Modular Workholding Design

Modular Workholding Design

 The effort to design modular work holding design is just as important as the design of the manufactured part. As machine shops become more automated and intelligent, workholding must advance in design efficiency as well. Workholding is now often required for small-to-medium-sized production runs and demands accuracy, versatility, and repeatability for a variety of similar operations. The investment of hundreds of thousands of dollars on automated CNC machines for a shop does not want to see them sit idle for any longer than is necessary. Modular workholding design is allowing faster transitions and use on multiple machines with smart pre-made kits containing an assortment of clamps, risers, studs, blocks, and rails.

A New Approach

The basics of workholding design (tag blog Choosing Workholding…) are to keep the tool in cut and depend on the material, speed, tolerances, dimensions, and the cutting tool itself. Moving into hydraulics, for example, will not repair a manual fixture that isn’t performing well to begin with.

As the trend towards smaller lot sizes and higher accuracy parts continues, many manufacturers are finding that dedicated workholding systems end up on the shelf quickly never to be used again. Even in designing your own workholding consider the addition of pre-machined screw and dowel holes for quick mounting and attachment of preconfigured tooling blocks. Modular Workholding systems, available from a variety of manufacturers, allow multiple machining operations to be performed in one setup, often slashing both production time and cost. Adding clamping studs, retention knobs, or more advanced buttons or switches, eliminates the manual labour of loosening and tightening bolts for each production run.

Cost of Production

Modular systems generally have a high price tag, but considering run cost, scrap reduction, and machine downtime, they quickly provide payback depending on lot size.

The machine downtime, or setup cost. is the labour cost to retrieve a fixture, set it up on a machine, and return it to storage after use. Since dedicated fixturing and power workholding are faster to set up, they create lower costs than modular fixturing for larger projects.

The lot size is the average quantity manufactured each time the fixture is set up.

Initial Tooling cost is the total of labour and materials to design and build a fixture. Here, modular fixturing is cheapest because parts are reused, while the more complex power workholding systems initially cost more.

Total quantity over tooling lifetime is the lesser of the total anticipated production costs. Generally speaking, as quantities increase, the efficiency of power workholding yields the lowest cost per part.

Finding the right modular design for your shop can also lower production costs if the vises or chucks can be used on multiple machines, and multiple applications, such as hydraulic, pneumatic, and electric as you expand.

 Modular Design

The capabilities of 5-axis machining create the most complicated workholding challenges. The benefit of a standard base plate with a series of holes and threads to accept various adapters, pallets, and clamping devices creates the fluid design capability for workholding to match the complexity of machining.

Stackable components can grasp the workpiece to allow maximum exposure for the tooling operation. And accuracy does not have to be sacrificed for speed. Selecting modular workholding systems that can be loaded into CAD systems increase design accuracy.

Even lathe operations, when changing out top jaws, or switching from a three-jaw to a collet chuck or arbor are common in a standard operation, can be assisted by modular workholding. This same modular system can often be used on a milling machine, creating a multitude of holding setups for each.

Care

Some of the biggest economies in a CNC machine shop relate to maintenance. Clean workspaces, clean equipment, and preventative regular maintenance increase the life of tools, machines, and costly downtime on the floor. Using modular workholding still involves exposure to contaminants in changeover. Any addition or elimination of a modular workholding piece during phases of production must include cleaning of the CNC machine, the piece, and the workholding. Debris, lubricants, and dirt will affect the accuracy, as well as the life of the tool.

Intelligent Tooling

Robotics can now change out modular tooling setups as easily as they load raw material and remove completed parts. Electronic communication doesn’t end there. New modular workholding design is moving into the IoT (Internet of Things) to both send instructions and receive data for setup and production.

Moving into modular workholding is a capital investment that must follow the needs of the machine shop. Be sure to consider both immediate and future needs to find modular workholding designs that can grow along with your business.

See our previous  blog about Choosing Workholding to Meet Machining Challenges