"Thronborg solves problems you never thought was solvable!"


Casting aluminium

In many years i wanted to casting aluminum. But there was a lot of things i needed to have and i had lack of knowledge.

What do you want to now?

I tried internet to get information about how to do metal casting. There was a lot of pages and Youtube movies. Sadly, professionals dont share their information but amateurs do. But why was their way to do it so diffrent and why does so many had failure in their casting? I realised that i had to understand the process from the beginning and metalurgi was one of the most complicated and difficult process i ever tryed to understand.

The No:1 source i found was this Foundry manual from 1958. Yes its old, but the knowledge in metal casting started in the 1800 b.c. so much has been improved since then until the industry revolution and wwII, it's only 63 yers ago.

Other good links:







Size ratio

2.3.1 Sprue bottom(choke) area 2. Runner area 3. Gate area 1.

Choke 10mm, Runner 15mm, Gate 5mm

Riser volume

must be large enough to provide a sufficient amount of liquid metal to compensate for shrinkage in the cavity.

Pouring basin

ensure that the metal flow into the sprue is uninterrupted

Gate length

The minimum gate length should be three to five times the gate diameter.

Dross traps

are placed at the ends of the runners, and the runner projects above the gates to ensure that the metal in the gates is trapped below the surface.

Sprue inclination 5% aprox.

Sprue well 2-3 gg diameter of choke

Runner 2-4 times bigger area then choke

1. Pouring basin

Here is the melted Aluminum pored at 677°C - 760°C. Since the Aluminum oxidize direct in air is it important to keep the Basin filled up ALL the time over the Ridge.

2. Ridge

The Ridge prevent air to get into the Aluminum by letting the aluminum flow under the top.

3. Inlet basin

After the molten Aluminium run over the Ridge it should contain little dross and air.

4. Tapered sprue

The melten Aluminum now in high speed that must been slown down and thats happend in the Tapered Sprue. The Tapered Sprue should be 1/2 diameter of the total area of the gates.

5. Blind runner (Dross trap)

Is both a pressure releaser, dross trap and make less turbulence in the flow.

6. Well

In the well the the pressure is built up and slow down the flow before it goes to the runner where its choked and the flow slow down.

7. Runner

The runner should be filled now with Aluminum only, and it runs slower untit it passes the first gate. The Runner should be 3 times bigger than the diameter of the gates.

8. Blind riser

Trap air and help even pressure to the Runner.

9. Choke

For every gate the Aluminium passes the Runner should be smaller.

10. Gate

Here the melted Aluminum enter the Casting, just hope the temperature is high, speed sloww, minimum air and dross entered here.

11. Open riser

When you starting pour the whole system is filled with air and that must escape some where.

12. Blind runner (Dross trap)

Is a dross trap and make less turbulence in the flow.

13. Open riser

Here mostly of the air in your system will escape. The hight should be 1.5 times higher than the diameter.

14. Vent

You can make it easier for traped air to leave the sand by pick several small channels down to the mols, important to do if you are using a core.

15. Casting

Your part you cast.

What do you need?


           Ugn, El, Sten, kol, fläkt

           Degel metallrör Ø50-75mm höjd 80-140mm gods 2-4mm



           Degassing nedsänker


           Flask 200x200mm

           Sil finmaskig


           Vattenglas (Natrium silikat) (Sodium silikat) För Core 5-10%. (MyFordBoy 6.5%)


           Flussmedel Cupral 102

           Flussmedel Crystal 3000

           Pottaska=kaliumkarbonat Tar bort magnesium


95% Sand, 5% bentonit, water (som say 5-20% bentonit) Maritime  

Core CO2

sand,  3-5% Waterglass.

Core oilsand (Petrobond)

95% sand, 5% bentonit, 1% mjöl, 1% linolja, 1-2% vatten, baka i ugn 200-210°C 1 timme

98,5% sand, 0,2 Bentonit, 1% linolja, 0,3 vete/majsmjöl, 5% vatten baka i ugn 200-210°C 1 timme. Maritime

Thin wall 99% sand, 0% bentonit, 0,5% linolja, 0,5% vete/majsmjöl, 5% vatten baka i ugn 200-210°C 1 timme

Make your own CO2

Mix Vinäger och bikarbonat. Ställ  i en burk tillsammans med blandningen. Sätt på lock och låt stå en timme.


vid 640C, ca 3 minuter efter att all aluminium smält ta bort slagg

Degassing Sodium carbonate, Natriumkarbonat (Hushållssoda) (Kristallsoda) (Målarsoda)

1/2 tesked linda in i alufolie. Tryck ned i botten och låt bubbla upp. Tar bort Hydrogen (Väte)


Drossing flux. Rör inte om. Tillsätt Potassium Aluminium fluorid (Kaliumaluminiumfluorid), wait 3 minutes.

Rör om ta bort slagg

Häll i formen snabbt

677°C - 760°C (Myfordboy (720C). Tunnare material högre temperaturen

Ta ur formen

När tempen sjunkit till 260C


           Lägg undre formen med uppsidan ner.

           Lägg i modellen upp och ner

           Fyll på med sand, använd sil

           Packa och skrapa av

           Vänd undre formen upp och ned så man ser pluggen


           Sätt fast den andra halvan av pluggen

           Sätt på den övre formen

           Stick ned påfyllning och ventrör

           Packa med sand runt rören, jämna av

           Ta bort rören

           Dela formen

           Gör kanaler för inlopp och ventilation

           Ta bort den undre modellen med skruvar

           Ta bort pluggen i den övre halvan.

           Gör bassäng

           Gör rent med blås

           CORE lägg i den här

           Gör ventilationshål

Partly in Swedish, sorry.