Should You Quote by Weight or Geometry

Most shops start quoting by weight. It’s simple: take the part volume, multiply by material density, add a markup, and send the number. For early-stage 3D printing bureaus running one or two machines, that works fine. But as soon as you add processes, materials, or part complexity, weight-only quoting starts leaking margin.

The alternative is geometry-based quoting — analyzing actual toolpaths, support structures, nesting efficiency, and machine time. It’s more work upfront, but it reflects what really drives cost. The question isn’t which method is “better” in a vacuum. It’s which method fits your current mix of work, and where the crossover point lives.

When Weight-Based Quoting Works

Weight-based quoting shines when:

• You run a single process (e.g., FDM or MJF) with consistent material pricing.
• Parts are simple, solid, and don’t require extensive supports or post-processing.
• Volume is high and variety is low — think production runs of identical brackets or housings.
• You need to turn around quotes in minutes, not hours.

In these scenarios, material cost dominates. Machine time correlates tightly with volume, so a $/kg or $/cm³ rate gets you 90% of the way there. The risk is low, and the speed payoff is real.

Where Weight-Based Quoting Breaks Down

The model fails when geometry drives cost more than mass. Common failure modes:

• Support-heavy parts: A 200g lattice structure can take 3x the print time and post-processing labor of a 200g solid block.
• Large flat parts: They consume disproportionate build plate area, limiting nesting and reducing throughput per run.
• Multi-material or multi-process jobs: Weight doesn’t capture setup changes, material changeovers, or secondary operations.
• Thin-walled or hollow parts: Low weight but high failure risk, longer cooling, or special orientation needs.

If you’re quoting these on weight alone, you’re either losing money on complex jobs or overpricing simple ones — and losing both to competitors who quote accurately.

What Geometry-Based Quoting Actually Measures

Geometry-based quoting looks at the manufacturing reality:

• Machine time: Layer count, scan path length, laser exposure, spindle runtime.
• Support volume and removal effort: Auto-generated supports vs. manual cleanup.
• Nesting density: How many parts fit per build, including orientation constraints.
• Post-processing steps: Bead blasting, dyeing, heat treatment, threading, inspection.
• Failure probability: Thin features, overhangs, residual stress zones.

This data comes from slicer output, CAM simulation, or historical job analytics. It turns quoting into a physics problem, not a guessing game.

The Hybrid Approach Most Shops End Up With

Pure geometry quoting for every RFQ is overkill. Pure weight quoting leaves margin on the table. The practical middle ground:

1. Default to weight-based for standard parts in your core process/material combo. Set a baseline $/kg that covers average machine time, supports, and post-processing.
2. Flag geometry outliers automatically: parts with high support-to-volume ratio, low nesting density, or features that trigger secondary ops.
3. Apply a geometry surcharge only to flagged parts — e.g., +15% for support-heavy, +20% for large-footprint, +fixed fee for threading or heat treat.
4. Track actuals vs. quotes monthly. Adjust baseline rates and surcharge triggers based on real data.

This keeps 80% of quotes fast while protecting margin on the 20% that actually determine profitability.

How to Know When to Switch

Watch three signals:

• Quote-to-close rate drops on complex parts — you’re overpricing.
• Margin erodes on high-volume simple parts — you’re underpricing.
• Estimators spend hours manually adjusting weight-based quotes — the model has outlived its usefulness.

When two of three hit, it’s time to invest in geometry-aware quoting logic.

What This Looks Like in Practice

A sheet metal shop running laser cutting and bending might start with $/kg for flat blanks. But once they add forming, tapping, and powder coating, weight stops correlating with cost. They switch to a hybrid: base rate per kg of raw material, plus per-bend, per-tap, and per-finish line items driven by CAD geometry.

A 3D printing bureau running MJF and SLA might use $/cm³ for solid SLA parts, but switch to build-time-based pricing for MJF nests where packing density swings utilization by 40%.

Solvi’s quoting engine supports both models — weight-based formulas for speed, geometry-driven rules for accuracy — and lets you apply them per process, material, or customer tier. You define the logic once; the system applies it to every RFQ. See how it works.

Bottom Line

Weight-based quoting is a startup strategy. Geometry-based quoting is a scale strategy. Most shops need both, deployed intelligently. Start with weight, measure the gaps, add geometry rules where they pay off, and automate the decision so estimators don’t have to think about it every time.