You can get overwhelmed by the different jargon surrounding a new lathe or mill. G-code, CNC, vector files – without prior knowledge of what each stands for, potential buyers can get confused.
Two of the more common acronyms you might encounter are PLC and CNC. Both refer to methods of automatic control, and both are in widespread use across multiple industries in countless machine tools from lathes to milling machines.
However, there are key differences between the two. In this article, we’ll break down some of those differences, talk about how each one is used, and explain how each plays a role in modern machine tools.
What is PLC?
The less sophisticated of the modern control systems was actually invented second. Programmable Logic Controllers originated in the 1980s. A PLC is an interconnected system of I/O switches; essentially, it’s a circuit board that can be expanded as needed to dictate which machines need to be turned on, and in what order.
The programmable element comes in when multiple PLCs are interlinked via a computer system. PLCs have the advantage of being simple and inexpensive. The actual units are small and easily obtained, and the programming is simplistic and easy to learn.
What is CNC?
CNC began in the 1950s, and has experienced exponential growth since the widespread adoption of computerized control systems around the turn of the century. It stands for “Computer Numerical Control.” Operators of CNC-equipped tools use a specialized programming language known as G-code to instruct the machine on the correct sequence of operations. These commands tell the machine tool exactly where to move its axes, at what speed, and with what force.
In addition to controlling movement along three (or more) axes, most CNC systems also allow operators to specify rotation speeds and angles. For example, if you want your spindle to rotate 360 degrees every minute, then you’d enter that command into the software.
CNC is not without its imperfections; each new operation needs to be programmed from scratch, making single-use operations extra work on the front end. However, CNC’s capabilities are nearly limitless. Just about any operation imaginable can be programmed into a CNC machine, and then executed without human interference. CNC is also extremely precise, capable of delivering highly accurate, consistent results even across production runs with thousands of parts.
How are PLC and CNC used?
Both PLC and CNC are widely used throughout industry today. They’re often found together in large manufacturing facilities, but they’ve been adopted independently too.
Industries that still rely heavily on manual labor to operate machine tools might turn to PLC control systems to achieve low levels of automation. PLC is easy to implement, and excels at system-level control – dictating which machines to activate and in which order.
Most modern machine tools can be integrated with PLC controls. Summit’s HBM 110H Horizontal Boring Mill features fully programmable electronics, PLC-equipped and easily run from the control panel.
Despite their many similarities, a shop will choose PLC or CNC control based on the work they will be doing. Due to CNC’s greater flexibility and more powerful programming, some high-end manufacturing facilities rely on fully CNC-equipped machine tools. Most CNC machines look and feel like “ordinary” digital readouts. Many come with conversational programming interfaces, allowing operators without extensive knowledge of g-code to run them normally.
Despite their many similarities, PLC and CNC aren’t as comparable as they seem. For individual machine automation, CNC is generally preferred. Where PLC is used, it does better with specialized machine tools that regularly perform the same task.
PLC in action – the Summit HBM-110H
Boring mills, like Summit’s HBM 110H, are a good example of the utility of PLC for high-end machine tools. The HBM 110H is a boring mill, a machine regularly used for the same specialized tasks, boring and threading holes and centerlines in larger work pieces. That specialization makes the HBM 110H perfect for PLC programming.
The HBM 110H features a multi-axis digital readout, precision hardened and ground bedways, spindle load readout, a centralized, fully automatic lubrication system, and a host of other features designed to provide long-term, reliable performance at the industrial level. With full PLC control equipped with state of the art electrics and a 360-degree built-in rotary table, the HBM-110H is ready for the toughest jobs, up to and including double end boring.
High-end machine tool manufacturers like Summit offer both PLC and CNC-equipped machines. Each has distinct strengths and advantages, and both play a critical role in modern manufacturing.