Tribal knowledge is any unwritten information that is not commonly known by others within a company. This term is mostly used when referencing legacy facts and data that may need to be known by others in order to produce quality products or services.
By nature, tribal knowledge contributes to an "our way of doing things" mentality that creates resistance to change or outside knowledge. Such closed thinking is a death knell to a manufacturing company that is locked into outmoded operating methods when its competitors or entire industries are stressing continuous waste-cutting and productivity improvement in response to ever-growing customer demands.
Productivity improvement is all around us, particularly in multiaxis and multifunction machine tools or simultaneous machining with both static and rotating tools of identical design. Manufacturers are cutting at higher speeds on more rigid, accurate, and flexible machines. They are using advanced cutting tool materials and controls that allow innovative part processing and use programming functions for tool management, gaging, and in-process tool sensing.
They have adopted modular workholding devices, in-process and post-process gaging for workpiece and cutting tool with feedback for tool compensation, and tool condition sensors along with tool identification and management software that interfaces with gaging, storage, tool kitting, and production software.
Though none of these are radical breakthroughs that will displace traditional machining methods for lathes, machining centers and transfer lines, outstanding results can be derived by effectively using these technologies we already have on hand.
This requires going beyond tribal knowledge and establishing standardized, open processes that can be used by all. What?s needed is new thinking for implementing an improved machine utilization strategy.
BEYOND CUTTING ALONE
Process improvement involves more than faster spindles or multi-function machines. It begins with understanding the three functional areas of the manufacturing process ? inventory planning and control, pre-production planning and setup-reduction programs, and in-process manufacturing.
Producing smaller lots more often can slash inventory carrying costs and eliminate shelf-life problems like rust, contamination, and deterioration. For example, instead of producing a single 8,000-unit lot of goods to deplete over a four-month period, producing four lots of 2,000 units each at one-month intervals is more cost effective because it reduces the average inventory from 4,000 to 1,000 units, cuts carrying costs by 75 percent, and reduces shelf-life problems.
However, achieving these savings means increasing setup time by 300 percent. Conventional tooling systems, setup procedures, and production planning are about 20 percent efficient today. With 60 percent of available machine time traditionally used in setups, and idle and stop time absorbing 10 percent each, only 20 percent remains for cutting.
To improve machine and operator efficiencies and minimize machine downtime during tool and part changes, we need to eliminate that 60 percent bite into machine time. A Machine Utilization Strategy composed of these products and services can provide significant cost savings:
1. Quick Change Tooling ? reduces downtime through the reduction of tool change and set-up time.
2. Advanced Cutting Tool Materials ? increases production by utilizing the most advanced cutting tools which enable you to run faster and longer between tool changes.
3. Tool Kitting ? provides all the tooling necessary (including fixturing) to complete a production run or shift of operation.
4. Pre-Gaged Tooling ? eliminates time spent measuring cuts during the set-up process, reduces the risk of human error at the machine control and provides a quick and efficient method for changing worn tools.
5. A specific system designed to facilitate the effective management of cutting tools that is equally effective in controlling other types of inventory and consumable goods.
This manufacturing strategy transfers tool maintenance from the machine tool to the tool room, thereby improving tool maintenance, increasing machine uptime and productivity, and decreasing nonconforming percentages.
TOOL KITTING, PRE-GAGED TOOLING AND
The objective of tool kitting is to eliminate time spent searching for tools and performing on-machine tool maintenance. It pulls together all of the tools required to complete a production run or shift of operation and places them in a tool taxi near the machine.
When tool change is necessary, the process is quick and efficient, permitting more machine run time and increasing productivity. Once all of the necessary tools are fitted with new cutting edges and assembled in the tool taxi, the "F" and "L1" dimensions should be measured and recorded for each tool. This data will later be used for making offset adjustments following tool changes.
Additionally, all tool maintenance is performed in advance of the production run to avoid catastrophic tool failure and in-process tool maintenance. The objective of pre-gaging and pre-production tool maintenance is to eliminate lost production time due to the following:
1. Insert and insert pocket cleaning
2. On machine tool maintenance
3. Measuring cut
4. Manual test cuts
7. Offset adjustments
QUICK-CHANGE TOOLING COMPARISON
Given this improved level of preparation, quick-change tooling that is recognized internationally as ISO standard 26622 can push productivity gains even further. This sort of quick-change tooling consists of two basic components: the clamping unit and the cutting head.
The clamping unit mounts to the machine tool and is the receptacle for the interchangeable cutting unit. When a tool change is necessary, an operator simply releases the locking system, replaces the cutting unit, and locks it into position. Machine downtime is a matter of seconds.
Consider the following example. Assume that the machine has been set up, the first part has been checked, adjustments have been made and the production run is in progress. The Tool Condition Sensor has detected that the finish turn tool (station #8) shows signs of wear and it has a ±.003 in tolerance to hold on the part.
A typical tool-change sequence follows these steps:
1. Open door.
2. Loosen clamp to change insert.
3. Clean insert pocket.
4. Clean insert and remove build-up.
5. Perform tool maintenance.
6. Index insert and tighten clamp.
7. Close door.
8. Make offset corrections to set cutting tool a minimum of .006 in away from finish diameter.
9. Run test cut.
10. Open door.
11. Gage part.
12. Compute math to determine part deviation.
13. Make offset adjustment within the machine tool control for the correct tool number and offset.
14. Close door.
15. Resume production run, or return to step 10 for final offset adjustment.
16. Complete part and gage for accuracy.
17. Resume production run if part is acceptable, or return to step 10 if further corrections are required.
Using quick-change and pre-gaged tooling can change this sequence to:
1. Replace quick-change tool.
2. Make offset correction from pre-gaged data.
3. Close door.
4. Resume production run and place the used tool in the tool caddy. It will then be returned to the tool crib where maintenance, pre-gaging, and tooling for the next production run can be accomplished.
Such a process change takes an 8-minute tool-change sequence down to 30 seconds, saving 7.5 minutes per tool change multiplied by the number of tool changes per year. This can easily gain hundreds of hours of additional run time per CNC lathe or machining center.
FURTHER ECONOMIC JUSTIFICATION
Let?s consider, hypothetically, that we have a ten-station turret lathe. Four stations will remain as static tools and six will be converted to quick-change tooling. Each station that is converted requires four sets of tools, one on the machine, another next to the machine ready to use, and two in the tool crib. Each tool set consists of four OD cutting units and two ID boring bars.
It should be noted that the initial set-up of the machine requires four OD and two ID clamping units, but only one of each type will be needed as backup tooling. Keeping all of this in mind, the typical cost of a quick-change conversion package is seen in Chart 1.
By comparing the economics of this conversion package versus the conventional tool holders and boring bars, the advantages of quick-change tooling becomes evident. Chart 2 calculates the time savings for quick-change versus conventional tooling. These figures are based on national averages within the metalworking industry and will be the basis of our economic justification.
To calculate the potential annual time savings, let?s consider that the ten-station lathe will be in operation two shifts per day for 200 days per year. Also, consider that one set-up is needed per shift and that four tools are changed at each set-up.
Finally, consider that ten inserts per shift need indexing and 25 percent of the tools require trial cuts (see Chart 3). The total potential annual time savings is equal to 27,000 minutes or 450 hours for one lathe. This is equivalent to 56 eight-hour shifts.
NO QUICK FIXES
Advanced cutting tool materials and integrative tool-management systems are also important components of an effective machine utilization strategy, and volumes of information abounds on such products and systems for interested manufacturing companies.
However, it is very important to realize that effectively improving production is not a quick-fix, one-time process. It is both resource- and time-intensive for you and your technology partners. It involves input and commitment from departments outside of production and engineering, such as inventory, purchasing, and IT.
Many benefits await those willing to commence on such a journey. Tribal knowledge, or "the way we?ve always done it", is no longer enough to succeed in your business.
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