Molding & casting 📋

🕘 Date / Time:

Heyyy lovely fellows ^^. It's 22.07.2020 and here I am trying as hard as I can to complete my weekly tasks in "Injury Time" just like they say in football. :D

In the begining I thought that this week will be for manufactuing my final project marionette puppet, but after all what happened and the huge loss of time I decided against that because of:
1- The complexity of the molding and casting process.
2- The time it consumes.
3- The errors that may happen.

So I chose to make something simple as a tribute to my dear friend Anan Adel Ali ❤️️.

Part I: Design & machining

First trial: (Failed)

Design (Fusion 360):

Drew a sketch of a 40 mm circle, extruded it then added a sketch of the Text on its face. I Exploded the text while I was still in sketch mode.

Added a smaller circle on the sketch then I extruded the text inwards after extuding the smaller circle outwards.

I then added a hole for a keychain to be attached to it later.

Created a box slightly bigger than my keychain pendant to fit my mold in.

I then aligned my pendant face with the box face then moved the pendant into the middle of it.

I also toggled the opacity of the box to be able to see the pendent when moved into it.

From modify I chose combine, then selected the box as target body and the pendant as tool body. Operation >> Cut, Keep tools >> Checked.

I then selected the pendant and moved it again out of the box to find its shape was cut out of the box successfully.

That successful operation left me with what I thought my to be machined mold! But as usual I was Wrong! :D This was the exact negative of it .. this is what's gonna be my silicon mold the same part to be milled out! :D

I then realised that to get my to be machined part I should just have my pendant and put it inside a box. Yeah! It's that simple! :D.

I then created a component from that body to be able to save it as an .stl file.

Then it was time for learning about the software I needed to produce the gcode for milling the mold of my mold :D.
I was advised to visit a 2018 fab academy student Mr. Haitham Abdelkhalek and it was of a great help for that matter.
I learnt all I needed to know about SRP Player and one sided milling from that video he included in his documentation.

Generating gcode (SRP Player):

I downloaded, installed and upgraded SRP player easily. I then opened my .stl file and started following the really ice steps the program provides.

Step one I confirmed the size of my model and selected its top surface (that was going to be milled first).

Step two was to choose the type of milling. I chose 1.Better surface finish (that was not necessary at all) 2.Flat planes and 3.Top only.

Step 3 I chose the material we had in the lab for that purpose which was modeling wax, selected model placement.

Step 4 was to edit the tool path inorder to select the end mills I was going to use.(ZHS-400) for roughing and (ZCB-200) for finishing.

Note:
that I was of a really little experience with that software and the whole process that uptill this point I thought it was going to mill the locket only on a really small corner as I chose smaller "work piece size" than the piece of material we had in the lab
But that was Really wrong ⚠️ because (as you may know by now or you are going to discover in a couple of steps later) I did not know that it was going to mill the outside box as well and I shouldn't have put the locket on any boxes (in fusion) in the first place..

Machining (MDX-40A):

First I installed the 4 mm flat (ZHS-400) end mill for roughing.
Then I fixated my piece of modeling wax to the machine working bed usig double tape.
Then using Roland V Panel I assigned the (X, Y & Z ) origin pont in the middle of an (80 x 80) square I marked on one side of the wax.

This was the result of the roughing file. Everything seemed to be going just fine.

Then it was time for the finishing file.
I installed the ball nose end mill and I was confused whether to set the Z origin on the new surace or on the old one. I asked one of my colleages and he confirmed that both of the tool paths for finishing and roughing must have the exact same Z origin.

and there was when I discovered the stupid mistake It was going to be milling the box I had put around the locket too.😭

That was when I realised. (What!! 😨)

Decision:

At this particular point of time I needed to decide quickly whether to continue milling or abort the mission, remove the box from my design and start over again.
My decision was to continue milling my mold even though it was going to waste a whole load of time milling the box around the locket, given the fact that I was going to get the locket itself either ways.(I was proven to be naive one more time. 😏😂)

Because as I let the milling being finished and after hours of waiting I noticed the other mistake I'd made 😂.

The 4mm ball nose end mill was so large that it missed all the small detailes of the name and that destroyed the output model. How on earth can I be that brainless! 😩😩

Second trial: (succeeded)

This trial was conducted almost 3 months after the first one for reasons of final project and COVID-19 lab lockdown for the millionth time.

Design (Fusion 360):

I decided to make another keychain lockdown for Anan that only a star that has the letter "A" (for fewer complications).

And that was the 3D design. (No boxes this time :D )

Generating gcode (SRP Player):

I followed the same steps with SRP Player except for the following:
1. I scalled my model down by 95% in order to fit the size of the piece of wax.
2. I chose faster cutting time.
3. For roughing I used 4 mm flat end mill (ZHS-400).
4. For finishing I used 3 mm flat end mill (ZHS-300) no ball nose this time :D.

Machining (MDX-40A):

As per the old saying: "with new design come new mistakes :'D"

Once the roughing was done, it was time that I installed the other end mill for finishing. An here was the mistake I forgot that the Z origin was to be set on the original surface not the new one.
I realised what I've done wrong about 10 seconds after the machine started milling in a really loud sound. I pressed the emergency stop button at once.

That was the cost. A really deep "A" triangular groove as well as a small broken part shown in the image.

Despite what happened I set the finishing Z origin in the right palce and proceeded milling.

And that was the final result. Not perfect yet good enough. :')'

Part II: silicone Rubber

It was time to mix some silicone rubber with some hardner 😄. Because we ran out of silicone stock in our lab I bought some from a stationary store, the silicone an hardner jars they had had no labels on.😅
Almost every one on every documentation / video I reviewed before starting this procedure said that the mixing ratio is 10 silicone to 1 hardner. Unfortunately mine did not upply to that ratio. 😅 And I had to learn that the hard way when it totally solidified within 1 minute of mixing. 😂
For that matter I had to improvise I mixed the next batch in hardner to silicone ratio of 1:40.That was also relatively thick but it worked. 😄

My beloved silicone mold is ready to get removed.

Part III: Epoxy Resin

I let my silicone mold solidify over night and went to the lab next morning for the next step. Casting my staaaaar.😍
As I wanted to decorate my friend's keychain yet forgot to get some glitter before getting to the lab. So I had to improvise as usual 😂.
I searched the lab for shiny stuff 😂 and found a roll of copper foil sheet. And that was it.😂

A very small piece of copper foil made me a real nice amount of bronze glitter confetti. 😂

With a sharp cuttere I fixed the little "defaux" in caused by the wrong z origin incident.

To 3 parts of epoxy resin (90 grams). (And that was alot of mixture I did not use all of that for this mold).

Just keep mixing .. just keep mixing.. calmly to avoid bubbles.

And that was the final result.. "A" for Queen of the letter A, miss "Anan Adel Ali" my dearest friend. :)

YOU THINK I AM DONE !! ABSOLUTELY NOT 😂
Starting my evaluation it seemed like I missed a part of what was required from this task. I was supposed to design an object that needed 3 axis milling. Which means that it should have smooth tilted or curved surfaces instead of steps towards Z axis. So here we go again for a 3rd design.

Part IV: Redoing the whole process

I decided to make some kind of a flower design and I made it already then I knew that we do not have a collet that can support an end mill that is less than 3 mm in daimeter. I chose against complicated desgines and went for something simple that would do.
So I started designing a hexagonal chocolate mold.

Drew the base hexagon in an ordinary sketch.

Added an offset plane to draw the smaller top hexagon.

Then created a loft between the two hexagons.

It was time to fillet the edges for a smoother output.

Added a decorative topping for elegance. 😂

I wondered whether to extrude the star in or out then I chose to extrude it out.

Generating gcode (SRP Player):

1. Better surface finish.
2. Model with many curved serfaces.
3. Cut top only.
4. Modeling wax.
5. Align top.
6. For roughing I used 3 mm flat end mill (ZHS-300).
7. For finishing I used the same 3 mm flat (ZHS-300) as I had no 3mm ball nose end mill.

I followed the simple steps through SRP Player to create the tool path for milling.

Here I am setting the x, y, z origin on the "miserable" peice of modeling wax that is fed up with my trails.😂

A peek of my mold design after the first round of milling aka "Roughing".

That was what it looked like after the second round aka "Finishing". I was satisfied with the result.👌

Gathering all the stuff needed for making the silicone mold.

Then added 3 grams of hardner. Ratio of (35:1).

Mixed them well then poured the mixture into the positive mold. I added those wooden sticks so that I am able to add more thickness to the silicone mold base.

The negative silicone mold is was ready after about two hours and a half of waiting.🎊

It's epoxy resin time. I measured 60 grams of epoxy. (added one graf after taking the image.😂)

Then 20 grams of hardner for a (3:1) ratio.

Here we are .. The epoxy was thoroughly mixed with the hardner then poured gently into the silicone mold.

Here it is my prestigious epoxy resin cast looking like an ice cube.😍

Downloadables: 💾

Star Fusion 360 .f3d file, .stl file, roughing and finishing .prn files Here
Chocolate mold Fusion 360 .f3d file, .stl file, roughing and finishing .prn files Here

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