Thermal expansion: Plastic Molding

In summary, the ABS plastic used in the injection molding process has a melting and solidifying point of 105 °C. To achieve a desired length of 7.250cm when the part comes out at 20°C, the steel mold should be designed to have a thermal expansion coefficient of 11.0x106. Using the equation for linear expansion, a length of 7.282cm is calculated, but the given answer is 7.276cm, suggesting that the steel may affect the thermal expansion. However, after researching and using the equation for thermal expansion in two materials, a length of 7.276cm is obtained, matching the given answer. Therefore, the final answer is 7.276cm.
  • #1
jonw39
7
0

Homework Statement


ABS plastic melts (and solidifies) at 105 °C. You want to inject it into a steel mold. When the part comes out at 20°C you want it to be 7.250cm long. Edit: If this isn't clear, it wants to know how big the steel mold should be.
α for ABS plastic α= 53.0x106/C°, for steel α= 11.0x106

Homework Equations


ΔL=αL0ΔT

The Attempt at a Solution


Ok so I used the equation for linear expansion and I come out with an initial length of 7.282cm. The answer I'm given is 7.276cm. I'm think this has something to do with the steel but I have no idea what.
Edit: I tried a similar problem and got the right answer using the same method. I have no idea.
 
Last edited:
Physics news on Phys.org
  • #2
Edit 2: Ok, so I looked up the equation for thermal expansion in two materials and used that. I came out with a length of 7.276cm which is the same as the answer. So my final answer is 7.276cm.
 

Related to Thermal expansion: Plastic Molding

1. What is thermal expansion in plastic molding?

Thermal expansion in plastic molding is the phenomenon where plastic materials expand or contract due to changes in temperature. This occurs because as the temperature increases, the molecules in the plastic material vibrate more and take up more space, causing the material to expand. Conversely, as the temperature decreases, the molecules vibrate less and the material contracts.

2. How does thermal expansion affect plastic molded products?

Thermal expansion can affect the dimensions and shape of plastic molded products. If the plastic material used has a high coefficient of thermal expansion, it may expand significantly when heated, causing warping or distortion of the product. On the other hand, if the material has a low coefficient of thermal expansion, it may not expand enough to fill the mold properly, resulting in incomplete or defective products.

3. What factors can influence thermal expansion in plastic molding?

The coefficient of thermal expansion of the plastic material itself is the main factor that influences thermal expansion in plastic molding. Other factors that can also have an impact include the temperature range the product will be exposed to, the design of the mold, and the cooling process used during molding.

4. How can thermal expansion be controlled in plastic molding?

To control thermal expansion in plastic molding, it is important to choose a plastic material with a suitable coefficient of thermal expansion for the desired temperature range. The design of the mold can also be adjusted to account for any anticipated expansion or contraction of the material. Additionally, controlling the temperature and cooling process during molding can help minimize the effects of thermal expansion.

5. What are the potential issues caused by thermal expansion in plastic molding?

The main issue caused by thermal expansion in plastic molding is the potential for dimensional changes or defects in the final product. This can result in products that do not meet specifications or are not functional. In extreme cases, thermal expansion can also lead to damage or failure of the mold itself, which can be costly to repair or replace.

Similar threads

Thermal Expansion Problem Involving a Brass Ring
    • Introductory Physics Homework Help
Replies
4
Views
6K
Thermal expansion of air bubbles in plastic
    • Materials and Chemical Engineering
Replies
1
Views
1K
Finding Increase in Temperature for Two Rods
    • Introductory Physics Homework Help
Replies
3
Views
1K
Temperature of a bar to produce certain force on wall
    • Introductory Physics Homework Help
Replies
6
Views
2K
Volume expansion and sea level rise
    • Introductory Physics Homework Help
Replies
6
Views
2K
Misc. Can Ethyl Acetate be Used to Remove PLA from Plaster of Paris Molds?
    • DIY Projects
Replies
9
Views
2K
Stress in cylinders due to thermal expansion
    • Mechanical Engineering
Replies
16
Views
638
How does temperature affect the expansion of steel railway track?
    • Introductory Physics Homework Help
Replies
2
Views
923
Confusion Calculating Young's Modulus
    • Introductory Physics Homework Help
Replies
4
Views
224
Thermal Expansion of a Wire Connected To a Rod
    • Introductory Physics Homework Help
Replies
6
Views
2K

Hot Threads

Recent Insights

Back
Top