Machine Tool Foundations, Indeed Part of Machine Tools

By Niraj M Wanikar, Chief Editor, CNCTimes.com, 2016-05-30 03:00:00

Machine Tool Foundations are more often neglected areas / aspects at many places. While customers are investing millions of rupees in machine tools, the question of investing a fraction of the total investment in making good quality foundation is compromised in many cases.

The most asked question is:

Can we install the machine on the existing floor and at what point does the machine need a foundation?

A foundation is an important part of a machine and it holds the machine rigidly and transfers its loading to the subsoil.

Foundations are critical in maintaining and getting consistent quality / accuracy over a long time of usable life of the machine.

Foundation of the machine allows it to perform at its full design capabilities and to deliver consistent results over time.

Machine tool foundations are very important elements. Machine tool must be rigid under static & dynamic conditions, in order to perform to the desired level of accuracies. Static stiffness produces dimensional accuracy, while dynamic stiffness produces surface roughness and maximum material removal rate of the machine. Foundation plays an important role in providing static stiffness to the machine tool by ensuring the correct level and machine alignment accuracies.

While designing machine tools, it is usual to establish target stiffness of each component or sub-assembly of the structure.

Foundation influences overall deflection of the structure. Hence, it is important to ensure that the threshold values exist for depth of concrete. Reduction in the depth of concrete below threshold values will cause overall stiffness of machine to be reduced considerably.

Alignment critical machines require support from foundation to maintain alignments between machine elements.

Following are important for alignment of critical machines:

1. Foundation Thickness: Stiffness of foundation varies with the cube of its thickness.
2. Stiffer the required support, more the amount of concrete required i.e. the depth of foundation.
3. All machine tool elements must be mounted on the same foundation block.
4. Local soil conditions must be taken into consideration, to ensure the stability of foundation.

Anchor bolt & grouting provides strong rigid support between machine & foundation. Grouting is used to ensure that the voids between machine base and foundation surface are completely filled, and to spread concentrated loads over a larger area.

Foundation and machine tool must become an integral part.

Some of the points to be taken into consideration in installation process are as under:

1. Foundation must carry super imposed loads without failing / crushing.
2. Foundation settlements must be within specified limits.
3. Center of gravity of machine and foundation to be in one vertical plane, as far as possible.
4. Selection of space is also important – is the site subjected to external vibrations, exposed to sunlight, exposed to dust or changes in ambient temperature?
5. Foundation concrete must be of single pouring.
6. Do not connect foundation to existing building foundations, such as one for a building column that supports a crane etc.

Inappropriate foundations will have adverse effects on:

1. Dimensional accuracies of parts.
2. Surface roughness and designed material removal rate.
3. Total designed life of machines.
4. Levelling & alignment of machines.
5. Spindle bearing life.
6. Ball screws and LM guide ways life.

Correct installation is as critical as correct selection of machine tools. The cost that is incurred in making a proper foundation is just a fraction of the investment you make while buying a machine.

This picture will explain how roots are important for holding trees. Roots are a vital part of the tree’s anatomy. They feed, strengthen and anchor the tree. Similarly, foundations are extremely important for holding and supporting machine tools securely. 

Mr. B.P. Poddar is the Vice President of Sales and Marketing at Fatty Tuna India P. Ltd. He has 30 Years of experience in Metal Cutting Machine Tools & Auto Component Manufacturing industry and was associated with German & Swiss Machine tool makers in various technical & management positions. He has been a keynote speaker for many events, written articles for leading magazines/portal and is a member of many leading organizations in the manufacturing domain. He is also on Editorial Board of a leading magazine in Metal Cutting Domain.

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