Getting a Fix on Welding Fixtures:
Custom Fixtures vs. Welding Tables
by Mike Edmonds, President, Cobb Tool, Inc
Manufacturers and operations engineers are frequently faced with making tough choices about machinery and tooling. Challenged with the demand of balancing both limited budgets and the efficiencies/cost benefits of a range of machinery and tool solutions, they constantly battle how to get the required production results while building in the best and longest-term value.
This struggle has never been more obvious than in weighing the installation of custom dedicated welding fixtures or the purchase of modular welding tables with sets of universal table-top accessories. The answer to this question, as in so many of these instances, is “it all depends.” The two – custom tooling and welding tables – can be easily used in conjunction with each other and complement production needs within a manufacturing facility. But many times, one choice over the other can be more advantageous to the operation in the immediate and long-term.
Modular welding tables come in a variety of shapes and sizes. They are also available in a variety of lengths and widths – up to as much as 30-feet. They are usually made of specially hardened steel with added protective coatings and feature a consistent hole pattern that allows for a variety of set-ups. When fashioning a table-top fixture, manufacturers build out a frame by adding the prescribed combination of universal accessories – clamps, pins, shims, brackets, blocks, squares, holds, prisms and stops to match the part. These accessories can be bought individually or in a fixturing kit. If the part being manufactured with the welding table has any kinds of unique characteristics, the table framework is likely to also require custom table-top tooling to complement the universal accessories.
Welding tables offer considerable flexibility. By design they are intended to be for short-run, varied applications – for example for prototype parts, low volume production or a series of different one-off basic components. They are also used for parts that are going into rapidly evolving machinery or technology – where long-term production is unlikely. They are intended to be built, used, broken down and reused for different purposes. These fixture layouts – once designed, can be re-created in the future based on set-up drawings.
A fixed custom welding fixture is designed and built specifically for a dedicated purpose – to hold a group of standardized parts in position to allow manual or robotic welding to take place efficiently and with predictably repeatable results. Custom tooling is designed for high-volume production and is built to last. There are custom fixtures in place in some manufacturing operations that have been performing day-in and day-out for 20 years or more – only requiring periodic maintenance.
Custom tooling is also well-suited to highly complex assemblies requiring a wide variety of components to be positioned and held in place simultaneously to allow for robotic or manual welding. If faced with a complex assembly to be produced in high-volume and over a long period of time, then custom production fixtures are both better suited and will deliver efficiency and value over the long haul.
Advantages and Disadvantages
To determine which fixture approach to take, manufacturing engineers need to look at several characteristics of the part they plan to produce. The first considerations are about production quantities and the consistency of the part design over time. These are some of the easiest questions to weigh. What are the quantities required? Will parts be produced continuously for a long period of time? How complex is the part or assembly? Are they producing a series of different low-volume parts that require a set of different basic set-ups? Is there flexibility in the production timetable to allow set-ups to be broken down and re-set in between part deadlines? Are we making the same part over and over in high volume for the foreseeable future?
One of the toughest questions that should be considered is about the need and availability of skilled labor. Modular welding tables are labor-intensive and require skilled resources to create, break down and re-create consistent table-top fixtures. Even with detailed drawings, unskilled staff can all too frequently build in errors. These unintentional “modifications” can compound and gravitate to extremes over time – to the point where the assembled piece does not function as intended. Welding tables are frequently hand-loaded and hand-clamped which can lead to slight variations in positioning. Table clamps are usually manual and pneumatic clamping is usually reserved for fixed tooling.
On the other hand, fixed tooling is fairly bullet-proof from a staffing standpoint. Because in permanent tooling, fixture elements are static and immovable, it is difficult to go off target. Even labor without in-depth skills can load components into place in only the prescribed way. Pneumatic clamps hold the parts securely. The result of these characteristics is the welding and assembly of the part with highly precise and repeatable regularity. Custom tooling also results in a dramatic reduction in wasted parts or ruined material. It is also essential for robotic welding applications – where consistency is required every time – even up to hundreds of welded pieces and precise assemblies in a day.
Ultimately, there is room and demand in manufacturing for both welding tables and custom tooling. The key is to make decisions wisely so that operators are tapping into the strengths of both approaches for the applications they are facing on their production floors. For answers, or for help in asking the right questions, consult a trusted expert – from an experienced fixture designer, robotics manufacturer or sales rep.
To aid in the process, following is a checklist that can help lay out the kinds of considerations to make the best decision for your operation:
Cobb Tool, Inc.
5886 Dodgen Road
Atlanta, Georgia 30126
18 miles from the Atlanta airport
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