QUICK DIE CHANGE AS A WAY TO INCREASE OEE AND IMPROVE PROCESS REPEATABILITY

In the last few years quick die change on forging presses has become the hot topic of the industry.  A large number of forging companies have implemented QDC systems of various types and levels.

Despite those efforts, in some cases the bottom line was not improved.

In this post we will try to systemize all issues related to QDC and demonstrate solutions that were provided by us to customers worldwide.

1. Purpose of implementing QDC.

• The first and most obvious reason is cutting time of die changing. By incorporating various QDC systems this time can be cut 10-fold, sometimes more.  Well-built systems allow for quick die change on a medium size press as fast as 20-25 minutes.

Besides that you can save time by pre-heating tools outside of the press.  In our experience heating tools inside the press requires from 3 to 5 hours.

In general, in some cases the QDC can increase overall production more than implementing press automation (robotic or transfer).

• The second reason is repeatability of the process. If the whole die set is prepared outside the press it gives a chance for a better set up.  The use of shims, incorrect settings, and unnecessary additional stops of the press for die setting corrections can be eliminated completely.

Please note that the technical accuracy of the press itself can greatly affect die setting.  In order to remove this factor from the equation we recommend performing thorough press inspection by our instructions (please see our post on LinkedIn Forging press inspection and forging process repeatability) and correct all problems that are found during the inspection.

• The last but not least reason to implement QDC is a greater opportunity to exercise TPM. The first and mandatory requirement of TPM is a thorough cleaning of the equipment.  In this respect cleanness of equipment in the die mounting area is the dominating factor.  The QDC system allows cleaning of this area as frequently as a die change is performed.

1. Factors affecting die changing time using QDC.

At first glance the only important thing for QDC is how fast you can roll a die set or cassette in and out of the press.  However, there are a number of factors affecting the time of die change.  Those factors are as following:

• Clamping and un-clamping of die sets and cassettes. Manual clamping can take as long as 1.5-2 hours while quick clamps allow doing the same in 5 minutes.
• Easy rolling of a die set or heavy cassette in and out of the press. For that purpose it has to be equipped with wheels. 
• Proper die cart for each scenario. If you consider an assembled die set of a 12,500-ton press it weighs 80 metric tons (176,000 lbs), and a cassette for 1,600-ton press weighs 1.5 metric tons (3,300 lbs).  Naturally, each case and die set design requires different cart designs.
• One of the crucial points that is not directly related to QDC but affects it immensely is the correct preparation of a die set or cassette before it is put into the press. This is an organizational issue that requires following certain techniques and preparing a proper workplace for spare die set or cassette assembly.

1. Our solutions for QDC.      

We can offer 3 scenarios of QDC.

• A whole die set change. Please see the following picture.

In this case a heavy custom-made self-moving cart equipped with Serapid chains or hydraulic cylinders pulls old die set out and goes from the press on rails.  Then the old die set is replaced on the cart with a new die set, and the same cart pushes the new die set into the press.  This scenario has been implemented on a 12,500-ton press in Mexico and allows 80 tons die set change as fast as in 45 minutes.

• A cassette change.

 In this case a lighter cart has its own drive for moving along the rails and rotary platform that is moved manually.  You put a new cassette on the back of the cart, come to the press, pull out the old cassette with a hydraulic cylinder which is part of the cart, rotate platform, and put the new cassette in.

Please note that this solution is good for small and medium size presses only.  A heavy cassette requires incorporating rollers (wheels) for easy moving.

• Individual die change.

This solution is used when it is necessary to make a die repair or replace one die due to a premature failure.  It is simple and relatively inexpensive.  It cannot substitute first two methods but can be very useful as an addition.

A die changing arm is shown on the picture above.  It is moved in and out of the die area manually, and the up and down motion is done by a hydraulic cylinder.

These fixtures have already been installed on over 200 presses and used for changing dies as heavy as 800 kg (1,700 lbs).

• Clamping and un-clamping of die sets and cassettes.

For this purpose we use custom clamps of our own design that require hydraulic pressure for un-clamping only.  The clamping is done by Bellville or nitrogen springs.  During operation the clamping hydraulic port is disconnected from HPU.

In the pictures below you can see various clamps.  These are working on many presses and proven to be very reliable.

 Shown above are heavy forging press clamps.  Mounted on the press frame for lower clamps and on the ram for upper clamps.  The insert on the right shows the design of upper clamps.

 This picture shows clamping of cassettes and the design of the clamping cylinder. 

• There is one more problem that needs to be solved for easy rolling of die sets and cassettes. It is not enough to incorporate rollers (wheels) into a die set or cassette. You need to make sure that the rollers are located in proper places while the die set is in operation.  For this purpose we have developed a die set lifting system that can be operated from the same HPU as the clamping cylinders.

When the die set is in, the lifting cylinders are going down and the rollers are sitting on the top of the cylinders thus bringing the lower surfaces of the die set flash to the table. 

Our experienced design team has already designed and built a large number of systems.  We can easily provide a tailored solution for each QDC case.

We will analyze your requirements and provide a solution with the best ratio between technical advances and investment amount.

As always I would like to thank our Russian partner KB Pressmash Ltd. and personally its President Mr. Dibner for providing invaluable input and design materials for this post.

Please call us at +1-248-224-4756 or send mail to mpslavin@gmail.com