CNC milling machines & conventional mills for every need147
One machine but many variants. A milling machine is an essential instrument for any metal workshop. Fully automated milling machines (CNC machining centres) dominate in the series production sector. Also the knee type milling machine, the universal milling machine, the bed type milling machine or the hobbing machine -to name just a few- have a central role in the production process. The differences concern, amongst others, the design, the position of the milling spindle, the spindle holder (e.g. SK40, SK50), the controlling system (e.g. SIEMENS, HEIDENHAIN), etc. At Surplex you will find a wide selection of second hand milling machines from leading manufacturers such as, MAHO, HERMLE, DECKEL, etc.
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More milling for your money! Bid on affordable CNC mills at auction
The milling machine, or simply mill, is a machine tool for the machining of metal, wood or plastic via chip/layer removal. According to DIN 8589, milling, drilling and turning – together with other production processes – form a sub-group of machining that uses geometrically-defined cuts.
Milling machines, milling tools, the milling process
The milling machine removes material from workpieces by rotating its milling tool at high speed around its own axis while either the cutting tool moves along the desired contour or the workpiece moves accordingly. In milling, the feeding movement is performed perpendicularly or at an angle to the rotational axis of the tool; for drilling, in the direction of the rotational axis; and for turning on a lathe, the milling parts rotate around their own axis while the tool moves along the intended contour.
The main area of application for the milling machine is metalworking. Since at least three feed paths can be used, the variety of complex shapes that can be produced is much greater than on other devices and of much better quality. Applications include creating notches, chamfers, planing surfaces or profiles, complex bodies such as spindles, worm gears and gear wheels, through to heavy-duty milling of solid parts. The fields of wood and plastic processing feature their own specialist versions of milling machines.
Milling machines are used in machining metals by removing outer layers of material
Feeding takes place perpendicularly or at an angle to the tool’s rotational axis
Milling is suitable for complex forms, such as spindles, gear wheels etc.
How does a milling machine work?
From a historical point of view, milling is a relatively new form of processing. The first milling machine for metalworking was built in 1818 and it soon replaced the painstaking and uneconomical processes of planing and filing by hand. The basic forms of milling machines we know today came into existence in the early 20th century, e.g. the tool milling machine by Deckel (1918), the gear hobbing machine by Pfauter (1912) and the groove milling machine by Hurth (1954).
A milling machine is based on a machine body which carries the other components. Heavy-duty machines are also anchored to the ground with a foundation. When it comes to small- and mid-sized mills, the frame and stand form one unit which leads to a high level of dynamic resilience (mono-block design).
Large-scale milling machines are generally designed in a modular fashion, but for any size of mill, the milling head is the key component. It can machine the workpiece on three sides simultaneously. In conventional milling machines, the milling head holds a vertical or horizontal main spindle and a retractable tailstock. In a universal milling machine, the slides and head can be adjusted vertically and horizontally, which enables the workpiece to be machined at any angle required.
The basic forms of modern-day milling machines arrived on the scene in the early 20th century.
Mono-block or modular design (depending on the size of the milling machine)
Conventional mills evolved into the CNC machining centre
Horizontal/vertical milling spindles are used to machine light- to mid-weight workpieces. The workpieces to be processed are placed on a horizontal clamping table. If a cross table is used, a third axis will be available. A common issue with machine tables is that consoles tend to tip over in the end positions. This is why heavy and cumbersome milled parts are clamped onto beds since these extend across the entire surface.
A CNC milling machine features an automated tool-changer and a digital tailstock stroke display, amongst other features. A modern 3- or 5-axis machining centre can produce a large number of parts with narrow tolerances in a short space of time. But even older, conventional mills are still used for one-offs, small series and for training purposes.
One machine, many variants
The various types of milling machine can be difficult to categorise and some device functions overlap those of other devices. However, the following criteria can be used as a rough way of dividing the machines into categories:
Spindle position (horizontal/vertical)
Control type (conventional/CNC)
Machine body (console-, bed-, gantry-design)
Application (e.g. high-speed milling)
Below you will find a (non-exhaustive) list of some widespread types of machine:
Knee Type Milling Machines
A standard milling machine with a fixed-location spindle (horizontal or vertical), movable machine table and adjustable console.
Milling machines in operation
Universal milling machine
A standard milling machine with two spindles (horizontal or vertical), movable machine table and adjustable longitudinal and transverse slides.
CNC processing centre
A milling machine designed for complete, automated processing. Vertical milling machines and horizontal milling machines are available. A further distinction can be made in terms of machine body (console design etc.).
Bed-type milling machine
The securely positioned machine bed prevents tipping. Suitable for heavy and cumbersome milled parts. Conventional or CNC.
Gantry milling machine
The milling unit is guided along a transverse beam between two uprights. Long travel distance and enhanced rigidity. Conventional or CNC.
Copying milling machine
Scans models or templates, transfers the pattern to the milling unit and mills the required contours into the workpiece without any numerical controls.
High-speed milling centre (HSC)
Extremely high cycle and feed rate speed, the resulting chip thickness is substantially less than with other milling methods.
A machining process for gear cutting, as well as cutting splines/sprockets, and offsetting profiles at any desired angle.
Other metalworking machines
Long milling machine, slot milling machine, thread milling machine, engraving milling machine, switching table mill, shift drum milling machine etc.
Distinction made depending on spindle position, control type, machine body, etc.
CNC machining centres are the standard choice for automated serial production
A universal milling machine with pivoting head is indispensable for any type of wood- or metalworking operation
Second-hand milling machines: as good as new
Wood and metal milling machines for industrial and craft operations are usually in service for 20 to 30 years. If regularly maintained and repaired, however, many older machines can continue to work as well as on their first day of operation. Buying second-hand milling machines instead of brand new models can thus be a smart economic decision, but the machine always requires a close inspection. The motors, attachments, slides and thread drives – especially in CNC milling machines – should not exhibit any increased play since this could lead to rippling and inaccuracies during climb milling. When it comes to older models, consideration should also be paid to the software to ensure it is compatible with modern computers and that the licenses are subsequently transferred to the new buyer.
Milling machine auctions: bidding properly
One of the best ways of buying used milling machines is by visiting www.surplex.com. Here you will find large-scale industrial auctions on a daily basis featuring many types of milling machines for sale – from small milling machines to large-scale to large-scale CNC devices – awaiting your online bid. The range covers conventional wood- and metalworking mills through to a range of specialist devices for serial production. You can benefit from many advantages: the machines come straight from a production environment so they do not need running in, they are immediately available in most cases, and best of all: the prices are amazingly low. Place a bid today on a high-quality, affordable machine.
The best-known milling machine brands feature in almost every online auction, including a wide variety of models. Manufacturers include:
DROOP & REIN
If you cannot find what you are looking for on a given day, we recommend subscribing to the Surplex newsletter. You will then be informed when the right milling machine for sale is available in one of our auctions. If you have any general questions or want to know about a particular CNC milling machine for sale or another used milling machine, simply contact our friendly customer care team who will be glad to provide advice.