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Evolution in the Cursors of the Pocket Duplex Slide Rules

Explore the evolution of pocket duplex slide rules, focusing on shapes, materials, and manufacture processes from 1958-1975 by J.G. Fernández. Learn about the considered models from Faber Castell and the factors influencing their development.

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Evolution in the Cursors of the Pocket Duplex Slide Rules

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  1. Evolution in the Cursors of the Pocket Duplex Slide Rules Shapes, materials and Manufacture 2012-06-09 By J.G. Fernández

  2. The Slide Rules The considered pocket duplex models from Faber Castell (1958 – 1975): 62/82 62/83 62/82N 62/83N 63/82 63/83

  3. The Cursors 1 2 3 4 Evolution reasons • Market competition • Technology improvements • Product optimization Evolution tracking • Patents? • Time on sale? [1] 62/82-1 62/82-2 63/82 62/82N 63/83 62/83-1 62/83-2 62/83N

  4. 4 3 5 2 6 1 7 8 Cursor Elements • Faces (front and rear) or windows • Runners • Spring strap • Closure screw (and nut) • Cursor Lines (peripheral and central or main one) • Cursor Marks • Letters to identify the use of the marks (usage letters) • Sliding Rods

  5. First Cursor: 1956 (62/82, 62/83) • Runners • Two halves • White (green text) • Rounded corners (& square) • Plastic? • Faces • Transparent plastic • Red peripheral lines at same distances from face edges • Main line not centred with face (62/82) • Widths • Runners: stability without protruding from rule body • Faces: marks and lines layout, readability, end of scales reach, aesthetic ratio?

  6. Pouring sense Assembly Face Runner Main Elements • Faces • Planar surfaces from acrylic resin “plexigum” (or plexiglass) [4] from injection • Holes on top of runners • Thicker at top and bottom ends • Runners • Halves of white resin, poured “through” the cursor face holes. • Ambient temperature process, not to affect the faces.

  7. 3 4 1 2 Other Constructive Elements • Riveted spring strap • Closure-screw nut • Hand assembly elements • Metal rods to complete cursor halves fixation

  8. Lines, Marks & Text • Engraving process [4]: • Soft impression of lines with a “warm” dividing tool (clean and sharp results) • Red colour rubbed into peripheral lines • Black colour rubbed into central line and marks • Final wet polishing of cursor inner face • Printing process: • Thermal printing • Green colour rubbed into characters • Final wet polishing of runner surface

  9. Engraving Options HOT WARM

  10. Second Cursor: 1967? (62/82, 62/83) • Runners • Two halves • Integrated in face (white text) • Same width as face • Faces • Transparent plastic • Mould-injected piece combines one face and two runner halves • Peripheral lines at same distances from face edges • Main line not centred with face • Only black colour (62/82) • Manufacturing • Single injection process completes halves (maybe both at same time) • Designed for much simpler assembly and adjusting process

  11. 2 5 9 7 6 1 8 3 4 Constructive Elements • Openings to hold spring strap • Small assembly elements • Longer holes for assembly elements • Grooves for handling • Cuts for assembly positioning • Internal spacing surface • Star-shaped closure nut • Sliding rods • Hand-disassembling opening

  12. Injection Step 1: • Mould parts (at least 2) are open • Injector is filled with melted plastic Mould Injection Process Summary

  13. Injection Step 2: • Mould is hold closed at high pressure • Injector fills mould cavity and plastic solidifies Mould Injection Process Summary

  14. Injection Step 3: • Mould opens • Piece is attached to one part Mould Injection Process Summary

  15. Injection Step 4: • Mould ejects the piece • Piece falls to container Mould Injection Process Summary

  16. Injection Step 4: • Mould ejects the piece • Piece falls to container • Injection with Insert Step 1: • Insert piece is placed in mould with mould open • Injector fills with melted plastic Mould Injection Process Summary

  17. Injection Step 4: • Mould ejects the piece • Piece falls to container • Injection with Insert Step 2: • With mould closed melted plastic is injected in cavity • Plastic solidifies with insert Mould Injection Process Summary

  18. Injection Step 4: • Mould ejects the piece • Piece falls to container • Injection with Insert Step 3 & 4: • Mould opens and ejects the piece • Plastic piece falls to container Mould Injection Process Summary

  19. 3 2 3 2 2 1 1 Details of inserted metallic pieces • Inserted Nut • In a cylindrical hole • Knurled body to interfere with the plastic wall • Air spaces between nut and plastic • Nut has been inserted after injection • Inserted Rod • Cylindrical hole in the plastic • Rod has chamfers in the ends • Air spaces between chamfers and walls • Rod has been inserted after injection

  20. Lines, Marks and Texts • Engraving process: • Lines, marks and usage letters from injection mould • Black colour rubbed into all of them • Final wet polishing of cursor inner face • One mould per cursor (62/82 and 62/83) • Printing process: • Thermal printing • White colour rubbed into characters • Final wet polishing of runner surface

  21. Third Cursor: 1970 (63/82, 63/83) • Runners • Two halves • Integrated in face • Wider than face (like 1st type) • Faces • Transparent plastic • Mould-injected piece combines one face and two runner halves • Main line centred with face • Peripheral lines asymmetrical from face centre • Only black colour (63/83) • Manufacturing • Single injection process completes halves (maybe both at same time) • Cost optimization by material savings, process communalization and robustness reduction

  22. 3 6 2 4 1 7 5 Constructive Elements • Openings to hold spring strap • Small assembly elements • Openings for right cursor assembly • Star-shaped nut (inserted after injection) • Plastic sliding rods • Internal spacing elements • Hand-disassembling opening

  23. Nut Placement Specific Engraving 63/82 or 63/83 Painting in Black Injection Common Engraving Lines, Marks and Texts • Engraving process: • Lines, marks and usage letters by thermal printing • Black colour rubbed into all of them • Final wet polishing of cursor inner face • Same mould for both cursors (63/82 and 63/83) Cursor face manufacture process (assumption)

  24. Fourth Cursor: 1972 (62/82N, 62/83N) • Runners • Two halves • Integrated in face • Same width as face • Faces • Transparent plastic • Mould-injected piece combines one face and two runner halves • Main line centred with face • Peripheral lines asymmetrical from face centre • Only black colour (62/82N) • Manufacturing • Single injection process completes halves (maybe both at same time) • Robustness from second type with cost optimization from third type

  25. 4 1 2 6 7 3 5 Constructive Elements • Small assembly elements • Star-shaped nut • Sliding rods • Hand-disassembling opening • Internal spacing elements • Closed holes for spring strap • Wrong assembly disabler

  26. 2 3 3 2 1 2 1 4 4 Details of inserted metallic pieces • Inserted Nut • In a cylindrical hole • Knurled body to interfere with the plastic wall • Air spaces between nut and plastic • Rests of ripped-off plastic • Nut has been inserted after injection • Inserted Rod • Cylindrical hole in the plastic • Rod has chamfers in the ends • Air spaces between chamfers and walls • Heat excess when drilling or when inserted? • Rod has been inserted after injection

  27. Lines, Marks and Texts • Engraving process: • Lines, marks and usage letters by ultrasounds printing • Black colour rubbed into all of them • Final wet polishing of cursor inner face • Same mould for both cursors (62/82N and 62/83N) • Printing process: • Thermal printing • White colour rubbed into characters • Final wet polishing of runner surface

  28. First Step: • US head descends, already vibrating • The moment it touches the plastic surface, the friction generates heat • US head ends descent already vibrating • Second Step: • US stops • US head stays in place, cooling the plastic • Third Step: • US head returns up leaving the printed plastic • Extra plastic rims are flattened Ultrasound Thermal Printing

  29. Acknowledgements: • Thank you for such good advice and support: • Jorge Fábregas • Antonio Medina • Dieter von Jezierski • Peter Holland …although any mistake is only my fault! Bibliography: [1] “Rechenschieber – Slide Rules A.W.Faber, A.W.Faber-Castell”, by Peter Holland. Fourth edition of 2011 [2] “Exterior hairlines in Faber Castell cursors”, by J.G.Fernández, 2009 [3] British Plastics Federation - http://www.bpf.co.uk/Plastipedia/Processes/Default.aspx [4] Manufacturing process indications recollected by Dieter von Jezierski

  30. Taking Pictures… Impossible colours Annex: Open Issues for next… Complete this study (more specimens per type, screw standard…) Why there was no magnifying effect in these cursors? Cursor assembly process in the manufacturing plant? (screws automatically inserted…) Cursor dimensions ratios? Why? Desktop duplex slide rule cursors? Impossible thickness

  31. Thank You! 2012-06-09 By J.G. Fernández

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