Yes, but not necessarily in the way you may be thinking.
Designing a product with mechanical motion control often means working with hinges that help control torque. Torque does not necessarily mean friction, though.
Friction hinges and counterbalances, two of the most common solutions in torque-related product design, actually behave quite differently in practice. This distinction trips up a lot of engineers because both involve torque, and both address a lot of the same challenges of lid torque.
Below we’ll explain how torque influences product design, and how friction hinges are only the answer some of the time.
At a glance, here are the key differences between friction and counterbalance hinges:
|
Friction Hinges |
Counterbalance Hinges |
|
|
Goal |
Hold object in place at any angle |
Lift assistance; can hold object at any angle and have opening/closing biases |
|
Free-Stop? |
Yes (stays where you release it) |
Yes, unless customized to do otherwise |
|
The Guts |
Disc friction, omega clips, press-fit pins/washers |
Torsion springs, coil springs, spring cartridges |
|
Example Uses |
Laptops, monitor arms, machine guards |
Grills, medical centrifuges, industrial toolboxes |
Torque hinges are friction hinges, and vice versa.
As you’ve probably noticed, torque (friction) hinges have a more complex design than the type you’d find in the $3 bin at Home Depot. They consist of a spring and a clutch pack or disc in the barrel of the hinge, creating a known frictional force that will hold a lid or screen open in different positions.
In simpler terms, they resist motion.
You can generally count on a friction hinge to have these qualities:
The most obvious example is an adjustable display. A laptop or monitor screen wouldn’t be very useful if it sagged or flopped in the middle of someone’s workday.
Counterbalances are also more complex than your typical big-box store hinge, but take “heavy-duty” to a whole new level. Unlike friction hinges, they actively apply force to assist the movement of a lid or screen. Even a 105 lb. bar gate can feel like 5 lbs. thanks to a counterbalance.
How does this magic happen? Internal, heavy-duty counterbalance springs (torsion, coil, etc.) generate torque that pushes the hinge when someone opens the door or screen. The stored energy that the spring releases helps to balance the load and hold it in place, with minimal effort from the user.
So, to summarize the key traits of a counterbalance, it:
The easiest and most obvious example is a self-closing door or a lid that pops open when unlatched, but there are many other potential uses for counterbalances.
Torque-resistive hinges and torque-generating hinges are two different approaches to largely the same problem. They address many of the same pain points – drifting, unsafe slamming, and general user convenience.
As with many things in engineering, there’s a cost vs. performance battle at play.
Typically, a friction or torque hinge has a lower initial cost. It’s generally only capable of a constant frictional force.
A counterbalance hinge generates torque to counteract the load, and it varies as the load varies. This requires more complex engineering, and naturally more cost.
The main appeal of a counterbalance is how reliable and smooth the experience is – literally – for the user.
This is why counterbalances are best for heavy-duty, high-reliability applications.
In the past, product designers needed gas struts or other components to provide lift assistance. Today’s counterbalance hinges can provide the same boost – or better – in a single more economical device. They’re even capable of integrating a latch to provide a pop-up open – lifting a few degrees, and allowing the user to do the rest.
Anytime an operator needs to routinely open and close a heavy door or lid, counterbalancing tech is the way to go. This allows the user’s required operating force to stay comparatively low, reducing fatigue and boosting efficiency.
On a friction-based hinge, the user is always fighting that movement. There are limited options for the “feel” you can create.
Have you ever owned an old laptop whose screen eventually struggled to stay in the position you want it? Frictional components like monitor hinges wear out over time. Less friction means less support.
A well-designed counterbalance will almost always have a higher cycle life. Your needs will depend on your application, but 200,000 cycles is achievable on the high end. Your hinge manufacturer should be able to test to those numbers before you make any purchase.
A torque hinge is more of an off-the-shelf solution. There are limits to what it can accomplish.
A counterbalance hinge is often custom-made for the buyer’s product. If you can’t find what you need from a friction hinge, a good counterbalance manufacturer often has the flexibility to build something that’ll work.
For example: There's a limit on how much resistance a friction component can generate within a hinge assembly. That could lead to you needing 15 of them so that your product’s lid will stay open. … Or, you could order two custom counterbalances that’ll perform the same work (and last longer).
A pivoting object with 15 hinges on it might also be a bit lacking in the aesthetics department. Reducing the amount of hardware with higher-performing hinges can result in a sleeker, more marketable product.
Your hinge manufacturer may also be capable of helping adapt the design to be more visually attractive. For example, the supplier could integrate the hinge into your lid or housing, where it stays out of sight. This is doable with both friction and counterbalance hinges.
The way you install a hinge dictates how stress transfers through it. The mounting has to support the assembly in a way that prevents sagging.
Most friction hinges are butt-style, so they have very specific mounting requirements. One leaf mounts to the frame, while the other attaches to the edge of the door or lid. Because of this, the load concentration is in a narrow area and the hinge relies heavily on the strength of the material where it’s attached.
If the mounting surface lacks sufficient strength, the repeated resistance force of the hinge can eventually loosen fasteners or cause sagging in a heavy lid.
Counterbalance hinges offer more flexibility in mounting design. Your manufacturer can add custom brackets or mounting tabs to distribute force across a larger portion of the assembly. Instead of attaching only to the thin edge, it can also attach underneath or behind the panel. This makes for a more rigid assembly and reduces stress on weaker mounting surfaces.
Hinges are available in a wide range of torques, typically measured in newton-meters (Nm). This is the amount of force you need to rotate a hinge to a certain angle.
At a certain level of torque, it’s going to be a struggle for the user to move the cover or door. This is where you should pivot to a counterbalance.
The ideal amount of torque for your product will depend on:
We recommend adding a little extra resistance beyond the bare minimum. This helps you account for external forces beyond your control (humans, wind, etc.).
The rule of thumb is this:
When your desired specs hit a certain threshold, an off-the-shelf hinge likely won’t support the product. At that point, a counterbalance hinge will offer the most long-term value – for both you and your own customer.
To learn more about putting counterbalancing and motion control to work in your designs, download this free e-book: