wax, and other substances.
machinable blanks An adapter for dovetail fixtures that uses a custom-cut slot to hold and protect one of the five finished sides of a multi-axis workpiece so that the sixth side can be machined. Machinable blanks are made of softer materials that do not damage the workpiece.
machining columns A vertically oriented multi-part fixture that can hold workpieces on two or more wide mounting surfaces. Machining columns, or tombstones, are often used to machine a series of workpieces at the same time.
machining forces A push or pull that the cutting tool or machine movements exert on a workpiece during cutting. Machining forces can be affected by cutting speed, cutting pressure, table movements, and feed rate.
magnetic Possessing a force that attracts or repels other metals. Magnetic workholding devices offer some of the best cutting tool access but only work with ferrous parts.
material The substance out of which something is made. The material of a workpiece can affect workholding selection for multi-axis parts.
mills A machine tool that performs cutting operations on flat, square, or rectangular workpieces. On a conventional mill, the cutting tool can move only linearly.
modular Consisting of interchangeable and discrete parts. Modular workholding devices can be combined to create more accurate setups and for use on a range of multi-axis machines.
multi-axis CNC machine A machining center that has four or more linear and rotational axes. Multi-axis CNC machines, or multitasking machines, combine the functions of a mill and a lathe.
multi-part pyramids A triangular multi-part fixture that can hold workpieces on at least three different surfaces. Multi-part pyramids are often used to support other workholding devices, especially dovetail fixtures.
multi-part setups A workholding setup that supports more than one workpiece during an operation. Multi-part setups often require special workholding devices.
multitasking machines A machining center that has four or more linear and rotational axes. Multitasking machines, or multi-axis CNC machines, combine the functions of a mill and a lathe.
negative pressure Air pressure that is lower than the ambient air pressure. Vacuum workholding devices use negative pressure to suction workpieces to the table.
optimized Improved to be more efficient and effective. Optimized multi-axis workholders provide more grip with less material to give the cutting tool the most access to a part and to reduce collisions.
pallets A plate-shaped workholding device with holes that are used to attach other components. Pallets can attach directly to parts or attach to other workholding devices and enable simple multi-part setups.
part program A series of alphanumerical instructions that guides the movements of a CNC machine. A part program begins at the program zero location.
perpendicular Intersecting another line or plane at a right angle. Tombstones hold workpieces so that they are perpendicular to the worktable.
plates A flat component that provides the base for the other devices or components of a workholding setup. Pallets are a type of workholding plate.
pneumatic Powered by the controlled movement of compressed gas, usually air. Pneumatic systems are sometimes used to provide extra clamping power to a workholding device.
polymer A material made of long chains of molecules. Polymers include plastic, rubber, and other natural or synthetic materials.
post-processing A procedure used to clean, improve, or otherwise finish a part after it has been manufactured. Post-processing procedures include abrasive finishing, heat treatment, and painting.
program zero The position that acts as the origin for a specific part program. Program zero acts as a reference point for all part dimensions.
properties A defining characteristic of a material. Properties include mechanical properties, which describe how a material responds to external forces, and physical properties, which describe basic qualities of the material.
push/pull-type A workholding device that is usually a type of vise with one movable jaw. Push/pull-type workholding devices can ensure that program zero remains in a fixed position during and after setup.
pyramids A triangular multi-axis riser with three or four sloped sides. Pyramids can be used alone or with more common workholding devices to increase clearance and improve stability.
quick-change operations A type of operation in which machine setups can be quickly changed to run another size, type, or batch of product. Quick-change operations on multi-axis machines often involve using pallets for workholding.
reactions A chemical process during which one or more substances are changed due to the introduction of another substance. Reactions between chemicals and light or heat create the bond in adhesive workholding.
recess An indentation or hollow area. The recess on a dovetail fixture is angled so that a matching dovetail on the bottom of a pre-machined part can slide into it.
repeatability The ability of a machine or process to continually deliver consistent and uniform results. Repeatability is crucial for efficiently producing quality, identical parts.
risers An adapter that elevates a workholding device to reduce interference. Risers for multi-axis workholding include plates, flanged platforms, and pyramids that increase clearance.
robots A machine that automatically performs complicated and repetitive tasks. Robots can automatically change pallets on a multi-axis CNC machine.
rotation Travel around a circular axis. On a multi-axis CNC machine, rotation usually describes movement around the C axis by either the spindle or the worktable.
secondary operation An additional manufacturing process required to bring a workpiece into tolerance and create a final part. Secondary operations include removing pre-machined features like dovetails and machining sides of a part that were obscured by the workholding device during primary operations.
self-centering A workholding device that can have two moving jaws or other components that interlock with features on the workpiece. Self-centering devices are more likely to move program zero away from its expected position.
serrated jaws A multi-axis workholding device with notched teeth that dig into the workpiece on two sides to provide better grip. Serrated jaws give the cutting tool more access to the part than a standard vise.
serrations A series of ridges or grooves notched into a surface. Serrations improve a workholding device's gripping ability without restricting tool access on multi-axis machines.
setup The process of arranging tooling and fixturing on a manufacturing machine. One of the most important aspects of multi-axis machine setup is choosing the correct workholding devices.
simulate Represent real-world and real-time situations with computer-driven technology in order to evaluate behavior under real conditions. Using CAM to simulate workholding devices helps model the behavior of a manufacturing process to test for clearance and interference before it is used to make an actual product.
slot A channel in the surface of a fixture or part. Slots on dovetail fixtures have the same shape and angle as the dovetail on the bottom of a workpiece.
soft jaws An adapter for hard jaws that uses a custom-cut slot to hold and protect one of the five finished sides of a multi-axis workpiece so that the sixth side can be machined. Soft jaws are made of softer materials that do not damage the workpiece.
stickout The distance between the end of the toolholder and the tip of the cutting tool. Excess stickout can increase the risk of collisions or cause tools to bend, break, or vibrate undesirably.
strength A material's ability to resist forces that attempt to break or deform it. Strength may refer to tensile, compressive, or shear strength, depending on the type of force.
table The part of a multi-axis CNC machine that supports the workpiece. The table, or worktable, can move along a combination of linear and rotational axes, depending on the configuration of the machine.
thermochemical A chemical that responds to heat. Thermochemical adhesives form bonds when introduced to a heat source.
tilt Swing or change in angle. On a multi-axis CNC machine, tilt refers to the angle at which the part and cutting tool contact each other.
tombstones A vertically oriented multi-part fixture that can hold workpieces on two or more wide mounting surfaces. Tombstones, or machining columns, are often used to machine a series of workpieces at the same time.
toolpaths The course followed by the tool as it creates the workpiece. Toolpaths are described by a series of coordinate positions.
ultraviolet UV. A potentially harmful wavelength of light that is below, or shorter than, violet on the light spectrum. Ultraviolet light is used to selectively harden an adhesive in some multi-axis workholding applications.
vacuum A space with negative air pressure created by removing the air with suction. Vacuum workholding devices are sometimes used for non-metallic or delicate workpieces.
vises A workholding device with two jaws that grip and hold a workpiece in place. Standard vises keep parts in a fixed position on conventional CNC mills.
work offsets The distance between machine zero and program zero. Work offsets help CAM communicate the location of the part to the machine before cutting begins.
workholders A device used to hold and locate a workpiece on a machining center. Workholders, or workholding devices, are used to keep the workpiece stationary.
workholding devices A device used to hold and locate a workpiece on a machining center. Workholding devices, or workholders, are used to keep the workpiece stationary.
workpiece A part that is in the process of being machined. A workpiece may be subject to cutting, grinding, forming, welding, or other operations to produce a finished part.
worktable The part of a multi-axis CNC machine that supports the workpiece. The worktable, or table, can move along a combination of linear and rotational axes, depending on the configuration of the machine.