All You Need To Know About Clamping
Clamping or clamping pressure is a very important concept in engineering and injection molding. It helps to hold the clamping device against the clamping plate, which will allow for an even clamping force on all sides of the mold cavity to create an even, bubble free workpiece.
What Is Clamping Pressure?
Clamping pressure is the clamping force exerted by injection mold clamping devices on a molded part or parts. Clamping pressure can be measured in pounds per square inch (psi) and is an important factor when determining the clamping force required for different injection mold clamping devices.
Clamping pressure controls how much force a clamp exerts onto its mating surfaces when clamped together. This ensures that no air bubbles form between the two halves of a mold during injection molding, creating an efficient cavity filling with little wasted material. This means reduced costs per part produced. The higher the clamp pressure applied by your machine means more overall contact area for each half-mold cavity surface making up less room for any air pockets within the product.
There are five different clamp types depending on what you need: hydraulic, mechanical, vacuum, electrical and pneumatic devices.
The clamping pressure and device will vary depending on what type of material you are trying to clamp, how much it expands from its original state, and if any special features need to be accommodated such as undercuts. A good rule of thumb would be that the clamp should exert at least 1/2 pound more than the expansion due to temperature change or shrinkage of your workpiece.
Clamping pressure is important to have an accurate measurement when it comes down to injection molded parts. Without proper clamp pressure there can be many issues such as warping or misalignment in the final product.
How Does Hydraulic Clamping Work?
This is the most commonly used clamping device with an external source of energy. It works with a piston being forced through hydraulic fluid to exert clamping pressure against your workpiece which is placed between two clamp plates. This type of clamp allows for fast setups and quick tool changes, however, it does require manually adjusting the clamp’s position in order to fill every cavity on the mold uniformly.
How Does Electrical And Mechanical Clamping Differ?
The clamping force in the electrical clamp is electrically controlled by a clamp controller. This allows for clamp forces to be decreased or increased depending if there are any issues that arise with filling every cavity evenly, or perhaps when parts could not be ejected properly because of how thick they were made.
Another method that can be used instead of hydraulic clamps are mechanical ones because they have more accurate control over force levels, but take up space within your machine setup area due to their larger size. The downside to this option would be its slower speed compared to hydraulics when changing out parts or setting up new tools (due to needing time for springs and linkages).
What Is Vacuum Clamping?
Vacuum clamping is a method where the mold halves are held together by either pulling or pushing them with atmospheric pressure. This process does not require any clamp force to sustain clamp pressure, rather it uses vacuum suction action which applies an even clamp load throughout the entire surface of the shot part both vertically and horizontally.
This method is used in clamping thin-wall moldings and is very effective when clamp load uniformity is required. This method can also be combined with other clamp methods such as pneumatic, hydraulic or mechanical clamping to enhance the clamp pressure.
How To Choose The Correct Clamping Method?
The clamping method that is used should be based on the production process, space restrictions, the cost and the load required. Based on these three criteria, an engineer can choose which type of clamping force would work best for their injection molding application. Clamping devices are available in many different forms including pneumatic cylinders, hydraulic pistons or mechanical tourniquet-style clamps.
Pneumatic air cylinders are very popular clamps because they provide quick clamp speeds to high pressures but tend to take more space than other clamp types due to their large size.
Hydraulic piston clamp systems have become increasingly popular over the last decade as smaller form factors enable faster clamp times, and greater control of pressure profiles during cavity filling & cycle time.
With all these options, it comes down to preference and personal experience within the machine setup area when deciding which one would suit best.
