W&WP February 2004
Case clamps have found a home on the assembly line where they help save manufacturers time and money.
By J.D. Piland
Case clamps have found a home in cabinetmakers' shops, whether big or small. They have proved invaluable when finishing a cabinet case or any type of box, but alas, not all woodworkers have decided they are worth it. Granted, a case clamp can get pretty expensive, some costing close to $30,000 or more, but the productivity benefits help pay for the clamp.
Wood & Wood Products talked to case clamp distributors and manufacturers across the country to see just how much money and time a case clamp could save and how much it could increase productivity.
Why Do You Need One?
Tritec Associates President Gary Wells agrees and adds that if a manufacturer decides he or she wants higher quality boxes and a more finished look, then dowel construction is preferred because a screw can be harder to conceal. Thus, a case clamp is needed.
Because a case clamp can cost tens of thousands of dollars, shop owners must commit to dowel construction to join cabinet cases or boxes. Because the dowel does not have much of a locking mechanism, glue is needed to help set the joint. Once the glue is applied, something needs to hold the box together to let the glue cure. Enter the case clamp.
Woodworkers used to - and still do - use several bar clamps to keep the joints together, but this can become time consuming. Also, if the clamps are bumped, they could come loose - not to mention any pressure marks the clamps may create. A case clamp uses larger clamping plates and disperses pressure evenly, rather than pinpointing it like bar clamps can. And, there are no worries about bumping the case clamp accidentally because the clamp weighs so much it would take a truck to move it.
But those are just offshoots of the real reason to use a case clamp: dowel construction. The glue holding the dowels and panels together needs time to cure. With the case clamp, the box can sit in the clamp without too many hands touching it and possibly messing up its alignment.
Joe Keilen, product manager of material handling for Stiles Machinery, says most woodworking shops will find that the bottleneck in production is in the assembly department. He says that companies should analyze where, or if, a delay is taking place. If the company finds that there tends to be accuracy problems and that the boxes do not come out perfectly square or have to be trashed, a case clamp could be the answer.
"If you are not using a case clamp and there ends up being damaged boxes or a loss in shippable goods, then a case clamp is key because it minimizes error and keeps the box rigid," Keilen says.
First and foremost, they save time. Nicola Giombini, product manager for the Assembly Division of Biesse America, says set-up time is key. Depending on the type of case clamp you decide on, whether manual or automatic, your set-up time could decrease dramatically. A manual clamp may take slightly longer than an automatic clamp, but nonetheless, times will drop because there are no bar clamps to adjust.
The setup is a snap. Place the box in the clamp and either set the pressure plates to the box sides or press a button and the motors do it for you. Some clamps automatically measure the box's dimensions and adjust accordingly. Using a case clamp also frees up workers to start or finish other projects, like installing hardware or the back of the box.
"A case clamp allows the worker to walk around and work on multiple items," Keilen says. "It allows more people to become more aggressive with their glue cure times because it's going to be in the clamp."
The changeover time decreases as well. When the box is done, simply release the hydraulic, pneumatic or electric pressure, remove the box and put another one in.
When considering the set-up and changeover times, the question of how long the case must stay in the clamp inevitably arises. This, however, has nothing to do with the clamp nor the case. It has everything to do with the glue being used, says J.C. Uhling Products President Jeff Uhling. No matter what type of clamp is used, the glue determines how long the box is in the clamp.
"The length of clamping time is still primarily a function of the glue," Uhling explains, saying some glues cure in only a minute while others take 20 minutes or more. There are other things that factor into the amount of time, such as the construction method and whether the case will be handled after it is removed from the clamp. If a manufacturer decides to use staples, nails or screws, as well as glue, to fasten the case, then it can be removed earlier. So, basically, it all depends on the preferred way of assembling the cabinet case.
At first glance, case clamps may seem to be expensive. Shelling out a lot of money could have some manufacturers afraid to invest for fear the clamp would not pay for itself. But as Dave Ortmayer, chief operating officer at Italpresse USA, puts it, the clamp has already paid for itself the first time it enters the shop.
"The payback is strictly a labor issue," he says. "The shop will have to evaluate the amount of output they want to produce. They could do it the hard way or get a case clamp." He adds that even though a case clamp could cost $30,000, it could replace one employee on average factory wages, and then you break even. "For the shops that see the price tag and say, 'I'm not spending that much,' look at what you eliminate with [a clamp]."
Keilen agrees. "In the past, companies used to throw more people at the problem and it didn't really solve anything," he says. "If you [do that], you aren't going to be sure when it will be in the clamp. There will be so many hands it has to go through before it makes it to the clamp," that rigidity could be lost.
Each of the manufacturers and distributors interviewed for this article say there is no definitive way to determine exactly how much time is saved because there are so many variables [glue cure time being one] that factor into making and finishing boxes. However, the rule of thumb from many of the case clamp manufacturers is about 100 boxes per day can be assembled with a case clamp. In a larger shop, that amount of work could require one or two workers manning the clamp, while it would take four to six to do the same amount of work manually, Keilen says.
Each of the manufacturers and distributors interviewed add that if a larger shop is completely automated, an automatic, feed-through clamp is recommended. Ortmayer says that some of these clamps could produce as many as one cabinet per minute, but warns, "The glue isn't really cured all the way, but the box is squared."
In the end, it depends on the production process, the glue cure time and the manpower available.
Small Shop vs. Large Shop
The cost issue is obvious. A smaller shop may not have the money to invest in a case clamp, and if it does, then the payoff may be too far down the road to justify buying one. While there are case clamps that total tens of thousands of dollars, there are some in the four-digit range; more often than not, these are the manual clamps. Plus, generally speaking, the more expensive an item, the larger it is. Case clamps are no exception. Both large and small shops have to take into consideration space limitations.
Because a small shop often works with different-sized orders, the ability to decrease changeover/set-up time is essential, especially if there are only a couple workers on the job. "[Smaller shops] may do 10 different cabinets 10 different sizes; it's just more flexible with a manual," Wells says.
Uhling agrees. "What small shops need to look for is set-up time," he says. "They have to decide if they want to spend 15 to 20 seconds adjusting the clamp or press a button and wait for approximately one minute for the clamp to close."
On the other end of the spectrum comes the larger shop. It may have more money to invest, more workspace and more product volume with less diversity. The case clamp that would suit them best is an automated, often through-feed, clamp. In addition, a large manufacturing shop probably will have its products on a conveyor belt. If this is the case, it is advisable, Stornetta says, to use a feed-through case clamp, which measures, clamps and releases the case in one press of the button.
Supply and Demand
Manual clamps are the biggest market because there are so many small shops, Uhling says.
While the economic downturn of the last three years has not helped sales, Ortmayer and Uhling agree that demand is still pretty consistent. There may not be as much business as before - some manufacturers simply cannot afford a clamp during this economy - but there is still a need and still those who turn to a case clamp rather than bar clamps.
"The case clamp industry is growing quite a bit in terms of demand and number of clamps on the market," Giombini says. Of the manufacturers and distributors interviewed, there are more than 20 different case clamps, some available with custom or ordered options, on the market. He adds there has been a growing demand for case clamps with zero set-up time.
Wells agrees with Giombini, saying more users are going hands-free. "The demand has been fairly steady with us, but we are seeing more swing to automation," he says. "There's more of an emphasis on automatic or semi-automatic clamps. [Manufacturers] are economizing on labor as much as possible. Many companies who have worked with them can't live without them."
Stornetta adds that he has seen some shops use a case clamp on dadoed cases. He also says furnituremakers have used case clamps when attaching end panels to desks because it makes the furniture more workable for assembly.
The Pressure's On
Uhling says there are side pressure-only clamps available on the market. He is adamant about the fact that top pressure is not necessarily needed in general cabinet clamping. "The system 32 method of building cabinets was invented by Europeans whose assembly was more automated and on conveyors. The cabinets were laying down and the joints would be horizontal, and you would need side and down pressure for that," Uhling says.
Top pressure is not needed if there are no vertical dividers in the case. All that is needed is to turn the box vertically and then apply side pressure; gravity takes care of closing the joints, Uhling explains. However, he adds that when making a box with vertical partitions, pressure from both axes is required to close the joints.
Despite the debate over axes pressure and whether automatic or manual, whichever case clamp you decide to purchase for your shop has a high probability of paying off in the long run.
As Giombini says, "[Manufacturers will] find their efficiency increases and they save on labor because there is no one that has to pull the cabinet out of the clamp and hold everything together. There is higher quality because there is nothing bumping around and there is less space wasted because the machine can do everything."
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