For any manufacturing company to be a market leader and become more competitive, it is vital to reduce costs, increase productivity, maintain quality, and provide timely delivery. These goals demand a comprehensive approach to manufacturing process improvement.
Eliminating operator intervention is an obvious place to start, as human error is the major source of delay and non-conformance in many factories. One simple and easy way to enjoy the benefit of automation and to maximise the performance of machining operations is the use of tool setting solutions.
Tool Setting And Broken Tool Detection
To ensure that the tool can be brought accurately to the component during machining, we need to establish tool dimensions and record this information in the CNC control’s tool offsets. The traditional method was to make a trial cut and measure the result, but this is time consuming and prone to human error.
Off-line pre-setters are another method, but crucially do not allow the tool to be measured in-situ, and therefore fail to account for dynamic effects, including pull-up where the shank settles in the spindle nose, and tool/spindle run-out.
A tool setter can measure the length and diameter of tools during the machining operation, and store the data in the CNC machine. This means that tools can be introduced to the part and cut close to nominal, avoiding manual ‘cut and measure’ activities and operator errors introduced whilst keying height offsets (a major source of crashes in shops).
The advantage of using the tool setter not only limits to just length and diameter measurement to identify a broken tool, but also provides automated on-machine measurement.
On form tools, a tool setter can check for tool projection and stop the process if a tool assembly has been built incorrectly — vibration and chatter can be induced in tools that are over-extended, adversely affecting process capability. It can also check delicate tools for breakage after each cutting cycle to ensure that a single broken tool does not result in further damage to tools and parts. This increases confidence in unmanned machining.
Accurate & Versatile
The growth in on-machine probing is being driven by technology advances that make machine tool setters more accurate, more productive, easier to use, and easier to afford. Tool setting products are referred to as ‘contact’ or ‘non-contact’, depending on the technology they employ.
Contact Tool Setter
Contact tool setting systems require physical contact between the device and the loaded tool. Systems can be further classified as ‘plunger’ style, ‘probe’ style or as tool setting arms (used for turning centres).
Contact tool setters such as the Primo LTS from Renishaw allows users to set tool length, check for breakage, and compensate for thermal growth on a CNC machining centre.
The tool setter is a single-axis, hard-wired product with an integrated interface for straightforward electrical connection: the hardware can be bolted onto the machine table and be operational with no additional set-up required. It is resistant to swarf or coolant ingress and prevents false triggers caused by shocks or vibration. An integrated air blast provides swarf removal when necessary.
Automated on-machine tool length setting is also faster than manual methods, and the tool setter is suitable for use on small to large CNC machining centres. During the machining process, dimensional accuracy is dependent on a number of variables, including tool length and tool breakage. The tool setter monitors these variables automatically, enabling users to compensate for variations which may occur and benefitting the overall machining process.
Non-Contact Tool Setter
Non-contact tool setting systems employ an optical (laser) beam to detect tool presence. Systems can be sub-divided into ‘fixed’ systems (transmitter and receiver units housed within a single assembly), or ‘separate’ systems having individual transmitter and receiver assemblies. Non-contact tool setters can also check for breaks and/or chips on a tool’s cutting edge.
Examples include the NC4 and TRS2 from Renishaw. The former is a flexible laser tool setting system, with a laser tool setting transmitter and receiver units that can be mounted on separate brackets, or as a single fixed unit. The latter is a single-sided, non-contact, laser-based tool breakage detection device.
The NC4 allows non-contact tool setting and tool breakage detection on machines previously unsuitable for such applications. At 30 mm in diameter and 35 mm high, it allows for probing on machines previously unsuitable for larger non-contact tool setting and tool breakage detection systems. Depending on system, separation distances and mounting, it can measure tools as small as 0.03 mm in diameter at any selected point along the beam, and check for breakage.
The TSR2 allows detection of solid tools on all sizes of vertical and horizontal machining centres, all gantry machining centres and multi-tasking machines. The single unit can be mounted outside the working environment, saving space on the table.
Once positioned within the machine tool, cutting tools pass through the TRS2 laser beam in between cutting and tool change operations. When broken tools are detected, the machining process is stopped or a replacement tool is substituted via the automatic tool changer. The setup has potential for scrap reduction and improvements to process control.
Munjal Castings' machines with the contact tool setter installed
saw overall equipment effectiveness (OEE) increased from
50 percent to 76 percent
Munjal Castings is part of the Hero Group, and caters primarily to Hero Majestic in the automotive industry in India. The company has two plants where it manufactures aluminium die cast components using 20 machine tools. The aluminium and zinc die cast company supplies 600 tonnes of castings each month with a turnover of 1.5 billion INR (US$22.9million), and key customers include Hero Motor Corporation Limited, Suzuki Group, Hyundai, Hero Cycles, Nissan, Tata, GM, and Daimler Chrysler.
P L Arora, senior vice president of Munjal Castings, said: “Maintaining quality, cost and delivery within stringent deadlines is our company’s unique selling point, which has helped us to stand apart from others. Daily, we supply 200,000 castings with 150 different component types to the automobile industry.”
A major challenge to overcome was frequent tool breakage, which caused delays in production and led to high levels of scrap and financial loss in terms of materials and time. Sixteen units of TRS2 systems were installed at Munjal Castings to address this challenge. The TRS2 determines whether a tool is present by analysing reflective light patterns and ignores any that are created by coolant and swarf, thereby eliminating false indications of a broken tool.
Machines with the contact tool setter installed saw overall equipment effectiveness (OEE) increased from 50 percent to 76 percent.
Following this, the target is to increase the OEE to 85 percent. Previously, 250 finished components were produced daily on each machine. After installation of the systems, production increased to 270 components per day.
APMEN Metrology & Design, Apr 2017