Clamping is one of the basic systems in CNC manufacturing. Tools and workpieces are clamped in chucks. There are many types of clamps for CNC machine tools. However, their selection for CNC machining must meet production requirements. If the wrong chuck is selected, the workpiece and tool can be damaged by vibration, broken tool tip, loose material, etc. All these factors can cause errors in machined products. This article discusses tips for selecting a chuck for CNC machining based on production requirements.
Guide to selecting the right type of CNC machining chuck
The CNC machining chuck method should be selected according to production requirements. Typically, the cutting process is done in batches. Products may have simple or complex designs, and depending on these factors, tool inclination, workpiece orientation, etc., may vary. Clamping during CNC machining also affects the development time of the workpiece and the time of the entire production (including preparation and waiting). Here are some tips on how to choose the right type of CNC fixturing system for low- and high-volume CNC fabrication.
Choosing CNC fixtures for low-volume manufacturing
In general, combination fixtures are suitable for low-volume production. Here’s a closer look at what to opt for if you don’t operate on a large scale.
Block/combination clamps
This is a unified terminal system. It has a building block with multiple sockets for connecting different CNC machining tools. It is equipped with a universal standard design and can be adapted to various CNC cutting equipment. In small-scale CNC processes, this type of toolholder is suitable because it reduces the overall production cycle time. The blocks can be rotated to match specific CNC components to the workpiece, positively affecting tool changeover times. This makes these combination clamps ideal for seamless CNC machining. Combination clamps can have two additional components, listed below.
Precision pliers:
These are mounting parts in the combination jig that help align the tools in the jig. They are recommended for use when the clamping force exceeds 5,000 Kgf. They prevent clamping forces from damaging the tool body.
Clamp:
A clamp is a platform between the positioning surface and the workpiece. They are used to precisely position the plastic to ensure proper tool interaction with it during the CNC process.
Choosing CNC chucks for high-volume production
High volume production has longer wait times, longer lead times, and changeover times. Hydraulic or pneumatic chucks are used to shorten the overall production range.
Hydraulic/pneumatic clamps
This is a special type of clamp used to hold tools securely during long production runs. These chucks use hydraulic or pneumatic energy as a power source for the clamping tool. They can withstand higher cutting forces and achieve a high positioning accuracy of the tool and workpiece. Permanent magnet electric grippers are suitable for both types of CNC production cycles.
Electric clamp with permanent magnet
These are magnetic clamps that can be ready to hold tools within 1 second. These clamps reduce clamping time, and thus the time of the entire production, and are suitable for small- and large-scale production with a holding force of no less than 450 Kgf. Selecting fixtures for CNC machining is a task for CNC machine operators. Operators should be trained to make the right choice. However, clamps come in various forms and formats. Let’s take a look at the different types and evaluate how to choose the right type for a specific application.
Clamp types
First, let’s quickly go through the different types of clamps for a basic T-frame CNC machine:
Wood screws
Using wood screws to hold objects to spoilers is not something very complicated. On the contrary, it is one of the basic fasteners for CNC machine tools and, in addition, relatively easy to install. Although it is solid, secure, and provides a solid holding point, it can damage the finish of the spoiler.
Double-sided tape
The double-sided tape method is another simple method of securing workpieces. In this case, cover the storage base with double-sided tape and stick the other side to the work surface. Note that this method will only work if you use high-quality tape and may not work with some materials.
Toggle clamps
Cross clamps provide the fastest system for holding and releasing material of the same thickness. They are easy to use and convenient but have limited scalability because height is a major concern when adjusting.
Step blocks clamps
Step blocks require an additional work area with a T-slot or mesh with threaded inserts. However, this excess hardware provides greater security while overcoming the problem of adjusting hinge clamps. The only possible disadvantage of this chuck is that it cannot be surface machined.
Eccentric clamping system
Eccentric clamps use lateral force to hold the material in place and clamp it to the work area. This allows you to hold the workpiece without placing anything on the magazine, making it easier to reach the surface. However, they require T-slots or grids with threaded inserts, which can be a big drawback for some.
Vacuum cnc machine clamps
Vacuum grippers or vacuum pads provide great versatility for clamping parts on CNC machines. They can be clamped anywhere in the work area, and a vacuum pump will hold the workpiece in place, pulling it into place. They are easy to use, quick to clamp and release, and require minimal setup time. Therefore, the cost of such systems is often a major obstacle.
Summary
The selection of fixtures affects CNC machining productivity. Operators must be trained in the ins and outs of tightening, the different types of tightening, and when to use what. By using this knowledge to supplement CNC machine tool production, operators help increase the productivity, accuracy, and safety of operations.