jigs and fixtures; what's the difference? (MFTLDES)

TARGET AUDIENCE: Students, Academics, Industry Professionals, Employers, and Tech Enthusiasts; Self

Note:

OVERVIEW: One of the crucial topics that defines a modern assembly line is the use of jigs and fixtures throughout each process station. The use of course, is to do tedious and repetitive jobs consistently. I have witnessed this in my field trip and also in my internship. An example to this is my time in SCPA where there is a roll rewinding process for big ply of tissue discarded when a defect is seen by operator. A simple fixture clamps the ply of roll and operator gets the core paperbond (the hard carton inside) to separate it for recycling. Granted that this may be automated in the future, J&Ts ease the operator's life of segregating the two different materials from the compounded product. To know, more about this, below is a summary of the learnings that I have regarding J&Ts design. I also provide a consolidated document of lesson slides below for reference! :>

Jig vs. Fixture?

One of the many things that confuses a lay person in regards to this topic is the differene between jig and fixture. Simply put, jigs act as a guide for a tool to follow to the desired position and reference. This is meant to help the manufacturer or operator to create a product in a consistent manner. Fixtures, on the other hand, is a device that holds a workpiece in a specific position. This is meant to help the operator ensure that there is no deviation from the manufacturing operation to be done on the workpiece. Of course, the concept is interchangeable and there are tools now that can do both. Like a fixture plate in a drilling machine both clamps the workpiece and also ensure that the drill on top firmly touches the product upon contact.

In the field, many things may happen. Machines are feared to break and operators prone to human error therefore making a tool that ensures consistency is the name of the game. The difference is that jigs are used

TLDR:

• Jigs: Locate and hold workpieces, positioning and guiding cutting tools.
• Fixtures: Locate and hold devices used with machine tools, inspection, welding, and assembly

Tool Design:

Tool design is the process of creating tools, methods, and techniques to improve manufacturing efficiency and productivity, providing industries with machines and tooling for high-speed, high-volume production at competitive costs. It’s a continuous problem-solving process adapting to various manufacturing needs.

• Lower manufacturing costs while maintaining quality and increasing production.
• Provide simple, easy-to-operate tools for maximum efficiency.
• Reduce manufacturing expenses by producing high-quality parts at the lowest cost.
• Increase production rates with existing machine tools.
• Design foolproof tools that prevent improper use.
• Select materials for adequate tool life.
• Ensure maximum operator safety.

Tool tolerance should generally be 20–50% of part tolerance to ensure consistency without excessive precision costs.

Planes of Movement

• Workpieces have 12 potential directions of movement (6 translations + 6 rotations).
• Proper fixture design must restrict all of these DOF using locators and clamps.

Design Specifics:

• Special tooling vs. modified equipment.
• Multiple-spindle vs. single-spindle machines.
• Single-purpose vs. multipurpose tools.
• Cost justification.
• Gauge types for each operation.

Jigs and Fixture Design Conventions

• Fixtures should be designed so that parts fit only in the correct orientation.
• Prevents assembly errors and ensures repeatability.

1. Strong frame to minimize deflection and prevent chatter.
2. Frames built from sections, fastened with screws or welds.
3. Provisions for correct workpiece positioning.
4. Easy workpiece insertion and removal.
5. Rapid clamping with minimal operator effort.
6. Accessible and easily positioned clamps.
7. Spring-supported clamps.
8. Controlled clamp swing.
9. Visible and accessible clamps, supports, and locators.
10. Uniform wrench sizes for adjustments.
11. Attached loose parts.
12. Stable workpiece positioning with three fixed support points.
13. Adjustable support points for smooth, flat workpieces.

Clamping and Workholding Principles

• Workholders must clamp, chuck, hold, or grip parts securely.
• Clamp against locators to prevent shifting.
• Strong enough to resist tool forces.
• Must not damage or deform the part.
• Fast-acting for productivity.

Positioning of Clamps

• Apply force at the most rigid point of the part.
• Avoid interference with tools or machine operations.

Burr Clearance

• Primary and secondary burrs must be considered in fixture design.

Installation

• Correct fit is critical.
• Jig Plates hold and position bushings. Thickness depends on bushing size.
• End of the bushing should not touch the workpiece (exceptions for high accuracy).

📍 Methods of Locating Work

From a Flat Surface

• Solid supports
• Adjustable supports
• Equalizing supports

From an Internal Diameter

• Shank-type locators
• Pin-type locators
• Diamond locators
• Relieved locators

From an External Profile

• Nesting locators
• Partial nesting locators

Quick-Die Change Systems:

As a culmination of the topics, aside from the CAD work, we were tasked to present a modern manufacturing concept that applies J&Ts. We chose qucick die change systems that is often seen in mold injection process or metal stamping process where a need to have varying operations done on a machine is needed. Below is a summary of this concept and our report regarding this beauty~!

Quick Die Change systems:

• Improve safety, productivity, and quality compared to traditional die handling.
• Reduce risk of injury and machine downtime.
• Ensure consistent product quality through precise and repeatable die changes.

Advantages of QDCs

• Reduced Downtime & Increased Productivity: Faster changeovers increase available production time.
• Shorter Production Runs: Frequent changeovers possible without loss of capacity.
• Reduced Manufacturing Lead Time: Increases operational efficiency and responsiveness.
• Improved Safety: Automation reduces manual handling accidents.
• Higher Quality: Accurate die positioning prevents tool damage and ensures consistency.

Synthesis of Advantages of QDCs

Main Advantage	Key Notes
Reduced Downtime	Enables more uptime with rapid die swaps
Shorter Runs	Flexibility for smaller lot production
Reduced Lead Time	Greater adaptability in operations
Improved Safety	Fewer manual interventions, less risk
Higher Quality	Stable positioning minimizes die wear

General Parts and Configuration of QDCs

QDC systems generally include:

1. Die Clamping Systems
   • Mechanical, hydraulic, or permanent electro-mechanical clamps.
   • Hydraulic clamps: safer; prevent press operation if misaligned.
   • Types: single-acting and double-acting.
   • Permanent electric magnetic clamps: optional, for delicate workpieces.
2. Die Transport & Positioning Systems
   • Automates die loading/unloading and alignment.
   • Prevents damage from manual handling.
   • Examples: Rigid chain rolling bolster systems, die cart systems.
3. Other Components
   • Die arms (bolster extensions): help move dies into position.
   • Can be movable, fixed, or pivot-positioned.

Implementation of QDCs

• Considerations extend beyond shape and tolerance — dies must produce usable parts without constant revisions.
• Reliability and repeatability are essential for long-term success.

QDC Design and Implementation Considerations

QDC Component	Design / Method Selection
Clamping	Hydraulic, mechanical, or electro-magnetic clamps
Transport	Rolling bolsters, die carts, chain systems
Positioning	Precise locator pins, automated alignment
Safety	Interlocks, misalignment prevention
Productivity	Faster cycle times, flexible changeovers

Relevant Formulas in QDC Systems

1. Die Clamping Force

To ensure safe operation, the required clamping force must exceed the tool separation force:

\[F_c = P \times A \times SF\]

Where:

• ( F_c ) = required clamping force (N)
• ( P ) = working pressure of press (N/mm²)
• ( A ) = clamping area (mm²)
• ( SF ) = safety factor (typically 1.5–2.0)

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2. Die Lifting Force

For lifting heavy dies during transfer:

\[F_l = m \times g\]

Where:

• ( F_l ) = lifting force (N)
• ( m ) = mass of die (kg)
• ( g ) = acceleration due to gravity (9.81 m/s²)

If multiple lifting points are used:

\[F_{per\ point} = \frac{F_l}{n}\]

Where ( n ) = number of lifting devices.

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Payback Period (Economic Assessment)

Used to evaluate investment feasibility of a QDC system:

\[Payback\ Period = \frac{Initial\ Investment}{Annual\ Savings}\]

Where:

• Initial Investment = cost of QDC system implementation
• Annual Savings = reduced downtime costs + productivity gains + quality improvements

REFLECTIONS: One of the few things that I appreciate in my course but was under delivered was this type of discussions of machines and tools that I will be often seeing in the assembly line or in my line of work. I mean who wouldn’t want to learn more and dive deep into the usage of these types of J&Ts tools and design something from that knowledge. I know in other countries, becoming a tool designer pays mad money. Its a niche work. The YOE and knowledge to pull out the needed requirements for tools design is a few to none type of expertises. Alas, here in the PH, its not typically a route for engineers to do that type of work. The technology needs a craftsman that we are not specialized to do.

Further certifications and education is needed to hone this skill towards creating these beasts in the field. It also needed to determine the usecase of such tools so that we can provide the appropriate costing and assessment to be presented to our stakeholders.

Kung ako lang, gagawin ko na, but the fear of being unemployed pushes me to hone other skills that is readily accepted in major manufacturing. At the end of the day, knowing this is very huge since CAD work is our bread and butter. This can be a future application if wanted!