Savings Through Spindle Up Time

The quick change concept is a means for the machinist to change out a fixture, workpiece, or other workholding device in a matter of minutes with up to 5µ (0.0002") repeatability.

U.S. manufacturers have invested billions of dollars in new equipment during the past two decades to grow their manufacturing base, only to miss two key areas: people and processes.

To counteract an aging workforce – the average age of manufacturing workers in the United States is 45.6 years for machinist and 51 years for tool and dies makers (Bureau of Labor Statistics) – companies need to invest in people and processes.

For example, many shops invest in new machines to initiate change, but spending $500,000 for a new 5-axis or high-speed machine is not enough. Placing an $800 vise with 1920s technology on a new machine to make one part at a time while spending 30 to 60 minutes changing over the workholding, is not a being productive. That would be like buying an HDTV without investing in HD channels.

It takes more than a new machine to increase productivity. Increased productivity is about increasing spindle up time. Machines do not make any money if they are not making chips, and there are numerous ways to increase spindle up time. A few of these solutions include setup time reduction, greater flexibility, increased table capacity, and improved part quality.

A quick change pallet system is one of the easiest ways to increase spindle up time. The most advanced systems locate and clamp the pallet in the same step. The quick change concept is a means for the machinist to change out a fixture, workpiece, or other workholding device in a matter of minutes with up to 5µ (0.0002") repeatability.

However, one area the shops lose productivity is with changeover. Traditionally, shops across the country seem to consider it acceptable to spend anywhere from 30 minutes to two hours, or even longer, to change over a machine one or two times a day. This equates to one to four hours of loss productivity per day. At $60/hr machine rate, only one hour a day equates to more than $15,600 per year lost per machine.

Another benefit of a highly accurate quick change pallet system is being able to interrupt a job. Parts can be removed from the machine while still in the fixture and inspected. If additional work is required, the fixture can be returned to the machine within 5µ from where it was removed and re-machined, without the painful loss of time relocating the part.

In addition to the quick changeover, a quick change pallet system makes it easier for off-line accurately setup. Off-line setup also allows robotic pallet systems to load and unload machines.

Facilities that standardize with a quick change pallet system increase flexibility. The ability to change over a machine, quickly and accurately, enables a shop to interrupt jobs on a machine for a more urgent project, creating a lesser impact to the cost and delivery of the interrupted job. It also allows production parts to run in smaller batch sizes. In addition to interrupting a job, the flexibility to be able to move a job from one machine to another provides additional value. If a machine goes down for service or is committed to another job, a standard quick change system enables moving the part to another machine in minutes.

A second area where productivity is lost is table capacity. Many shops are not aware of compact flexible fixturing that allows 16 parts to be uniformly clamped on a 16" x 16" pallet, or the ability to load multiple parts on a 5-axis machine, and access up to five faces per part.

Many shops investing in 5-axis machines often do not invest in 5-axis workholding, therefore, their investment is not utilized to its full extent. Some forms of fixturing increase the accessibility of the workpiece, reducing the number of operations which include: magnetics, vacuum, and some quick change systems.

Many shops are not aware of compact flexible fixturing that allow 16 parts to be uniformly clamped on a 16" x 16" pallet or the ability to load multiple parts on a 5-axis machine.

For ferrous applications, magnetics provides an excellent option for workholding. Magnetics allows exposure of up to five faces of the workpiece for processing, including through-hole work. Although there may be some tradeoffs, like adjusting cutting forces, in most cases the benefits outweigh the costs. The ability to access five faces not only increases spindle up time, it also allows for processing of all five faces from the same set-up datums. By reducing the number of setups, the risk of set up errors decreases, resulting in improved part quality. An additional time saver in magnetics is the use of self-shimming poles. This option allows for parts to be held in their natural state without inducing stress and pulling a workpiece to the table. This feature eliminates costly time spent shimming, significantly improving workpiece flatness.

The entire increased spindle up time and workpiece access is irrelevant if the part quality is sacrificed. When choosing workholding for increased productivity, the choice of quality is essential. The true difference between top quality solutions and inexpensive solutions may be nothing more than an additional two to three months payback; however, the cost of less than quality parts, lost time, high scrap costs, and lost reputation is detrimental to the company. To purchase anything less than quality actually costs more.

U.S. manufacturing does not have to be headed for a crisis, but it will take investment in both the right people and the proper technology. Therefore, manufacturers need to invest in the tools that will allow for the maximum number of parts to be produced as quickly and flexibly as possible, and with the best quality. This will not only allow for U.S. manufacturing to survive but to lead the world again.
 

SCHUNK Intec Inc.
Morrisville, NC
www.us.schunk.com