Comparative Study about Dimensional Accuracy and Surface Finish of Constant-Breadth Cams Manufactured by FFF and CNC Milling
Abstract
:1. Introduction
2. Materials and Methods
2.1. Design Process of the Cam–Follower Mechanism
- Designing the displacement law. The designer defines the displacement law of the follower according to the movement required by the technological process or function that must be met by the mechanism. As mentioned in Section 1, the displacement law for this particular type of constant-breadth cam mechanism with a double-translating follower must meet a design restriction (expression 1) [2,3,4]. Thus, consists of two segments: the designed segment and the calculated segment.
- 2.
- Obtaining the cam profile that drives a certain type of follower according to the designed displacement law.
- 3.
- Verifying that the cam profile obtained does not present geometric characteristics that prevent the right contact between the cam and follower. In the case here exposed, the curvature radii of the cam profile must always be positive, in order to guarantee correct contact between the cam and the follower. The expression to calculate is as follows [1]:
2.2. Manufacturing Processes of the Cams
2.2.1. Manufacturing Processes of the 3D-Printed Cams
2.2.2. CNC Milling of the Cams
2.3. Measuring Process of the Cams
3. Results
3.1. Dimensions
3.2. Surface Roughness
4. Discussion
5. Conclusions
- Two principal design desmodromic constraints must be considered in the design process of a constant-breadth cam that drives a double flat-translating follower. The first constraint is that the motion law s(θ) consists of two segments: the designed segment, which can only be designed in the interval from 0 to 180° of cam rotation), and the calculated segment, which is obtained using the expression 1. The second constraint is that the value of the constant-breadth cam dc is equal to the diameter of the base circle plus the maximum displacement of the cam follower.
- Similar dimensional relative errors were obtained for the 3D-printed cams and the machined parts when the x, y plane was considered (maximum relative error of 0.75%). However, when the z direction was considered, which is orthogonal to the depositing plane of the printed layers, higher dimensional relative errors were reported for the 3D-printed cams (up to 1.64%) than for the machined ones (up to 0.54 %);
- As for the surface finish on the lateral surface (working face) of the cams, the average roughness Ra was around 20 times higher for the 3D-printed cams (10.41 µm) than for the machined ones (0.50 µm).
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Geometric Parameter [Units] | Numerical Value |
---|---|
Radius of the base circle of the cam [mm] | 17.5 |
Breadth of the cam [mm] | 50 |
Offset of the translating follower ε [mm] | 0 |
Inclination angle of the translating follower β [°] | 0 |
Parameter [Units] | Numerical Value |
---|---|
Nozzle diameter [mm] | 0.4 |
Infill ratio [%] | 18 |
Print speed [mm/s] | 60 |
Infill pattern | Linear |
Shell thickness [mm] | 0.4 |
Layer height [mm] | 0.15 |
Printing head temperature [°C] | 200 |
Build plate temperature [°C] | 60 |
Raster angle [°] | 45 |
Number of wall lines | 3 |
Operation Number | Operation (Machine Tool) | Tool | Fixture System | Cutting Conditions |
---|---|---|---|---|
1 | Cutting off of the starting cylinder (band saw machine) | Band saw | Bench vice | Cutting speed: 30 m/min |
2 | Face milling (CNC machine centre) | Face milling tool of diameter 40 mm and z = 8 | Bench vice | Cutting speed: 150 m/min; feed speed: 955 mm/min; depth of cut: 2 mm |
3 | Rough contour milling of the cam hub (CNC machine centre) | Face milling tool of diameter 25 mm and z = 4 | Bench vice | Cutting speed: 120 m/min; feed speed: 611 mm/min; depth of cut: 5.40 mm |
4 | Rough contour milling of the cam profile (CNC machine centre) | Face milling tool of diameter 25 mm and z = 4 | Bench vice | Cutting speed: 120 m/min; feed speed: 611 mm/min; depth of cut: 20 mm |
5 | Marking of the cam hole (CNC machine centre) | Drilling tool of angle 90° and diameter 12 mm and z = 2 | Bench vice | Cutting speed: 95 m/min; feed speed: 302 mm/min; depth of cut: 5 mm |
6 | Drilling of the cam hole (CNC machine centre) | Drilling tool of angle 120° and diameter 12 mm and z = 2 | Bench vice | Cutting speed: 95 m/min; feed speed: 302 mm/min; cutting length: 22 mm |
7 | Contour milling of the keyway of 6 × 4.36 mm (CNC machine centre) | Face milling tool of diameter 4 mm and z = 2 | Bench vice | Cutting speed: 120 m/min; feed speed: 1910 mm/min; depth of cut: 22 mm |
8 | Contour milling of the cam profile (CNC machine centre) | Face milling tool of diameter 10 mm and z = 4 | Bench vice | Cutting speed: 120 m/min; feed speed: 1528 mm/min; depth of cut: 15 mm |
9 | Contour milling of the cam’s hub (CNC machine centre) | Face milling tool of diameter 10 mm and z = 4 | Bench vice | Cutting speed: 120 m/min; feed speed: 1528 mm/min; depth of cut: 5.40 mm |
10 | Cutting off the machined cylinder (band saw machine) | Band saw | Bench vice | Cutting speed: 30 m/min |
11 | Face milling to final length of the cam of 17.40 mm, obtaining a width of the working face of 12 mm (CNC machine centre) | Face milling tool of diameter 40 mm and z = 8 | Bench vice | Cutting speed: 150 m/min; feed speed: 955 mm/min; depth of cut: 2 mm |
Cam Manufacturing Process | Parameter | Theoretical Value (mm) | Mean Value (mm) | Standard Deviation (mm) | Relative Error (%) |
---|---|---|---|---|---|
3D-printed | dc | 50 | 49.98 | 0.06 | 0.12 |
dic | 12 | 11.91 | 0.05 | 0.75 | |
l | 15 | 15.17 | 0.01 | 1.16 | |
h | 12 | 12.20 | 0.01 | 1.64 | |
Machined | dc | 50 | 49.99 | 0.06 | 0.07 |
dic | 12 | 11.97 | 0.01 | 0.30 | |
l | 17.40 | 17.31 | 0.08 | 0.54 | |
h | 12 | 11.99 | 0.09 | 0.08 |
Cam Manufacturing Process | Mean Value [µm] | Standard Deviation [µm] |
---|---|---|
3D-printed cams | 10.41 | 0.12 |
Machined cams | 0.50 | 0.03 |
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Zayas-Figueras, E.E.; Buj-Corral, I. Comparative Study about Dimensional Accuracy and Surface Finish of Constant-Breadth Cams Manufactured by FFF and CNC Milling. Micromachines 2023, 14, 377. https://doi.org/10.3390/mi14020377
Zayas-Figueras EE, Buj-Corral I. Comparative Study about Dimensional Accuracy and Surface Finish of Constant-Breadth Cams Manufactured by FFF and CNC Milling. Micromachines. 2023; 14(2):377. https://doi.org/10.3390/mi14020377
Chicago/Turabian StyleZayas-Figueras, Enrique E., and Irene Buj-Corral. 2023. "Comparative Study about Dimensional Accuracy and Surface Finish of Constant-Breadth Cams Manufactured by FFF and CNC Milling" Micromachines 14, no. 2: 377. https://doi.org/10.3390/mi14020377