Molding and Casting

This week is all about Molding and Casting. On 21st of the March 2018, Professor Neil gave us a detailed lecture on the whole process of Molding and Casting. This is unique thing for me to do mold any design then cast it, I have never been through such process before. I am very much thankful to my instructors here at FabLab Khairpur, who guided us on many steps where we stuck. this whole process is very interesting and interactive for me.

Molding and Casting are two different things, where Molding means to make a hole or empty space on a block of any solid material (I used wax block) used to give shape any liquid material (I used liquid rubber). Where as Casting is the process which involves introducing of liquid material into the molded part and wait till the material solidified well then ejected from the mold. To complete the process, we have to fill the hollowed empty spaces of the resulted solidified (liquid rubber in this case) material. which we got just before by pouring liquid material into mold. The material which we can use for casting are plastic, metal, rubber, clay and many more. The end product will be in our hands as soon the material solidified.

So, roughly I can define these both terms as:
Molding refers to shaping a soft material (but not fully liquid) according to the design which actually we want.
Casting involves pouring of the liquid material into the solid mold and allowing to cool and solidify. Then the solid materials takes the shape of the mold. The resulted shape is known as casting which then eject out from the mold to complete the process.

Tasks of the week

Group Assignment

This week group assignment is to review the datasheets of the materials we are using in making mold and cast. Below we are sharing some important points after reviewing safety datasheets of Mold Max 60 for molding and Smooth-Cast 305 for casting materials.

Mold Max 60 Safety DataSheet Review:

Product/Chemical Name: Mold Max 60 Part A:

Product/Chemical Name: Mold Max 60 Part B:

Smooth-Cast 300 Series Safety DataSheet Review:

Product/Chemical Name: Smooth-Cast 305 Part A:

Product/Chemical Name: Smooth-Cast 305 Part B:

Individual Task
For this week task, I decided to mold then cast an "Ajrak block". As, Ajrak is considered the sacred cloth of our Sindh province in Pakistan. Ajrak is an unique form of block-printed shawls found in Sindh Pakistan. These shawls display a unique patterns by using block printing stamps. So, finally I decided to mold and cast an Ajrak block. As, here, locally these blocks made manually on piece of woods, my this attempt may change their way of printing Ajrak in some advanced way! Few of the pictorial forms of the Ajrak are given below for better understanding of this unique thing.

These are the samples of the Ajraks

Locally used wooden Ajrak blocks/stamps

Designing 3D mold for Ajrak

For designing its model in CAD software, I used Rhino 3D for this purpose. Here few snapshots are given:

Designing of block/stamp in process

Used extrudeCrv command to extrude them up to 3.5 mm in z-axis

This shows the height of the outer box as 10 mm, and 3.5 mm is the height of the actual design

Preview of design, opened in 'Cura' by .stl file, exported from Rhino 3D

Now, its the time for generating .prn files from "Modela Player 4" by importing .stl file.

01. I opened modela player 4 in lab's PC.~~~~~ 02. Go to "file" and select 'Select Machine'.

03. Go to "Set" and 'Model'.~~~~~ 04. Check on 'Origin'.

05. Go to "Set" and 'Modeling Form' then check on 'Manual'.~~~~~ 06. Go to "Set" and 'New Process' then check on 'Roughing', then Next.

07. Check on 'Top [+Z]' then 'Next'.~~~~~ 08. Select '3 mm Square' then 'Next'.

09. Check on 'Partial' then resize the red boundary line inside the box, then 'Next'.~~~~~ 10. Check on 'Contour Lines','Up Cut', then 'Next'.

11. XY speed as '24' mm/sec, then 'Next'.~~~~~ 12. Name it, like 'Nadir_Roughing', then 'Finish'.

13. Again, go to "Set" and 'New Process' then check on 'Finishing', then 'Next'.~~~~~ 14. Check on 'Top [+Z]' then 'Next'.

15. Select '1 mm Square' then 'Next'.~~~~~ 16. Check on 'Partial' then resize the red boundary line inside the box, then 'Next'.

17. "Scan Lines" as 'X+Y', "Contour lines" as 'Up Cut', then 'Next'.~~~~~ 18. XY speed as '14' mm/sec, then 'Next'.

19. Name it, like 'Nadir_Finishing', then 'Finish'.~~~~~ 20. click on "Cut",which can be found on right bottom of the main page.

21. Click on 'OK'.~~~~~ 22. Check 'Output to file' and then 'OK'.

23. .prn file for Roughing is created, set the path to save file, then 'OK'.~~~~~ 24. Set the path to save .prn file of Finishing , then 'OK'.

Now, I fed the resulted .prn files of Roughing and Finishing one by one to "Roland SRM 20".

Result after Roughing process.

Result after Finishing process, this is the final result of Mold.

Weighting the empty glass and again setting it on zero gram

Filling the mold with water, pouring water back in glass then weighting the water in digital weight machine

Adding part A and part B of the material and then mixing them up

From rubber liquid, the output is like a jelly and not good for casting, because it takes much time to be solidified

Again same procedure for metal mold

Adding 3% catalyst and 100% metal mold material, with 3/100 ratio

Mixing up the mixture and pouring it to the wax mold then wait about half an hour

After half an hour, extract it back from wax, now it's solidified

Make it ready for adding material for casting

Use of cardboard walls:
Here is the time for filling the silicon mold with final product's liquid material of casting. As, the liquid was thin, if I flow that liquid on the silicon mold then there was a chance of material to flow down through the edges of the design on mold. The corners of design from where there was a solid chance of liquid to flow out of the mold are shown in below image.

By using these cardboard walls, the liquid for casting stayed on the design of the silicon mold.

This was my mistake in designing the mold. I must increased the extra space where the edges of the design ends. So, by recovering this, I used cardboard walls for not flow the casting material from the design on silicon mold.

Removing air bubbles

Removing unwanted layers from the cast

Final result of casting the Ajrak Block/Stamp.

Again I decided to design the logo of our FabLab Khairpur for molding and casting. I import the 2D image of FabLab logo in "Rhino 3D" then following the line command I drew the boundaries of imported image and then I used extrudeCrv command to extrude it upto 3.75 mm up in z-axis. I used "text function" in "Rhino 3D" and wrote the text as "F A B L A B KHAIRPUR", again used line command, extrudeCrv command, and extrude the text upto 3.75 mm up in z-axis.

Following the line command on FabLab Logo, and then extrude it upto 3.75 mm using extrudeCrv command.

Following the line command on the text of FABLAB Khairpur, and then extrude it upto 3.75 mm using extrudeCrv command.

Result of Roughing and Finishing process respectively.

As, my assignment of the week is complete by molding and casting an "Ajrak block/stamp". For more learning of this process I decided to mold another thing like FabLab Khairpur Logo. I just Mold the Logo of FabLAb Khairpur, I will cast it when I get free slot of time. I am happy with my this week's molding and casting.

Download all files from here

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