Sami Salila examines three examples of how low-profile clamps have been used to get the best out of machining centres.

The effectiveness of a machining centres does not lie in the speed of a machine nor the number of pallets, but in the extent to which the capacity of potential workspace can be utilised, in other words how many workpieces can be machined at the same time.
Designing the free workspace so that you can fill your t-slot table or your columns with most workpieces possible is an equally important factor for time savings and productivity improvement as is the speed of your machine. In order to get the best out of your machines you need effective clamping elements preferably small in size.
OK-VISE clamps function on the principle that when tightened down they expand, simultaneously thrusting the pieces to be machined against the guide and preventing any possibility of play. These clamps are designed to fit between the pieces to be machined and take very little space on the fastening base. Small in size, yet possessing an excellent clamping force up to 9000Kp these clamps guarantee a holding capacity which clearly exceeds the load imposed by machining forces.
Sandvik Tamrock Oy is a globally known rock-bore manufacturer in Finland. Mr Aarre Lehtimaki is in charge of tooling design in their Tampere factory.
"Being flexible and easy to use, the OK-VISE low-profile clamping units have met our requirements in full. Now, with a single fastening operation, three-directional machining is possible, unlike before, when conventional fixturing devices were used. Operators for their part consider speed of use and variability from one fastening base to another being indispensable features. Fastening of workpieces for machining now takes only one third of the time it did previously," reports Mr. Lehtimaki.
Valtra Oy Ab is one of the world's leading tractor manufacturers and part of the AGCO group.
"The FM (flexible manufacturing) system has caused us to develop completely new way of thinking, when planning the fixtures for machining operations is required. Efficient use of the fastening surface with OK-VISE low-profile clamps has meant a significant reduction in tool changes and in the number of pallets required. In order to convince ourselves of the effectiveness of the OK-VISE low-profile clamping units we conducted a number of tests. Along with efficient space consumption they demonstrated conclusively that the machine«s thrust was not sufficient to produce any sideways measurement deviation", explains Mr Iikka Kaipio, production manager of Valtra transmission plant.

One company using the OK-VISE technology to optimise the performance of its CNC machining centres is Denison Lokomec Oy, Northern Europe«s largest producer of hydraulic manifolds. The company caters for a diverse range of marine, mobile, offshore and industrial machinery manufacturers such as the Rolls-Royce marine group, Timberjack and Caterpillar forest machines.
"We began switching from conventional vices and plain clamps to OK-VISE«s low-profile clamps in the mid-90«s and today some 80percent of all pallet fixtures are made using the OK-VISE clamps", says Denison Lokomec process technician, Ilkka Hakala.
According to Hakala, "the company machines black-iron pieces weighing up to 45kilogrammes, in HMC tombstones nearly a metre high. Thanks to the simple but brilliant construction of the clamps, they generate a clamping force of some 9000Kp and the structure itself prevents the workpieces from sliding. There is no need to use side support - a great help when executing a three-directional machining. In addition to the horizontal clamping action, the clamps we use, generate a simultaneous pull-down action to secure the workpieces to the fastening base".
"We typically have 12 to 32 workpieces mounted in one column," says Hakala. "By using the OK-VISE clamps we can utilise the capacity of the machineable area more effectively because the clamps are designed to fit between the pieces being machined, thus leaving more space for workpieces."
He says the clamps also save time because it's not necessary to remove them from the fastening base. "Using a pneumatic bolt driver, unloading and loading of our columns is now accomplished in a matter of seconds rather than minutes. The clamps are extremely reliable and allow us to run the machining centres unmanned during the nights and weekends. That's effectively created a seven-days-a-week production regime."

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Sami Salila is with OK-VISE Oy, Muurame, Finland. www.ok-vise.com