Tolerances are key to the principle of parts interchangeability that underpins modern manufacturing and assembly, and CNC helps us maintain tighter tolerances than would otherwise be achievable. In this blog, we’ll explain what Computer Numerical Control is and how it helps us deliver consistently high-quality fabricated parts to our customers.

A Brief Intro to CNC

CNC, short for computer numerical control, refers to using a computer to control the motors driving each axis in a machine tool. The motors are fitted with encoders that send position information back to the computer. Using this feedback, the computer drives each axis to a series of positions dictated by a part program.

Machine tools equipped with CNC can usually be programmed at the machine, but many engineers prefer to program offline. Today this is largely automated by CAD/CAM software. This takes the CAD file and generates the sequence of moves needed to produce particular features.

Today, many fabrication machines, including those used in our forming and shaping services, come with CNC. Laser and waterjet cutters, turret punches, and press brakes have powered axes controlled by a computer program. CNC machines are accurate, repeatable, and usually faster than manually-operated versions. The advantages of it for fabricators like ourselves are seen in the areas of:

  • Precision and accuracy
  • Reproducibility and scalability
  • Productivity and efficiency
  • Design versatility and customization
  • Quality control and inspection

Precision and Accuracy

Two of the biggest benefits of Computer Numerical Control are higher repeatability and accuracy than are otherwise achievable. (These two go hand-in-hand because one without the other results in parts that are out of specification.)

On many CNC machines, the limiting factors are machine stiffness and material variability. In some applications, CNC cutting by laser or waterjet, for example, variability is caused by the beam or jet wandering slightly. Machine and tool stiffness are important factors in high-load operations like CNC punching, and, just like a human press brake operator, its bending struggles with variation in spring back.

If you’re wondering how accurate we can be, the short answer is that it depends on many things, like the material, the part design, and the operations needed. For specifics, we suggest you contact us to discuss your requirements.

Reproducibility and Scalability

CNC has greatly improved reproducibility between machines of the same type and even between different types performing the same operation. Our CNC cutting/material processing services provide an example. Whether using a laser or a waterjet, (material permitting), is possible to get almost identical results from both. Likewise, CNC bending lets us move work between machines to suit workload and manning.

Scalability – the ability to flex production volumes up and down – is a very interesting aspect of CNC manufacturing. In the early years of the technology CNC was seen as a way of satisfying small to medium-quantity orders, thanks to the flexibility it provides. More recently though CNC has become the standard control technology for almost all metal cutting and shaping machinery.

Productivity and Efficiency

CNC machines get more done in less time. There’s also less waste, both in terms of fewer scrap parts, because of higher repeatability, and because they can utilize material better. For CNC cutting and punching, for example, software “nests” different pieces to minimize sheet material waste.

However, it is important to take into account the time needed to write and prove a part program. CAD/CAM software has made this relatively fast, but it still requires steps and time that aren’t needed with manually-operated machine tools. For this reason, it’s sometimes faster to make very small quantity orders – 1 to 5 pieces – on non-CNC machines.

Design Versatility and Customization

The ability to coordinate the motion of two or more axes lets us do things that just weren’t possible before CNC. Interpolation is the process of calculating curves, which is something laser and waterjet CNC cutting machines use to great advantage. Both these types of machines can quickly cut blanks in shapes that would be almost impossible any other way.

These increased capabilities give designers more options, and they let us fabricate things that are much closer to what they really want. An additional benefit is fast and easy customization.

Say we’re laser cutting fascias for control panels and the end customer wants an extra hole for an additional light. With a CNC turret punch or other cutting machine, it’s a simple matter to modify the part program and then cut a unique panel just for this customer.

Quality Control and Inspection

The repeatability of CNC means there’s rarely any need for 100% inspection. All that’s required is to verify the program produces the required geometry and then we can run the job or batch.

CNC also has a role to play when using coordinate measuring machines (CMMs). These are effective CNC measuring systems that drive to multiple points to make measurements. As with metal cutting and shaping CNC, these require a part program that dictates movements and positions.

The Future of CNC in Fabrication

Looking ahead, it’s hard to envisage buying many machines that don’t have Computer Numerical Control. For those that do, the controllers themselves are going to get faster and more capable, which will help us boost productivity and turn out even more complex work.

Further out, it seems CNC fabrication equipment is going to develop a level of intelligence – likely in the form of multiple sensors feeding into some form of AI. This will help us further reduce variability and increase productivity.

Bending appears an obvious candidate. In this kind of work, we have to pay attention to sheet grain in order to avoid cracking and minimize spring back variability. With an AI-equipped CNC press brake perhaps the process will be controlled for us to minimize scrap and give us more flexibility in how blanks are cut.

Quality Fabrications With CNC Technology

Producing quality metal fabrication work requires high levels of consistency. We achieve this by using CNC equipment. It helps us meet and exceed the expectations of our customers and create the complex shapes and forms they need. It also helps us minimize waste and maximize productivity, which is something else that benefits us and our customers.

If you’re in the market for high-quality fabrication work – single pieces, large quantity orders, or somewhere in between – we can help. Contact us and let’s talk.