Assembling the whole lathe!

1. 1
5/4/16

2. • Schedule Updates
• Assembly
– Dancing Man
– Z-Axis Drive
– Base
– Drive Train
– Miscellaneous
– Assembly
– Testing
– Pimp
2

3. • Finished
assembly!
• Behind Schedule
– Could use more
characterization
– How to improve
errors we see
• Gantt Chart on
Next Slide
3

4. 4
Link to schedule:
https://teamgantt.com/gantt/schedule/?ids=582767#&ids=582767&user=&custom=&company=&hide_complet
ed=false&date_filter=&color_filter

5. 5
Parameter Value Comments
Max
Misalign-
ment
X 0.003” Accounting for misalignment in carriage
rails and bowing of rails & leadscrewY 0.003”
Theta X 0.0015 rad Assuming bowing in leadscrew plus some
rail misalignmentTheta Y 0.0015 rad
Stiffness
X <5000 lb/in Radial stiffness of leadscrew is about 2E4
in/lb; putting stiffness of DMF at 1/4 of
leadscrew should reduce leadscrew
deformation by ~1/5
Y <5000 lb/in
Theta
X/Y
Falls out from maximizing theta z stiffness, minimizing x
and y stiffness, and other design constraints
Z error budget 5 microns
Theta Z error budget 0.0008 rad Contributes to z error by thetaz/(2pi) * pitch
Torque to turn < 5 lb-in Hands exert ~3-5 lb-in to twist a doorknob
Nut preload

6. 6
• Purpose is to transfer
load along z direction.
• FACT used to
determine constraints
to be used.
• 4 DOF required.
• Middle stage (arms of
man) essential.
• 3 pieces allow for
planes and rods to be
made.

7. 7
Constraint
s in the
form of
planes
and rods
for correct
DOF
Manufacturability
considered – has
to fit through
structural tube
slot.
Compliant
only in
theta-z
and delta-
z
Preload can be
adjusted by a bolt
which clamps the
legs

8. 8
• Effective
Cutting Force
– 0.040” depth
– 0.003”/rev feed
• Fx = 4.40 lb
Fy = 7.56 lb
Fz = 3.76 lb
• Forces FOS of
2

9. 9
• With a Lilly
on top:
– Fy = 120 lb
– Fy, applied = 6
lb
• FOS > 10
• Ky ≈ 8000
lb/in

10. 10
• Law of Superposition
• Max stress at fillet of lower wire flexures
– Cutting forces (without 2x FOS): 0.91E4 psi
– Misalignment: 1.98E4 psi
– Total: 2.89E4 psi
– FOS (yield @ 3.99E4 psi): 1.4
• Wire flexure width limited by machining
capability of waterjet

11. 11

12. 12
Flat for
Tightening
Positive
Locking
Thrust BearingBrass Bushing
Dancing Man
Positive
Locking

13. 13
Shortened
Bushing
Lengthened
Slit
Hole for
Preload
Adjustment
Z-Axis
Constraint
Preload
Washer

14. 14
• Everything went
smoothly
• Threaded into
dancing man a bit
low
– Fixed with a
bottoming tap
• Band-sawed off
non-vital side
support

15. 15
• Issue with pre-
drilled holes
not matching
spindle holes
– Drilled holes
out more – a
bit skew
• Included hole
to avoid
leadscrew
interference

16. 16
• Few adjustments for dancing man and extra travel
distance

17. 17
• 1C Epoxy
– Easier than J-B Weld to un-pot if
potted wrong
– Stiffness of all were close
– Cure time worth it
– Price lower than similar options

18. 18
• Rails Specs
– ¾” Diameter
– 12” Long
– 1566 Ground Steel
– Max Deflection:
• 1.5 microns in y, non-
critical direction

19. 19
• Flat belt is more
efficient, flat belts
themselves are
commercially
available
• Flat belt pulleys in
appropriate
ratio/size are not
commercially
available

20. • Two parts: outer crown
and inner shaft seat
– Crown was 3D printed,
solid infill for optimal
support strength
– Shaft seat was machined
out of aluminum
– Pieces were joined with
Gorilla glue

21. • Made of 2
waterjetted parts:
One tensions the
belt, the other
compresses the
flexure (to prevent
overextension)
• Polyethylene
• Bill picked the
“PIMP” text

22. 22
• Thermoformed belt/pulley
guard
• 1/16” plastic

23. 23
• Checked for full
travel
• Checked for
interference

24. 24
• Assembly done on a flat surface for alignment
• Systematic assembly

25. 25
• Testing preload vs effective stiffness on z-axis
bearings
• Flanged nut rotation accurate to within 1/16 of a rev.

26. 26
• Testing turning torque based on DMF preload
• Bearing preload is expected to dominate at
asymptote.

27. 27
• Issues with belt order, so used rubber band

28. 28

29. 29
• Pulley’s:
– they glow!

30. Thank You
30
Questions?

31. EXTRA SLIDES
31

32. Requirement </=/> Number Unit
Cutting Depth </= 0.030 in
RPM </= 1300 rpm
Material Removal Rate </= 0.010 in3/s
Lifetime >/= 3120 hours
Repeatability
(without temp effects)
</= 50
Microns (for
</=2xOD)
Be Pimp-Tastic > 8 infinite
**Runs at 8V, or 1067RPM

33. 33
• Misalignment
– X: 0.0025”
– Y: 0.0025”
– Θx: 0.001
– Θy: 0.001

34. 34
Mode No. Freq (Hertz) X direction Y direction Z direction
1 0.010359 2.4313e-018 4.0277e-020 0.99982
2 416.1 0.0083849 2.8548e-008 6.2394e-018
3 507.49 0.13095 1.5347e-005 8.5241e-019
4 794 0.85357 1.3126e-005 2.4342e-018
5 825.86 3.8203e-005 0.00081055 7.4597e-020

35. 35

36. 36

37. 37

38. 38
• 72 hour process
• Assembled on a flat
surface

39. • Allow for Z-axis misalignment (+1 DOF)
• Allow for human hand movement increments to
produce a x-axis motion of < 50 microns
• Error Allotment </= 7 microns
• Stationary Handle , </= 250 microns linear
movements
• Start Torque </= 4lb-inch (ideal </= 2lb-inch)
• Lifetime =/> 3120 hours (12 hrs/week, 52
weeks/year, 5 years), at 60 rpm for rotary
• Natural Frequency =/> 80Hz
• Withstand: Fx=20lbs, Fy=135lbs, Fz=60lbs,
• Range of Motion =/> 0.3 inches

40. 40
• text