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USB Printing Guide

Design Preparation and Tolerance

Before exporting your model, make sure it has been designed with 3D printing tolerances in mind.

In this guide, tolerance means designed clearance between printed parts. In other words, it is the small gap you intentionally leave between parts so that they can fit, slide, rotate, or connect properly after printing.

If two parts, for example a peg and a hole, are designed to be exactly the same size, they may become very tight after printing. On the Bambu H2D Pro printers, this can sometimes still work for a very tight fit. However, on the Ultimaker S7 printers, the parts are more likely to be too tight and may not fit at all without sanding or adjustment.

How tolerance is measured

When we say 0.1 mm tolerance, this usually means 0.1 mm clearance on each side.

For example, if a cube is 10 mm wide and you choose a 0.1 mm tolerance, the matching hole should be designed as:

10 mm + 0.1 mm + 0.1 mm = 10.2 mm

So the hole should be 10.2 mm wide, allowing 0.1 mm clearance on each side.

Tip: Tolerance is usually added to both sides of the part.
A 0.1 mm tolerance normally means 0.2 mm total extra space in the hole.

Quick comparison

Printer General starting point Notes
Bambu H2D Pro 0.15 mm Usually produces tighter and cleaner fits.
Ultimaker S7 0.2 mm Usually needs more clearance than Bambu.
Moving parts 0.2–0.4 mm+ Use more clearance for sliding, rotation, hinges, or large contact areas.
Press-fit parts 0–0.2 mm Always test first. Press-fit depends heavily on printer, material, and orientation.

Important: These numbers are starting points, not fixed rules. Always test a small sample first if the fit is important.

The Bambu H2D Pro printers can usually produce slightly tighter and cleaner fits than the Ultimaker printers, but you should still design with clearance.

For the Bambu H2D Pro printers, we usually recommend allowing a tolerance of around:

0 mm, 0.1 mm, 0.15 mm, or 0.2 mm

depending on the type of fit you need.

Bambu H2D Pro tolerance guide

Use case Suggested tolerance Notes
Peg and hole for alignment or basic assembly 0.1–0.15 mm Good for parts that need to locate or align without too much wobble.
Peg and hole for removable parts 0.15–0.2 mm Better for parts that need to be assembled and removed by hand.
Peg and hole for free movement 0.2 mm+ Use for rotation, sliding, repeated removal, or larger contact areas.
Joints, hinges, or sliding parts 0.15–0.2 mm Leave enough clearance so the parts can move after printing.
Press-fit parts 0–0.05 mm Very tight. Always test first.
Interlocking parts Depends on contact area Avoid making the fit too tight, especially for large contact areas.
Screw holes Depends on fixing method See screw hole guidance below.

Tip: Peg and hole parts do not always need to be very loose.
The tolerance depends on whether the peg is used for alignment, removable assembly, or free movement.

Bambu screw holes

For screw holes, the tolerance depends on the fixing method: brass threaded inserts, screwdriver tightening, or hand-tightening.

Fixing method Suggested tolerance Notes
Screw bites directly into printed plastic -0.2 mm, -0.1 mm, or 0 mm The hole is slightly smaller so the screw can grip the plastic.
Screw tightened with screwdriver -0.1 mm or 0 mm Depends on screw type and how strong the fixing needs to be.
Hand-tightened screw 0 mm or slightly loose Useful when the screw needs to be removed easily.
Brass threaded insert Based on insert outer diameter Do not use screw diameter. Check the insert size and test first.

If the screw is meant to bite directly into the printed plastic, the hole is usually designed slightly smaller than the screw diameter. This is why you may use a negative tolerance.

For example, if the screw diameter is 3 mm and you use -0.1 mm tolerance, the hole diameter would be:

3 mm - 0.1 mm = 2.9 mm

This gives the screw some material to grip into.

Important: If you are using brass threaded inserts, do not simply design the hole based on the screw diameter.
The hole size should be based on the outer diameter of the brass insert and the manufacturer's recommended hole size.

Different insert types, materials, and printer settings can change how tightly the insert fits. Always test with a small sample first.

The Ultimaker S7 printers usually need more clearance than the Bambu H2D Pro printers. If you use the same tight tolerance as Bambu, the parts may not fit after printing.

For the Ultimaker S7 printers, we usually recommend using larger tolerances.

Ultimaker S7 tolerance guide

Use case Suggested tolerance Notes
Peg and hole for alignment or basic assembly 0.2 mm per side Safer starting point for general assembly.
Peg and hole for removable parts 0.3 mm per side More reliable for parts that need to be taken apart.
Peg and hole for free movement 0.4 mm+ per side Use for rotation, sliding, repeated removal, or large contact areas.
Joints, hinges, or sliding parts 0.3 mm+ Use more clearance if the part needs to move freely.
Press-fit parts 0.2 mm Safer starting point on Ultimaker. Always test first.
Interlocking parts Depends on contact area Avoid making the fit too tight.
Screw holes Depends on fixing method See screw hole guidance below.

For example, if a peg is 10 mm wide and you use 0.2 mm tolerance per side, the matching hole should be:

10 mm + 0.2 mm + 0.2 mm = 10.4 mm

So the hole should be 10.4 mm wide.

Warning: On the Ultimaker S7, using the same tight tolerance as Bambu may cause parts to become stuck or not fit at all.

Ultimaker screw holes

For screw holes, the tolerance depends on the fixing method: brass threaded inserts, screwdriver tightening, or hand-tightening.

Fixing method Suggested tolerance Notes
Screw cuts or bites into printed plastic -0.1 mm, 0 mm, or 0.1 mm The hole may need to be slightly smaller than the screw diameter.
Screw tightened with screwdriver 0 mm or 0.1 mm Depends on screw type, material, and required strength.
Hand-tightened screw 0.1 mm or slightly loose Useful when the screw needs to be removed easily.
Brass threaded insert Based on insert outer diameter Use the manufacturer's recommended hole size. Test first.

Important: If you are using brass threaded inserts, design the hole based on the insert's outer diameter and the manufacturer's recommended hole size, not the screw diameter.

You should always test a small sample before printing the full object, or check the tolerance sample board in our lab.

Choosing the right tolerance

For parts that need to fit together, the tolerance depends on how tight or loose you want the fit to be.

Tolerance Use case Notes
0 mm Very tight fit, or parts not meant to move after assembly Often too tight on FDM printers. May need sanding, force, or adjustment.
0.1 mm Tight fit Good for small connectors or parts that should not wobble too much.
0.15 mm General-purpose tolerance for Bambu H2D Pro Good starting point for reliable assembly without too much force.
0.2 mm Easier or looser fit Good for removable parts, lids, slots, hinges, or larger contact areas.
0.3 mm+ Moving parts or Ultimaker prints Good for sliding parts, larger assemblies, or parts that need to fit reliably.
0.4 mm+ Free movement or large contact areas Useful for hinges, rotation, sliding, or looser fits on Ultimaker.

Simple rule

If you are not sure, start with:

Printer Recommended starting point
Bambu H2D Pro 0.15 mm
Ultimaker S7 0.2 mm

Use 0.1 mm if you want a tighter fit.

Use 0.2 mm or more if the parts need to slide, move, or be removed easily.

Use 0 mm only if you are prepared to test, sand, or adjust the print afterwards.

Use 0.3–0.4 mm or more for moving parts, large contact areas, or looser fits on the Ultimaker printers.

Things that can affect tolerance

Tolerance is not fixed. It can change depending on:

  • Material
  • Print orientation
  • Wall thickness
  • Print speed
  • Nozzle size
  • First-layer squish
  • The size and shape of the object
  • Contact area between parts
  • Whether the part needs to move or stay fixed
  • Whether the part will be assembled once or repeatedly removed

Tip: Always test a small sample first when the fit is important.
You can also check the tolerance sample board in our lab before printing the full object.

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