Workholding

Quick Change Fixturing: The Link to Manufacturing Efficiency

I. Efficiency of a Well Designed Quick-Change Workholding System

A well designed workholding system holds the part in a fixed position to allow for precise fabricating within a specified tolerance.  Workholding is comprised of two primary components:

  • The actual workholding tool, such as a vise to hold the piece in place.
  • A device to firmly attach the workholding tool to the machine. This can include the use of fixture plates, universal T-Slot bolts, clamps and other devices which can firmly position and hold the part into place.

Today there are more quick change technologies available than ever before for multi-axis, horizontal and vertical machining centers.

Highly engineered quick-change workholding systems allow for significantly more machining time out of every shift.  There are systems that offer dramatic improvements and savings under the spindle when compared to traditional workholding methods.

Manual Systems

Some manual mounting systems can shave up to 75% from your set up times by implementing a quick change fixturing system for a fraction of the cost of traditional methods, such as; clamps, T-Slot bolts, strap clamps, locating pins and more.  A manual quick change system can also be enhanced with either pneumatic or hydraulic release for faster part change over.

Some provide repeatability of up to +/-0.0005" (+/-0.013mm) or better, all allowing for increased uptime and much higher accuracy.

By using Ball Locking shanks with receivers, Quick Locating System fixture plates and subplates, the operator can quickly and accurately locate and hold down fixtures to the machine table in minutes.  These specialty ball locking shanks incorporate internal ball bearings.  As the hex key is tightened the shank locking mechanism moves the spring-loaded ball assemblies outward, locking them into place.  They can have holding forces ranging from 625 lbs. for a 1/2″ (13mm) shank to 15,200 lbs. for a 2″ (50mm) shank.

To mount the system receiver bushings are preinstalled into the subplate or fixture plate, and then a vise can be easily mounted without the need for indicating.  Simply install the shanks into the jigsaw base of the vise and tighten them down with a hex key.  Then load the parts into the machine and it’s ready to go.

This method is far more efficient than setting up with a traditional vise, which is time consuming and labor intensive.  Using the right quick change system can allow your spindle to be cutting, not waiting to cut.  In addition, some of these set-ups can hold two parts at once, eliminating the need for an extra set-up, while doubling the production.

See Quick Change system in action

Automated Systems

There is revolutionary technology available that allows for fixing, positioning and clamping in a single operation.  The most efficient is a Zero Point Clamping System which allows the operator to fix, position and clamp in a single step.  Zero Point Systems can cut set up times by up to 90%.  They are available with either pneumatic or hydraulic release.  The positive locking locating modules allow operators to quickly change out large and small fixtures with extreme accuracy and minimal effort.

Extremely accurate automated mounting systems permit accuracy, speed and repeatability of up to <0.0002” (0.005mm).

The features of Zero Point Systems include pull studs that can be installed directly into the workpiece, which is ideal for large or heavy parts.  They can have corrosion-resistant construction suited for use in food service, pharmaceutical and chemical applications.  Plus, their variable dimensions allow for optimal use of traverse displacement.

Zero Point Systems can be ideal for a variety of mountings.  Their features include Installation Mounts which are manufactured to match specific machine table requirements, Surface Mounts that are designed for table surface installation and Flange Mounts that have internal or external line options, making it easy to adapt to existing columns or plates with low installation depth.

To recap, many automated system benefits include:

  • High Accuracy – .0002” Repeatability
  • Speed – Air or Hydraulic Release
  • Automation – Release can be controlled by the program
  • Flexible Positioning of Receiver Module for Large and Odd Shape
  • Easy Locating Self Centering Stud
  • Application Opportunities Beyond Machining

 

II. The Benefits of Quick Change Fixturing

A fully optimized workholding operation provides versatility in machine automation and robotics applications.  It will:

  • Reduce the number of set-ups required
  • Maximize machine capabilities
  • Allow for complete utilization of the machine table envelope
  • Reduce changeover time
  • Minimize spindle down-time
  • Free-up additional capacity
  • Increase overall output, productivity and profitability

 

Any of these systems can be custom made to the specific needs of the application.  When selecting a manufacturer of a custom workholding system it is important to consider those companies with broad product design and build capabilities.

III.       Conclusion:  Cost Savings Associated With Quick Change Fixturing

The cost savings associated with quick change fixturing can be substantial.  It is not unusual to eliminate two hours of set-up time per shift, which in an average shop can provide approximately $50k in annual overhead cost savings at typical shop burden rates.  Perhaps more importantly, the two hour savings can provide an additional 500 machine hours/shift per year in available machine time.

In the case of one company, the average set-up time was virtually eliminated over their prior process, by:

  • Reducing average set-up from 3 hours to a few minutes
  • Saving approximately $68,000 in overhead cost
  • Gaining an additional 750 machine hours

Quick change fixturing can play a significant role with highly increased efficiencies in manufacturing production.  It is all about saving time and money by changing what is under the spindle, not on it.  When selecting the right workholding partner with the broadest line, operators of CNC and other automated machining can realize efficiencies, cost reductions and increased machine time that will set them ahead of the competition.  Securing jobs for more prototyping is a great opportunity for growth in machine shops.  Yet, for major manufacturers the benefits of quick change fixturing can provide tremendous opportunities to gain market share.

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