When using dowel construction, your shop’s case clamp may be the company’s unsung hero.


If you are using dowel construction on your cabinets, chances are that a case clamp is the workhorse of your shop. It isn’t a sexy piece of machinery with high-speed tooling or CNC control.



“The job that a case clamp has to do is a fairly simple one,” says Dave Ortmayer of Italpresse USA. “It’s going to draw the joints up tight and square the box — that’s it.”



According to many machinery manufacturers, however, the variations in case clamp technology can result in dramatic production gains and labor savings. Wood & Wood Products sought the expertise of various case clamp distributors and manufacturers to find out what’s new in the cabinet assembly process. From feedthrough to manual, and hydraulic to pneumatic, there are plenty of clamping options out there for any size shop.



The one universal truth with case clamps, obviously, is that they are a must if using dowel construction. While face-frame cabinetry has appeared to take the lead in domestic cabinetry as of late, the dowel construction and frameless cabinet style from Europe have made more inroads into the United States as well. Ase Stornetta of Ritter Mfg. says the advent of nested-based manufacturing has done a lot to phase out the need for case clamps.



According to Stornetta, nested-based routers have a difficult time with horizontal boring. As a result, a supplemental horizontal boring machine is often necessary for cabinet manufacturers who wish to stay with dowel construction. Stornetta says that more cabinet manufacturers are simply avoiding the bottle neck of a separate horizontal boring machine, and instead constructing boxes using dados or mortising.



While the face-frame route can be productive and cost effective, Joe Keilen of Stiles Machinery Inc. says frameless cabinetry and dowel construction has grown in popularity in recent years, and thus the use of case clamps has increased.



Dowel VS. Dado

Keilen says he has seen a trend over the past three or four years, moving domestic cabinet manufacturing more toward the “European-style” products. The construction methods used for this type of cabinets have their perks, Keilen adds.



“There are a few advantages to using case clamps and dowel construction. One, it does create a stronger box. Two, it is more repeatable and reliable. Another is that it is less labor content per box, and is faster to produce per box. The assembly process does not take as long and it is not as cumbersome,” Keilen says.



Gary Wells of Tritec Associates Inc., says that 80 percent of his company’s business is centered around machinery for dowel construction.



“It’s a growing market, no question about it,” Wells says. “I think back on previous woodworking shows, and there is no question from our standpoint that the level of interest and sophistication of people coming to our IWF booth this year to discuss dowel construction was the highest it has ever been.”



Keilen notes that face-frame boxes can be difficult because manufacturers want to build on the face frame to ensure that the front is square and flush. The problem there-in, Keilen says, is that when building the rest of the box, any tolerances go from the front of the assembly to the back.



Stornetta says that while his company has seen more and more dado and face-frame construction lately, it is not always the preferred method of production.



“The most important thing to know is that it is a matter of preference. The cabinet manufacturer needs to determine whether he is going to go with dowel construction or another method of construction. A lot of it is based upon the four-letter word: time,” Stornetta says.



What’s New?

Although case clamps haven’t quite experienced the technological renaissance that other woodworking machines have in recent years, there have been notable advancements in cabinet construction. The developments in throughfeed case clamps, for instance, have allowed more and more shops to seek an automated assembly line.



“I’m working on getting some people away from some really old technology — some of the older, really big manual case clamps that don’t allow you to work on both sides and don’t have a lot of safety built into them — and getting them more into throughfeed clamps,” says Jason Varalli of Biesse America.



Keilen breaks case clamps into two categories: stationary (manual) and throughfeed. With stationary case clamps, the operator manually feeds a roughly constructed box into the clamp, and uses controls to start the cycle. Once the cabinet has been squared and assembled, the operator manually removes the box and sends it on its way.



Where clamp manufacturers see the industry heading is toward a more automated, throughfeed clamping process. In this case, an operator roughly assembles the cabinet components, and feeds the box down a conveyor where it enters the case clamp. The case clamp notes the size of the box, applies the appropriate clamping measures and, upon completion, sends the box out of the clamp to the next step in the assembly process. Some case clamp systems even feature a process that automatically glues or nails the cabinet back during the clamping sequence. By assembling boxes on a throughfeed case clamp system, cabinet manufacturers can drastically reduce set-up time.



“As the cabinets approach the case clamp, the machine takes it in, sets itself, clamps it and spits it out the other side. Nothing to setup. The case clamp sees what is coming and adjusts itself,” Ortmayer says.



The downside to throughfeed technology, according to some, is the cost. Despite the basic nature of the case clamp, adding a throughfeed system can double or triple the price of a stationary (manual) case clamp. As such, the stationary clamps continue to be a better fit for the small to mid-size shops, whereas high-production cabinet manufacturers will enlist the help of multiple throughfeed case clamp lines. It’s all about walking the fine line between cost, set-up time and production capability.



“These conveyor systems could be manual, automatic or semi-automatic, depending on the volume, size of the cabinets and batch sizes,” Wells says. “But there is no question that we’re seeing more interest in throughfeed systems. It still ratchets up the price quite a bit. Any time that you replace a person and take them out of the equation, things need to work pretty flawlessly because you don’t have a brain there to make adjustments.”



Another advancement in case clamp technology, though currently less prominent than throughfeed systems, uses plastic dowels and ultrasonic energy to assemble a box. This process abandons traditional wooden dowels and wood glue and instead inserts plastic dowels into cabinet components. The pressure pad applied to the box then vibrates at nearly 20,000 cycles per second, creating friction that melts a portion of the plastic dowel. Once the vibrating pad is removed, the melted dowel solidifies and creates a weld to the porous wood. The process takes roughly two seconds, according to Keilen who says Ligmatech, along with Titusonic, introduced this technology as an IWF Challengers Award entry.



“When you talk about assembly in the U.S. cabinet industry, it’s really more of an art than a science. And this type of technology makes it more of a science than an art. It takes a lot of the intense labor out of that area and creates stronger bonds — there are a lot of advantages to this type of process.”



Under Pressure

Traditionally, case clamps have applied pressure to cabinet boxes either hydraulically or, more recently, pneumatically. Both methods have their advantages and disadvantages.



Hydraulics provide an increased pressure capability and can be more precise. And although most high-end case clamps were hydraulic in the beginning, according to Ortmayer, they are expensive to maintain and are not necessarily competitive in price to other options on the market. Keilen adds that hydraulic clamps can also have inherent problems, such as oil leaks.

Another technology is pneumatic pressure. Those interviewed claim this option is cleaner than hydraulic methods, but the air pressure of pneumatic case clamps is known to be inconsistent.



“When you are attempting to place a dowel in a hole filled with glue and you push the dowel in too fast you can actually rupture the panel because the pressure the dowel creates can push the glue through the panel or even split the panel,” Ortmayer says. “With hydraulics, you can control the movement speed so that this problem is never an issue. With pneumatics, it is difficult to control the speed compared to the hydraulics.”



One option to combat the downside of hydraulic and pneumatic case clamps, according to Keilen, is the use of electronically controlled clamps. This technology uses electric motors to power the pressure frames and secure the box. Keilen says this option offers increased power and pressure control, but also allows the box to be edge-aligned on the clamp, as opposed to center-aligned, which is the norm on most hydraulic and pneumatic case clamps. When aligned along the edge of the case clamp, the box is more accessible to an operator who may be gluing or nailing the back to the cabinet once it is squared.



The size, shape and number of frames actually applying the pressure to the box have also changed over time. Newer case clamps no longer use a single pressure frame on each side of the cabinet. Multiple frames and interlocking pressure beams (known as lamellar clamps) help ensure that all sides of the cabinet carcass receive even and accurate pressure. The pressure beams move and conform to the size and shape of the box giving added flexibility when assembling a variety of boxes.



“Lamellar case clamps, where you have interlacing beams, seem to be the way that people want to go because there is no pre-setup for different size boxes,” Wells says. “We build both types of clamps, and orders have been 10 to 1 for the lamellar version of case clamps.”



But Wait, There’s More

The obvious application for a case clamp is cabinet assembly. But there are other opportunities to put your case clamp to work — ranging from furniture to drawer box construction.



“We have seen case clamps used primarily in the industrial, or office furniture sectors, for assembling the pedestals of the desk or whatnot,” Stornetta says. “We have seen customers utilizing the case clamps for smaller assemblies, like drawer boxes. We do sell equipment for doweling drawer boxes together. We have seen case clamps used in anything from a 7-inch square box, to a 50-by-100-inch square box.”



Wells, too, says he has seen case clamps used for alternative applications.



“We sold a few case clamps to people who are manufacturing hardwood furniture for colleges,” says Wells. “They’re taking chair parts that are doweled together and putting them in a case clamp. Some people are using case clamps for drawer boxes, and putting multiple boxes in at a time. I think that anyone in the architectural field who has a case clamp has found out along the way that there are things that you can use the technology for that don’t necessarily involve boxes, because it does give you square pressure which obviously has pretty general applications.”



Regardless of the application, case clamps are an invaluable asset to any woodworker looking to piece boards together with dowels. And with many predicting an increased interest in frameless cabinetry in the United States, it appears that case clamps may be a necessity of the future.

Companies like General Casework Inc., Denver, CO, that broke the $2 million mark for sales revenues in 2005, use case clamps to assemble their cabinets.

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