Powder Bed - SLS / MJF

Why this process is unique

Powder bed processes (SLS, MJF, HSS) don't use support structures - the unfused powder supports the part during printing. This has two major pricing implications:

1. Cost is driven by chamber volume occupied, not just part volume. A small dense part and a large hollow part with the same actual volume cost very differently.
2. Build setup is expensive - depowdering, cake extraction, powder sieving, and material refresh are significant fixed costs per build. These must be amortised over all parts in the run.

The standard cost metric is shrinkWrapVolume - the tightest wrapping around the part including overhangs. It's the best proxy for how much of the chamber the part consumes.

Core methodology

Variable cost: shrinkWrapVolume × cost per cm³

Fixed cost: setup fee per build, divided by quantity ordered

Quantity discount: banded, reflecting better chamber utilisation and batch efficiency

Review gate: parts exceeding the chamber in any dimension

HP MJF 5200 Pro specifications (reference)

• Build volume: 380 × 284 × 380 mm
• Layer height: 0.08 mm
• Typical cycle: 8-12 hours per full build

Numerical example

Part: 50 × 50 × 100 mm bracket, shrinkWrapVolume = 210,000 mm³ (part has overhangs)

Calculation:

• Volume cost: (210,000 / 1,000) × 0.18 = €37.80
• Setup per part: 80 / 5 = €16.00
• Subtotal: €53.80
• Qty 5 discount (none below 10): ×1.00
• Unit price: €53.80

At qty 50: setup = €1.60/part, discount 10% → unit price €35.46. Material cost is now ~90% of the price.

Complete algorithm

const { shrinkWrapVolume, length, width, height } = specification
const { quantity } = requisition

// Machine chamber limits — adapt to your printer
const CHAMBER_LENGTH = 380
const CHAMBER_WIDTH  = 284
const CHAMBER_HEIGHT = 380

const costPerCm3 = material.variables['costPerCm3']
const setupCost  = material.variables['setupCost']

// Variable cost: shrink wrap volume × rate
const volumeCm3  = shrinkWrapVolume / 1000
const volumeCost = round(volumeCm3 * costPerCm3, 2)

// Fixed cost: setup amortised over order quantity
const setupPerPart = round(setupCost / quantity, 2)

const baseCost = volumeCost + setupPerPart

// Quantity discount: smaller batches pay more per part
const getDiscount = createBands({ 5: 0.97, 10: 0.93, 25: 0.88, 50: 0.83, 100: 0.78 }, 1.0)
const unitPrice = variable('unitPrice', round(baseCost * getDiscount(quantity), 2))

// Review gate: part exceeds chamber dimensions
const oversized = length > CHAMBER_LENGTH || width > CHAMBER_WIDTH || height > CHAMBER_HEIGHT
done(unitPrice, 0, oversized)

Material variables to create: costPerCm3, setupCost

When to use this

Use this model for any powder bed process: MJF, SLS, HSS, SAF. All share the same pricing structure.

Do not use for metal powder bed (LPBF) - print time dominates there and requires a time-based model.

You could also think of a packing algorithm to predict the usage of the build chamber at larger quantities.