How do you calculate sintering shrinkage cost?

Multiply compacts sintered by material value lost per part by the scrap rate to get the variable loss, then add furnace overhead. For 8000 compacts at $6.50 each, 8% scrap, plus $5000 overhead, that is $4160 + $5000 = $9160.

What is the per-unit sintering shrinkage cost in the example?

$9160 total divided by 8000 compacts is $1.145 per compact. That is the shrinkage burden baked into every part whether it passes or not.

Why do NdFeB magnets shrink so much during sintering?

Green compacts are pressed powder with 40-50% porosity. During sintering at roughly 1050-1100C the particles bond and densify, removing that porosity and producing 15-20% linear shrinkage, which must be predictable to hold final tolerance.

How can I reduce shrinkage scrap?

Improve die-fill uniformity, use isostatic pressing for even green density, optimize the ramp and soak profile, and design setters that support the part evenly so it does not slump or warp during densification.

Is furnace overhead really a shrinkage cost?

It is a fixed cost of the sintering step that gets amortized across whatever passes. When scrap rises, the same $5000 overhead spreads over fewer good parts, so the effective cost per good magnet climbs even though the overhead line itself does not change.

Shrinkage cost vs scrap cost: are they the same?

Shrinkage cost is a specific slice of scrap cost driven by dimensional loss during densification. Total scrap cost also includes powder defects, coating rejects and magnetization failures, so shrinkage is one contributor.

Rare Earth Magnet & Motor Materials calculator

Sintering Shrinkage Calculator

Sintering shrinkage cost captures the money lost when green NdFeB compacts densify unevenly in the furnace and end up out of dimensional tolerance, plus the fixed cost of running that furnace cycle. Rare earth magnets shrink 15-20% linearly during sintering, and any warping, cracking or over/under-density means the part misses final-grind stock and gets scrapped. Cost and process engineers use this to see the true burden of shrinkage scrap per compact, because the neodymium and dysprosium locked into a rejected part is expensive to write off. It combines a variable loss that scales with scrap rate and a fixed furnace overhead that you pay whether or not parts pass.

What this calculator does

Estimates the cost of sintering shrinkage on rare earth magnet parts from compact count, per-part material loss, and out-of-spec scrap rate.
Use it to budget yield loss from dimensional shrink when sintering NdFeB or SmCo magnet blanks.
It sums the material value lost to shrinkage scrap plus fixed furnace overhead, then divides by compacts to give a cost per piece.

Formula used

Total shrinkage loss = compacts sintered x material value lost per part x shrinkage scrap rate% + furnace overhead
Shrinkage cost per compact = total shrinkage loss / compacts sintered

Inputs explained

Green compacts sintered:
Rare earth material value lost per scrapped compact:
Shrinkage-related scrap rate:
Furnace run and atmosphere overhead:

How to use the result

Use it when quoting a magnet grade, evaluating a furnace profile change, or justifying investment in better die filling and setter design.
It treats scrap rate as a single average and does not distinguish shrinkage from cracks versus density gradients, which have different fixes.

Current U.S. benchmarks

The producer price index for copper and brass mill shapes stands at 559.593 (BLS, May 2026), up 76.8% from a year earlier. Quotes priced off last quarter's material cost miss this move. Global copper trades at $13,484 per tonne (IMF via FRED, May 2026).
The U.S. has 5,397 electrical equipment and appliances establishments employing about 369,437 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate sintering shrinkage cost? Multiply compacts sintered by material value lost per part by the scrap rate to get the variable loss, then add furnace overhead. For 8000 compacts at $6.50 each, 8% scrap, plus $5000 overhead, that is $4160 + $5000 = $9160.
What is the per-unit sintering shrinkage cost in the example? $9160 total divided by 8000 compacts is $1.145 per compact. That is the shrinkage burden baked into every part whether it passes or not.
Why do NdFeB magnets shrink so much during sintering? Green compacts are pressed powder with 40-50% porosity. During sintering at roughly 1050-1100C the particles bond and densify, removing that porosity and producing 15-20% linear shrinkage, which must be predictable to hold final tolerance.
How can I reduce shrinkage scrap? Improve die-fill uniformity, use isostatic pressing for even green density, optimize the ramp and soak profile, and design setters that support the part evenly so it does not slump or warp during densification.
Is furnace overhead really a shrinkage cost? It is a fixed cost of the sintering step that gets amortized across whatever passes. When scrap rises, the same $5000 overhead spreads over fewer good parts, so the effective cost per good magnet climbs even though the overhead line itself does not change.

Last reviewed 2026-05-12.