Implementation of an Academic Learning Module for CNC Manufacturing Technology of the Part ”Double Fixing Fork”

Abstract

The paper presents the CNC manufacturing technology of the ”Double fixing fork” part as a module with educational purpose, being designed as a training support for students and other parties, facilitating the practical learning of CNC processing technology. Its technological manufacturing process involved a careful analysis of the geometry, material, tolerances, as well as functional requirements to ensure precision and reliability in operation. The material from which the part was made is a polymer material (PEHD 1000) selected both for its mechanical characteristics and for its compatibility with processing technologies. The results demonstrated high precision and adaptability, reduced execution times and the possibility of achieving complex geometries in a relatively short time. The developed module supports skill development in CNC programming and operation and is suitable for replication in other academic environments. Programming allowed for more precise control of the cutting tool trajectory and processing parameters. The paper represents an important contribution to the training of future specialists, paying special attention to the growing interdisciplinarity in manufacturing technology and the development of technical skills necessary for future engineers in the numerically controlled machinery sector.

1. Introduction

In support of the fastest and most efficient processing of industrial products, numerous information storage systems in virtual environments have been developed. Coupled with the constant development of cutting tools and modern machine tools, they are capable of optimizing geometric and constructive parameters before the products are physically made. Computer numerical control—CNC machines—are those that streamline production processes through high precision, increased work capacity and shorter activity duration [1,2].

These require a high degree of operator expertise, but have a working interface that is easy to learn and use, offering the possibility to simulate the operation of the equipment. By automating the control of machine tool movements, CNC has revolutionized the machining processes, providing high precision, repeatability and efficiency in production. From milling and turning, to drilling or laser cutting, CNC is used in a variety of industries—from machine construction to the medical or aeronautical industry. One of its main advantages is the ability to produce complex geometries with minimal human intervention, thus reducing errors and increasing the quality of the finished product [3,4].

In recent years, with the evolution of materials, the use of polymers in CNC processes has become increasingly common. Polymeric materials, such as HDPE, POM, PVC or PMMA, are chosen for their high machinability, low weight and wear resistance. They offer the advantage of operational safety and are ideal for laboratory exercises, allowing the rapid production of parts, with minimal risk to operators and equipment. Compared to metallic materials, polymers exhibit different behavior during processing—they have a greater tendency for thermal deformation and require adapted cutting regimes. Therefore, the choice of appropriate technological parameters is important for obtaining quality parts [5,6,7].

In the specialized literature, more and more studies emphasize the importance of practical components in the training of engineers. The authors Roman O. et al. [8] addressed the issue of integrating CNC systems into the university curriculum, showing that access to such equipment allows students to better understand the CAD–CAM–CNC chain and promotes active learning. Petru C.D. et al. [9] developed a small-sized CNC machining center, using accessible controllers (Arduino, Pololu) and advanced simulations for calibrating axis movements. The proposed solution allows not only physical machining, but also digital replication, ideal for modern educational environments. Baroiu et al. [10], presented a machining cycle on an educational CNC machine, emphasizing the importance of going through all technological stages, from 3D modeling to programming and execution, offering students the complete experience in machining a reference with complex geometries.

On the simulation and optimization side, Zahid M.N.O. et al. [11] propose a methodology for integrating end mill tools into fast CNC processes, highlighting the benefits of simulation on part quality and reducing the volume of unprocessed material. Also, Vishaldeep S. et al. [12] propose a tool path verification and simulation system for three and five-axis CNC machining, using APIs in SolidWorks 2018 version 26 and ray tracing verification, which supports the idea of using simulation for CNC program validation, including for didactic purposes. Mishra S. [13] shows that CNC machining has been successfully adapted for medical applications (PMMA bio-chips), and Carta M. et al. [14] have demonstrated that CNC machining can improve the surface of parts obtained by FDM (fused deposition modeling).

Fountas N. et al. [15] explore the evaluation of machinability of graphene composite materials, while Szadkowska K. et al. [16] analyze the influence of machining regime on tool wear in polyurethane milling. Both studies provide useful insights for understanding the effects of materials and parameters on the CNC process.

Shuling Z. and Jie B. [17] proposed an approach to CNC programming using CAD/CAM integration, and Xiangsong Y. [2] extended this integration to include industrial robots. Martins A. et al. [18] presented the integration of CNC machines in smart factories using industrial protocols (OPC UA), highlighting the direction in which advanced technological training is heading. Hongyi W. et al. [19] conducted an analysis of CNC design from the perspective of energy consumption, and Gołebski R. [3] presented the advantages of CNC parametric programming for flexibility and efficiency.

In this context, the paper proposes a practical application involving the use of a didactic CNC equipment, EMCO MILL 55 CNC, to create the ”Double fixing fork” reference, representative both in its geometry and in the chosen material. EMCO MILL 55 CNC is a three-axis numerical controlled machine, which allows the execution of small-sized parts (maximum 180 mm × 120 mm × 70 mm). It consists of three slides, the tool holder and the tool changer, Figure 1.

Figure 1. EMCO MILL 55 CNC: (a) CNC machine; (b) tool holder; (c) tool changer [1,10].

The slides allow movement on the x, y and z axes (x—worktable, y—worktable movement, z—main axis that allows tool change). The part is fixed on the tool holder, and depending on the difficulty of the part, it is chosen to be positioned directly on the flat bench vise or to be fixed. In order to fix the parts, rulers with seating surfaces larger than 60 × 60 mm are used directly on the machine’s worktable [1]. The tool clamping system of EMCO MILL 55 CNC equipment uses an SK30 cone clamping system, according to the DIN 2079 standard [20]. This system allows the mounting of various types of tools through dedicated tool holders, ensuring precise and secure fixation during the machining process.

For the control and operation of the EMCO Concept MILL 55 machine, an advanced CNC system, developed by Siemens—SINUMERIK 840 (Munich, Germany) [21]—is used. This is a high-performance CNC system, recognized for its flexibility and advanced capabilities in machine tool control. It also offers a robust hardware architecture and intelligent control algorithms, ensuring high dynamics and precision in machining. For the programming and operation of the machines, SINUMERIK 840 includes various technological functions such as advanced work cycles and transformations that simplify complex machining. At the same time, it supports programming in an advanced level language and according to DIN-ISO standard, offers flexibility in creating CNC programs [21,22].

The paper is part of the current efforts to integrate CNC technologies into the engineering educational process. Created for educational purposes, in the Research Center in Manufacturing Engineering Technology (ITCM), ”Dunarea de Jos” University of Galati, it aims to familiarize students with real manufacturing processes by developing a CNC machining technology of a part with relatively complex shape. This study also reflects a contribution to the formation of students’ applicative and analytical skills, emphasizing the technological understanding of the entire manufacturing process.

2. Materials and Methods

2.1. Part Analysis

The part from Figure 2 is called a ”Double fixing fork”.

Figure 2. Execution drawing of the ”Double fixing fork”.

The types of surfaces of the part are presented in Figure 3 and Table 1. The part can be used in industrial machinery, clamping mechanisms or fixtures, both to clamp and guide components in a mechanism, ensuring their correct alignment and positioning.

Figure 3. Numbering of the surfaces of the part “Double fixing fork”.

Table 1. Types of surfaces.

Crt. no.	Surface Type	Code	Dimensions [mm]	Tolerances, TD [mm]	Roughness, Ra [μm]
1.	Horizontal plane surface	SPO—01, 02	63 × 16	-	6.3
2.	Vertical plane surface	SPV—03, 04	45 × 16	-	3.2
3.	Vertical plane surface	SPV—05, 06	3 × 45°	-	-
4.	Vertical plane surface	SPV—07, 08	16 × 16	-	-
5.	Inclined plane surface	SPΗ09, 10	21 × 16	-	-
6.	Vertical connected plane surface	SPRV—11	29 × 26 × 16/R6	+0.11 0	3.2
7.	External cylindrical surface	SCE—12	Ø36 × 16	-	-
8.	Inner cylindrical surface	SCI—13	Ø14 × 20	-	-
9.	Inner helical cylindrical surface	SCEI—14, 15, 16	3 × M6	-	-
10.	Inner cylindrical surface	SCI—17, 18, 19, 20	Ø11 × 10	-	-
11.	Inner cylindrical surface	SCI—21, 22, 23, 24	Ø7 × 6	-	-
12.	Horizontal plane surface	SPO—25, 26	63 × 16	-	6.3
13.	Vertical plane surface	SPV—27, 28	4 × 45°	-	6.3
14.	Vertical plane surface	SPV—29	58 × 16	-	-
15.	Vertical plane surface	SPV—30, 31	35 × 16	-	3.2
16.	Inner cylindrical surface	SCI—32, 33	Ø5 × 9.5	-	-
17.	Horizontal plane surface	SPO—34, 35	25 × 6.5	-	-
18.	Inner cylindrical surface	SCI—36	Ø20 × 12	H8	3.2
19.	Connected profiled surface	SPR—37	28 × 16/R8/R18	-	-

The list of processing operations is as follows:

• Operation 1. Roughing milling
• Phases:

  1.1.

  Side face milling—3, 4, 30, 31

  1.2.

  Face milling—7, 8, 29

• Operation 2. Contour milling 1
• Phases:

  2.1.

  Cylindrical face milling—2

  2.2.

  Contour profile milling 1—27, 28, 29, 30, 31, 37

  2.3.

  Center drilling—13

  2.4.

  Drilling—13

  2.5.

  Counterboring—13, 36

• Operation 3. Contour milling 2 and 3
• Phases:

  3.1.

  Cylindrical face milling—25, 262

  3.2.

  Contour milling 2—5, 6, 7, 8, 9, 10, 123

  3.3.

  Contour milling 3—11

• Operation 4. Drilling
• Phases:

  4.1.

  Center drilling—14, 15, 16, 17, 18, 19, 20

  4.2.

  Drilling—14, 15, 16

  4.3.

  Drilling—17, 18, 19, 20

  4.4.

  Counterboring—17, 18, 19, 20

  4.5.

  Threading—14, 15, 16

• Operation 5. Milling and drilling
• Phases:

  5.1.

  Channel milling—34, 35

  5.2.

  Center drilling—32, 33

  5.3.

  Drilling—32, 33

2.2. Technological Regime Elements

Phases and processing methods of the part are presented in Table 2.

Table 2. Processing methods.

Phase	Processing Method	Workstation	Tool Type	Tool—Geometric Parameters [mm]
				D	R	Lt	Ls
1.1	Face milling	T7	Cylindrical end mill	14	7	20	70.98
1.2	Face milling	T2	Cylindrical end mill	10	5	45	96.12
2.1	Cylindrical face milling	T7	Cylindrical end mill	14	7	20	70.98
2.2	Contour milling 1 CYCLE 72	T7	Cylindrical end mill	14	7	20	70.98
2.3	Center drilling CYCLE 81	T8	Center drill	3	-	9	66.55
2.4	Drilling	T7	Helical drill	10	-	38	84.83
2.5.a	Counterboring POCKET 2	T2	Cylindrical end mill	10	5	45	96.12
2.5.b	Counterboring POCKET 2	T2	Cylindrical end mill	10	5	45	96.12
3.1	Cylindrical face milling	T7	Cylindrical end mill	14	7	20	70.98
3.2	Contour milling 2 CYCLE 72	T7	Cylindrical end mill	14	7	20	70.98
3.3	Contour milling 3 POCKET 1	T6	Cylindrical end mill	10	5	22	-
4.1	Center drilling CYCLE 81	T8	Center drill	3	-	9	66.55
4.2	Drilling CYCLE 81	T3	Helical drill	5	-	48	-
4.3	Drilling CYCLE 81	T2	Helical drill	7	-	31	-
4.4	Counterboring CYCLE 89	T4	Counterbore	12	-	26	-
4.5	Threading CYCLE 840	-	Metric tap	M6	-	40	85.30
5.1	Channel milling	T5	Channel mill	8	4	13	90.15
5.2	Center drilling	T8	Center drill	3	-	9	66.55
5.3	Drilling	T3	Helical drill	5	-	48	-

2.5.a and 2.5.b are the phases corresponding to the processing of surfaces 13 and 36; the D is the diameter of the cutting tool; R is the radius of the cutting tool; L_t is the length of the cutting tool edge; L_s is the length of the cutting tool.

The part is made of a polymeric material—PEHD 1000 (high-density polyethylene (Ensinger GmbH, Nufringen, Germany) [23]), having the mechanical properties presented in Table 3. Also, the geometric parameters are presented in Table 4.

Table 3. Mechanical properties of PEHD 1000 [23].

Yield Strength, σc [MPa]	Tensile Strength, σr [MPa]	Elongation at Break, ε [%]	Hardness HB	Elasticity Modulus, E [MPa]
19	15	>50	36	750

Table 4. Geometric parameters.

Phase	Tool Type	Number of Teeth (z)	Basic Parameters				Programmable Parameters
			t [mm]	Sd [mm/rot]	Sb [mm/rot]	V [m/min]	S [rot/min]	F [mm/min]
1.1	Cylindrical end mill	4	13 (32)	0.06	-	25	568.69	136,48
1.2	Cylindrical end mill	4	13 (32)	0.15	-	25	796.17	477,70
2.1	Cylindrical end mill	4	5 (16)	0.15	-	25	568.69	314.21
2.2	Cylindrical end mill	4	4 (16)	0.15	-	25	568.69	314.21
2.3	Center drill	-	2.5	-	0.30	25	2653.92	769.17
2.4	Helical drill	-	5	-	0.15	24	764.33	114.65
2.5.a	Cylindrical end mill	4	4 (12)	0.05	-	25	796.17	159.23
2.5.b	Cylindrical end mill	4	2.5 (32)	0.05	-	25	796.17	159.23
3.1	Cylindrical end mill	4	5 (16)	0.15	-	25	568.69	314.21
3.2	Cylindrical end mill	4	4 (16)	0.10	-	25	568.69	227.47
3.3	Cylindrical end mill	4	4 (16)	0.10	-	25	568.69	227.47
4.1	Center drill	-	2.5	-	0.3	25	2653.92	769.17
4.2	Helical drill	-	3.5	-	0.1	25.28	1610.2	161.02
4.3	Helical drill	-	3.5	-	0.12	23.07	1049.59	125.95
4.4	Counterbore	-	6	-	0.16	24.39	647.29	103.56
4.5	Metric tap	-		-	0.75	4.48	238.29	178.72
5.1	Channel mill	2	3 (6.5)	0.013	-	25	995.22	25.87
5.2	Center drill	-	2.5	-	0.30	25	2653.92	769.17
5.3	Helical drill	-	2.5	-	0.10	25.28	1610.2	161.02

t represents the cutting depth, in [mm]; S_d —milling feed (on one tooth of the tool), in [mm/rot]; S_b —drilling feed, in [mm/rot]; V—cutting speed, in [m/min]; S—tool speed, in [rot/min]; F—feed rate, in [mm/min].

The cutting regime parameters—F, S, S_b, V—related to each machining phase are calculated with the following relationships:

-

In the case of milling and counterboring operations:

$$F=S_d\cdot z\cdot S\left[\mathrm{mm}/\min .\right];$$

(1)

$$S={\displaystyle \frac{1000\cdot V}{\pi \cdot D}}\left[\mathrm{rot}/\min .\right],$$

(2)

-

In the case of center drilling operations:

$$S_b=C_s\cdot D\left[\mathrm{mm}/\mathrm{rot}.\right],$$

(3)

where C_s = 0.1 [24] and D = 3 mm.

$$F=S_b\cdot S\left[\mathrm{mm}/\min .\right].$$

(4)

-

In the case of drilling operations:

$$S_b=K_s{C}_s\cdot D^{0,6}\left[\mathrm{mm}/\mathrm{rot}.\right],$$

(5)

where the coefficients K_s = 1 and C_s = 0.038 are taken from [24].

$$V=K_V\cdot K_M\cdot {\displaystyle \frac{D^{0,4}}{S_b^{0,5}}}\left[\mathrm{m}/\min .\right],$$

(6)

where the coefficients K_V = 3.7 and K_M = 1 are taken from [24].

-

In the case of threading operations:

$$S_b=p\left[\mathrm{mm}/\mathrm{rot}.\right],$$

(7)

where p represents the thread pitch.

$$V=K_{VM}\cdot {\displaystyle \frac{M^{1,2}}{p^{0,5}}}\left[\mathrm{m}/\min .\right],$$

(8)

where the coefficients K_VM = 0.45 and M = 6 are taken from [24].

2.3. Structure of CNC Technology

The part ”Double fixing fork” was created using the EMCO CONCEPT MILL 55 CNC system [20,25,26]. The CNC technological sketches are presented in Figure 4, Figure 5 and Figure 6 and the coordinates of the characteristic points (CPs) are in Table 5, Table 6, Table 7, Table 8, Table 9, Table 10 and Table 11.

Figure 4. CNC sketches at (a) side face milling, (b) face milling.

Figure 5. CNC sketches at (a) contour milling 1, (b) contour milling 2, (c) contour milling 3.

Figure 6. CNC sketches at (a) drilling, (b) channel milling and drilling.

Table 5. Coordinates of characteristic points at side face milling and face milling—Figure 4.

W1	Side Face Milling				PS1
	1	2	3	4
X	0	153	153	0	−10
Y	0	0	32	32	0
Z	−0.5	−0.5	−0.5	−0.5	5
W1	Face milling				PS2.1	PS2.2
	5	6	7	8
X	134	134	0	0	−10	163
Y	0	60	0	60	−10	70
Z	−1	−1	−1	−1	5	5

Table 6. Coordinates of characteristic points at face milling, drilling and counterboring.

W2	Cylindrical Face Milling				Drilling—Counterboring	PS3	PS4	PS5	CS
	1	2	3	4	5	-	-	-	-
X	82	126	126	82	63	136	−10	63	63
Y	−29	−29	29	29	0	40	0	0	0
Z	−16	−16	−16	−16	−5—center drilling −35—drilling Ø10 (32 + 3) −33—counterboring Ø14 −12—counterboring Ø20	5	10	20	-

Table 7. Coordinates of characteristic points at contour milling 1—Figure 5a.

W2	Contour Milling 1
	6	7	8	9	10	11	12	13	14	15
X	63	63	43	35	35	0	0	35	35	43
Y	−18	18	18	26	29	29	−29	−29	−26	−18
Z	−16	−16	−16	−16	−16	−16	−16	−16	−16	−16

Table 8. Coordinates of characteristic points at cylindrical face milling.

W3	Cylindrical Face Milling				PS5
	1	2	3	4
X	0	0	44	44	−10
Y	−30	30	−30	30	40
Z	−15.8	−15.8	−15.8	−15.8	5

Table 9. Coordinates of characteristic points at contour milling 2—Figure 5b.

W4	Contour Milling 2							PS6
	5	6	7	8	9	10	11
X	0	0	−45	−63	−63	−45	0	10
Y	0	29	29	18	−18	−29	−29	0
Z	−15.8	−15.8 CHF=3	−15.8	−15.8	−15.8 CR=18	−15.8	−15.8 CHF=3	5

Table 10. Coordinates of characteristic points at contour milling 3—Figure 5c.

W4	Contour Milling 3
	PS	CP
X	−11.5	−11.5
Y	0	0
Z	−18	−18

Table 11. Coordinates of characteristic points at drilling and channel milling—Figure 6.

W4	Drilling
	PS7	G1	G2	G3	G4	G5	G6	G7
X	0	−23.5	−37	−23.5	−10	−37	−10	−37
Y	0	21	0	−21	21	21	−21	−21
Z	20	−18.5	−18.5	−18.5	−19/−10	−19/−10	−19/−10	−19/−10
W5	Channel milling. Drilling
	PS8		CP1		CP2		G8	G9
X	0		−6		−6		21	21
Y	0		18		−18		18	−18
Z	20		-		-		−8 −18.5	−8 −18.5

The program blocks and technological phases are presented in Table 12.

Table 12. Program blocks and technological phases.

Program Block—BP	Tool	Workstation	Technological Phases
PROGRAM 1
BP1	Cylindrical end mill	D = 14 T7	(a) Face milling, Phase 1.1
BP2	Cylindrical end mill	D = 10 T2	(a) Face milling, Phase 1.2
PROGRAM 2
BP3	Cylindrical end mill	D = 14 T7	(a) Cylindrical face milling, Phase 2.1 (b) Contour milling 1, Phase 2.2
BP4	Center drill	D = 3 T8	(a) Center drilling, Phase 2.3
BP5	Helical drill	D = 10 T7	(a) Drilling, Phase 2.4
BP6	Cylindrical end mill	D = 10 T2	(a) Counterboring, Phase 2.5.a
BP7	Cylindrical end mill	D = 10 T2	(a) Counterboring, Phase 2.5.b
PROGRAM 3
BP8	Cylindrical end mill	D = 14 T7	(a) Cylindrical face milling, Phase 3.1 (b) Contour milling 2, Phase 3.2
BP9	Cylindrical end mill	D = 10 T6	(a) Contour milling 3, Phase 3.3
PROGRAM 4
BP10	Center drill	D = 3 T8	(a) Center drilling, Phase 4.1
BP11	Helical drill	D = 5 T3	(a) Drilling, Phase 4.2
BP12	Helical drill	D = 7 T2	(a) Drilling, Phase 4.3
BP13	Counterbore	D = 12 T4	(a) Counterboring, Phase 4.4
BP14	Metric tap	D = M6 T	(a) Threading, Phase 4.5
PROGRAM 5
BP15	Channel mill	D = 8 T5	(a) Channel milling, Phase 5.1
BP16	Center drill	D = 3 T8	(a) Center drilling, Phase 5.2
BP17	Helical drill	D = 5 T3	(a) Drilling, Phase 5.3

3. Results

Several sequences from the main programs for obtaining the ”Double fixing fork” part, using the Siemens SINUMERIK 840D program [21,22], as well as the subprograms, are presented in Table 13 and Table 14.

Table 13. The main programs.

Program Block	Technological Phase	Program Structure (Technological Lines)
BP1	Face milling Phase 1.1	G54 TRANS X-25 Y-32 Z40.5 T7 D1 M6 S568.69 M3 G0 Z-12 Y0 Z5 G1 X-10 Y0 Z0.5 F136.48 G1 X0 Y0 G1 X153 Y0 G1 X153 Y13 G1 X0 Y14 G1 X0 Y26 G1 X153 Y26 G1 X153 Y32 G1 X0 Y32 G0 X-10 Y0 Z5 G0 Z100
……	……	……
BP4	Center drilling Phase 2.3	T8 D1 M6 S2653.92 M3 F769.17 G0 X63 Y0 Z20 CYCLE81 (5, 0, 3, −7.5, 0)
……	……	……
BP13	Counterboring Phase 4.4	T4 D1 M6 S647.29 M3 F103.56 G0 X0 Y0 Z20 MCALL CYCLE89 (5, 0, 3, −10, 0, 3) CYCLE801 (−37, −21, 0, 27, 42, 2, 2) MCALL Z100
BP14	Threading Phase 4.5	T5 D1 M6 S238.29 M3 F178.72 G0 X0 Y0 Z20 MCALL CYCLE840 (5, 0, 3, −18.5, 0, 04, 3, 0, 0.75, 0, 3, 0, 0) CYCLE801 (−37, −21, 0, 27, 42, 2, 2) MCALL Z100
……	……	……
BP17	Drilling Phase 5.3	T3 D1 M6 S1610.2 M3 F161.02 G0 X0 Y0 Z20 CYCLE81 (5, 0, 3, −18.5, 0) G0 Y18 CYCLE81 (5, 0, 3, −18.5, 0) Z100 M30

Table 14. Subprograms.

MOG C1	MOG C2
G1 X0 Y0 G1 X0 Y29 CHF=4 G1 X35 Y29 G1 X35 Y26 G3 X43 Y18 CR=8 G1 X63 Y18 G2 X63 Y-18 CR=18 G1 X43 Y-18 G3 X35 Y-26 CR=8 G1 X35 Y-29 G1 X0 Y-29 CHF=4 G1 X0 Y0 M17	G1 X0 Y0 G1 X0 Y29 CHF=3 G1 X-45 Y29 G1 X-63 Y18 G3 X-63 Y-18 CR=18 G1 X-45 Y-29 G1 X0 Y-29 CHF=3 G1 X0 Y0 M17

Figure 7 shows the part ”Double fixing fork”, obtained using the EMCO CONCEPT MILL 55/TURN 55 CNC system.

Figure 7. ”Double fixing fork” part.

This paper is not limited to an academic approach for purely didactic purposes, but proposes an applied research in the field of industry, with a potential for technological transfer in industrial production processes. Although the activities were carried out in an educational environment, the developed methodology faithfully reproduces the essential stages of an industrial CNC machining process, respecting the principles of design, simulation, programming, selection of working regimes, choice of technical materials and actual manufacturing of a functional part.

The analyzed part is a real component used in mechanical assemblies. Its design, the choice of material (PEHD 1000—a technical polymer frequently used in industrial applications) and the applied machining strategy were carried out according to industrial technological standards. The program used (Siemens SINUMERIK 840D), as well as the structure of the generated CNC program, are in line with modern factory practices, which proves that the process can also be implemented in real production contexts. This paper fits within the area of applied scientific research because it is not limited to a simple demonstration of educational skills, but offers a fully documented and experimentally validated solution for the manufacture of a real part, with applicability in prototyping, small series production and industrial training. In addition, the proposed flow can be transferred within a small- and medium-sized enterprise (SME) or production workshop to be tested under concrete working conditions, which would allow its integration into a functional technological system.

In terms of Technology Readiness Level (TRL), the paper can be classified as TRL 3, as it has been experimentally validated in a controlled laboratory environment, using real equipment and respecting industrial technological constraints, as seen in Figure 8. This can progress to TRL 4, as it is necessary to validate the method in a relevant industrial environment by testing the part under production conditions and evaluating the performances obtained in terms of quality, productivity and reliability. The paper provides the concrete foundations for this step and the methodology can be scaled and replicated for industrial purposes without major modifications.

Figure 8. Technology Readiness Levels of the paper.

Therefore, the paper is scientific in nature and aligns with modern directions in the field of applied engineering, contributing both to the practical training of future specialists and to the development of reproducible solutions for digitally assisted manufacturing. The potential for transfer to industry is real and well supported by the methodological structure and experimentally obtained data.

4. Discussion

Numerical control (NC) machine tools allow complex machining processes to be carried out with minimal human intervention, thus increasing the efficiency and productivity of a company. Their continuous modernization has led to the emergence and evolution of compact and intelligent systems, integrated with online diagnostic functions and automatic corrections. Future engineers also need a broad understanding of information technology and, above all, of the interrelationships between current technologies. For this reason, it is necessary to implement modules that facilitate the acquisition by future experts of the basic interdisciplinary skills addressed and thus prepare them for future professional challenges. The integration of CNC equipment into teaching activities allows not only a theoretical understanding of manufacturing processes, but also the development of skills related to programming, the choice of machining modes and the interpretation of technological parameters.

The paper contributes to the field of technical education, by implementing a didactic model that emphasizes learning through practice and solving real problems. The modular structure of the proposed technology, the adaptation of the processing sequences to the complexity of the part and the final evaluation of the quality of the part constitute an example of good practice for laboratory activity. This methodology can be easily replicated in other university centers, providing a clear framework for training in the field of CNC, including in the context of limited technical resources.

Based on the results obtained, directions for expanding the research can be outlined. The study can be continued by evaluating the behavior of other polymeric or composite materials in CNC processing, by developing advanced digital simulation modules (example: digital twin) or by integrating modern technologies such as augmented reality for operator guidance. Also, program optimization through evolutionary algorithms, testing different tools and applying automatic quality control methods can transform a didactic exercise into an applied research base.

5. Conclusions

The paper presented the manufacturing technology of the ”Double fixing fork” part using the EMCO CONCEPT MILL 55/TURN 55 CNC system. The use of the CNC system in the manufacturing of this part brought multiple advantages over traditional machining, such as the following: reduced execution times, high adaptability, but also the possibility of achieving complex geometries in a relatively short time.

The programming of the part allowed for more precise control of the cutting tool trajectory and machining parameters. EMCO numerical controlled machines have an intuitive interface, with the possibility of testing various machining scenarios. The process was scalable and precise, providing a solid technical basis for the training of future engineers in the numerical controlled machine sector.

The paper proved to be an effective framework for learning through practice, offering students the opportunity to go through a complete manufacturing process—from the design of the part to its physical realization in the laboratory, thus contributing to a solid and industry-oriented technological training. The ”Double fixing fork” part proved suitable for an educational study, both due to its complex geometric shape and the functional requirements it implies. This part allowed the application of a wide range of CNC operations (face milling, contour milling, drilling, counterboring, threading).

The use of high-density polyethylene (PEHD 1000) required the adjustment of technological parameters in order to avoid common defects associated with the processing of plastic materials, such as local melting, burr formation or loss of tolerances. It was thus demonstrated that a correct understanding of the material properties (strength, hardness, coefficient of thermal expansion) is important for the correct choice of tools, cutting speeds and feeds. EMCO Mill 55 CNC equipment, together with the SINUMERIK 840D control system, provided the ideal framework for carrying out a modern and efficient didactic activity. The intuitive interface, simulation capability and compatibility with the ISO standard language allowed the creation of precise and reproducible machining sequences. At the same time, it is possible to intervene in a controlled manner on the programs, observe the impact of changes on the tool path and evaluate the quality of the results obtained.

In relation to the current literature, the paper confirms the importance of integrating CNC machining methods in the industrial field, reinforcing the need to correlate theoretical training with practical experience in a context where digital and interdisciplinary skills are becoming important in modern production. Unlike other approaches focused exclusively on virtual simulations or simplified theoretical processing, this paper validates a complete manufacturing process—from 3D modeling to the physical realization of the part. Thus, the gap between academic learning and real industry requirements is reduced.

The equipment used, EMCO MILL 55, is a three-axis CNC machining center, which allows the execution of small-sized parts (maximum 180 mm × 120 mm × 70 mm). This limitation requires working with small-sized parts and excludes complex machining requiring five axes or advanced interpolations. Also, the technical characteristics of the machine—such as the maximum speed of the main spindle, engine power and rigidity—impose constraints on the regime parameters. In the case of polymeric materials, such as PEHD 1000, it was necessary to adjust the cutting speeds and feeds to avoid defects such as local melting, the appearance of burrs or the loss of tolerances, a task achieved through tests that allowed the selection of optimal parameters of the processing regime (Table 4 and Equations (1)–(8)). These adjustments, although adequate for didactic purposes, may limit the immediate applicability of the method in industrial processes of high productivity or high precision. Despite these constraints, the proposed methodology provides a solid, reproducible and scalable technological foundation, which can be extended to industrial environments by using higher-capacity CNC equipment.