Doesn't the CNC just do all the work?

It's a question I get asked a lot. Someone sees a video of our CNC cutting out a table top and says, "Well, the machine does all the work for you, doesn't it?"

I get why people think that. You press a button, the spindle spins up, and a few minutes later there's a perfectly cut shape sitting on the bed. It looks like magic.

The honest answer is no. The machine does the cutting, and it does it brilliantly. But cutting is only one part of making a good table top or shelf. Here's what actually goes on either side of that button.

Before it cuts a thing

A CNC can't think for itself. It only knows what it's been told, and somebody has to tell it.

Every job starts with a drawing. Sometimes that's one of our standard shelf or table designs. Often it's a customer's own sketch or CAD drawing for a custom table top, with measurements taken in their van. Those need checking and turning into a proper drawing before anything else happens.

Then the drawing becomes a program. That means choosing which cutter does which bit, how deep each pass goes, how fast it feeds, and which order the cuts happen in so the part doesn't move on the bed. Get any of that wrong and you'll find out the expensive way.

We also work out how to fit the parts onto a sheet so we waste as little ply as possible. Good ply isn't cheap, so this matters.

Setting up and running

Our machine is a 10x5 with an automatic tool changer, so it can swap cutters by itself mid job. That's a real help. It still needs the right tools loaded, sharp and set correctly before you start.

Those cutters aren't cheap either. A cheap cutter is around £60, and something more specific runs into the hundreds. We spend a few hundred pounds a month on cutters alone. Laminate is hard on an edge too. A cutter that's past its best doesn't just cut slower, it chips the laminate and leaves a rough edge. So tooling gets changed long before it's worn out, and that's a cost you have to build into every job.

Most of our table tops start life as Garnica poplar ply with the laminate already pressed on (there's more on why we use the materials we use). A board like that has a good face you really don't want to mark. So the sheet has to go down flat, clean and held firmly, and the program has to cut it the right way up.

That's the job of the vacuum bed. A big pump sucks the sheet down onto the bed so it can't move while it's being cut. Sounds simple, but it only works if the bed is looked after. The spoil board on top has to be kept flat and resurfaced now and then, and any gaps let the vacuum leak away. Small parts are the tricky ones, because as the cutter goes through, there's less and less board left for the vacuum to grip. Hold down is half the battle with a CNC.

Once it's running, you don't just walk off and put the kettle on. You listen to it. You watch the first cuts. A cutter going blunt sounds different, and a part starting to lift needs stopping straight away. Years at the bench is what tells you something's not right before it shows.

It's not cheap to run, either. When it's cutting you've got the spindle, the motors, the extraction and that vacuum pump all going at once, and the vacuum pump on its own is hungry. With electric prices what they are, every hour the machine runs shows up on the bill. That's another reason the program and the sheet layout need to be right first time.

When the machine stops, we start

This is the bit nobody sees in the videos. When a part comes off the bed it's cut, but it's nowhere near finished.

The edges go through our curved edgebander. It's a clever bit of kit with laser edge detection, and it'll follow any shape on a full 8x4 sheet. Even so, somebody has to feed it, guide it and check it.

Here's the thing though, an edgebander is only as good as the edge you give it. The banding is glued straight onto the cut edge, so if that edge is rough, chipped or not square, it shows. You get a visible glue line, gaps, or banding that lifts later on. A clean, square edge straight off the CNC is what makes a good edgebanding job possible, which is why the tooling and hold down matter so much in the first place.

After that, every edge is finished by hand. Trimming, easing and checking all the way round until it feels right. No machine does that for us.

Then each piece is checked over, wrapped carefully so it survives the courier, and sent on its way.

So does the machine do all the work?

I think of the CNC like a really good saw. It's accurate, it's quick, and it never gets tired. But a saw doesn't make a table, the person using it does.

After 30 odd years as a cabinet maker, I wouldn't be without it. It lets us cut things accurately and repeat them time after time. The knowing what to cut, how to cut it, and how to finish it properly still comes from people.

So what you're getting isn't a plank of wood from a builders' merchant. It's made in the thickness, size and colour you've chosen, cut on a precision machine, then edged and finished by hand 😊

If you'd like to see the finished article, have a look at our motorhome shelf kits or our table legs.

Keith (aka Chippy)