Week 12 - Molding and casting

This week we had to make a mold and casting. We are going to mill a piece and we will fill it with a liquid material (or not).

 

 

First design - minimal surface

 

I want to recycle my "super simple" minimal surface, to make it thin I have extruded the surface and made a boolean with a parallelepiped.

 

W12 2 by josereal on Sketchfab

 

 

Starting - minimal surface

 

I have one problem with my stl. When I load the file and configure all, Fabmodules do nothing. I have tried everything and I can`t use fabmodules with this stl. I have exported this with Rhinoceros 3D as binary stl. I have this problem with the next 3d that I want to mill. I think that maybe the problem is exporting in rhino because when I try to use a PNG file everything is ok.

I have start using P1000 polyethylene which is the material used in kitchens as cutting surface.

My solution was to use another program: Rhinocam. I have configured it for my Roland MDX-40A.

I created three routines, one horizontal roughing and two parallel finishing. I have used a 2mm flat mill.

 

CUT SETS / HORIZONTAL ROUGING

 

This is RhinoCAM’s principal method of roughing, also known as waterline or constant Z cutting, in which the material is roughed out in horizontal layers. This type of machining is very efficient to remove large volumes of material, and is typically performed with a large tool. Roughing is typically followed by semi-finishing or finishing toolpaths.

TOOL: First select the tool, to make an axis profiling I will only use a plane mill. 2mm flat mill.

REGIONS: I select the region to make the cut. They are the closed curves of the chair.

FEEDS&SPEEDS: This panel doesn’t work with the big CNC but with the Roland MDX-40a it does . I selected the same forward speed as when I mill boards, 120mm/min and the transfer speed I put it in auto. (use rapid)

CLEARANCE PLANE: this is the height where the milling head will pass, for more security, being a small piece we take 3mm.

CUT PARAMETERS: The stock is the distance between the curve and where the mill will pass. In this case 0,5 mm. Mixed cut direction will save a lot of time cutting. Cut pattern is stock offset (spiral pattern within stock and part). Cut direction is Mixed. the Cut Direction to Mixed. This enables the tool to cut either up or down, so that the tool does not have to retract each time the direction changes. Minimizing the number of tool retractions creates a cleaner toolpath. Stepover tells us when it passes each honey by the material. In this case half the mill, 1mm

CUT LEVELS: I will not cut all the material so I’m going to program it to lower each 1mm each time. The cut levels ordering is important so I choose depth first.

ENTRY/EXIT: Along 3d entry (ramp). This is very important because if the cut depth is too long and the entry is only in 2d, the mill can break. It’s better get out perpendicularly for the mill.

 

 

 

 

 

 

 

 

CUT SETS / PARAREL FINISHING

We use Parallel Finishing again as the final step to clean up any remaining material left in the previous tool path.

TOOL: First select the tool, to make an axis profiling I will only use a plane mill. 2mm flat mill.

REGIONS: I select the region to make the cut. They are the closed curves of the chair.

FEEDS&SPEEDS: This panel doesn’t work with the big CNC but with the Roland MDX-40a yes. I selected the same forward speed when I mill boards, 120mm/min and the transfer speed I put it in auto. (use rapid)

CLEARANCE PLANE: this is the height where the milling head will pass, for more security, being a small piece 3mm.

CUT PARAMETERS: Stock is 0. Angle of cuts 45 (I made two routines, one with 45 and other with -45)

ENTRY/EXIT: Vertical dist 0,6mm and the cut connections are straight.
The finishing is fine, now I’m going to cast this with a lot of materials.
 

 

 

 

The finishing it's fine, now I'm going to cast this with a lot of materials.

 

Molding - minimal surface

 

The first material used was liquid silicone. his silicone has the peculiarity that it needs to be mixed with a catalyst 5%.
With a plastic cup I mix measurements and, getting a little more than the desired mass, I pour it on my surface.

I set the weight to the mass of the glass as zero.

This is the plastic glass with silicone.

Catalyst. I don’t know what the weight of the stopper is so I used the weighing machine.

 

I weighed the glass again with the remaining material

 

This is the result. I wait one day to cast this piece.

 

The second material used was alginate. What's alginate? I wanted to try alginate because it has an instant setting. The mass is made by mixing alginate with water resulting in a pink viscous mass. It only need a few minutes to harden.

 

I went to a Chinese shop and bought several curious materials such as modeling clay and flexible paste.

The third material that I use is modeling clay. It is a clay-like material. The result didn’t convince me.

 

Second design - FablabUE logo

 

As Fabmodules aren’t working I wanted to use a PNG image. I modified the logo of my Fablab to enter a mill 2mm size as it was the one we had at that time.

I went to try on a piece of polyethylene which had before been used to test the largest CNC machine and which is fill with blue polyester resin.

This time the fabmodules worked properly. I have milled with a rough finishing and finish cut finishing.

 

After this I milled the wax with the same design and fabmodule options.

 

Molding - logo FablabUE

 

I used alginate and silicone impression material for dentist. My wife is a dentist and had some at home, so I decided to try new materials. :)

 

The dentist silicone is similar to the other that I used. I use two cups to mix the material and I can join with my hands.

 

 

Now with the wax. I can compare them, I think that the wax has a bit better finishing.

 

The wax mold has a better finish. The pieces are best removed from the mold and have more definition.

 

Casting

 

I decided to try many materials. Crayon pencils, soap, wax, water, even a material that I bought at the Chinese store that looked like  Jake the Dog.

First I created a formwork to make discharges.

 

The first material that I use was soap. It smells well , all my home smelled like this soap during the workflow. I used the silicone mold first. Iused a casserole to melt the soap.

 

 

In only few seconds the soap is melted.

 

I have wait almost 15 min to unmold it.

 

 The second cast was with a candle wax and the alginate mold. The result it’s neat. I used a casserole to melt the candle. It's very quick to melt.

In almost 5-10 min the candle is ready to be unmolded.

 

The third material were crayons. It’s very similar to candle wax. I used a casserole to melt the crayons. This material is nice, but very delicate. When I unmold a part brokes also the mold broke too.

 

I had used this material with the polyethylene milled with the fablabue logo. Is very delicated and some pieces broke.

 

I used water to freeze and get ice, but it was not a good idea. The alginate was broken because this material have water too and it became frocen... I also used the “jake the dog” material with water. It did not work but I found a fun and easy material to use.

 

I used the “dentist” silicone with candle wax, here are the results. This is the best material that I used. The pieces have a very good finish.

 

Final result

 

This is the result of all the pieces that have “survived” to this practice.

 

 

 

 

One more thing

 

In my final project I want to use a mesh that has the ability to move with a impulsion. This can be a fabric, but I want to experiment with other materials.
My idea is to use latex. I used a metal plate and liquid latex to produce it. For this I used eye protection, respiratory protection and gloves. Besides the place where I did it had forced ventilation.
To get the desired surface I have done several layers of latex.

 

I waited for 24h. I thought that the cured is faster. To unmold I use talcum powder to prevent sticking surface to look like a pizza!

It had some problems. I must repeat the experiment with more layers because broke taking off the latex. But the result is very nice. I did a small test to look how it stretched. It feels strong and the material allows light to pass through. I like it!!

 

One more thing 2!!!

 

Now I´m milling my own made material. This is plaster and silica because the silica withstands high temperatures. I want to mold an aluminum piece. To make the mold I used mdf wood.

 

Casting aluminum

I used a small oven to heat aluminum, from materials laboratory at Universidad Europea , for this I had to wait about 20 minutes to reach about 800 ° C.

To melt the aluminum I used a steel container. When I got it out I used a brick to avoid burning the table.

 

CASTING ALUMINIUM from Jose Real on Vimeo.

Removing the dross. By not casting on a completely clean container, there is always slag other smelters and they need to be removed before casting.

 

 

RESULT:

The result is not ideal because to make a good mold it is necessary to have a “chimney” to let the air out. In my case what happened was that an air bubble was created and no aluminum was deposited there. It didn’t go well but I learned a lot.

The second thing that is not ok is the mill. I wanted to try mill plaster with silica. It’s better to use a 3d printed piece to make the mold. I learned how abrasive is mill “stone” and milling cutter is needed to do so (tungsten). …

With FUEMs guys we tried to do another piece, which itself went well.

Special thanks to Luis Soliverdi, he helped me to make the casting aluminum.

*missing files mill process

FILES

minimal surface + mill files

fablabuemlogo+ mill files

origami stl+ gh files

Fab Lab UE