Holding parts
Most of the 5-axis machines come with a round, square, or rectangular table or plate. They don’t, however, come standard with quick-change workholding ready to go. There are different bolt hole patterns and pins used to locate and stabilize the workpiece. Having to match these locations with each different workpiece adds another cumbersome step in a process that needs to be closely controlled—before cutting even starts. Add the fact that 5-axis machining is rarely used for processing the same part over and over, and the right workholding can be a difference maker.
Specifically, the ability to use a zero-point system as a primary datum locator for all workholding, regardless of if it’s a vise, magnetic clamping or a dedicated fixture, is indispensable for setup reduction.
While zero-point workholding was initially developed and has long been used for setup-time reduction, the system has had great success in 5-axis machining for another distinct reason: access. A standard vise will block the sides of a part and low-profile vises leave sides more open, but grips only along the part’s lower edge. Alternatively, the option to use a zero-point system to clamp exclusively on the underside of the part leaves the workholding hidden—concealed from all these interferences by the workpiece itself—for a freer state of machining. Pulling a part down is also better than squeezing it, because the squeezing process puts stress on the raw material and the material removal process can compound the negative effects of this stress. What’s more, the closer the part is to the table, the higher the risk of collision with the tool or tool body. Solutions include using a longer holder, which only tickles the part, or raising the part off the table. There are many dedicated workholding solutions dedicated to this, even in confined work zones. 5-axis table adapters, for example, allow 5-axis base chucks to be mounted anywhere they are needed to access the table T-slots or grid holes, all while providing a strong foundation. Another example, the UNIFLEX System, is made up of a clamping ball and collar that are attached to the underside of the part or fixture. The part and fixture are then lowered on to either a clamping base or a clamping extension. The clamping collar is then rotated to tighten the six bearing balls on to the main ball. If the part or fixture is warped or needs to be set at an angle, the clamping ball can pivot up to 15° in any direction.
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