What Are the Operating Requirements?

The first decision you need to make is whether to use an electric or pneumatic-driven gripper. So what are the differences?

• Electric Grippers – generate significantly less operational noise and are well suited for minimizing contaminates into sensitive environments, such as food, pharma and electronic applications. They also provide additional analytical feedback information about their own operating performance or about the part being gripped, such as size and weight. They are easy to install and operate, and connect directly to a control system/PLC with basic standard wiring.
• Pneumatic (or air-powered) Grippers – the traditional standard. They provide faster actuation speed, a smaller footprint and lower cost, but are noisy and generally limited in providing feedback information to the control system in the format of grip part, open or close status. While the initial cost may be lower, significant hidden costs to be aware of include airlines, filters, fittings, valves, compressor, etc. required for connection to a control system or PLC.

Is The Environment Clean or Contaminated?

The two common classes of operating environments must be considered:

• Clean Environment – commonly found in medical, pharmaceutical, electronics and food production operations where only very minute amounts of airborne or surface contaminants are allowed. The aim is to keep any grease or contaminant on or in the gripper from being released into the work environment to avoid contaminating the part or process. Look for a gripper that is Clean Room-certified and approved for Clean Room environments.
• Contaminated Environment – high levels of dirt, debris, oil and grease that are common in automotive, foundry, machining and general industrial applications can adversely affect the internal workings of the gripper and its operation. Here it is critical to protect the gripper from any external contaminants to keep the gripper functioning trouble-free.

Is a Sealed or Shielded Gripper Required? 

Whether operating in a clean or dirty environment, standard or custom-designed shields (or seals) can be used to reliably deflect debris away from the gripper mechanisms in a dirty environment or help keep grease and internal containments from escaping into a clean environment. Shielding may be offered as part of the gripper as standard, optional or as a special request by the end user, who may also add their own shielding as a part of a system integration.

What Are the Key Gripper Specifications? 

When selecting a gripper, considerations for any application should include:

• Appropriate finger length – noting that excess finger length can cause a gripper to bind.
• Grip force – too much will damage the part and too little will drop parts.
• Gripper stroke – too much is wasted operation time and too little will incorrectly grip or release parts. Typically, repeatability is more important than accuracy and becomes a key specification when picking up very small objects or working in a high-precision application where one object is being placed inside another object for assembly.

What Type of Jaw-Support Mechanisms Should I Consider?

The specific application will help to determine which type of gripper jaw-support mechanism to consider. It is important to align the right mechanism to the application to ensure reliable and accurate actuation of the gripper. From an application point of view, common jaw-support mechanisms include:

• High-Impact Loading Application: Use a plain or wedge-type bearing design identified as a large sliding surface contact bearing.
• Low-Friction High-Accuracy Applications: Use a line-contact roller-bearing gripper design.
• Low Air Pressure Precision Applications: Use a point-contact ball bearing design.

What Mode of Power Transmission Is Needed? 

The mode of power transmission refers to the linkage and transfer of power from the internal air piston(s) to the gripper jaws that open and close, producing a grip force. Here are some general guidelines to follow:

• High Grip Force to Gripper-Size Applications require high grip force, but are constrained by the system’s working space and can require a double-sided wedge gripper design that provides a large surface area for transmitting power to the jaws with the power equally divided between both.
• Cost-Effective Parallel-Gripper Solutions. A direct drive design uses a pin or rod to direct couple the piston to the jaw. This is your basic gripper design, a simple, cost effective and easy to shield twin-piston design that requires a jaw-synchronizing linkage.
• Cost-Effective Angular-Gripper Solutions. Many angular grippers use a cam-driven design with direct, synchronized power transmission and bearing-line contact for sending power to the jaws. This has one pivot point per jaw with a minimal number of moving parts. The cam can generate mechanical advantage, resulting in a gripper with high grip force in a relatively small overall package.
• High-Precision High-Repeatability Applications. The smooth synchronous operation of a rack-and-pinion transmission is very popular for precision applications because it produces minimal wear on the drive components for long durability.

It’s important to consider all options and answer all of the above questions thoroughly in order to determine the right size and type of required for the application.If you have any doubts regarding the suitability for a gripper to an application, it’s best to contact the manufacturer.

DESTACO is the industry’s leading global supplier of high-performance automation, workholding and containment solutions. Our product line is comprised of end effectors, grippers, indexers, manual and power clamps, and remote handling. Contact us today to find out more.

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Things to Consider When Selecting a Toggle Clamp

For most ordinary applications consideration of the following points will lead to the proper clamp selection:

• Size and shape of the parts to be held
• Uniformity of part size
• Holding capacity required
• Strength and dexterity of the operator
• Operator’s position (should you use horizontal or vertical handle models?)
• Frequency of operation (should you plan for a temporary or permanent fixture?)
• Time cycle of operation (should you consider a turntable or conveyor set-up if curing time is required?)
• Cycling time and sequence (should you consider air-operated models that can be operated faster and in sequence?)
• Environment (should a stainless steel model be considered?)

Processing Applications

Remember, the same toggle action force multiplying principle can be applied to other tasks besides holding. Certain models can be used to position parts, power fixtures or perform mechanical functions such as piercing sheet metal, staking rivets or locating.

Safety

A certain clamping force will be necessary to safely hold a part. This force is determined by taking the following into account:

(A)  the part material: such as, steel, wood, plastic or glass, etc.

(B)  the surface finish of the part: such as, polished, hard or soft, etc.

(C)  the machining or assembly operation: such as, milling, welding, drilling, bonding, joining or sealing a mould, etc. In order to ensure clamp strength is not compromised, use all the mounting holes provided.

How Toggle Action Works

Toggle action clamps operate through a linkage system of levers and pivots. The fixed-length levers, connected by pivot pins, supply the action and clamping force. Toggle action has an over-centre lock point which is a fixed stop and linkage. Once in the over-centre position, the clamp cannot move or unlock unless the linkage is moved. All types of toggle clamps have this same action, just oriented differently.

What Are the Most Important Toggle Clamp Models?

1. Straight line action clamp

• Forward movement of the handle pushes the plunger into the forward position
• Can be used as a push clamp and pull clamp, locking in two positions
• Holding capacities of 445N-71,200N [100–16,000lbf.]

2. Vertical hold-down clamp

• Handle is vertical in clamped position
• Holding capacities up to 22,500N [5060lbf.]
• Opening angle between 65° and 215°

3. Horizontal hold-down clamp

• Very low profile
• Handle is horizontal in the clamped position
• Holding capacities up to 5,780N [1,300lbf.]
• Opening angle between 90° and 105°

4. Latch clamp

• Convenient one-hand operation due to the patented thumb control lever
• Compact models
• Holding capacities up to 33,300N [7,500lbf.]

5. Plier clamp

• Flexible clamping and fixturing
• Also equipped with quick release lever
• Holding capacities 450N-5,340N [100-1200lbf.]

With over 40 years’ experience supplying the Australian Automotive and Manufacturing Industry with world leading products and expert advice, DESTACO Australia is well equipped to meet your clamping needs. Our insightful engineering experts develop innovative, custom solutions that competitors simply cannot match. Contact us today to find out more.

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