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In order to clarify the parameters of the product to be developed we shall need to make a comparative analysis of existing similar types of machines. With this in view we selected several product types manufactured by commonly known and traditional companies in the metal-cutting equipment market. We have classified the results of this technical data analysis and the prices in the comparative Table 1.

Table 1. Technical data and price comparative table

Company KNUTH KNUTH TRAPANI BGU SERRMAC MAXION

Model KB 13 KB 16 16 B TB 16 RAG 16 BT 13

Technical data

Drilling capacity on steel mm 13 15 16 16 16 13 Drilling capacity on

cast-iron mm 15 17 18 17 18 15

Transmission Belt Belt Belt Belt Belt Belt drive

Morse taper of spindle B16 MT2 MT2 MT2 MT2 MT2 Column diameter mm 50 80 85 80 98 65 Spindle stroke (drilling dept) mm 60 80 100 110 90 70

Table working surface mm 165x165 255x255 260x260 250x250 230x170 Clearance between spindle

and column mm 190 190 201 180

Max. clearance between

table and spindle mm 335 350 465

Max. clearance between

base and spindle mm 500 665 415

Feed manual manual manual manual manual manual Driving motor (capacity) kW 0,18 0,37 0,7 1,1 0,55 0,45 Number of spindle speed 5 12 5 5 5 5 Spindle speed rpm

600-2500

200-3250

560-3550

250-1966 450-3000 480-4000 Dimensions (LxWxH) mm (H) 1016 680x970

x360 (H) 1000 770x1120

x460 (H) 855

Weight kg 21 66 110 96 90 65

Price $670 $1050 $900 $890 $1150 $930

Тhe common feature in all machines being considered is that they all have belt drives that transmit the rotary motion from the motor to the spindle thus providing the main operating motion. Considering the type and dimension of the machine and the power required to drill 15

÷ 16mm holes the belt drive seems to be the simplest and simultaneously the most efficient and sufficiently powerful type of drive [2]. Therefore, it is the most

commonly incorporated type of drive in bench drilling equipment.

All machines are fed manually. This is performed by rotating by hand 1, 2 or 3 handles of a hub mounted on a shaft with a gear and the gear is engaged with a gear rack cut into the tailstock barrel.

Thus, the rotary motion is transformed into a linear movement and the spindle is advanced (Figure 1). The maximum steel drilling diameter for most types of machines is 16mm. The front end of the spindle has a Morse taper 2. All machines being considered here have an intermediate-working table, which moves vertically up and down the column. This is achieved by manual rotation of a handle positioned on the left of the column (operator’s right) providing movable connection between the table and the column. The table and the support base usually have 2 T-slots each used to secure rigs or the component being drilled. Column diameter varies depending on the size of the machines between 50 mm and 98 mm.

From the technical parameter analysis of the product types being considered we can draw up the conclusion about the preferred

parameters of the bench-drilling machine being designed. Fig. 1

Table 2. Initial technical parameter table

Drilling capacity on steel 15 mm

Drilling capacity on cast-iron 17 mm

Morse taper of spindle MT2

Transmission Belt drive

Column diameter 65 mm

Spindle stroke (drilling depth) 80 mm

Table working surface 230x180 mm

Clearance between spindle and column 190 mm

Max. clearance between table and spindle 415 mm

Feed manual

Driving motor (capacity) 0,45 kW

Number of spindle speed 5

Spindle speed 240÷4000 rpm

Dimensions (LxWxH) 659x340x839 mm

Above parameters will serve as a starting point in the design process. This is the place to mention that the decision for their particular selection was made considering the overall evaluation of the technical, market and economical, technological and production factors.

From the analysis of the ergonomic characteristics we can draw the following conclusions about the ways to provide agreement between the design characteristics and the anatomic, physiological and psychological man peculiarities. A subject of the ergonomic study and design were: the height of the machines, its conformity to the size of the human body (consideration for the anthropo-metric and physiological requirements of the ergonomic characteristics), the size and slope of the spindle feed handles, which should allow convenient grip and their location on machine’s left-hand side [3].

Also, the direction of rotation of the handles should be:

• towards the operator (counter-clockwise) when the spindle moves downwards;

• from the operator outwards (clockwise) when the spindle moves upwards.

The upward movement is also provided by a return coil spring, which retracts the spindle in

KB13 KB16 16 B

Fig. 2 Fig. 3 Fig. 4

TB16 RAG16 BT 13

Fig. 5 Fig. 6 Fig. 7

Similarly, the direction of rotation of the handle to move the working table up or down the column complies with human psychological and physical requirements [4].

With respect to hygienic ergonomic considerations, their requirements are met by providing a clear protection shield mounted on some of the machines. This shield protects the operator from accidentally escaping metal chips and also provides sufficient visual access to the operating area (for example, see Figure 6 for SERRMAC Model RAG 16). Above considerations can be observed during the

design stage by means of correctly defining the Man - Machine - Environment relationship.

From the aesthetic considerations analysis we can conclude that bench-drilling machines are a favoured subject when solving modular arrangements. Machine lay-out arrangements is very similar among various models – a modular head with an electrical motor positioned in its far bottom end, a column, a working table and a support base. Differences are mainly noticed in the colour selection with the green definitely prevailing. The SERRMAC Model RAG 16 (Figure 6) successfully blends blue and

white and the MAXION Model BT 13 (Figure 7) does the same with blue and gray. These two models have the most satisfactory aesthetic appearance. There are some differences with respect to some exterior details, such as handles, the shape of covers and graphical elements [5].

The main requirements for the lay-out of the basic sections of the product are functionality, compactness and provisions for maximum technical, economic, ergonomic and aesthetic characteristics. Therefore, the function of the machine is going to be the basic principle to be observed in the shape layout, i.e. the shape of the head should express the basic drilling function of the machine and also, provide for the movement of the head along the column.

The shape of the bracket could be made to conform to the rotation requirement and simultaneously suggesting this. The right colour and graphical solutions also facilitate function transparency and would very much assist to improve the visual perception of the machine.