by Patrick de Vos
Achieving efficiency, productivity and cost savings in machining operations
All machine shops face the same task: converting raw material into finished workpieces. The products must be machined to the specified level of quality, completed in the required quantity and delivered within the desired amount of time. To remain competitive and profitable, shops continually seek the most economical and productive ways to accomplish their work.
Start by viewing the production process as three phases. First is a selection phase, involving choices of cutting strategy, tools and cutting conditions. Next is collection, in which the selected tools and strategies are grouped together in a machining process. Third is realization, which puts the process into action. Here are ten steps shops can use to improve metalworking operations.
1 Intelligent budget control
A common approach to budgeting in metalworking operations is to acquire every element of the process at the lowest price possible. However, it is best not to base tool selection on price alone. Before discussing prices, a shop should consider the desired end results. If a tight tolerance, top quality part is the goal, more expensive precision tooling will be required to machine it.
2 Intelligent handling of constraints
Reducing cutting parameters overall is not an intelligent way to deal with process constraints. For example, changes in depth of cut have a greater effect on the consumption of machine power than changes in feedrate. The combination of decreasing depths of cut and increasing feedrate can improve productivity within the constraint of limited machine power.
3 Tool application rationalization
Machine shops typically make tool application choices one operation at a time, choosing a specific tool to create a certain feature on a part and then picking another tool to machine another different feature.
A contrasting tool selection strategy is to develop a highly specialized custom tool that can create multiple features in one machining pass. The strategy is convenient, but the design and manufacturing of special tools is expensive.
Between the two extremes is an approach that utilizes a standard tool engineered to perform more than one operation, such as multi-directional tooling, which, in the case of Seco’s MDT, can turn the diameter, plunge in to create one shoulder, move across the shaft to cut the groove, then withdraw to form the second shoulder. Even if such a multi-directional tool does not operate at the optimized cutting parameters of the two separate tools, the savings in tooling, programming, tool change time and inventory costs make the multi-directional tool the preferred choice.
4 Complex workpiece approach (group technology)
To expedite the machining of complex parts, a shop can view similar features as a group and choose a tool optimized for a certain operation, such as holemaking, that is repeated on different parts. The optimized tool maximizes productivity and also reduces cost when considering the engineering time that goes into repetitively programming tools for each separate part. The group technology approach also helps reduce tool inventory.
5 Minimal functional workpiece quality
Shops must realize that it is necessary to achieve only the lowest possible workpiece quality that meets customer specifications and functional requirements. There is no need to exceed those requirements. If a part tolerance is 5 microns, achieving 3 microns is a waste of time and money. Higher quality tooling and more precise operating processes will be required to achieve the tighter tolerance. But customers will refuse to pay for such unrequested higher quality, and the job will be a money-losing proposition for the shop.
6 Predictive tool maintenance
Traditional tool maintenance is reactive. When a tool wears out or breaks, it is replaced. That approach, however, generates costs beyond those of the tool itself, including manufacturing process downtime and possible damage to the workpiece. Preventive tool maintenance is a step beyond reactive maintenance.
The useful lives of even identical tools usually vary above and below an average length of time. Preventive tool maintenance is based on replacing the tool before it reaches its shortest expected working life to be sure that the change is made before the tool wears out too much or breaks. That approach, however, wastes tools with a tool life that is at or above average.
7 Tool inventory control
Tool inventory control is different than tool management. Tool management refers to organizing an existing tool inventory and making it available for production. For that task, a variety of automated tool management systems is available. Tool inventory control, on the other hand, is an effort to rationalize and consolidate the number of tools a shop possesses to focus on what is really needed. If tools are not rationalized before being loaded into an automated tool dispenser, the result is simply automated disarray.
8 Practical work analysis
In his 1907 book “On the Art of Cutting Metals,” Fredrick Winslow Taylor noted that some of the activities in a workshop, such as milling a surface, clearly add value to a workpiece, but that many activities necessary for the production of a finished workpiece do not directly add value.
Manufacturers typically believe the best way to reduce processing time is to increase machining parameters. Most shops do not fully recognize the time consumed by activities such as engineering, task that can represent as much as 40 per cent of the total time for a part to travel from drawing to delivery. Unplanned downtime caused by tool failure, quality issues or chip control problems also may be overlooked. When analysing work activities and costs, it is essential to consider all the contributors to part production time.
9 Practical application of optimization
Rarely does a process work exactly as planned, and it is at this point where optimization of the operations in terms of speed, reliability and other factors is necessary. Additionally, most shops also seek to improve ongoing processes. After carrying out the organization and rationalization steps of phases one and two, practical optimization enables a shop to find technical and economic benefits in a combination of feed, speed, and depth of cut that produces the desired results.
10 Intelligent introduction of new technology
Today’s manufacturers face a range of relatively new challenges including mandates for sustainability and environmental protection. Intelligent introduction of new technologies and processes enables shops to fulfil the challenges. Dry machining, for example, permits a facility to reduce the use of coolants, which in turn reduces the potential effects of the fluids on the environment, as well as the cost of safely disposing of them. Growing use of lead-free workpiece materials is aimed at removing the harmful metals from the environment. Improving process parameters and production tooling performance will result in measureable savings in energy expenditures.
As manufacturers utilize the ten simple steps to improve their operations, a fourth phase of the production process involves ongoing internal education. The goal of that education is to ensure shop personnel realize solutions to productivity issues do not always necessitate huge investments, high technology and expanded workforces.
The lessons learned while improving an operation or a family of operations can be reapplied and expanded to include similar situations throughout an entire shop. SMT
Patrick de Vos is corporate technical education manager, Seco Tools
