The Advantages of Using Fixtures in your CNC Milling Processes news

The Advantages of Using Fixtures in your CNC Milling Processes

Recently, while speaking with a prospective Sales Representative, I was surprised to learn that nearly 90% of the CNC Machine Shops that he visited on a regular basis, were using only Vises for their workholding.  Although this has been very good for the sales of our ParaKeep 5S Kits, it surprised me in this day in age, that more companies are not using more sophisticated workholding. 

At Rimeco Products, we have been using Fixtures in most of our processes, since I started working there in 1997.  We have hundreds of different Fixtures for the hundreds of different jobs we have run over the years.  It has been one of the most significant factors of our success and growth, as we have been able to use the quick-change functionality of our Kwik-Clamp System to mount them and also to combine multiple operations into one process and complete parts in one machining operation.

After hearing this fact from the prospective Sales Representative, I started thinking about the advantages of using custom fixtures, verses only using Vises in the processes done on Vertical Machining Centers.  I came up with six main advantages of using Fixtures and a Quick-Change Mounting System, like the Kwik-Clamp:

  1. The ability to Mount and Qualify your work holding in less than a Minute, on a Fifth axis or Vertical Machining Center table or on a 4th Axis Rotary Table.
  2. The ability to machine 5 sides of any part, without removing the part from the Fixture, using a Rotary Table and a quick-change mounting system, like the 4 Axis OnePro and Vertical Kwik-Clamp.
  3. The ability to combine multiple machining operations into one process, a term we call Combinative Manufacturing. Multiple fixtures and a quick-change mounting system allow you to finish parts in one operation.
  4. Reducing spindle idle time, by changing out parts in your Fixtures and Workholding outside of the machine and swapping the Fixtures in less than 10 seconds when the machine stops.
  5. The ability to add automation to your process with the addition of robotics. Fixtures can easily be modified to be mounted to 4th Axis Rotary Tables and 5th axis machines utilizing quick-change mounting products.
  6. The safety and ergonomics of loading fixtures outside of a machine greatly reduce the potential for injury, as opposed to loading and unloading workholding and vises inside of the machine.

I will review and expand upon each of these points throughout this paper and describe why the future of machining involves Custom Fixtures and quick-change mounting systems.  Just to be clear, when discussing vises, I am referring to the standard machine vises found in all machine shops.  The newer 5 Axis style vises have moved towards a more versatile style vise that can easily be mounted onto any rotary table or 5th axis machining center with a quick-change mounting system.  We have incorporated the fifth axis vises, along with other small workholding products into our processes with the use of custom Adapters.

Most CNC Machine Shops in the United States are running multiple jobs each year on each of their CNC Machining Centers.  It would be rare to find a Machine Shop that is running just one job on a machine day after day.  For this reason, it is imperative that Machine Shops have the ability to rapidly change from one job to the next, with as little downtime as possible.  Using a Fixture and being able to mount that fixture to your rotary or machine table and qualify it unless than 1 minute, is one of the first steps to Set-up Reduction.  Using a Fixture and using a standardized method of mounting that fixture, allows Process Designers and Programmers to program off a centralized X, Y, Z and A coordinate system.  When a fixture is mounted to a Rotary table or machine table with a quick-change mounting system with at least .0002” precision and repeatability, the work offset can be qualified immediately and the first step of the set-up completed in less than 1 minute.

GD&T has become more and more prevalent in recent years, as Engineers have determined they can design off of the important areas of engagement, rather than tolerancing each dimension.  Being able to machine 5 sides of a part without removing it from a fixture, will give your Process Designers and Programmers the ability to machine all of the major Datums and many of the most important characteristics, without ever removing the part from the fixture.  The second fixture in the process, can be designed to locate off of the major Datums and key characteristics and finish all remaining dimensions and attributes.  This greatly increases quality and reduces scrap; it also gives your Fixture Designers that ability to design a second fixture that will work as a functional gage for the major dimensions machined in the first fixture.  Parts can also be taken to the CMM or other inspection equipment to be measured, without ever removing the part from the fixture.  If a dimension is found to be out of tolerance, there is the potential to put it back into the machine for more material removal.

One of the greatest aspects of using Fixtures in your CNC Machining Process is, Combinative Manufacturing.  Combinative Manufacturing is the process of combining what would be multiple machining operations into one process.  Combinative Manufacturing uses many of the principles of Lean Manufacturing to make processes more efficient.  By finishing processes in one operation, Machine Shops will reduce Work-In-Process, simplify the Scheduling of jobs through the shop and reduce scrap by being able to measure all of the dimensions on a part at one time.  At least 80% of the parts we manufacture in our CNC Machine Shop, incorporate Combinative Manufacturing and allow us to complete parts in one operation.  This also reduces lead times and allows us to expedite partials to our customers when needed.

Reducing spindle idle time is a theme that all machine shops strive to achieve.  It is a key to winning new customers and will lead the way for the Re-shoring Initiative we have been hearing about for many years.  One of the keys to bringing in new work and new customers, is to show them spindles that are always running.  We use Machine Monitors in our shop and we have seen up time as high as 100% utilization when using Fixtures with our Kwik-Clamp mounting system, especially in applications we have incorporated automation into.

Automation is the Future of all manufacturing.  Although it has been around for many years, we are starting to see the flexibility of incorporating automation into high mix, low volume applications.  Most CNC Machine Shops I speak with are running a high mix of many parts with 50-500-piece volumes.  Up until recently, it has been hard to justify the investment to incorporate automation, but with the low unemployment rate, lack of qualified workers and the advancement in automation, it is becoming more of a reality with many shops.  Using Fixtures to hold your parts, gives you a standardized system for robots to grip and load onto CNC Machines.  Using a quick-change mounting system, like the Kwik-Clamp and a solenoid valve, fixtures can be loaded and unloaded onto machines, unattended 24 hours a day, seven days a week.

Although mentioned last, the most important thing inside of any Machine Shop, is our Employees Safety.  What steps can we take to give our Employees the safest work environment?  Using Fixtures and a quick-change mounting system, Machine Operators can load and unload fixtures outside of the machine and when the process is complete, fixtures can be exchanged with a simple flip of the switch.  Rather that bending over, inside of a machine, in order to load material inside of a Vise or other workholding system, Operators can load and unload material and machined parts in Fixtures outside of the machine.  This will greatly reduce the potential for injury and also make your workplace a more comfortable and happier place to be.

In summary, using Fixtures in lieu of Machine Vises, will continue to become more popular as companies look to become more competitive and bring more work back to the United States.  Being able to quickly and efficiently mount Fixtures to Rotary and Machine Tables will make Machining Processes more efficient, reduce scrap, reduce work-in-process and simplify scheduling inside of any CNC Machine Shop.