Vacuum Tables for CNC Machining Centers and Milling Machines

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Finding a method to secure parts on the table of a machining center has been a challenge since before CNC was invented in the 1940’s. For years, there has been a very keen interest in vacuum table or vacuum chuck technology for securing material. Traditional vacuum systems, however, have a lot of limitations that often disqualify the technology for part holding.

Limitations of the Traditional Vacuum Table:

  • Small parts don’t have enough surface area for the vacuum to hold them
  • Parts with through cuts cause the loss of vacuum suction
  • Parts that are not flat either can’t be held or require additional setup time – which is often too long, particularly in short run or low volume scenarios

Successful CNC Vacuum Table Design:

 

Vacuum table design is critical to its ability to hold very small parts securely during the high speed milling process on a CNC machining center
Vacuum table design consists of a the vacuum chuck, an air-permeable sacrificial layer and a powerful vacuum pump.

 

Fortunately, DATRON has developed a unique vacuum table that solves all these traditional vacuum table limitations. Here’s how each of the limitations mentioned above have been overcome.

Holding Small Parts with a Vacuum Table

One of the biggest limitations with traditional vacuum table technology is that parts are often too small or don’t have enough surface area for the vacuum to hold them securely on the table. This exact situation was presented to DATRON when a knife manufacturer contacted us with a requirement for both a high-speed machining center and efficient means of holding knife handles during the milling process. Adding to the challenge was the fact that the product line had many different sizes and shapes and was constantly changing.

 

Vacuum table for CNC machining centers made by DATRON allow for batch machining of many small parts from a single sheet of material.
Vacuum table with a batch of Harley knife handles milled from aluminum sheet material.

 

The vacuum table solution that we delivered was inspired by elements used on vacuum tables for much larger router-type table formats. These large scale systems use a permeable wood fiber board with a large flow vacuum to hold or secure large sheets for machining. Our smaller vacuum table, made from aluminum, features a dense grid of small holes in the top plate. A special thin permeable substrate sits on top to distribute the vacuum evenly and allows us to hold much smaller parts than the conventional or larger scale vacuum tables. In cases, where the parts are particularly small, we have a special version of the permeable substrate with a light tacky surface (kind of like the adhesive on a Post-It note) which is enough to secure the parts. The combination of our vacuum table design, the substrate material and a powerful vacuum pump – all developed to secure knife parts for one customer, has ultimately become an integral CNC accessory for many other customers and different applications in the years that followed.

 

Vacuum tables held aluminum sheet material during machining on a high speed milling machine to produce a batch of Harley Davidson knife handles.
Harley Davidson knife with handles made on DATRON milling machine equipped with vacuum table workholding.

Milling Through Holes on Parts Held with a Vacuum Table

Another common problem associated with conventional vacuum tables is that when you cut through sheet material, you get a loss of vacuum. If open holes allow too much loss of vacuum and the parts let go, often damaging the cutting tool, the machined part and even the CNC equipment. With DATRON vacuum tables, you can have up to a 40% open area and still hold your parts. This of course varies depending on the part, but typically, you have no problem with through holes or profile cuts. This allows for the flexibility and efficiency of cookie cutting each of part out without special tabs, screws or second operations to remove the parts from the sheet. In the case of the knife manufacturer, they would typically lay down a 24” x 36” sheet of 1/8” aluminum, start the machine, and within a couple of hours, they’d harvest over a 100 pieces of finished parts simply by sliding the permeable sheet off the vacuum table. The permeable substrate also allows you to cut completely through the material without machining into the vacuum table top. The swapping out of sheets was usually less than a minute, so almost no production time was lost due to new material change-overs.

 

Vacuum table holding small parts machined from sheet material using a high speed CNC milling machine.
Vacuum table holding small parts that have been milled free from a large sheet of material.

Holding Non-flat Parts with a Vacuum Table

But, not all materials are perfectly flat. Most machinists would never consider holding slightly warped material or objects like an aluminum extrusion with a protruding lip with a conventional vacuum system. However, the DATRON vacuum tables also accommodate a thicker version of the permeable substrate material that we call Magic Board. With a thickness of 1/8”, the Magic Board still allows for adequate vacuum suction while providing the flexibility to mill special pockets or contours into it that accommodate non-flat parts. Milling pockets or cavities in the material can also be a technique to secure or locate a nesting of preexisting parts. Additionally, the added thickness of this substrate also provides reduces the risk of cutting into the vacuum table when using cutting tools like drills or thread mills that need to penetrate through the work piece further than normal.

 

Vacuum table permeable substrate called Magic Board distributes vacuum flow evenly and allows for cutting through holes without damaging the top of the vacuum table.
Vacuum table diffuser (called Magic Board) – an air permeable sacrificial layer between material and vacuum chuck.

Reduce Setup Time with Vacuum Table Workholding

It is common with traditional vacuum table systems to spend a great deal of time setting up a job before getting started with the machining cycle. Dealing with cutting gasket material and having to place it correctly for your corresponding parts is often a very time consuming and tedious practice. In some cases, special custom tables need to be designed with supplementary screws, locating pins, guides, extra clamps, etc. to hold parts down properly or in the correct locations. In cases when a conventional vacuum table will not work, countless hours of applying double-sided tape is sometimes a method used to secure parts. This can create all sorts of issues such as coolant attacking the adhesive, glue getting on parts, or the tape simply letting go.

 

Vacuum table made for DATRON high speed CNC machines provides 24" x 26" of vacuum workholding.
Vacuum table called QuadraMate combines four 12″ x 18″ segments for 24″ x 36″ of vacuum workholding.

 

With the permeable substrate system, usually there is no setup involved. Quite often you simply load in the desired material, turn on the vacuum pump, and start machining right away. This saves many hours of setup time over a production week and reduces part rejection resulting from improper setups. The DATRON vacuum table is a revolutionary and unique design that reduces production time significantly in many applications. It also allows a greater flexibility and in some cases the capability to machine parts that otherwise were impossible. It often reduces part rejection rates and improves part quality. From small thin parts that cannot be mechanically mounted, to parts with free-form outside contours, the DATRON vacuum table offers unique machining advantages that provide a competitive edge.

Here’s a video showing how the DATRON vacuum table works:

Fill out the form below to read a real-world vacuum table case study:

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bill.king@datron.com'

About the Author

Bill King is the President of DATRON Dynamics and oversees all aspects of company operations. He founded the company in 1996 and has been in the manufacturing sector for over three decades. He holds a Bachelor of Science degree in Industrial Design from Humber College in Toronto, Canada.

One thought on “Vacuum Tables for CNC Machining Centers and Milling Machines

  1. That is a really good idea to have a vacuum table to hold the sheet of material in place while it is being cut. I wonder how much suction the vacuum has in order to hold down the material. It must vary with different material. This is because one material might require more suction to keep it in place than other material.

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