It is now common to build upholstered frames from machined plywood. Parts are nested on a plywood sheet and then cut out using a CNC router. Thermwood is a pioneer in this application and has developed unique technology that efficiently addresses specific issues associated with the process. As a result, Thermwood equipment is used extensively for production machining of plywood upholstery frames.

Click Here for a demonstration video of our Load/Unload process as well as the Roller-Hold Down procedure (Video Size: 58 Megs)

The first consideration is holding the plywood sheet for machining. This material normally has a rough, uneven surface and is often warped making typical vacuum hold-down systems unsuitable.

To address this, Thermwood developed a roller hold-down system using urethane covered rollers operating on a fixed table, moving gantry machine. There are four rollers that hold the sheet to the table for cutting, two in front of the cutting head and two behind. The cutting head travels between these rollers. This system works well for typical plywood, can work for some stacked material and is able to process material that is warped, provided the warp is not excessive.

Although the approach seems simple enough, there are many details that determine the difference between a truly efficient system and one that is plagued with continuing inefficiencies and problems.

The fixed table machine Thermwood uses, besides requiring less overall floor space than a moving table machine, also lends itself to a simple and effective automatic load and unload. A skid of material is placed on a scissor lift in front of the table. To load, the machine gantry moves to the front and a series of vacuum cups attached to the gantry lift the top sheet. The gantry then moves back, pulling the sheet onto the table. After machining, the gantry again moves to the front and a bar located between the rollers drops down in front of the nest of machined parts. As the gantry moves back, it pushes the finished parts off the back of the machine table to a sorting area where the operator unloads and sorts parts while the next cycle is running. This approach is simple, efficient, relatively inexpensive and highly reliable.

Another difference in Thermwood’s approach concerns how the considerable hold down forces from the rollers are handled. Others simply clamp the rollers to the table, placing the full hold-down load on the table bearings and rails. This dramatically increases bearing load, increases wear and decreases bearing life. Thermwood uses a patented approach to eliminate these bearing loads by using a set of wheels that ride under the table edge. The sheet material and table are both pinched between the rollers and the backup wheels under the table. No extra load is placed on the linear rails and bearings, so you get full bearing life.

These CNC routers can be equipped with ultra-high speed acceleration producing high cutting speeds for fast cycle times in high-production environments. Thermwood CNC routers are developed using finite element analysis, all major weldments are fully stress relieved and the machine is laser calibrated for maximum accuracy.

There are other differences in the Thermwood system. While others leave the rollers exposed, Thermwood places a metal shield with emergency stop sensors on each side of the rollers. The moving rollers and forces involved present a real hazard should someone inadvertently move into the working envelope. While no system is perfectly safe, Thermwood’s approach does offer better protection.

Others specify a down spiral router bit to pack sawdust into the cut areas hoping to remove it when the parts are removed rather than engineering a proper dust collector. This adds axial load to the router spindle, reduces cutter life and increases clean-up labor. Thermwood instead supplies an effective dust collection hood between the rollers to remove sawdust, keeping the area cleaner, resulting in fewer problems.

Thermwood also offers an at-the-head tool changer for roller hold-down machines. This patented system uses the simplest mechanics in the industry to quickly and reliably change tools without the need to move to a remotely located carrousel mechanisms and then return. Shorter tool change time mean faster cycle time.

Although these machine differences are important, the real difference is Thermwood’s control. In addition to efficiently running nested programs developed in the traditional way, Thermwood’s control also has built-in computer nesting. To use this you send it part design files in DXF format from any CAD or design software. You can even combine parts from different software in the same nest. The control nests the parts, performs the CAM functions and creates the CNC program, all automatically. You save software cost, the time to learn several software packages (nesting, CAM, Post Processor) and it’s easy.

Nesting at the control has other advantages. If you discover a material defect or broken corner, you can easily nest around it. This is a lot more difficult if you have to go back to the office to remake the nest. You can also use partial sheets left from one job on a new job. At the end of a job, the control prints a bar code label for each piece of material that is large enough to reuse. When you start a new job, simply scan the label and the control nests on these pieces first, then it uses new sheets and finally prints labels for any material remaining. Material savings, especially for shops that run a variety of frames, can be substantial.

If you don’t currently have a design program, you can get a copy of Thermwood’s eCabinet Systems software for free. This software can be used to create three-dimensional upholstery frames and then send the CNC file to the control to nest and machine. The nesting feature in the control even knows how to orient and cut the parts to minimize movement when using roller hold-down, and it’s all automatic.

There are a lot more features of Thermwood’s control that separate it from everyone else and make your production operation better, faster and easier. For more information on Thermwood’s control (Click Here).

Thermwood has pioneered roller hold-down machines, being the first company to use rollers to hold parts for machining. Continuous development and refinement has led to today’s highly efficient and popular systems for manufacturing nested upholstery frames. If you are considering CNC for your nested part applications you owe it to yourself to talk to the technical leader in this area, Thermwood.