pocket duplex slide rule cursors evolution evolution in the cursors of the pocket duplex slide rules...

Pocket Duplex Slide Rule Cursors Evolution

Evolution in the Cursors of the Pocket Duplex Slide Rules

Shapes, materials and Manufacture

By J.G. Fernández

2012-06-09


The Slide RulesThe considered pocket duplex models from Faber Castell (1958 – 1975):

62/82 62/83

62/83N62/82N

63/82 63/83


The Cursors

62/82-1

62/83-1 62/83N

62/82N63/82

63/83

62/82-2

62/83-2

1 432

Evolution reasons Market competition

Technology improvements

Product optimization

Evolution tracking Patents?

Time on sale? [1]


Cursor Elements

3

1

5

7

8

62

4

1. Faces (front and rear) or windows

2. Runners

3. Spring strap

4. Closure screw (and nut)

5. Cursor Lines (peripheral and central or main one)

6. Cursor Marks

7. Letters to identify the use of the marks (usage letters)

8. Sliding Rods


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

Widths• Runners: stability without protruding from rule body

• Faces: marks and lines layout, readability, end of scales reach, aesthetic ratio?

(62/82)


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.

Pouring sense Face

Runner

Assembly


Other Constructive Elements

1. Riveted spring strap

2. Closure-screw nut

3. Hand assembly elements

4. Metal rods to complete cursor halves fixation

1

3

2

4


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


Engraving OptionsW

AR

M HOT


Second Cursor: 1967? (62/82, 62/83)


• Integrated in face (white text)

• Same width as face


• 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

Manufacturing• Single injection process completes halves (maybe both at same time)

• Designed for much simpler assembly and adjusting process

(62/82)


Constructive Elements

1. Openings to hold spring strap

2. Small assembly elements

3. Longer holes for assembly elements

4. Grooves for handling

5. Cuts for assembly positioning

1 67

5

8

2

34

9

6. Internal spacing surface

7. Star-shaped closure nut

8. Sliding rods

9. Hand-disassembling opening


Mould Injection Process Summary

Injection Step 1:

• Mould parts (at least 2) are open

• Injector is filled with melted plastic


Injection Step 2:

• Mould is hold closed at high pressure

• Injector fills mould cavity and plastic solidifies



Injection Step 3:

• Mould opens

• Piece is attached to one part



Injection Step 4:

• Mould ejects the piece

• Piece falls to container



Injection Step 4:




Injection with Insert Step 1:

• Insert piece is placed in mould with mould open

• Injector fills with melted plastic


Injection with Insert Step 2:

• With mould closed melted plastic is injected in cavity

• Plastic solidifies with insert

Injection Step 4:





Injection with Insert Step 3 & 4:

• Mould opens and ejects the piece

• Plastic piece falls to container

Injection Step 4:





Details of inserted metallic pieces

Inserted Nut1. In a cylindrical hole

2. Knurled body to interfere with the plastic wall

3. Air spaces between nut and plastic

Nut has been inserted after injection

Inserted Rod1. Cylindrical hole in the plastic

2. Rod has chamfers in the ends

3. Air spaces between chamfers and walls

Rod has been inserted after injection

1

2 3

2

2

1

3


Lines, Marks and Texts

Engraving process:

• Lines, marks and usage letters from injection mould

• Black colour rubbed into all of them


• One mould per cursor (62/82 and 62/83)

Printing process:


• White colour rubbed into characters



Third Cursor: 1970 (63/82, 63/83)


• Integrated in face

• Wider than face (like 1st type)



• Main line centred with face

• Peripheral lines asymmetrical from face centre



• Cost optimization by material savings, process communalization and robustness reduction

(63/83)



1. Openings to hold spring strap


3. Openings for right cursor assembly

4. Star-shaped nut (inserted after injection)

5. Plastic sliding rods

6. Internal spacing elements


75

2

36

14



Engraving process:

• Lines, marks and usage letters by thermal printing



• Same mould for both cursors (63/82 and 63/83)

InjectionNut

PlacementCommonEngraving

Specific Engraving63/82 or 63/83

Paintingin Black

Cursor face manufacture process (assumption)


Fourth Cursor: 1972 (62/82N, 62/83N)


• Integrated in face

• Same width as face



• Main line centred with face

• Peripheral lines asymmetrical from face centre



• Robustness from second type with cost optimization from third type

(62/82N)




2. Star-shaped nut

3. Sliding rods


53

5. Internal spacing elements

6. Closed holes for spring strap

7. Wrong assembly disabler

12

6

4

7


Details of inserted metallic pieces

Inserted Nut1. In a cylindrical hole

2. Knurled body to interfere with the plastic wall

3. Air spaces between nut and plastic

4. Rests of ripped-off plastic

Nut has been inserted after injection

Inserted Rod1. Cylindrical hole in the plastic

2. Rod has chamfers in the ends

3. Air spaces between chamfers and walls

4. Heat excess when drilling or when inserted?

Rod has been inserted after injection

1

2 3

4

2

2

1

3

4



Engraving process:

• Lines, marks and usage letters by ultrasounds printing



• Same mould for both cursors (62/82N and 62/83N)

Printing process:


• White colour rubbed into characters



Ultrasound Thermal PrintingFirst Step:

a) US head descends, already vibrating

b) The moment it touches the plastic surface, the friction generates heat

c) 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


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


Annex: Open Issues for next…1. Complete this study (more specimens per type, screw standard…)

2. Why there was no magnifying effect in these cursors?

3. Cursor assembly process in the manufacturing plant? (screws automatically inserted…)

4. Cursor dimensions ratios? Why?

5. Desktop duplex slide rule cursors?

Taking Pictures…

Impossible coloursImpossible thickness


Thank You!

By J.G. Fernández

2012-06-09

pocket duplex slide rule cursors evolution evolution in the cursors of the pocket duplex slide rules...

Documents

opening slide

melted plastic slide

piece piece

piece plastic piece

container injection

injection holes

insert injection step

mould parts