It’s difficult to define a small woodshop. Is it one with limited physical space or with only a few employees or perhaps it has gross sales under a certain dollar figure? Maybe the most apt description is that a small shop is one where the owner still rolls up his or her shirtsleeves on Monday morning, knows how to operate every piece of equipment in the shop and is still more connected to actual production tasks than to management functions.
Successful small shops tend to grow and one of the biggest steps forward is adding a CNC router. Making the decision to do so involves more than just crunching numbers. It can even get quite personal. People on the shop floor are immediately going to wonder how such an acquisition will affect their jobs. Will it replace somebody? Who will be trained to run it? Will you be adding staff?
The bottom line is that small shops that manage to justify the investment over time will probably end up adding more crewmembers, because the business can handle larger projects and complete them faster. The quality of work tends to improve, too, because of CNC accuracy. And a shop owner can mention to the existing people on the shop floor that they will almost universally improve their skill set, making them more highly trained and more valuable in a modern woodshop environment.
There are a few ways to go when it comes to adding CNC capabilities. For some small shops, a CNC router is a desktop tool that can carve small cabinet door panels, signage elements or perhaps awards, trophies or gift items for the ad specialty market. Other shops might want to use the technology to refine components that have been reduced (cut roughly to size) with traditional machines such as band saws, table saws and miter saws, and for that they need a midsize bed. And shops building a lot of boxes will probably want a machine that can transform a full 5x5 or 4x8 sheet into usable components.
A timely decision
No matter which of those parameters describe your small shop, CNC routers all share one characteristic: they save time and that is the most common reason for purchasing one. A reduction in rework is another enticement, especially with larger machines. Most CNC router processes are accurate to about 3/1000”, so the parts they create are more precise and uniform. People don’t have to reach for a chisel or sander to make minor corrections.
Nesting (where software automatically arranges the most efficient way that parts can be produced from a sheet of material), tool changing (machines often have several heads that can be automatically programmed) and the lack of need for an operator’s physical presence can also save time. What used to be a painstaking routine that involved setting up a router (installing a bit, setting the depth of cut), clamping on guides or setting a fence multiple times, accommodating dust control and physically dragging a tool across the wood — all of those events disappear with automation. Some larger CNC processes are so automated that the operator can walk away and do other work while the router completes a task that he or she used to do. For example, the machine might spend several minutes releasing a number of parts from a full sheet of plywood and the operator can spend that time stacking or delivering parts or drawing the next component.
One of the big benefits of acquiring a CNC router is that uniform processes can be timed. While five shop employees might mill the same kitchen at five different paces, the CNC router is very predictable. It will always do the same job in the same amount of time and that can be extremely helpful when scheduling projects and workers.
Automated tool changes, combined with the fact that parts can be drawn once in a CAD program and thereafter called up when needed, means that a CNC router can quickly change tasks and that saves time. Standard cabinet sides, backs, door panels, drawer fronts and so on can be stored as files on the computer, so the machine can change over very quickly from one task to another. And a base drawing can be quickly modified for a custom solution when required, such as maybe adding 3” to a cabinet depth.
The physical steps that people take are usually reduced when a CNC router is added: fewer people are walking from one workstation to the next or moving parts or materials to and from several machines — and that saves time.
A CNC’s speed — as in how fast the tool moves in each axis — isn’t always as critical as one might think when looking at CNC routers. The machine’s abilities are usually more important: for example, the size of the bed and the maximum part size are often more essential. Think about what the machine will be asked to do before getting too involved in how fast it can travel. The cutter, the depth of cut and the material being milled will usually place more restrictions on speed than the motors do. Sometimes an older used machine can perform as well as a new model with all the bells and whistles and a shop can save a whole lot of investment capital by buying used equipment. Nowadays, parts and tooling can be purchased online and delivered the next day, so some of the restrictions associated with buying a used machine have given way to online shopping. However, if you’re looking at a used router, it’s a good idea to check with several parts vendors and repair/service facilities to make sure you have more than one option when it comes to finding help.
Training and other costs
One of the misconceptions about adding a CNC router to a small shop is that employees will no longer need to be as good at their jobs or at least as well-trained as traditional woodworkers, so there could be an opportunity to decrease the payroll. In general, the people operating the new machine will need to be just as skilled, only they will have a different set of skills. For example, the ability to pay attention to detail will be just as important and perhaps more so. A lax attitude on a CNC can lead to multiple parts being made the wrong way, while woodworkers doing things the old-fashioned way can often discover mistakes sooner. On a CNC, the key is to verify each process: run one part and check the results, before letting the machine (and the operator) make a large batch.
Real estate can be a huge issue for small shops. Sometimes, a CNC router can actually save floor space because it eliminates one or more other machines, workstations or benches. But, in general, the new machine is going to require more space because it needs to be loaded and unloaded. You’ll also need floor space to store milled parts. And the floor itself can even be an issue: some of the bigger machines can outweigh the capacity of a thin concrete slab or a wooden floor system. Check with the CNC manufacturer before arranging delivery.
Can you get tools sharpened locally or can you train somebody to do that in-house? If so, what costs are involved (sharpening equipment, instruction, time away from another task) and do these justify the investment?
Software can obviously be a bigger issue with used machines than new ones, so a buyer needs to talk with the salesperson about versatility. Sometimes programs become obsolete and you’ll want to be able to update your software package as new options become available.
A lot of machines will only work with Windows, so if a shop is running a Mac that can be an issue. If a new, dedicated computer is purchased, it can often be hooked up wirelessly. If not, a physical cable is a whole lot more efficient than burning a CD or saving to a memory stick and walking into the shop from the office every time you need to transfer a drawing to the machine.
Most shops train two people to draw cabinets and also to run the CNC router in case one goes on vacation or maybe gets the flu. That’s an indirect cost that needs to be considered. Software training is ongoing, but most of it can be done online through self-tutorials. Training doesn’t stop with the machine: the rest of the people on the floor will also need to be retrained as they will no longer be operating several of the traditional machines and will instead be assembling milled parts.
Some routers require 3-phase power or a converter and some of the desktop models only run on 220 volts, so you might need to include an electrician’s bid when you’re figuring out the cost of buying. And if the machine requires compressed air and/or a vacuum system, you might also need to add connections for a new compressor to the electrician’s bid: a CNC can use a lot of volume (cfm) and it takes a decently sized compressor to keep up.
There are some subtle savings in upgrading to CNC. For example, two factors combine to allow a small shop to implement aspects of lean manufacturing. First, there are the efficiencies offered by computer programs that can do very tight optimization (get the absolutely largest number of parts from materials). And, secondly, there is the ability to just pop in a program and make parts right away. Together, these can mean that just-in-time inventory management gets a lot easier, which in turn means that stocking fewer raw materials can free up operational funds and also floor space.
Another advantage to adding the versatility of a CNC router — and this is especially true for small shops — is cross-market ability. The machine can run 24/7, so downtime can be sold to other custom cabinet shops, furniture builders, sign makers and even closet/storage outfits. They can rent just the machine or the machine and your operator. But the CNC can also work in other materials such as foam, plastic and even leather, when it’s equipped with a knife head instead of a router bit. That means a shop can build cardboard or thin wood models for architects, balsa wood kits for model airplane manufacturers, parts for pattern makers and myriad other secondary uses.
CNC technology is constantly evolving and most of the upgrades can be applied to existing equipment. Many machines will allow the woodshop to exchange the single vertical spindle with an aggregate that has two or more vertical, horizontal or even angled heads. This allows a shop to work in more dimensions and add functions such as chamfering. And most machines now do something called interpolating. This means that the tool can essentially guess its way from one position to the next (some programmer somewhere just winced at that simplistic description) and create a more graceful curve or entry/exit solution than a strict, straight route. That can save a lot of sanding.
One of the more exciting technological advances in this field is functional amalgamation. Building on the basic combination of a CNC-controlled spindle, a few leading edge manufacturers are now combining functions into machines that can look very appealing to a small shop. For example, the Piranha FX from Ohio-based NextWave Automation combines a CNC router, a laser engraver and a 3-D printer in one desktop machine. The company says that it’s easy enough for a novice to operate, but it’s still a very serious CNC.
With CNCs, the term controller refers to the desktop or laptop computer or a built-in touchscreen that is being used to run the software program. Some manufacturers prefer that you run their proprietary software, while others invite you to purchase third-party programs. There are a lot to choose from and they change almost daily with new versions, modules and capabilities. Some speak English instead of “computereze,” which can really help the learning curve for new employees. Perhaps the best advice is to find out what packages work with your machine and then investigate all of them online before purchasing. One way to discover how other shops feel about a particular piece of software is to add the word “review” after the name when typing it into a search engine. Pay particular attention to automatic tool management programs: they can be very customized. Make sure you ask if they will do exactly what you need done. And find out if your software will “talk” directly to the company that provided it, so they can work on glitches. That can save a lot of time.
Pod and rail systems have become a lot more popular in the last few years. They are a way of holding parts in place while they’re being milled (as opposed to a flat table or a matrix) and they allow the CNC operator to mill the sides and ends of parts more efficiently. Pod and rail is worth looking into before committing to a system.
The number of axes (most commonly 3 or 5) is a big issue when choosing a machine. A 3-axis CNC will work in the X, Y and Z planes (side-to-side, back-and-forth, up and down), and that can usually handle most tasks in a small woodshop. A more expensive 5-axis head can rotate the way your wrist does, so it can make more complex parts. If your shop makes awards, signage, wooden items such as canoe paddles or tennis rackets, components for another industry and other non-linear products, take a look at what a 5-axis can do.
Stepper motors move in small steps and one generally has to choose between speed and strength when purchasing a router equipped with them. Server motors constantly correct their path so they are generally more precise (and more expensive). Brushless AC servo motors are more up-to-date than DC servos.
A spindle is essentially a motor that holds and spins a cutting tool. In simple terms, it’s like your portable router without the base. They come with brushes (a lot less expensive and noisy) or brushless or AC. The latter require less maintenance and, in general, they’re more accurate. They come with fixed collets (like your router) or else a manual or automatic quick-change. This means the collet opens electrically, rather than you having to reach for wrenches. Manual versions require the operator to tell the machine to change bits and automatic ones (usually used where large volumes of parts are being made) do it without an operator having to be present. Spindles also need to be cooled as they generate a lot of heat and the options are air, compressed air and liquids. Air-cooled versions simply use a fan (either inside or on the body of the spindle). Compressed air generally requires hookup to a compressor, although some larger machines come with one. Ask if you’ll need to upgrade or replace the shop’s compressor to handle the extra load. The third option, liquid, works like the radiator in a car and is generally reserved for high-end machines.
When choosing a spindle, look at both the horsepower (hp) and the speed at which that hp was recorded. If it was determined at 10,000 rpm, it will be less when the tool is spinning at 20,000 rpm. Compare apples to apples. And keep in mind that a CNC router behaves a lot like a small, handheld portable in many ways. For example, deep cuts or dense materials can make a huge difference in its behavior. So let your salesperson know all of the possible scenarios you’ll put it through and not just the most frequent ones before selecting the right CNC for your woodshop.
This article originally appeared in the October 2015 issue.