1. Center for Research in Engineering Sciences and Technology
Topic: Rotomolding method for manufacturing modular structure
Center for Research in Engineering Sciences and Technology

2. Basic Background of idea
Construction of an Automotive Body in White(BIW) [1] structure is achieved by processes stamping (making the sheet metal panel to form) , the stamped panels are joined (assembled) by welding/ bolting/ riveting/ bonding.
This further goes through a painting process. This is required to protect the metal panels from corrosion.
After painting the BIW goes for wiring harness fitment, usually done by fitting clips to hold the harness to the BIW.
Trimming required to hide the harness and the metal body ( functions for aesthetics as well as safety of the passenger)
Fitment of other aggregates done at the trim chassis final assembly line.
Fig 1. shows a cut section through the BIW , A Pillar of the automotive.
Fig 2. Shows electric harness which are assembled on the BIW with clips.
Fig 1
Fig 2
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3. Basic Background of idea
Assembly process for making any structure example Automotive & Aircraft interiors, exteriors Construction etc. has a huge scope of reduction in terms of Time and Cost.
The idea is to reduce the processes , cost and time for making structures for any application in general. This can be achieved by a integrated modular structure.
Example taken is the Automotive assembly line for cars
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4. Time Savings – Car Body Assembly comparison.
Welding of Structure ~ 5 Hrs.
Painting & Sealing ~4 Hrs.
Assembly ,Wiring, Trimming ~6 Hrs.
Body Assembly Time(~15 hrs.) Inside Plant
Current Process *
* Unaccounted Sheet metal stamping time
Proposed Process
Rotomolded structure with harness, trim, carbon fiber embedded and painted~ 8 Hrs.
Rotomolded Body Assembly Time(~3 hrs.) Inside Plant
Assembly of Structure ~ 3Hrs.
Rotomolded Body Assembly Time(~8 hrs.) Outside Plant
Savings of 4 hours per vehicle.
Is 25% increase in productivity
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Sample Footer

5. Description of the innovation – How to make an integrated modular structure
Available state of Art.
Rotomolding is a process in which powdered plastic is introduced into a set of molds and is heated till the plastic powder melts to a viscous fluid which can stick to the mold walls when rotated in a biaxial direction. The mold is rotated inside a furnace for a set time period which makes the plastic form(stick) on the sides of the mold forming a hollow component which has a shape of the mold.
Process advantages of rotomolding. [2]
Used to reduce components by combining functions of different parts to one part.
Can have painted components coming out directly from the mold. Paint is applied to the mold wall before introduction of plastic.
Low cost of tooling as process requirements are not like injection molds ( does not require to withstand pressure of plastic being injected)
Higher accuracy can be achieved as inserts can be used on mold to function for attachments required to interfacing part.
Advantages of Carbon fiber cloth instead of metal for automotive structure.[3]
High tensile strength
Coverage of full area of panel not required as require to reinforce structure only in direction of load.
Predetermine the strength accordingly changes can be made in
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6. Description of the innovation – How to make an integrated modular structure
Continued Available state of Art
Parameters
Carbon Fiber
Sheet metal
E Modulus
300,000 mPa
210,000 mPa
Tensile strength
1300 mPa
250 mPa
Density
1.75 g/cm3
7.8 g/cm3
Above parameters show the strength and weight reduction that can be achieved using carbon fiber.
Methods of using carbon fiber for automotive panels. [4]
The BMW i3 is an electric car which uses carbon fiber body, the panels are transfer molded to contain the carbon fiber reinforcements.
They use carbon fiber to make the body lightweight to accommodate weight of batteries.
Using Rotomolding technology to suit requirements of strength by carbon fiber cloth, embedding of harness and trim is the proposed innovation.
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7. Description of the innovation – How to make an integrated modular structure
Innovation : To have a structure which embeds the wiring harness and also the trim
Brief Process:
Step 1
Hold the harness in the mold M0 & M1 .Also hold the carbon cloth which reinforces the structure.
Step 2
Heat the mold in the furnace and rotate it bidirectional.
Allow it for cooling to a certain predefined temperature.
Step 3
At predefined temperature remove Mold M1 and replace with M2. Before closing introduce the Material 2 for trim.
Allow the cooling cycle for rotomolding process.
Step 4
Remove the Molds and eject component.
We obtain a integrated structure which can be assembled together to interfacing parts.
Stage 4: Ejected Component after cooling.
Trim
Structure
Electric Harness
Carbon Cloth
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8. Description of the innovation – How to make an integrated modular structure
Turret
Moving Oven
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9. Description of the innovation – How to make the Harness
The harness should be such that it does not move in the lateral direction when material flows on it embedding it.
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10. Applications of the idea
Reduction of time for manufacturing, assembly
Reduction of Manufacturing Costs
Modularity of Design
Smart Structures
Alternate Materials for Manufacture of structures
Integrated modular structures
Recyclability
Reduction of Environment footprint of Manufacture
Construction
Medical Devices
The idea focuses towards finding solution to mentioned technological challenges.
The idea proposed has many areas of application where rotomolding has been used as a manufacturing method.
Automotive structures
FMCG
Automotive interiors
Aerospace structures
Railway interiors
Heavy Commercial Vehicles
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11. Advantages and Disadvantages
Sr. No
Advantages
Impact to Industry
Impact to Customer 1
Reduced Assembly time
Time for Production, Cost of Production.
Cost of ownership 2
Reduced Tooling cost by more than 50% 3
Part Count 4
Weight Reduction 5
Reduce Processes like ED Coating, Corrosion protection. Thus Reduced part cost. 6
Easy Accident Repair
Cost of Warranty/insurance
Cost of Ownership 7
Tamper proof Wiring in Structure
Safety & Planning of Design
Safety 8 9
Ease in change of Styling as low tooling cost of Rotomolded structure
More Styling Options for Automotive.
More Options in styling. 10
Improved NVH and reduction in squeak and rattle
Improves Quality of build
Satisfaction on Build Quality
Sr. No
Disadvantages
Impact to Industry
Impact to Customer 1
Pre Planning of wiring harness is required
Planning of harness in case of variant's of vehicle
None 2
Cannot tamper the harness to attach external connections.
Product tampering can be detected
Stricter Warranty norms.
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12. Related literature survey
Patents US
US 2009/
US. Pat. No Led by Belloso et al
US. Pat. No. 5,286,080 led by Ringdal et al.
US. Pat. No by Monary et al.
United States (12) Patent Application Publication, Ellis et al. US 2012/ A1
Notes: All patents searched and found near to the idea do not mention on embedding wiring harness in structure and also method for strengthening structure using carbon fiber cloth.
This is a New method of Producing modular structures which can be Patented and then allowed to be used for the industries across sectors where such a structure is required. It can be provided as a service for design and manufacturing and charged on case to case basis.
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13. Results A section of the structure embedded with the harness.
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14. References
[1] [2] [3] [4]
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15. Thank you
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