Clamping for CNC Machining: How to Select Suitable Type of CNC Machine Clamps

Automation and autonomy are two of the most significant advantages of CNC machining. However, it needs to be paired with the proper setup to minimize manual intervention. Clamping is one essential element in the setup that ensures that the workpiece is held securely and tightly. When done correctly, proper clamping will dampen vibrations, improve the quality of machining, increase safety, and reduce the cost of production.

However, clampings come in various forms and formats. Let us look at the different types of clamping and how to select the right type for a specific application.

Types of Clampings:

Let’s first quickly go over the different types of clampings for a basic T-slot frame CNC machine:

1. Wood Screws:

Securing the workpiece to the spoiler board using wood screws is no rocket science. It is one of the most basic CNC machine clamps and is comparably easy to set up. While it is strong, secure, and offers a set fixing point, it can damage your spoiler board surface.

2. Double-Sided Tape

The double-sided tape method is yet another simple way to clamp your workpiece. Here, you need to cover your stock base with some double-sided tape and secure the other side onto the working surface. Do bear in mind that it will only give results if you use high-quality tape and may not prove to be effective for specific materials.

3. Toggle Clamps

Toggle clamps offer the quickest clamp and release system for securing stocks of the same thickness. They are easy to use and convenient but have limited scalability as height presents to be a significant issue during adjustments.

4. Step Blocks

Step blocks would require an extra set up of a T-slot working area or a threaded insert grid for usage. However, this different hardware offers additional security while overcoming the adjustability issue of toggle clamps. The only possible drawback of this clamp is that you cannot surface treat the part you are working on.

5. Eccentric Clamps

Eccentric clamps use lateral forces to hold the stock in place and clamp it to the working area. As a result, you can secure the workpiece without putting anything on the store, thereby gaining greater access to the surface. However, they require T-slots or a threaded insert grid which can be quite an inconvenience.

6. Vacuum Clamps

Vacuum clamps or vacuum pads offer immense versatility to clamp your workpiece on the CNC machine. These vacuum pads can be attached to any spot on your working area, and the vacuum pump will hold the workpiece by sucking it into place. They are easy to use, quick to clamp and release, and require minimal setup time. That being said, the cost of this clamping system is often a major deterrent.

How to Select the Suitable CNC Machine Clamps

What we have discussed so far are the most basic types of CNC clamps. However, when it comes to large-scale manufacturing, the clamps used can differ depending on the workpiece, batch size, CNC machining speed, etc.
Let us take a look at how we can select the CNC machine clamp depending on the volume of production:

CNC Clamps for Low Volume Production

For low-volume production, modular clamps can be handy. These may contain:

  1. Building Block / Combination Clamps: These are machine tools with a standardized design, different functions and specifications, and variable sizes for clamping purposes.
  2. Precision Flat Pliers: These help in aligning the tools to the clamp. They are highly recommended when the clamping force exceeds 5000Kgf.
  3. Clamping Base: This is a flat plate that is set between the positioning surface and the workpiece.

CNC Clamps for High Volume Production

For high-volume production, special clamps need to be put together with the following:

  1. Hydraulic / Pneumatic Clamps: These special clamps employ hydraulic or pneumatic components to help position, support, and compress workpieces.
  2. Electric Permanent Magnet Clamp: Such clamps use permanent magnetic materials to produce a magnetic force for clamping the workpiece into place. They are useful where the clamping force is more than 450Kgf. These clamps can also be used for low-volume production.
  3. Clamping Base: It offers a smooth base that grants a productivity boost for production on tight cycles.

Final Words

The selection of clamps affects the efficiency of CNC machining. Operators must be trained regarding the ins and outs of clamping, its various types, and when to use what. With the use of this knowledge to complement the production by the CNC machine, the operator will be contributing to the productivity, accuracy, and safety within your operations.
Use the guide above to make smarter and well-rounded decisions on the clamping mechanism that suits your production and manufacturing requirements. With the right care and consideration, you will notice fewer instances of downtime, error, loosening of the workpiece, the adverse impact of vibration, breaking of tooltips, etc.


Peter Jacobs is the Senior Director of Marketing at CNC Masters. He is actively involved in manufacturing processes and regularly contributes his insights for various blogs in CNC machining, 3D printing, rapid tooling, injection molding, metal casting, and manufacturing in general.

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