Swiss-type lathes: characteristics and differences.

Within machining processes, mechanical transformation machines that remove material can usually be grouped as follows: milling machines (or machining centers), lathes, and grinding machines. From these three definitions, we can further specialize the definition according to the machining characteristics. The next division would be whether the machine is manual, MDI (Manual Data Input) or numerical control "at the machine," and CNC (Computerized Numerical Control) with automatic digital control. For this entry, we will focus on CNC lathes since Swiss lathes only exist with CNC control, so the comparison will be between Swiss CNC lathes and conventional ones. So, what is a Swiss lathe?

First, let's define conventional lathes, as they share almost all their principles with manual and MDI lathes. In a conventional lathe, the workpiece is held in the spindle, while the tools remain stationary and are brought close to the material. Although multitasking CNC lathes exist where "live" tools such as solid cutters or drills can be mounted, the fundamental operating principle remains that the cutting tools do not move. Therefore, machining operations other than turning usually do not have the same capabilities as on a machining center (milling machine). This imposes limitations on the types of operations that can be performed on a lathe, especially for small parts, since the way the "live" tools fit into the turret limits the minimum size of the tools, as well as the machining accuracy. Swiss-type lathes address precisely these limitations.

Swiss-type lathes are designed specifically for working with small, complex machined parts, allowing for greater precision and fine finishes on pieces smaller than 32mm in diameter with a 4:1 length-to-diameter ratio, as they allow the tools to be positioned much closer to the workpiece.

Swiss lathes originated in the late 19th century for the manufacture of precision watch parts in Switzerland (hence their name), and are now also very common in the medical, aerospace, and electronics industries, as well as in the production of automotive parts for electric vehicles.

The main advantages of a Swiss-type lathe can be summarized as follows:

• High precision and machining speed: A Swiss lathe has two or more machining spindles positioned for milling operations, enabling more stable cuts.
• Complex machining: The ability to use milling tools on 7 to 13 axes allows for more versatile and precise cuts thanks to a greater number of available tools and multiple spindles working simultaneously.
• Automatic bar feeding capability: Similar to other lathe solutions, bar feeding can be performed through the chuck opening. This increases the workpiece gripping area, preventing deflection.
• Reduction or elimination of secondary processes: The versatility of Swiss lathes allows for a greater number of operations in a single station, eliminating secondary work that would be required on a conventional lathe. Furthermore, bar feeding reduces processing time by eliminating manual tool mounting.

Having said this, we must mention as "disadvantages" that Swiss lathes are limited to working on parts equal to or smaller than ∅32mm, their programming is usually more complex due to the number of tools and simultaneous cuts, and they usually have a higher cost compared to conventional lathes, although this last point is compensated for by the fact that the versatility of Swiss lathes tends to reduce or eliminate secondary processes.

So, when should you use a conventional lathe versus a Swiss-type lathe? The complexity and precision of the work will tell you where a Swiss lathe is best; a conventional lathe is very versatile, but has limits in terms of complexity/precision, while a Swiss lathe isn't designed for large parts.

Types of Swiss lathes:

Swiss lathes don't have "official" types, but broadly speaking, they can be divided into those with one or two opposing clamping points. However, we will use the characteristics of TSUGAMI lathes, a Japanese manufacturer represented by YAMAZEN, as a basis for explaining some of the design options in Swiss lathes.

TSUGAMI Independent opposed gang tool post lathe

Series BW: Independent opposing turrets reduce working time and optimize tool positioning.

TSUGAMI Opposed gang tool post lathe

Series P/B-VR/B-C/BM-VR/SA-II/SS-II/SS-III: Optimized for mass production of 'micro' products such as sensor tips or watch parts.

TSUGAMI Precision gang tool post lathe

Series C: Compact machines with superior precision.

TSUGAMI Vertical gang tool post lathe

Series BV-III: Machines with larger tool space.

We will have TSUGAMI equipment on display at our Silao office where you can evaluate your projects with real cutting tests. Let us help you choose everything you need to implement your requirements, including cutting tools, clamping solutions, sensors, jigs or fixtures, extractors, and pre-wired components—all working upon delivery as turnkey projects. We invite you to contact our machinery sales team by emailing info@yamazen.com.mx or calling 472-7486400 (..01/..02/..03).