This document describes the model-driven digital fabrication process used to design and construct a complex elliptical stair feature at the Seagram Building in New York City. Key points: - A parametric 3D model was used from concept through fabrication to enable simultaneous production of custom parts off-site, minimize on-site work, and reduce the tight construction timeline. - The model incorporated design, engineering, fabrication drawings, logistics planning, and installation instructions to enable production of prefabricated assemblies. - Off-site fabrication of steel, Corian, and other materials allowed construction of the stair sections in less than a week on-site through the use of custom jigs and perfectly fitting prefabricated components

1. VECTOR PRAXIS: MODEL DRIVEN DIGITAL FABRICATION

2. EVERY PART IN EXACTLY THE RIGHT PLACE
A MODEL DRIVEN APPROACH TO OFF-SITE,
HIGH- TOLERANCE, ULTRA-CUSTOM FABRICATION

3. THE PROJECT:
-‘AAA’ FEATURE STAIR
- SEAGRAM BUILDING, 375 PARK AVENUE, NY
-STAIR CONNECTS THE 23RD AND 24TH FLOOR
-PROJECT ARCHITECT: GENSLER
-GENERAL CONTRACTOR: TRISTAR CONSTRUCTION
-CONTRACT: DESIGN, DETAIL, BUILD SERVICES
-MATERIALS: STEEL, CORIAN, GLASS, STAINLESS STEEL

4. CHALLENGES/OPPORTUNITIES
FEATURE STAIR
-COMPLEX GEOMETRY (ELLIPTICAL STAIR)
-NYC SITE (LISTED BUILDING)
-TIGHT FABRICATION TIMELINE
-TIGHT COORDINATION REQUIRED FOR
ON-SITE WORK
-DESIRE TO MINIMIZE TENANT DISRUPTION
-UNDERSIZED FREIGHT ELEVATOR
-CORIAN CLADDING REQUIRES HIGH
TOLERANCE STEEL STRUCTURE (+/- 1/8”)
-ABSOLUTE NOVELTY OF PROCESS

5. CONCEPT
MODEL
DRAWINGS
JIGS
PART
ASSEMBLY
LOGISTICS
INSTALLATION

6. SIMULTANEOUS VERSUS SEQUENTIAL FABRICATION

7. PHASE 1
CONCEPT AND DESIGN DEVELOPMENT

8. SKETCHES QUICKLY LEAD TO A WORKING MODEL THAT GROWS
MORE ROBUST AS DESIGN DECISIONS ARE MADE

9. THE SITE IS CAREFULLY ANALYZED

10. CONCRETE CHIPPED AWAY FROM STEEL
GIRDERS, SITE MEASUREMENTS TAKEN

11. A PARAMETRIC MODEL IS PRODUCED THAT REPRESENTS A BUILDABLE
REALITY. THE MODEL BECOMES THE CARRIER OF ALL INPUT

12. WITH RENDERINGS THAT REFLECT ACTUAL
CONSTRUCTABILITY

13. ACCURATE ARCHITECT INPUT CAPTURE LEADS TO
FASTER RESOLUTIONS AND SPEEDIER APPROVALS

14. OUR SOLIDWORKS MODELS CAN BE RAPIDLY UPDATED AND VARIOUS
CONFIGURATIONS TESTED WITH FULL PARAMETRIC CONTROL
Ie. MAKE CHANGES TO THE THICKNESS OF A GIVEN MATERIAL AND THE MODEL WILL
RESPOND TO ALTER AFFECTED ASSEMBLIES AND COMPONENTS.

15. WE DESIGN MULTI-MATERIAL ASSEMBLIES FOR FASTER AND MORE
ACCURATE INSTALLATION- A PRECISE KIT OF PARTS

16. INTEGRATED ‘POUR
STOP’ ASSEMBLY
-COMPLETE GLASS SHOE
-ALL STRUCTURE REQ’D TO
CONNECT TO BASE BUILDING
-INSTALLED TO EXACT CEILING
HEIGHT FOR APPROPRIATE
REVEALS AND OTHER ARCH
DETAILS

17. -THIS INTEGRATED POURSTOP
ASSEMBLY COMBINES THE
WORK OF 5 TRADES IN ONE
PRE-FABRICATED PART
-WHAT COULD TAKE WEEKS TO
INSTALL USING TYPICAL
METHODS, TAKES A COUPLE
DAYS TO INSTALL
MONTHS BECOME WEEKS, WEEKS
BECOME DAYS

18. LOGISTICAL CONSIDERATIONS ARE UNDERSTOOD THROUGH THE
MODEL AND FORM A SIGNIFICANT PART OF THE DESIGN PROCESS

19. PHASE 2
MASTER MODEL
THE MODEL CONTAINS:
CUT FILES
BILL OF MATERIALS
WEIGHT OF MATERIALS
LOGISTICS AND SHIPPING INFORMATION
COST CALCULATIONS
DESIGN DOCUMENTS
FABRICATION DRAWINGS FOR OUTSIDE TRADES
ASSEMBLY DRAWINGS
JIG AND FIXTURE SYSTEMS FOR FABRICATION
INFORMATION FOR COORDINATION WITH CLIENT
ETC.
THIS IS TRUE PARAMETRIC BIM.

20. MODEL
GEOMETRY
READILY
EXPORTED TO
ENGINEERING
SOFTWARE FOR
LOAD ANALYSIS
AND STRUCTURAL
REFINEMENT AS
REQUIRED

21. TEMPLATES ARE PRODUCED FROM MODEL GEOMETRY TO
AID CONTRACTOR WITH LAYOUT AND DEMOLITION

22. A SIMILAR TEMPLATE RECREATES THE SITE
CONDITION IN THE SHOP

23. EXTREMELY ACCURATE ASSEMBLIES ARE
PRODUCED FROM THIS TEMPLATE SYSTEM

24. A SERIES OF JIG SYSTEMS ARE PRODUCED WITHIN THE
MODEL FOR THE FABRICATION OF STEEL AND CORIAN
COMPONENTS
STEEL ASSEMBLY JIG CORIAN ASSEMBLY JIG

25. FROM MODEL TO SHOP FLOOR
JIG FOR STRUCTURAL STEEL AND
HANDRAIL
JIG FOR CORIAN BENDING

26. CUT FILES SENT OUT TO STEEL FABRICATOR FOR
PRECISE CUTTING AND ROLLING

27. PHASE 3
SIMULTANEOUS PRODUCTION OF ALLIED PARTS &
ASSEMBLIES IN SEPARATE LOCATIONS

28. STEEL STRINGERS ASSEMBLED IN JIG

29. STAIR SECTIONS ASSEMBLED

30. FROM DRAWINGS EXTRACTED FROM THE MASTER MODEL

31. MEANWHILE CORIAN PRODUCTION BEGINS AT
SOLID SURFACE FABRICATOR

32. OTHER COMPONENTS CONTINUE TO BE
PRODUCED AT VP SHOP

33. FABRICATION DRAWINGS FROM THE MODEL ENABLE HIGH
PRECISION FABRICATION AND PERFECT FIT

34. HANDRAIL BENDING AND FITTING TO JIG

35. IN-HOUSE TESTING OF
COMPONENTS AND ADHESIVES

36. HOIST POINTS ARE CALCULATED THROUGH THE
MODEL AND ELIMINATE GUESSWORK

37. SPLICE PLATES CONNECT STAIR SECTIONS
AND ELIMINATE ON-SITE WELDING

38. ALL DETAILED EXCLUSIVELY
THROUGH THE MODEL

39. AS CORIAN SECTIONS ARE COMPLETED THEY CAN BE TEST
FIT TO THE MASTER JIG WITH STEEL STRUCTURE ASSEMBLED

40. WHILE FABRICATION CONTINUES ON OUR END, BASE BUILDING
STEEL IS GOING IN, READY FOR OUR WORK WITHOUT DELAY

41. PHASE 4
SHIPPING COMPLETE ASSEMBLIES ‘JUST-IN-TIME’ TO
SITE FOR IMMEDIATE ERECTION

42. STAIR ASSEMBLIES WITH CUSTOM CARTS DESIGNED TO
FIT WITHIN SITE ELEVATOR AID INSTALLATION

43. STEEL ERECTION
DETAILED INSTALLATION
DRAWINGS PRODUCED
FROM THE MODEL FOR USE
BY THE NYC ERECTOR

44. LOAD-IN OF STEEL

45. HOISTING STEEL SECTIONS INTO POSITION

46. THE STAIR SECTIONS ARE ERECTED ON-SITE IN
LESS THAN A WEEK

47. CORIAN INSTALLATION
THE CORIAN IS INSTALLED PERFECTLY, ENABLING CONCURRENT GLASS INSTALLATION WHILE THE CONTRACTOR
COMPLETES OTHER SITE WORK

48. CORIAN COMPONENTS SLEEVE OVER STEEL STRUCTURE

49. CORIAN COMPLETE, TREADS TO GO IN

50. MODEL DRIVEN FABRICATION ENABLES TREADS TO BE LASER CUT OFF-SITE.
TREADS AND RISERS ARE INSTALLED ON-SITE IN 2.5 DAYS

51. INSTALLATION OF HANDRAIL

52. A CENTRAL JIG ENABLES THE HANDRAIL TO BE OFF-SITE FABRICATED AVOIDING SEQUENTIAL
PRODUCTION AND SHAVING WEEKS OFF THE PROCESS

53. COMPLETION IMAGES