Daniel Paul Chairs

Senior Design ProjectME 450

Adrien Raucoules

Andrew (Tim) Northcutt

Michael Massey

Dillon O’Connor

December 12, 2014

1

• Stacking chairs are the chair of choice for most high volume public settings

• Hotels

• Restaurants

• Convention centers

• Corporate Offices

• Dependable construction

• Extensive customization options

• Stack for convenient storage

Introduction to Stacking Chairs

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• Most of the industry has moved production overseas

• Many aspects of the production are becoming more modernized

• Modernization has allowed some of the work to return to the United States

• However, a critical aspect of production has resisted modernization

• Chair back assembly has not experienced substantial improvement since 1953

Production of Stacking Chairs

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• Most chair backs are made with a “sandwich” construction, where separate front

and back pieces are upholstered and attached to one another

• Requires a skilled laborer to perform this task manually

• Tremendous range of customization options for chair back shape, material,

cushion, and upholstery

• Growing number of styles and combinations of chair backs as customers

demand more and more

• Each chair back is a significant investment of time

The Problem

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Sandwich Construction

Wood Panels without Upholstery Wood Panels with Upholstery5

• Clean and professional appearance

• No mounting hardware is visible to the user

• Staples are safely contained between the two pieces

• Most of the seam between the two pieces is hidden

within the frame of the chair

• Upholstery appears seamless

Finished Sandwich Chair Back

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Functions and Requirements• Not compromising the rigidity of the chair itself

• Decrease the time of assembly

• Increase production of as many chair styles as possible from the 2000 series

tubular steel frame chairs (with wood backs) from 12 per hour to 13~15 per

hour

• There are currently 31 total frame styles in this series

• Increase production of as many chair styles as possible from the 2000 series

aluminum frame chairs (from China) from 5 per hour to 6~8 per hour

• There are currently 25 total frame styles in this series

• As many back styles as possible with these frames

• Does not have to work for every design 7

Economizing Rigidity

• The more points of connection to the frame means better rigidity

• More points of connection means more parts and time spent making the

connection

• Stronger materials and/or a greater amount of material used in mounting hardware

(nuts, bolts, clips, fasteners, etc.) factors into rigidity

• Stronger materials or a greater amount of material comes at a higher cost

• Find a balance between time and cost of mounting hardware and rigidity of the

chair back

8

Brainstorming

• Injection molding

• Clip mounting tool

• Uniform hole pattern

• Grid pattern

• Asterisk pattern

• Clip modification

• Extended clips

• Universal sheet with Anti-Spin Receiver (ASR)9

Dead on Arrival

• We thought some injection molded designs would be ideal for mass production

• Molds are very expensive to design, and there are too many different backs that

would need separate molds

• Production of individual styles are not large enough to alleviate the initial

expense

• We thought a clip mounting gun or lever based machine would help save time

applying clips to chair frames

• Design of such equipment would be difficult

• The amount of time potentially saved here was deemed trivial

10

Dead on Arrival(Continued)

Lever Based Clip Application Machine Injection Molded Parts

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Uniform Hole Pattern - Grid

• A sheet of material with a grid pattern of holes that could be mass produced

• Almost any chair back shape could be cut out and the holes would already be in

place for mounting to corresponding chair frames

• Excessive hole count would compromise rigidity

• Intended for injection molding where holes are made as part of

the mold

• Wood requires additional time and expense of

CNC machining each hole

• Unused holes equate to wasted machine time12

Uniform Hole Pattern - Asterisk• A sheet of material with an asterisk shaped pattern of holes that could be mass

produced

• Work similarly to the grid hole pattern but with less holes and greater material

thickness around holes to avoid a loss in rigidity

• Intended for injection molding where holes are made as part of the mold

• Wood requires additional time and expense of CNC machining

each hole

• Unused holes equate to wasted machine time

• Thickness variation around the hole pattern is not feasible

• Possible companion to an extended clip design13

Extended Mounting Clip

• A longer clip with an assortment of holes to facilitate connection to chair back

faces regardless of frame geometry

• Increased size of clip improves rigidity of chair back

• Requires more material (at the thickness of current clips) to make and thus is

marginally more expensive

• Not substantial enough an improvement in production

time to validate the cost

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Anti-Spin Receiver (ASR)

• Mr. Barile expressed concern with current fasteners that spin while mounting chair

backs

• Hinders tightening of bolts

• Can snag loose strands of upholstery

• Suggested a plastic receiver in an oblong shape to prevent spinning

• Provided a preliminary prototype for reference

• We dubbed this design the Anti-Spin Receiver (ASR)

• Compatible with barbs that help in the upholstery process as well as threaded bolts

• Includes a slot for variable adjustments15

Anti-Spin

Receiver

(ASR)(Continued)

16

Uniform Hole Pattern - ASR

• A sheet of material with a standard pattern of holes that could be mass produced

and work for a variety of chair back styles is still a goal

• However, the hole pattern can accommodate the ASR

• Must work with wood

• Compatibility with injection molding for future endeavors is desirable

• Must have a lip at outermost perimeter of chair back for upholstery process

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Idea Cost Ease of

Manufacturing

Rigidity Efficiency

(Time)

Total

Grid Hole Pattern 2 3 3 7 15

Asterisk Hole Pattern 3 3 5 7 18

Extended Clips 3 7 7 5 22

ASR Hole Pattern 7 8 5 7 27

Scored 1 (poor) through 10 (great)

5 represents no change from current methods

Concept Selection

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Narrowing the Field• Variety is an understatement about possible chair styles

• Daniel Paul Chairs offers an immense variety of

stacking chair styles with very different chair backs.

However, some chair back styles work for multiple

frames

• The chair backs shown in models 2125-RFP-RGG,

2165-HH, 2155-HH, and 2115-HH are used in 21 of

31 steel frames and 13 of 25 aluminum frames

• Model 1900-HH has a simple chair back that can be

used for future steel and aluminum chair styles 19

Rectangular

• Demonstrated in frame 2125-RFP-RGG

• We call this chair back style the “rectangular”

chair back

• Named due to its basic four sided shape

20

Taper

• Demonstrated in frame 2165-HH

• We call this chair back style the “taper” chair

back

• Named due to its basic four sided shape with

a mild taper along its height

21

Oval

• Demonstrated in frame 2155-HH

• We call this chair back style the “oval” chair

back

• Named due to its basic shape

22

Ghost

• Demonstrated in frame 1900-HH

• We call this chair back style the “ghost” chair

back

• Named due to its shape, which we felt

resembled a traditional ghost

23

Lady

• Demonstrated in frame 2115-HH

• We call this chair back style the “lady” chair

back

• Named due to its elegant shape

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Proposed Design

• Works for rectangular, taper, oval, and ghost chair back shapes

• We were not able to factor in the lady chair back shape

• When crafting from wood, holes can be made using standard drill bits that are

drilled in and dragged along in a straight line for 1/2 in

• 3/8 in through for body of clip

• 1/2 in to recess for lip to lie flush into the chair back

• Ideal with injection molding

• Outermost lip for each shape is discretely included in the structural webbing

• Requires one mold to be made

• Some extraneous material will be wasted25

Proposed ASR

3D Model of ASR Drawing of ASR26

Proposed ASR Clip

3D Model of ASR Clip Drawing of ASR Clip

27

Proposed Uniform Sheet

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Analysis of Proto-PrototypeEngineering analysis was done using the following

setup:

• Smallest area frame (oval)

• Using the primary chair back material as ABS

Plastic

• Assuming the ASR pieces are made of ABS plastic

and the ASR clips and chair frame are made of

extruded aluminum (Aluminum 6061)

• Thickness of frame walls is 1/16 in

• The max pressure supported by the back frame is

0.68 psi which equates to a 150 lb force over the

220 in² surface area Oval Chair Back

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Analysis of Proto-Prototype(continued)

Results:

• Our analysis concludes that with proper spacing of the

ASR and ASR clips, the majority of the force is

distributed directly to the frame

• The back panel has no noticeable effect on the

performance and is merely aesthetic

• The max stress was ~40 ksi, centered around the bend of

the frame where it would attach to the base

• The max displacement appeared at the top portion of the

frame at ~3.5 in

Stress Analysis

Deflection 30

Preparation for Moving Forward

• Our work will continue into ME 460 in the spring

• To facilitate keeping our work on target we have established a work task

breakdown

• We have a Gantt chart to keep up with our deadlines and task progression in one

convenient diagram

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Work Breakdown

StructureGantt Chart

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Delegation

of Tasks

• Procure Materials - Michael Massey

• Prepare Test Plan - Tim Northcutt

• Fabricate Parts - Dillon O’Connor

• Assemble System - Adrien Raucoules

• Test System - Tim Northcutt

• Final Presentation - Dillon O’Connor

• Write Report - Adrien Raucoules

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Bill of Materials

Each chair would require the following:

• 1 frame of desired shape

• 1 wood/plastic chair front panel

• Cut to desired shape

• 1 wood/plastic chair back panel

• Cut to desired shape

• 6 ASR pieces

• 6 ASR clips

• 6 1/16 screws

• 6 barbed nails

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Cost Estimates

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Conclusion

• We are confident this idea can work

• However, we have our work cut out for next semester

• With the continued support from Daniel Paul Chairs and Mr. Barile we hope to

chip away at the stalemate in chair back construction

• We intend to try to verify the accuracy of our estimates about both the money

saved in materials and the time saved per chair

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References

• Slides 2, 6, 20-24: images courtesy of Daniel Paul Chairs

(www.danielpaulchairs.com)

• Slide 9, 19, 33: images courtesy of Google Images

• Slide 16: images courtesy of Pete Barile

• Slides 2, 3, 4, 35: information courtesy of Pete Barile

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Questions?

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