W15 - Molding and Casting

1. Weekly Assignments ( -> what I did this week )

  • Individual assignment

  • Design a 3D mould around the stock and tooling that you’ll be using, mill it (rough cut + (at least) three-axis finish cut), and use it to cast parts.

( -> I made a clear small object in which a LED lights up the bubbles and tool marks. )

  • Group assignment

  • Review the safety data sheets for each of your molding and casting materials

  • Make and compare test casts with each of them

Have you?

Questions from “Fab Academy 2020 Assignments and Assessment

Molding and Casting

( -> my answers )

  • Linked to the group assignment page ( -> yes )

  • Reviewed the safety data sheets for each of your molding and casting materials, then made and compared test casts with each of them ( -> yes )

  • Documented how you designed your 3D mould and created your rough and finish toolpaths for machining, including machine settings ( -> yes )

  • Shown how you made your mould and cast the parts ( -> yes )

  • Described problems and how you fixed them ( -> yes )

  • Included your design files and ‘hero shot’ of the mould and the final object ( -> yes )


3. Works, steps and some details

1) Planning

Through the engine development in my previous work, I made several kinds of casting products such as Aluminum sand-casting, Aluminum diecasting. etc, this time I planned to make something different, which has a kind of taboos for the ordinary casting technic for mass-production.

By the way, Ryukyu glass is one of the unique craftwork which has some amount of bubbles in it. I was inspired by this.

Ryukyu glass


So, this is “Bubble leaf”.

(1) transparent material ( epoxy ), which contains bubbles

(2) slightly inclined curved surface, which might cause slight tool marks ( steps )

(3) LED in the bottom part, which lights up the above bubbles and tool marks.

(4) parting line which divides upper & lower patterns is curved, not straight. ( generally, pattern suppliers are reluctant to do this. )

So, the key is the amount and distribution of the bubbles.

I plant to check them with small test pieces.

( probably, the tilt angle of the molding patterns need to be changed during the curing process. or, rotation might move the bubbles to the center. )


2) modeling by fusion360

product1 product2
pattern for wax ( positive )
pattern1 pattern2

I eliminated the walls on the sides of the molding pattern ( Y- direction ), and planned to attach some plates on them when I pour the epoxy resin. This is the way to maximize the product in the limited WAX dimension.

3) CNC data preparation

I used MODELA Player 4, via Zoom (during remote local session ( 2020/05/16 )).

modela_remote1 modela_remote2
parameters for rough cutting parameters for finish cutting
rough_cut_parameters finish_cut_parameters
about 1 hour for rough cutting about 1 hour for finish cutting
rough_cut_time finish_cut_time

But there was a problem that unnecessary walls remained on sides of the molding pattern ( Y- direction ).

Because, if the thin and weak wall remained, some portion of them would be destroyed during the rough cutting and/or finishing process, and would cause issue like spreading wax debris on the finished surface.

After the remote local session, I installed MODELA Player 4 on my MacBook Pro ( Parallels desktop + windows10 ), then retried the parameter settings ( margin & draft of modeling form ) to remove the unnecessary walls.

And it was successful. ( 2020/05/16 )

reduced the margin of modeling form set the draft of modeling form to be zero
margin_modela_player zero_margin_modela_player

But next day ( 2020/05/17 ), the wall appeared again, even if I set the draft parameters as zero.

( I’ll retry later, and if necessary, I’ll modify the fusion360 data. )


4) Machining the mold by CNC

On 2020/06/27, I made the molding pattern using “Ferris File-A-Wax Blue” on CNC, SRM20.

To avoid the “unnecessary walls” described above, I extended the Y-direction of fusion360 model so that it became larger than the wax size ( and, larger than the Cutting Area in MODELA Player 4 ).

The updated items in Fusion360 model are as follows.

(a) Y-direction length

Y-direction length ( 2020/05/16 ) Y-direction length ( 2020/06/27 )
Fusion360 model 87.55 mm 97.55 mm
Cutting Area in MODELA Player 4 90.52 mm 97.56 mm
( 48.78 mm x 2 )
( WAX length (measured) ) ( 88 mm ) ( 88 mm )
“walls” condition mold_sim_0516 mold_sim_0627

(b) “volume check” component to calculate the molding pattern ( silicon ) amount

128 cc, for the molding pattern 128 cc, for the product
volume_mold volume_product

Fusion360 model preview is shown blow.

The product and the molding pattern are not placed in parallel, because I started the product modeling with “Y-up” orientation, then placed the molding pattern as “Z-up” orientation to create the CNC tool path.

( “Open in Fusion360” button might not work on some browsers. To download the 3D model, please use the links in “5. Links to Files and Code” on the bottom of this page. )

Then, I used “MODELA Player 4” to create the tool path.

The parameter settings for CNC are shown in the table below ( same as those on 2020/05/16 ).

rough cutting finishing
Tool Type Square Square
Flute Diameter 3.18 mm 3.18 mm
Path Type Contour Lines, Up Cut Scan Lines
XY Speed 20 mm/sec 15 mm/sec
Z speed 10 mm/sec 10 mm/sec
Spindle rotational speed 7000 rpm 7000 rpm
Cutting-in Amount 1.2 mm N/A
Path Interval 1.8 mm 0.3 mm
Finish Margin 0.2 mm 0 mm
“wall” did not appear.
img_9006 img_9012
cleaning with detergent
img_9014 img_9019

5) Molding

Mold Star™ 16 FAST was used.

mixing and pouring
MDF plates were attached on the sides of WAX
after curing, molds were almost fine.
img_9017 img_9020
but, air bubble was found on one side.
img_9021 img_9022

6) Casting

I used “Cristal Resin NEO”, which is one of the epoxy resin for crafts.

Cristal Resin NEO

Color: Clear

Pot Life: 70 minutes

Cure Time: 36-48 hours ( 25 degC / 100g )

Mix Ratio By Weight, Resin : Curing agent = 2 : 1

cut the pieces,
to make pouring & air vent holes
tilt the molds for better air vent
img_9163 img_9164
weigh the Resin and Curing agent
weight ratio is 2 : 1
mixing, and making “air bubbles” !
img_9167 img_9168
pouring small air bubbles are coming up
img_9169 img_9172
after 48hours of curing time, took the epoxy from the mold
img_9260 img_9261
after deburring work, blue LED was set in the slit.
bubble_mold bubble_leaf

4. Important Learning Outcome

1) It was enjoyable process to make a casting model. It’s a brain training to imagine positive & negative shape. And, the “combine” command of 3D CAD is a powerful tool to make it.

2) MODELA Player 4 is simple tool, but the function seems to be limited. So, I’ll try fusion360 CAM if its needed.

3) As I planned, “LED in the bottom part, which lights up the above bubbles and tool marks.” was realized.

4) Epoxy is transparent, beautiful and good for this kink of craft. And, long curing time is suitable for avoiding the air bubbles.

5) So, the air bubbles were not as big as I expected this time. If I try next time, it’s better to improve the mixing process to get more air and/or use short-time curing materials.

fusion360 model

“Bubble leaf v48.f3d” download

CNC files

“Bubble leaf_pattern_longer_upper_lower.mpj” download

Rough cutting / Finishing .prn files ( “荒削り1.prn”, “仕上げ1.prn” )


“Bubble_leaf.mpj” ( 2020/05/16 file, for reference ) download

“Bubble leaf_pattern_longer_uppe_rev2.mdt”


6. Appendix

“Cristal Resin NEO”

Cristal Resin NEO