Source: Reid Supply

Simple mechanical clamps are often the most straightforward and inexpensive workholding solution for machining and milling. However, clamps and vises tend to get in the way, preventing you from accessing the entire workpiece.

Fortunately, vacuum workholding systems are here to help, particularly if you’re working with thin parts which are otherwise difficult to hold down or secure using a vise or a clamp. The same applies to irregularly shaped but flat parts and parts that are non-magnetic; the latter can’t be secured using a magnetic workholding system.

Vacuum systems work by applying a suction-holding force to the workpiece, thus holding the workpiece in place. The workpiece is typically mounted atop a rigid aluminum grid-pattern plate with holes called the vacuum table.

Vacuum fixtures need a vacuum pump to function, and most rely upon Venturi pumps that take the compressed air and rely on the Venturi effect to create a vacuum. Most vacuum chuck systems and tables have some gasket material that’s installed on top of the vacuum plate to form a seal against the workpiece, thus minimizing loss of vacuum pressure and strong clamping.

While parts with a large surface area are ideal for processing, as they generate the greatest clamping force, there are ways to hold small parts on the top plate as well.

Vacuum Workholding Applications

Using vacuum workholding systems is fairly straightforward and eliminates the need for typical mechanical clamps. You place the gasket, offer the top table, turn on the vacuum pump, and you’re good to go. The vacuum ports might require minor adjustments in position or vacuum pressure depending on the surface area that’s being clamped.

Vacuum workholding is best applicable for machining sheet or plate materials using a CNC mill or a CNC router or for pick and place applications. For example, instead of setting up and machining each workpiece individually, you can machine several parts using a single sheet or plate of your material.

Vacuum chucks will ensure that your workpiece doesn’t shift or move due to excessive work exerted upon the workpiece. Much like a magnetic chuck, the actuation is straightforward, but the vacuum works really well with non-ferrous or any other flat, non-porous material.

Additionally, in contrast to typical mechanical vises and chucks, the vacuum also applies uniform pressure across the workpiece’s entire surface, preventing deflection during machining. Another good point is that any sudden power failure won’t affect the vacuum like it would an electromagnet.

Due to the use of irreversible pneumatic valves in the vacuum workholding systems, loss of power may disrupt the pump, but it won’t immediately affect the vacuum, keeping the workpiece in place. Depending on whether your system has a vacuum leak or not, the vacuuming force might subside over time.

Benefits of Vacuum Workholding

Properly designed and properly set-up vacuum chucks offer several different advantages over other workholding methods. These include:

Ability to Hold Non-Ferrous Materials

A magnetic clamp is, admittedly, one of the simplest and quickest workholding tools to hold a workpiece made of steel or any other ferrous alloy. The magnet offers the holding force necessary to keep the part material in place while being cut. However, this doesn’t work on non-ferrous materials such as aluminum, brass, plastics, titanium, and various composites. Those materials could be held using a vacuum method.

Faster Clamping

Mounting and dismounting workpieces using traditional fixtures takes time, as it involves unfastening the finished part and then fastening the raw stock between each machining cycle. This requires time, even if you employ a quick-release clamp. Not to mention that machinists often have to clean the fixtures.

Vacuum chucks are great in this regard, as they allow you to make a transition from a finished part to an unprocessed blank much faster. Turning the suction off releases the material, which is then replaced with a new stock, after which the suction is turned back on, firmly clamping the material and preparing it for cutting.

More Efficient Cutting

Traditional mechanical clamps can prevent the machine from employing the most ideal cutting path. For instance, when cutting the entire periphery is necessary, clamp workholding arms can interfere with the milling or machining bit. Therefore, it’s necessary to perform some machining, relocate the clamps, and recut the unprocessed segments previously blocked by the clamps.

You can always finish the cutting by using an alternative part configuration with different clamp placement, but this drastically increases cycle time, decreases overall accuracy, and raises component costs. With no external clamps and a well-designed vacuum chuck, the entire item is exposed for a single-setup cut with nothing obstructing the cutter path.

Higher Accuracy

A vacuum chuck secures the component against the vacuum surface, and for high-precision applications, the surface of the vacuum chuck can be ground to a micron level. This results in a very precise securing surface, which yields components manufactured to a higher standard of accuracy.

Higher Throughput

Depending on size, most components are manufactured one at a time. However, if your production requires manufacturing many smaller, identical parts, vacuum chucks enable you to make more components using the same setup.

A single piece of material can be used to nest several parts in the chuck. This is much more efficient than just making one piece at a time, provided that your machine has the capacity.

Less Material Waste

In most cases, using the traditional clamping methods, such as vises and clamps, requires a larger-than-necessary stock to provide clamping space. This is particularly true for manufacturing aircraft parts.

With the actual component dimensions being just a fraction of the required stock, it’s easy to imagine just how much material is wasted, particularly metal, which is then sent back to the foundries. A vacuum fixture greatly minimizes waste and part size because it does not require external clamps. This translates to a cheaper part and possibly greater long-term profit.

Why Choose Vacuum Workholding Equipment?

Source: Reid Supply

Vacuuming workholding systems provide all the benefits of magnetic workholding systems, though they offer less holding force, with added benefits. These benefits mostly come down to working on thinner and non-magnetic materials, which make vacuum workholding worthwhile.

Find vacuum workholding and other workholding solutions from manual clamps to adjustable pneumatic systems at Reid Supply.