The document discusses redesigning the structure of a main spindle box for a machine tool using polymer concrete instead of cast iron. It summarizes the process undertaken, which included static, dynamic, and thermal analysis of the original cast iron design and redesigned polymer concrete design. The analyses showed the polymer concrete design had higher natural frequencies, better damping performance, and a 50% reduced mass compared to the original cast iron design while still meeting structural requirements. The document concludes the redesign successfully demonstrated the feasibility of using polymer concrete for machine tool structures.

1. Submitted by: Patel shivam

2. 1. INTRODUCTION
International of mcompetition in machine tool manufacture demands flexibility, high
quality, reaction to the market demands and low costs. Therefore the processes and
machines are designed with modular structure. A main spindle box could be such a
module achine tool.
The most important factor affecting machining accuracy is an accuracy of
the machine tool itself resulting from low stiffness and damping ratio of machine tool
structure. In this paperthe feasibility of applying new material is studied in order to
improve static and dynamicperformances of the structure to desire level. The new
design of a main spindle box structure is made of polymer concrete instead of cast iron
structure [1, 2, 3].
Polymer concrete consists of a mineral filler and a polymer binder. When
sand is used as filler, the composite is referred to as a polymer concrete. Generally,
any dry, non-absorbent, solid material can be used as filler [1, 2, 3].
The sand and the fillers are cheap and natural materials available for easy
use. The overall process of production of polymer concrete is performed on room
temperature and recycling of the materials is much easier than cast iron. Also, the
control of the properties of polymer concrete may be much easier and less costly in
comparison with cast iron. As a results of the above and some other advantages
(flexibility of the design, short development time, simple and less costly production
process) the overall competitive advantages of the company may significantly improve
[1].

3. Table 1.
General Characteristics of Constructive Materials

4. 2. REDESIGN OF SPINDLE BOX WITH POLYMER CONCRETE
The aim of this investigation is the possibilities of use of polymer concrete in building
machine tools structures. For that purpose, the NC lathe Mazak QT 10 headstock’s
housing is completely redesigned and polymer concrete constructive material has been
chosen and applied.
The available references [1, 2, 3] have shown same examples of use of
polymer concrete in substitution of cast iron in the design of machine tool beds. We
have decided to investigate the possibilities of the use of polymer concrete in main
spindle housing design due to the more demanding requirements connected with the
dissipation of temperature, damping and high accuracy of the structure. To be able to
redesign the original housing for the purpose of material substitution, we have
performed static, dynamic and thermal analysis of the structure.
The differences in the material properties (table 1) have initiated an iterative
process of redesign with the aim to achieve properties of the original design. Both
models, of original and redesigned housing are shown on figure 1.

5. a. Original b. Redesigned
Figure 1. Models of main spindle housing

6. 3. THEORETICAL AND EXPERIMENTAL STUDY OF NEW DESIGN
We have performed wide numerical and experimental investigations of static, dynamic and
thermal behaviour of original and redesigned housing, part of which are presented in this article.
3.1. Statical Modelling and Analysis
Modelling and processing of housing were performed with the use of ALGOR
and I-DEAS commercial packages [1]. Figure 2 shows maximal principal stresses of both
models. Comparative analyses of the statical characteristics (displacements, Von Mises,
Maximal Principal Stress, Mass and Young’s module) of both housings (original and
redesigned) are shown on figure 3. Despite worsening of Von Mises and maximal Principal
Stress the new design satisfied the limits. We have reduction of mass of redesigned housing
for approximately 50% in comparison with the original design which strongly recommend
the use
of polymer concrete [1].

7. a. Original b. Redesigned
Figure 2: Maximal Principal Stress of Models

8. 3.2 Dynamical Modelling and Analysis
We have used the same models, developed with ALGOR and I-DEAS,
for dynamic analysis of both housings [1]. The comparative analysis of Eugene
frequencies of both models is shown in figure 4. As we can see the Eugene
frequencies of polymer concrete design are twice higher then those of cast iron
design which represents certain improvement of the design. Figure 5 shown
comparative analysis of the experimental data of the damping ratio of both
designs. The results show superior performances of polymer concrete housing in
comparison with cast iron structure [1].

9. Figure 3. Comparative Analysis of Statical
Characteristics

10. Figure 4. Comparative Analysis of Dynamical
Characteristics

11. Figure 5. Comparative Analysis of Experimental
Damping Ratio

12. While two types of aggregate, ocean sand and Sierra Nevada
pea gravel, are fed into the hopper of the mixer, a pipe mixer
adds blended polyester resin. A screw-type auger thoroughly
mixes these materials then feeds them into the slip form paver
for placement.

13. After placing the overlay, workers use
a nuclear density tester to test its
compaction and density. Compaction
on this job averaged 99% to 100% of
the standard, exceeding the minimum
specifications of 97%. The overlay also
was tested for polyester resin content.
Results showed a content of about 11.05%.

14. Before choosing a resin binder, check its specifications
carefully. A good binder should have:
• A low viscosity so it’s easy to mix, place, and finish (viscosity can be varied
somewhat to accommodate different applications methods)
• A 15- to 45-minute gel time to give workers enough time to place and finish the
overlay before it cures
• No solvents or ingredients that can evaporate during curing and cause
shrinkage cracking
• A minimum bond strength to concrete of 250 psi
• A compressive strength capability of more than 5000 psi
• A tensile elongation of at least 30% and a tensile strength of more than 2000 psi
(both indicate good flexibility and resilience) Resin binders having these physical
properties can produce polymer concrete overlays with life expectancies of 20
years or more if the overlays are properly installed

15. Mixing polymer concrete
Poor-quality polymer concrete overlays often are the result of inaccurate
proportioning and inadequate mixing of the binder components and aggregate. Mixing the
binder components at the ratios specified by the supplier is critical. Once the components
are mixed they start a chemical reaction that continues until the polymer concrete hardens.
Any variation of the mixing ratios can result in a soft, uncured overlay. Thorough mixing of
the binder components also is important. Failure to mix the components completely can
result in a non uniform overlay with soft and hard areas.
If the premixed method of overlay placement is used (described below), aggregate
must be added to the mixed polymer binder. Again, attention to specified mix ratios and
thorough mixing are necessary to ensure uniformity. Polymer concrete components can be
batch-mixed in a convention a concrete or mortar mixer.
However, better quality control is possible by using a machine that automatically
proportions, mixes, and dispenses components. This ensures mixing accuracy and
eliminates batch-to-batch inconsistencies.
The machine should be carefully calibrated and the calibrations should be checked
frequently during machine use.

17. Two methods are generally used to apply polymer concrete overlays:
Premixed or slurry method—In this method, the binder components and aggregate are
premixed to form a polymer concrete which is then spread over the deck at the required
thickness. The mixture should contain an ll% to 14% resin content based on aggregate
weight. Using a trowel, bull float, or vibrating screed, apply the mixture over the primed deck
surface to meet specifications for compaction ,surface profile, and finish.
Use screed rails to establish a specified minimum application thickness.
Because polymer concrete has rheological properties different from portland cement
concrete, finishing tools may have to be modified somewhat to better handle
polymer concrete. Mechanical screeds designed to place polymer
concrete are available.
Immediately after placing the overlay, broadcast additional aggregate
onto it at a rate of about 2 pounds per square yard or until no wet spots are visible. The
aggregate adheres to the wet binder, forming a nonskid surface. Sweep away any un
bonded aggregate after the overlay cures.

18. Curing
A polymer concrete overlay cures much faster than a conventional portland
cement concrete overlay. But if polymer concrete isn’t allowed to cure
sufficiently before the overlay is opened to traffic, damage can result. Curing
time varies depending on temperature conditions and type of polymer used.
Generally, the warmer the ambient temperature, the shorter the cure time. At 95°
F, the overlay is ready to accept vehicle traffic in 1 to 3 hours; at 75° F, 2 to 6
hours is required.
An easy way to test for sufficient curing is to poke the overlay with a
screwd river. If the screwd river doesn’t leave a mark, the overlay is probably
ready fortraffic. However, have the project engineer or a representative of the
resin binder supplier confirm overlay readiness before reopening the bridge
deck.

19. Proven performance
Investigation into the use of polymers for preparing polymer concrete
and mortars began more than 30 years ago. But early attempts at using polymers for
bridge deck overlays met with limited success due to problems with material
properties and mixing and installation methods.
Most of these problems have been solved. In fact, the U.S. Department of
Transportation removed some polymer concrete systems from its list of experimental
materials in 1989. Now repair and rehabilitation projects using these systems may
be eligible for full federal funding. Technological advances in polymer materials have
improved their flexibility and their chemical compatibility with concrete, resulting in
overlays that are more durable and more resistant to shrinkage and cracking. Mixing
and application procedures have improved too, and equipment is now available to
speed these procedures and improve acc uracy.
Because of these advances, an increasing number of polymer concrete
overlays have been installed in the past 10 years in the United States and Canada.
Transportation departments are monitoring the performance of many of these
overlays and reports indicate that the overlays are performing well

20. Machine Mixing Instructions
The mixture is obtained by adding water into a clean container and
then gradually adding the powder. Add approximately 1 gallon of water for each
50 lb bag of Polymer Concrete Patcher to be used. If the mortar becomes too
difficult to mix, add additional water until the desired consistency is achieved.
The mixing process can be performed in a cement mixer or in a bucket (working
manually or with a mechanical agitator) or using a continuous mixer until
homogeneous, lump-free mixture is obtained. It is also possible to use a sprayer
to mix and simultaneously pump the mixture, using a rotor/ stator system
suitable for the granulometric gradation of the mixture.

21. Hand Mixing Instructions
Empty the bags into a suitable mixing container. Add approximately 1
gallon of water for each 50 lb bag of Polymer Concrete Patcher to be used. Work
the mix with the necessary tools, and add additional water as needed until the
desired consistency is achieved. Make sure all the material is adequately wet
before proceeding with the application.