**New design "Duplo–Headstock"**

The "Duplo-headstock" has been designed in order to achieve technological parameters comparable to the performance of standard electro-spindles, but at a lower production costs and with higher controllability. This particular headstock is assembled from readily available elements (bearings, single drives,). The demands on the other peripheral devices are reduced, as are the costs.

The "Duplo-headstock" can be described as a spindle with double supports, driven by two separate motors which can operate independently or together. Figure 24 - 28 show a "Duplo–headstock" design [20].

**Figure 27.** Disengaged, Speed: n1max=6000 (min-1); n2=6000 (min-1), nc\_sp= n1 + n2 by one direction of rotation, nc\_sp= n1 - n2 by opposite direction of rotation, Torque moment: Mkc\_sp=Mk1=1,75 (Nm) by n1max,

The spindle (1), with built-in armature (2), is supported by bearings (3), (4). The stator of the internal motor (5) is supported on bearings (7), (8). The clutch (9) connects a hollow shaft with an external electro-motor (10). The stator feeding rings (11) are located in the rear part of the shaft. The clutch (12) enabling switching between working modes is located in the front part of the shaft. The advantage of this innovative design, which is already in use, is

Power: Pc\_sp=P1=1,1 (kW)

**Figure 28.** Stand of "Duplo" Headstock



that the headstock can work in three different modes:

**Figure 24.** High-speed headstock "Duplo"

**Figure 25.** The stator engaged on spindle, Speed: n1max=6000 (min-1); n2=0, nc\_spi=n1 Torque moment: Mkc\_sp=Mk1=1,75 (Nm) by n1max, Power: Pc\_sp=P1=1,1 (kW)

**Figure 26.** The stator engaged on body, Speed: n1max=0; n2=6000 (min-1), nc\_sp=n2, Torque moment: Mkc\_sp=Mk2=3,5 (Nm) by n2max, Power: Pc\_sp=P2=3,5 (kW)

**Figure 27.** Disengaged, Speed: n1max=6000 (min-1); n2=6000 (min-1), nc\_sp= n1 + n2 by one direction of rotation, nc\_sp= n1 - n2 by opposite direction of rotation, Torque moment: Mkc\_sp=Mk1=1,75 (Nm) by n1max, Power: Pc\_sp=P1=1,1 (kW)

**Figure 28.** Stand of "Duplo" Headstock

The spindle (1), with built-in armature (2), is supported by bearings (3), (4). The stator of the internal motor (5) is supported on bearings (7), (8). The clutch (9) connects a hollow shaft with an external electro-motor (10). The stator feeding rings (11) are located in the rear part of the shaft. The clutch (12) enabling switching between working modes is located in the front part of the shaft. The advantage of this innovative design, which is already in use, is that the headstock can work in three different modes:


82 Performance Evaluation of Bearings

**Figure 24.** High-speed headstock "Duplo"

Mkc\_sp=Mk1=1,75 (Nm) by n1max, Power: Pc\_sp=P1=1,1 (kW)

Mkc\_sp=Mk2=3,5 (Nm) by n2max, Power: Pc\_sp=P2=3,5 (kW)

**Figure 25.** The stator engaged on spindle, Speed: n1max=6000 (min-1); n2=0, nc\_spi=n1 Torque moment:

**Figure 26.** The stator engaged on body, Speed: n1max=0; n2=6000 (min-1), nc\_sp=n2, Torque moment:

Connecting such a headstock with a suitable control system can provide optimal cutting conditions for various technological operations. The intelligent control system, Figure 29, can operate in any one of the working modes and ensure nominal or optimal technological parameters best suited to the machining process, [21]. Figure 30 shows the design for the

In the third mode, the clutch (12) is switched off. The spindle (1) is driven by both motors, (Figure. 27), providing the maximum speed, which is required, for example, in

construction of the "Duplo" Headstock.

**Figure 30.** Design for the construction of "Duplo" Headstock

**6.1. The new headstock construction for turning machine tools** 

Figure 34 shows the comparison between the original and optimized designs.

TRENS a. s. Trenčín, is a Slovak manufacturer of machine tools (mainly lathes) and offers a new generation of lathes implementing various technological advances in design, production, and control systems, [22]. The Department of Production Engineering has been asked to design an accurate running spindle for the SBL 500 CNC lathe (Figures 31 -33), [23]. All construction data and results of measurements were obtained from the producer. Table 2. shows the calculated (Spindle Headstock Version 2.8) values [23] of the optimized design.

**6. Application research** 

grinding.

**Figure 29.** Scheme of Machine Tool Headstock Control

Connecting such a headstock with a suitable control system can provide optimal cutting conditions for various technological operations. The intelligent control system, Figure 29, can operate in any one of the working modes and ensure nominal or optimal technological parameters best suited to the machining process, [21]. Figure 30 shows the design for the construction of the "Duplo" Headstock.

In the third mode, the clutch (12) is switched off. The spindle (1) is driven by both motors, (Figure. 27), providing the maximum speed, which is required, for example, in grinding.

**Figure 30.** Design for the construction of "Duplo" Headstock
