Precision, Repeatability, and How to Get the Perfect Fit

1. What is dimensional tolerancing, and why does it matter in HP MJF?

Dimensional tolerancing defines the acceptable variation in part dimensions. In HP Multi Jet Fusion (MJF), it ensures consistent fit and function in mechanical assemblies, preventing parts from being too tight or too loose.

2. How accurate is HP MJF compared to other manufacturing methods?

HP MJF typically achieves IT10 – IT12 tolerances, making it more precise than most other 3D printing technologies and comparable to precision machining in many applications.

3. What are IT Grades, and how do they apply to HP MJF?

International Tolerance (IT) Grades set standardized limits on dimensional variation:

  • IT5 – IT9: High-precision machining (e.g., aerospace components).
  • IT10 – IT12: Engineering fits, which is HP MJF’s range.
  • IT13 – IT16: Looser tolerances for castings and large parts.

4. What factors impact dimensional accuracy in HP MJF?

  1. Material shrinkage – MJF parts typically shrink 1-2% after printing.
  2. Thermal effects – Expansion and cooling cycles introduce small distortions.
  3. Post-processing – Machining, sanding, and dyeing can slightly shift tolerances.

5. How does HP MJF minimize dimensional variation?

HP’s Jet Fusion technology uses real-time thermal imaging and process control to manage powder fusion, reducing inconsistencies and ensuring repeatability.

6. What is Process Capability (CpkC_{pk}), and why does it matter?

CpkC_{pk} measures how well a process holds tolerances. In MJF, a CpkC_{pk} of 1.33 (4 sigma) means 99.94% of parts meet spec, reducing defects and rework.

7. How does HP MJF compare to CNC machining in terms of tolerances?

While CNC machining can achieve tighter tolerances (IT5-IT7), HP MJF is competitive for many applications while offering design flexibility that traditional machining cannot.

8. What’s the best way to compensate for shrinkage in HP MJF?

Design parts 1-2% larger in CAD, depending on material and part geometry. Some MJF software tools automate this compensation for you.

9. Can post-processing affect final part dimensions?

Yes. Sanding, dyeing, and machining can alter tolerances. If post-processing is required, it’s best to print parts slightly oversized and refine them after.

10. How does powder spreading affect tolerances?

Powder-based 3D printing isn’t perfect—microscopic variations in powder layering can cause slight dimensional shifts, especially on fine features.

11. How do wall thickness and part geometry impact tolerances?

Thin walls and unsupported structures tend to warp more during cooling, while uniform wall thicknesses improve dimensional stability.

12. What’s the best way to ensure part repeatability in HP MJF?

  • Use consistent wall thicknesses to minimize warping.
  • Design with rounded corners to reduce stress concentrations.
  • Leverage HP’s in-process monitoring tools to improve accuracy.

13. What’s the recommended minimum clearance for MJF-printed moving parts?

For snap-fits or interlocking components, aim for at least 0.3 – 0.5mm clearance to accommodate variability.

14. What are common tolerancing mistakes in HP MJF?

  • Ignoring shrinkage – Leads to undersized parts.
  • Assuming uniform accuracy – Certain features (like overhangs) may print less accurately.
  • Skipping tolerance testing – Always prototype before final production.

15. How does HP’s process control help maintain tight tolerances?

The HP Jet Fusion 5200 series includes:
✔ Automated dimensional profiling – Self-adjusts printing settings for better consistency.
✔ Fleet-wide calibration – Ensures uniform results across multiple printers.
✔ Closed-loop feedback – Makes real-time corrections for enhanced precision.

16. What’s the best way to verify dimensional accuracy in HP MJF parts?

Use digital calipers, micrometers, or CMM (coordinate measuring machines) to compare printed dimensions against CAD specs.

17. Is HP MJF suitable for high-precision mechanical assemblies?

Yes—with proper design and post-processing, HP MJF parts can meet engineering-grade tolerances for brackets, enclosures, and functional components.

18. Can HP MJF achieve press-fit tolerances?

It’s possible, but MJF’s inherent variability makes CNC finishing or oversized printing + machining a better strategy for press-fit applications.

19. How does HP MJF handle internal channels and complex geometries?

MJF can print intricate internal structures, but tolerances may vary slightly due to powder removal challenges in deep cavities.

20. How can I optimize my 3D printing process for better tolerances?

✅ Design for MJF-specific tolerances – Adjust CAD models for expected shrinkage.
✅ Use HP’s process controls – Leverage automated calibration tools.
✅ Test, measure, adjust – Always verify real-world tolerances before full production.

Looking to Improve Your MJF Tolerances? Let’s Talk.

Dimensional accuracy is the key to getting 3D-printed parts that actually fit and function. Whether you’re designing for tight engineering fits or functional prototypes, proper tolerancing makes all the difference.

Contact RapidMade at rapidmade.com to optimize your MJF prints today!