3D WERK
JEWELLER'S GUIDE · METAL WEIGHT
METAL WEIGHT CALCULATOR
The right metal
for every flask.
Too little metal and the casting comes out short. Too much and precious metal sits in the button waiting to be remelted. Work it out from your CAD volume, your pattern weight or the whole tree, with densities for the common casting alloys, from 9ct gold to 950 platinum.
Before you start
This guide is general information to help you get the most from your WaxJet. It does not replace the Flashforge manuals, the safety data sheets for your materials or your own safety checks. Where they differ, follow the manufacturer's instructions and safety data sheets. Isopropyl alcohol (IPA) is highly flammable, and warm IPA gives off more vapour. Flashforge's manual uses a mix of PPG400, ethanol and IPA at 40 °C, never above 43 °C. Ethanol is also highly flammable. Keep it away from heat, sparks and open flames, heat it only with equipment suited to flammable liquids, use it in a well-ventilated area, and wear suitable PPE such as gloves and eye protection. Investment powder contains crystalline silica, and wax burnout and metal melting give off fumes, so use ventilation and the PPE your safety data sheets list. As a business, you are responsible for work health and safety in your workshop, including risk assessment and how you store, use and dispose of chemicals. See our Terms and Conditions.
01
The calculator
05
Worked examples
02
Why the chart comes up short
06
Alloy densities
03
Measure your printed wax
07
Questions we hear
04
Weigh a tree, step by step
08
Where to next
1
The calculator
Choose your alloy, then how you want to work it out. Most fields start with example figures: replace them with yours and the result updates as you type. The printed wax density on the Whole tree tab starts empty, because it should be your own measured figure (section 3).
2
Why the chart comes up short
The classic shortcut is wax weight × the metal's specific gravity. Hidden inside it is one assumption: that your wax weighs the same as water, 1.00 g per cm³. Stuller's specific gravity table lists wax at exactly that. Most jewellery waxes, printed or not, are lighter.
Lighter wax, more metal. A pattern in a wax of 0.90 takes up the space of 1.11 g of water for every gram it weighs. It needs 11% more metal than the chart says, so the chart comes up 10% short.
Flashforge's figure is for hot, liquid wax. The WaxJet 51C specifications list the red model wax at 0.79 g/cm³ at 90°C. Wax contracts as it cools and sets, so a solid pattern on your bench is denser. Measure it instead (section 3).
The shortfall grows with the tree. On a 9 g sterling tree the gap can swallow most of a 15 g button (see the worked examples).
Printed wax is not one number. Pattern materials vary by maker, and at least one jetted material is heavier than water. Use the figure for your wax.
CAD volume skips the problem. The volume in your design file is the volume of metal you need, whatever the wax weighs. Metal weight in grams is density in g/cm³ × volume in mm³ ÷ 1000.
What the chart assumes
DENSITY (G/CM³)
1.00
WHERE THE FIGURE COMES FROM
Stuller's specific gravity table lists wax at 1.00
Carving wax
DENSITY (G/CM³)
0.92
WHERE THE FIGURE COMES FROM
Freeman, Ferris File-A-Wax technical data sheet
Injection wax, wax wire
DENSITY (G/CM³)
0.9 ± 0.05
WHERE THE FIGURE COMES FROM
Freeman, Ferris injection wax and wax wire safety data sheets
Jetted casting wax
DENSITY (G/CM³)
0.85 to 0.91
WHERE THE FIGURE COMES FROM
3D Systems, VisiJet M2 and M3 Cast safety data sheet
Flashforge red model wax
DENSITY (G/CM³)
0.79 at 90°C
WHERE THE FIGURE COMES FROM
Flashforge WaxJet 51C specifications, measured as a liquid. Not the solid density
Solidscape 3Z Model
DENSITY (G/CM³)
about 1.25
WHERE THE FIGURE COMES FROM
Solidscape safety data sheet (2012). Not a wax, and heavier than water
The short version
Use CAD volume for the pieces whenever you have the file. Use the weight routes when you do not, and always with the density of your own wax, never the chart's 1.00.
3
Measure your printed wax
Flashforge's specification figure for the red model wax is for the hot liquid, and its safety data sheet gives a wide range for the solid, so take ten minutes and measure it. You only need to do it once per wax, and again if you change wax.
1
Draw a solid 20 mm cube in CAD. That is 8000 mm³, heavy enough to weigh accurately on a 0.01 g scale. Print it in the same run as normal work if you like.
2
Clean and dry it like a pattern. Every trace of support dissolved and all the IPA evaporated, or the weight will be off.
3
4
Weigh it, then divide: weight (g) × 1000 ÷ CAD volume (mm³) = density in g/cm³.
Repeat with two or three cubes and use the average. Write the figure on your wax data sheet.
The printed cube can differ very slightly from CAD. The WaxJet 51C is specified at ±0.04 mm per 20 mm, which moves the result by about 0.6%. For a closer result, measure the cube with calipers and use its real volume.
4
Weigh a tree, step by step
This matches the casting tree guide. Three weighings give you both numbers the formula needs.
1
Weigh the printed patterns before spruing (A). Clean and fully dry, all together.
2
3
4
Weigh the empty rubber base (B). Use the same scale for every weighing.
Build the tree, then weigh the tree on its base (C).
Sprue wax = C − B − A.
5
6
Choose the button: about 15 g, or about 10% of the metal weight on larger trees.
Work out the metal with the Whole tree tab: patterns × (metal ÷ printed wax) + sprue wax × (metal ÷ sprue wax) + button.
5
Worked examples
Two jobs, worked through by hand. Type the same numbers into the calculator and you get the same answers.
Ten rings from CAD, 18ct yellow
CAD volume of one ring
250 mm³
250 × 15.5 ÷ 1000
3.875 g per ring
× 10 rings
38.75 g
38.75 g = 24.92 dwt = 1.246 oz t
Metal in the rings only. The sprue metal and button come on top, from the tree.
One tree, sterling silver
Patterns 6.00 g at 0.85: 6.00 × 10.4 ÷ 0.85
73.41 g
Sprue wax 3.00 g at 0.90: 3.00 × 10.4 ÷ 0.90
34.67 g
Button
15.00 g
123.08 g = 79.14 dwt = 3.957 oz t
0.85 is an example density, not a WaxJet figure: use your own. The chart shortcut would give 9.00 × 10.4 + 15 = 108.60 g, which is 14.48 g short. Almost the whole button would be gone before the tree was full.
6
Alloy densities
Density changes with the exact recipe of an alloy, so suppliers publish slightly different figures for the same carat and colour. The calculator uses the figure in the second column. For precision, use the density on your own alloy supplier's data sheet.
Sterling silver 925
USED HERE (G/CM³)
10.4
PUBLISHED FIGURES WE FOUND
10.36 to 10.40 (Stuller, Cooksongold, Hauser & Miller)
Fine silver 999
USED HERE (G/CM³)
10.5
PUBLISHED FIGURES WE FOUND
10.49 to 10.53 (Stuller, Cooksongold, Hauser & Miller, C.Hafner)
9ct yellow gold
USED HERE (G/CM³)
11.2
PUBLISHED FIGURES WE FOUND
11.0 to 11.2 (Cooksongold, C.Hafner)
9ct rose or red gold
USED HERE (G/CM³)
11.2
PUBLISHED FIGURES WE FOUND
11.1 to 11.3 (Cooksongold, C.Hafner)
14ct yellow gold
USED HERE (G/CM³)
13.1
PUBLISHED FIGURES WE FOUND
12.84 to 13.3 for most recipes (Stuller, Cooksongold, Hauser & Miller, C.Hafner)
14ct white gold, nickel
USED HERE (G/CM³)
12.6
PUBLISHED FIGURES WE FOUND
12.53 to 12.71 (Stuller, Hauser & Miller)
14ct rose or red gold
USED HERE (G/CM³)
13.2
PUBLISHED FIGURES WE FOUND
12.9 to 13.26 (Stuller, Hauser & Miller, C.Hafner)
18ct yellow gold
USED HERE (G/CM³)
15.5
PUBLISHED FIGURES WE FOUND
15.2 to 15.64 (Stuller, Cooksongold, Hauser & Miller, C.Hafner)
18ct white gold, nickel
USED HERE (G/CM³)
14.8
PUBLISHED FIGURES WE FOUND
14.62 to 15.0 (Stuller, Cooksongold, Hauser & Miller, C.Hafner)
18ct white gold, palladium
USED HERE (G/CM³)
15.9
PUBLISHED FIGURES WE FOUND
15.6 to 16.3, depending on the palladium content (Stuller, Cooksongold, C.Hafner)
18ct rose or red gold
USED HERE (G/CM³)
15.1
PUBLISHED FIGURES WE FOUND
14.9 to 15.4 (Stuller, Cooksongold, C.Hafner)
22ct yellow gold
USED HERE (G/CM³)
17.8
PUBLISHED FIGURES WE FOUND
17.6 to 17.86 (Cooksongold, Stuller, C.Hafner)
24ct fine gold
USED HERE (G/CM³)
19.3
PUBLISHED FIGURES WE FOUND
19.30 to 19.36 (Hauser & Miller, Stuller, C.Hafner)
950 platinum, ruthenium
USED HERE (G/CM³)
20.7
PUBLISHED FIGURES WE FOUND
20.7 (Platinum Guild International)
950 platinum, cobalt
USED HERE (G/CM³)
20.2
PUBLISHED FIGURES WE FOUND
20.1 to 20.2 (Stuller alloy chart, C.Hafner). Some older tables give 20.8
950 platinum, iridium
USED HERE (G/CM³)
21.5
PUBLISHED FIGURES WE FOUND
21.4 to 21.5 (Johnson Matthey, Platinum Guild International, Hauser & Miller)
950 palladium
USED HERE (G/CM³)
12.0
PUBLISHED FIGURES WE FOUND
11.7 to 12.0 (C.Hafner). Close to 12 for palladium ruthenium alloys (Santa Fe Symposium, Klotz and Held 2019)
Brass
USED HERE (G/CM³)
8.4
PUBLISHED FIGURES WE FOUND
8.40 (Stuller). Varies with zinc content
Bronze
USED HERE (G/CM³)
8.6
PUBLISHED FIGURES WE FOUND
8.62 (United PMR casting bronze 342). Varies with alloy
Specific gravity and density in g/cm³ are the same number for practical purposes. White gold density depends on whether it is alloyed with nickel or palladium, and 950 platinum on the second metal.
7
Questions we hear
Why is my casting short?
Rule out too little metal first. Work it out with your real wax densities, include the sprue wax and a button, and never guess. If the metal was enough, look at the tree: a sprue that is too thin or on a thin section can also cause incomplete fill, as the casting tree guide explains.
Does the CAD volume include the stones?
Only if you let it. Measure the metal body alone, with stones, cutters and display objects hidden. Stones set in the wax take up space in the mould, so counting them as metal over-orders.
Can I keep using my chart?
Yes, if you correct it. The chart answer assumes wax weighs 1.00, so divide the chart figure (before you add the button) by your wax density. For a wax of 0.90 that means about 11% more metal than the chart says.
How big should the button be?
Our casting tree guide uses about 15 g, or about 10% of the metal weight on larger trees, as a starting point. Not everyone agrees on big buttons: some casters prefer a tall main sprue with a funnel-shaped pour basin and a smaller button. Follow your own or your caster's practice. The calculator takes any figure.
Why weigh the sprue wax separately?
Because it is usually a different wax from your printed patterns, with a different density. One ratio for the whole tree is off by the difference between the two.
Can I get pennyweight and troy ounces?
Both are shown under every result. 1 dwt is exactly 1.55517384 g and 1 troy ounce is exactly 31.1034768 g, because both are defined from the grain (64.79891 mg).
Why not use Flashforge's 0.79 figure?
Flashforge's WaxJet 51C specifications give 0.79 for the red model wax as a liquid at 90°C, and its wax data sheet gives 0.76 as a liquid at 95°C. Both are for hot, liquid wax. Wax contracts as it cools and sets, so a solid pattern is denser than either, and dividing by them orders more metal than you need. Flashforge's WaxJet 51C build material safety data sheet lists 0.80 to 0.91 g/cm3 for the solid, with no test temperature. That is a wide spread, and its shrinkage figures do not say what temperature they are measured from, so measure your own with a test cube.
How close is the answer?
As close as the densities you put in. Alloy densities vary with the recipe (see the spread in the table) and wax densities vary by maker. Use your suppliers' figures and let the button cover the small remainder.
WHERE TO NEXT
From the scale to the flask
Weighing up a wax printer for your workshop?
Tell us what you make, and ask us for sample prints.
GUIDE 12 OF 13 · CASTING
THE BIG PICTURE
1 · DESIGN
2 · PATTERNS
3 · CASTING
4 · AFTER CASTING