TRIPLE TOOL Life
There are tooling costs, and then there are tooling costs
Historically, running 410 stainless in our fourslide department (more on fourslides here) went something like this; monitoring the produced parts for burrs. As they increase in size, shut down, sharpen the tool, restart / repeat until production run is complete. In this example, the part was a small tube clip .024 thick. During a typical production run of 60,000 pieces, the tool would require sharpening 3 times. Using D-2 tool steel as the current standard, DC-53 and powdered metal A11 tool steel with 10% vanadium was tested (Bohler brand name K294 Microclean).
Data was taken from the end of the coil change, and the operator made the decision as to whether to continue to the next coil or to pull the die out for sharpening. The first study involved the use of DC-53 tool steel. DC-53 is similar to D-2, but the steel is processed to reduce the size of the carbide phases. The graph shows that the operator decided that at the end of the second coil (18,650 hits) that tool needed to be sharpened in order for it to run for another coil. (Burr height was at .0026”)
The second study involved the use of K294 tool steel which is made using a powdered metal process that results in a finer dispersion of the carbide phases. In addition, this alloy contains 10% Vanadium which further stabilizes the carbide phase. Laboratory testing has indicated that this steel has 3X the abrasive wear resistance of D-2 steel. The graph shows that at the end of coil # 5 (57,060 hits) the burr was .0030”. Since the job was for 60,000 parts the operator loaded a partial coil and finished the job. The burr measured .0038” at the end of the run, (61,880 hits), well within customer spec. The job was finished and the tool was sent to the tool room for sharpening before the next run. The tooling was inspected and there were no other issues except normal wear. Standard D-2 steel would have resulted in a sharpening between every 9 to 15,000 hits. The DC-53 steel performed slightly better. The K294 steel performed roughly 3X better, which is comparable to laboratory test results for abrasive wear.
Cost Analysis Assumptions
- Burden rate used in the example is $35.00 per hour
- Average downtime for tool sharpening: 3 hours
- D2 baseline tool required 3 sharpening per run
- Assumes cost to manufacture detail is the same, but added tool life is not included in the cost savings
- Tool repair labor cost is part of burden rate
- Additional operator for teardown and setup time is $25.00 per hour. 1/2 hour per sharpening needed
- 60,000 parts per production run
Cost Savings Summary – 1 Production Run
Cost of D-2 Steel $ 41.54
Cost of K294 Steel $178.29
Additional Cost ($136.75)
Operator teardown and setup:
3 sharpenings x .5 hour labor x $25.00 per hour $37.50
Burden savings due to less down time
3 sharpenings x 3 hours x $35.00 per hour $315.00
Cost Savings per run: $215.75
The run time between tool sharpenings is increased from 20,000 hits to 60,000 hits using Bohler K294 tool steel. The cost increase for K294 is offset during the first run by savings in downtime. Additional savings can be gained due to the increase in the total tool life expectancy. PM A11 tool steel with 10% vanadium is a cost effective replacement for D2 tool steel on abrasive application such as 410 stainless steel.
Additional information on Bohler K294 Microclean can be found online. Testing and article details provided by PTM Plant Manager Paul Hafer PE. Additional testing support provided by Design Engineer Richard Bjornson, Tooling Specialist Gary Hartz and Fourslide Specialist Charles Palitti.