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AN EVENT ORGANISED BY,

Dr. D.Y. PATIL COLLEGE OF

ENGINEERING AND TECHNOLOGY .

A PAPER ON

PRESENTED BY,

SUHAS PATIL,

T.E.(Mech.)

Email:-crushsuhas@gmail.com

&

SWAPNIL PATOLE,

B.E.(Mech.)

Email:-crushswapkit@rediffmail.com

mob:-9890209301

SHIVAJI UNIVERSITY , KOLHAPUR.

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CONTENTS:-

SR.NO. TITLE PAGE No.

1.ABSTRACT

1

2.INTRODUCTION

1

3. EXPERIMENTAL APPARATUS 3

4.EXPERIMENTAL METHODS

4

5.MATERIALS AND PREPARATION

6

6.RESULTS

7

8.CONCLUSIONS

11

9. REFERENCES 11

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Abstract:-

The basis of this research involves the design, machining/molding and study of

multimaterial polyurethane parts. Specifically, the research deals with compliantmultimaterial molds designed in such a way so that one material of specific hardness isshaped into a block that is consistently punctured with holes and another material with a

different hardness is used to fill those holes, thus making a mesh of two materials. In

order to do this, a mold must be created in order to shape the block and create the holes.There are numerous variables and methods associated with creating the mesh and a

specific combination of those variables are needed in order to optimize the ease of

manufacturing and quality of the final product.

Introduction:-

The main motivation in creating a multi-material mesh is to test this mesh in

vibration damping. Vibration damping reduces the vibration and noise in vibrating

systems, which has many real world applications. Specifically, vibration damping is veryimportant in the design of airplanes, helicopters, and automobiles. If the system can be

designed to maximize the damping, then noise and turbulence can ultimately be

decreased. Currently only single materials are being utilized to create damping invibrating systems at the University of Maryland performed a case study on a power drill

to prove that certain materials can, in fact, increase damping, thus decreasing vibration

and noise.

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Figure 1 shows the out-of-plane stress in two power drills when they are bothturned on. The brighter colors indicate greater out-of-plane stresses. Figure 2 shows thenoise level of the two power drills when they are both turned on, with the blue plot

indicating the first power drill and the red plot indicating the second power drill. The first

power drill is normal and has all the stock features. The second power drill is identical to

the first one except that it has been lined with a layer of material on the inside of thewalls of the drill to create damping. As seen in the figures, the second drill has

significantly less out-of plane stress levels and less noise levels due to the lining of the

walls with a single material. has a theory that a multi-material mesh can create moresignificant damping than single materials can. A multi-material mesh is basically a solid

block consistently punctured with holes with another material filling those holes. One

possible way in creating this multi-material mesh is by using multi-material molding,which involves the molding of a shape using two different materials, with each material

molded in a separate stage. However, there are unlimited methods using multi-material

molding to create a mesh. The objective of this research is to investigate alternative

methods for manufacturing multi-material meshes. Identify the most promising method.

Then,identify the dimensional constraints imposed by the method

Experimental Apparatus:-

The molds are designed using the program Pro-Engineer (Pro-E) and the moldsare fabricated using a computer numerical controlled (CNC) milling machine. Pro/E is a

program that can create precision three dimensional computer models. It is a feature-

based, associative, and constraint-based system, meaning each feature created in Pro/E is

dependent on the sequence of commands and constrained to certain datum points, lines or

planes. Features can be combined to create parts. The geometries of features on a part

have to be fully defined in terms of size, shape, orientation, and location. These

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specifications allow the user to define how features on a part or parts relate to each other.

Once the part is created Pro-E uses Pro-Manufacturer to create the code for which the

mold is machined. The user gives Pro-E certain commands depending on the shape of themold and Pro-E converts these commands into G-code, which is the code that the CNC

milling machine reads and uses to create the part.

Experimental Methods:-

A compliant multi-material mold deals with two different materials, each ofunique hardness, poured in separate stages to allow bonding between the two materials.

For this specific model there are numerous ways in creating the mesh.

Core Pin-Mold:

One method in creating the compliant multi-material part is to create a mold to

shape out holes into the material for the first stage material in order to allow the secondstage material to be poured into those holes. This mold is designed in Pro-Engineer

(figure 3) and machined in the CNC milling machine to fit the specific shape of the partthat is going to be made (figure 4). In this case, the core of the mold is shaped with

densely packed pins (to create the holes in the part) and the outer part of the mold (cap

mold) is able to encapsulate the core to define the shape of the block.

Drilling Holes Directly into a Solid

Block:

Another method to create this part is

to create a solid block without any holes, using

just a plain solid block mold without pins. Aplain mold is designed in Pro/E and machined

in the CNC milling machine. Then, the first

stage material is poured into the mold and oncethis part is created, it is placed in the milling

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machine where holes are drilled out of the block (figure 5). The holes can either go a

specified depth through the block, or penetrate entirely through the block. Then the

second stage is poured into those holes after they are drilled in the same manner as the

plastic core method.

Inverse Core Pin-Mold:The final method in creating the compliant mesh is using the opposite idea

of the core pin-mold method. Instead of creating pins in the mold to shape out holes in

the first stage, this method would create holes in the mold to shape out pins in the first

stage (figures 6).

Within each method there can be variations among the pin size and mesh size.

The geometric variables dealing with the pin size include length, diameter and spacing.

The length of the pins can determine whether or not the pins penetrate all the waythrough the block. Pin diameter can determine how much of one material needs to be

filled into the second material. Pin spacing determines how densely packed the pins are

from each other.

Materials and Preparation:-Once the method is chosen the materials are prepared to be poured into the

molds. Two materials are needed to complete the mesh, however, there are threematerials that are available in the lab to make the mesh, therefore, different combinations

of two out of the three materials are considered. Each material is prepared using a resin of

that material and a hardener of that material. Once the resin and hardener are mixedtogether, the material is placed in a vacuum where all the air bubbles are removed from

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the mixture and then it is ready for pouring. The three materials can be seen in the table

below.

The hardness of each material varies significantly. IE-72DC is the hardest

material and is very rigid like a hard plastic when it hardens. IE-90A is the next hardestmaterial, however it is flexible when it hardens and can be subject to plastic and elastic

deformation. The softest material is IE-60A and it acts like a soft rubber when it

completely hardens with the most amount of flexibility out of all the materials. While the

first stage material is being prepared, the mold must also be prepared. The molds that will

hold the material have to be coated with a thin layer of conditioner using cotton tipped

applicator sticks, and then the molds must be sprayed with silicone mold release. Thepurpose of coating and spraying the molds is to create a nonstick surface for the material

so that when the material hardens it will be easy to remove it from the mold. Once the

mold and material is prepared, the first stage material is poured into the mold

using a syringe.

The second stage material is poured into the mold about halfway through the

demold/hardening time for the first stage material. Therefore the first stage material is

ejected from its mold in order for the second stage to be poured. This is done so that there

is chemical bonding between the first and second stage materials making them fusetogether better. Once the second stage is completely poured, the mesh sits until both

materials completely harden to create the final product.

Results:-

After Performing numerous tests and retests the results were very mixed in

terms of success for creating the multi-material mesh.

The experimental setup for each method is as follows:

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breaking them.

The last main

problem in the IE-72DC first

stage case occurred duringthe pouring of the secondstage material into the holes

of the first stage material. If

the holes did not penetrateall the way through the first

stage material then it became

very difficult to fill thoseholes with the second

material. On several

attempts, almost none of the

holes got filled after pouring the second stage, softer material, onto the first stagematerial. The main problems were that there was too much air resistance in those holes,

preventing the soft material from filling. Also, the surface tension from the walls of the

holes opposed the flow of the second stage material into the holes. The second stage

material, IE-90Aindustrial polyurethane, is also very viscous, reducing its ability to flow.Finally IE-90A gels in 15 minutes, meaning it starts to harden in 15 minutes, therefore it

becomes thicker and reduces its ability to flow even more, compounding the opposing

forces of airresistance and surface tension.

Using the core pin-mold with IE-90A as the first stage material also had itsproblems. The main problem with using the core pin mold was that the material had to

completely harden before ejecting it from the mold. The IE-90A material cannot beremoved from the mold halfway through the demolding time because the material is still

sticky and unable to be managed during this time. Therefore, very little bonding can

occur between the first and second stage materials. The same second stage pouring issues

were alsoencountered in the IE-90A first stage case.

Drilling Directly into the First Stage Block:

Drilling directly into the first stage block was considerably more successful than

the core pin-mold. Drilling circumvented any problems encountered while removing the

hard material from the core pin mold. Also the milling machine drilled all the way

through the first stage block, which reduced the air pressure in the holes for the secondstage pouring. Therefore, pouring the second stage into the holes was no problem. One

problem in using this method is that the first stage material must be completely hardened

before using it in the milling machine because when the material is still soft the vice in

the milling machine cannot grip the material well enough to securely hold it steady. This

means that there is less bonding between the hard material and the soft material when the

soft material is poured into the holes. There were no other issues in the IE-72DC case for

this method as it was predominantly successful (figures 9 and 10).

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However, there was a bigger problem when using IE-90A as the first stage

material. When using the CNC milling machine, the end mill would create a lot of heat

on the IE- 90A material, leading it to melt, therefore, the tiny pieces of the material from

the walls of the holes created by the end mill would melt and harden again once the endmill was removed creating a lot of debris in those holes. When using the 1/16 inch endmill, the holes were too small and the debris would fill those holes entirely leaving them

unable to be filled with the second stage. However, when using the 1/8 inch end mill, the

debris was more manageable and could be scraped out using a nail and was able to be

filled withthe second stage material, IE-72DC (figure 11).

Inverse Core Pin-Mold:

IE-60A was used as the softer material in this method because the softest material

available was desired in making the mesh. The core pin-mold method could not

incorporate IE-60A because if IE-72DC was used as the second stage material to fill theholes left by the first stage, the IE-72DC pins would shrink during hardening and not

bond to the walls of the holes created from the IE-60A. The drilling method could not

incorporate IE-60A because it simply cannot be used in the milling machine. IE-60A is

too soft and cannot fit stably in the vice of the milling machine.

This inverse core pin-mold

method was the most successful out ofall three methods. The inverse core pin-

mold was designed to have shallow

holes of less than 1/8 in length in orderto make the first stage part. This made it

easier to fill the first stage into the holes

of the mold because there is reduced airpressure. In the case of IE-72DC as the

first stage (figure12) it was also much

easier to eject the first stage materialfrom the moldbecause it did not have to

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be removed from tall pins, but rather had to be removed from shallow holes which were

much easier to be pulled out of. This allowed maximum bonding between the first and

second stage materials. Another benefit from this method and creating the pins in the firststage was that when the second stage was poured to surround the pins it shrunk onto the

pins to increase the bonding even more. The case of IE-60A as the first stage material

(figure 13) was also successful however it had the drawback of having to let the IE-60Acompletely harden before ejecting it from the first

stage mold.

Conclusion:-

A viable method for making a compliant multi-material mesh was found in

the inverse core pin-mold method. It had successful results in each of its cases no matterwhat the first stage material was. It was also the only method in which IE-60A, the more

desired soft material, could be used in both cases. The geometric constraints for this

method have much freedom as well. The width and length of the mesh sample is onlyconstrained to what can fit in the CNC milling machine. The only constraints on pin

diameter and spacing are the constraints of the end mill, which can be limitless with theamount of end mill sizes on the market. The only real constraint is in the pin length. The

pin length must be relatively small (less than 1/8) in order to fill the first stage material

into the mold, otherwise the air pressure in the holes would be too great to get filled.

References:-1. Vibration and Noise Control by

2. www.innovative-polymers.com

http://www.innovative-polymers.com/

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