Universal milling machines for metalworking industry
- Versatile metalworking with the universal milling machine
- Areas of application for universal mills
- Universal mill add-ons
- What do I need to know before buying a universal milling machine?
- Buying a used universal milling machine
- Manufacturers of universal mills
The universal milling machine is one of the most important types of cutting tool for metalworking alongside the universal lathe. Also known as universal mills, these machines are widely available on the market in countless versions.
The ‘universal’ part of machine’s name means that it is a versatile piece of equipment and can transform metal blocks into every type of product imaginable. Another key aspect of universal milling machines is the way in which they can be easily extended with every type of tool.
Structure of a universal mill
A universal mill comprises:
- A work table and
- two working spindles
The milling spindles and the milling table itself perform coordinated movements to create the finished product, which can vary based on the design and manufacturer. Generally, the table moves along an X and Y axis, while the spindles operate on the Z axis. Depending on the level of additional tools/attachments, there can also be two further movements: top-quality universal mills can rotate and pivot the table and move the milling head all around the workpiece.
Universal milling machines are available in manual, cycle-controlled, and CNC versions. Even though long-replaced for one-off production in an industrial context by CNC milling machines, there are still a small number of manufacturers still producing wholly manual universal mills.
Differentiating between various milling machine variants
The design of the universal milling machine is not suitable for every application: when it comes to especially large and heavy components, a moving work table is more a hindrance than a benefit. This is why industry came up with the gantry milling machine. These high-performance devices operate by moving the spindle around the workpiece using a gantry guiding system. Other specialist types of milling machine include the bed-type milling machine and the knee-type milling machine.
The universal milling machine is the standard tool of its class and is primarily used in one-off productions, but its computerised controls (CNC) mean that the exact same milling programme can be repeated at the touch of a button. Industry does offer a range of milling machines optimised for true serial production, but those looking to construct prototypes, produce small series, or train staff need look no further than the basic universal mill. Such milling machines are also found in a large number of repair workshops.
In order to reduce wear on tools and enhance precision, milling machines should always be fitted with cooling lubrication. And to ensure the surrounding area does not become soiled, machine housing or partition walls may prove to be very useful. A universal mill also needs effective lighting and long-term efficiency can be ensured by repeatedly recording work results over the course of time for comparison.
Universal milling machines vary greatly in terms of size, producible tolerances, and processing options. The universal design does mean the ability to equip an extensive selection of tools, but a given product cannot always be produced on every milling table while maintaining consistent quality. When choosing a suitable machine, it is worth clarifying the following questions:
- What material will usually be processed?
- How often do series need to be produced?
- How large are the workpieces to be manufactured?
- What tolerance ranges need to be met?
The harder, heavier, larger and more precise a completed workpiece, the higher quality the universal milling machine design needs to be. For infrequent milling process on trial prototypes or fittings, simpler machines will be adequate. If serial quality individual pieces need to be created from solid steel that are highly resilient and precise, the quality of the mill needs to match.
Minimum requirements for producing serviceable products would be:
- Choose a machine made by a renowned manufacturer
- SK 30 or SK 40 tool holder
- Minimum spindle speed of 50 rpm in slow mode – this enable thread holes to be cut
- 3000 rpm for contours
- At least 250 x 700 mm² of clamping surface
These benchmark characteristics are certainly sufficient for producing satisfactory results from soft metals, such as aluminium, bronze or copper, but even steel can be processed to some extent.
Another aspect to consider prior to purchase is the milling accessories available (box cubes, machine vices, dividing apparatus, additional milling tools, etc.), as well as any peripheral devices on offer. Buyer beware: extra costs may be incurred (depending on requirements) that can exceed the cost of the machine itself.
A close appraisal is a must when buying a second-hand universal milling machine and should involve inspection of the guide mechanisms to ensure they do not experience any play.
Electrical issues, on the other hand, are not as critical, as these can generally be fixed on used, manual universal mills without major effort.
It is much more important that all the tracks can be spun by hand with ease without any noticeable resistance on the hand wheel. If this is not the case, worn-out bearings will probably be the cause.
Scratches and dull paint are unavoidable in older used mills, so if a second-hand device is presented in a shining new coat of paint, the buyer should be very cautious. It may point to a painstaking restoration process, but can equally mean the seller is trying to conceal technical problems.
In an ideal scenario, buyers should perform a test run on a prospective second-hand machine with a sample piece and then measure it using a micrometre screw to ensure the machine is capable of attaining the quality desired.
The best-known producers of universal milling machines are: DECKEL, MAHO, EMCO, GROB, KNUTH, KUNZMANN, MAKINO, RAMBAUDI, IXION, and RECKERMANN and finding a universal milling machine for sale from these producers is generally easy.
A newcomer to the field of universal milling machines is OPTIMUM, which is known for its highly affordable universal mills – even when brand new. Entry prices offered by this company for new machining equipment are as low as 2500 euros – an almost unbelievable figure. However, the production quality on these affordable machines is commensurate with their price tag and they are also prone to high repair bills. Other manufacturers of affordable universal milling machines are EPPLE and HOLZMANN
The machines produced by ELMAG, by contrast, are of a noticeable higher quality. Prices start at 12000 euros but they more capable of meeting high industrial standards in terms of performance and quality.
For true professional quality, buyers need to spend two or three times as much on a top-of-the-line milling machine. As such, buying a second-hand universal milling machine from a brand-name manufacturer is a good economical alternative in the majority of cases.