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Let’s face it, using a simple mechanical clamp is the easiest and cheapest way to secure a piece of material to cut. You know, the way we usually do it - on a Bridgeport manual mill with steel clamps, threaded rods, and nuts. Although this is simple and effective, it’s not the most efficient way to hold parts for high-production CNC applications. Vacuum workholding systems provide an easier, more secure way to secure materials without the fear of drops or loss of connection while providing complete access to the part.
The Problem with ClampsClamps get in the way and are highly inefficient. They prevent you from accessing the whole part. So, you end up machining around the clamps and machine those missed areas in another setup with different clamp locations. In addition, the time required to remove the finished part and replace it with new material, re-tighten clamps, etc., is also excessive. Time is money.
What is a Vacuum Chuck?Utilizing a vacuum chuck is ideal for holding raw part materials - especially non-ferrous parts machined from large, flat plates. Vacuum chucks are very effectively used in the aircraft industry today to hold aluminum, titanium, and composite components.
Vacuum chucks are available in many forms and sizes. There are grid-style chucks, which can be used for various part sizes, and custom chucks made to hold specific parts.
Witte Vacuum Workholding Systems for Increased Strength and AccuracyWhat if there was an easy way to hold raw material with increased accuracy and strength? A solution without pesky mechanical clamps allows for very rapid part changes. There is, and it’s called vacuum workholding! The principle is relatively simple. A vacuum pump powers a specialized chuck, which holds onto your parts simply by evacuating the air pressure. The resulting force against the part surface equals 14.7 pounds per square inch. For a piece that measures 10” x 10”, that equates to 1,470 pounds!
The Heart of the Vacuum Workholding OperationThe first requirement for a vacuum workholding system is a strong vacuum pump. There are many types available for various applications, including:
- Mid-level vacuum capacity at high flow rates - Commonly used on large routers that hold substantial pieces of wood, particularly for the furniture industry.
- Full vacuum at capacity low flow rates – Used for metal cutting applications, the best vacuum pump should be able to provide full vacuum (defined as 29 inches of mercury) at low flow rates (leakage). This is ideal for most vacuum chucks holding a metal, plastic, or composite part.
- Heavy-duty vacuum pumps - Utilize oil or water to provide lubrication, cooling, and sealing. In addition, there are low-cost venturi vacuum pumps that generate vacuum by using compressed air. Each type of pump will match a particular application.
Chucks & Seals for Unsurpassed Vacuum Workholding CapabilitiesThe vacuum chuck is where the rubber meets the road. If it doesn’t work, the part will end up out of tolerance or, worse yet, fly off the fixture during the cutting. A good chuck must be designed to support the part material to the level of accuracy required, expose all the material to the vac,uum provided by the pump, and have a gasket that will provide a seal between the chuck and the part.
The most common type of gasket used is the O-ring. The O-ring seal prevents the vacuum from escaping and is critical. Without a good vacuum seal, you lose the vacuum to the atmosphere and reduce your part-holding force.
Witte Vacuum Workholding for Small PartsSo, what about holding small parts? Sometimes small plastic, aluminum or even glass parts must be kept for processing. There are unique ways to approach this problem and some reasonable solutions. The key is to limit the cutting forces on the part carefully. Custom vacuum chucks can be designed, and machining processes are written to optimize the manufacturing of small parts.
Vacuum Workholding is Often the Only Feasible “Choice”!Vacuum is sometimes the only solution for certain types of parts. Glass, ceramic, and precision optics production generally use vacuum chucks. Semiconductor wafers are also held using extremely flat vacuum chucks for inspection and other processes.
A vacuum chuck can be made with very high accuracy by grinding the chuck surfaces to very tight tolerances. Porous ceramic and even porous aluminum materials are available in flat or 3D vacuum chuck designs.
Vacuum Workholding Provides the Ideal Solution - In Most CasesVacuum sounds like the ideal work clamping solution for any part, right? Well, not exactly. Some features have too many through holes and window cutouts.a Vacuum only works on solid surface areas to create holding force. For instance, it would be impossible to securely hold a screen with vacuum.
IBAG Witte Vacuum Products – Your Workholding Solutions Experts
Vacuum is a great time and money-saving approach for many machining applications, particularly high-volume jobs. To determine if vacuum is the best solution, each part should be evaluated by an experienced application engineer. If you need any assistance, we’re happy to help!