When to use this guide
Use this page when the symptoms below match what you see on the printer. Work through the checks in order and avoid changing several variables at once.
- Peg-and-hole parts are too tight
- Lids, inserts, hinges, or clips do not fit consistently
- Outer dimensions measure close but holes are undersized
- Parts fit in PLA but not PETG or ABS/ASA
- A model works at one scale but not another
Most likely causes
These are the most common root causes. The correct fix depends on when the failure happens, which material is loaded, and whether the profile used to work before.
- XY compensation, flow, elephant foot, and material shrink are not accounted for
- Holes print smaller due to extrusion and polygon behavior
- First layer squish affects fit surfaces
- Different materials shrink or expand differently
- The model has no tolerance built into mating features
Safe fix order
This order is designed to prevent random tuning. Start with physical checks and material condition, then move into slicer changes.
- Measure the part before changing slicer settings blindly.
- Separate first-layer fit problems from overall XY problems.
- Calibrate flow before changing horizontal expansion.
- Use slicer XY/hole compensation carefully and document values.
- Design or choose models with real clearance for printed parts.
- Test small tolerance coupons before printing a large assembly.
Settings and decision notes
Clearance starting pointMany FDM assemblies need clearance; exact value depends on printer/material/nozzle.
Hole compensationUse carefully because it can improve holes while changing other features.
Elephant footFix first-layer bulge before blaming the whole part.
Material shrinkABS/ASA may need different compensation than PLA.
Bench checklist
Use this short checklist beside the printer before reprinting the full model.
- Measure X/Y/Z dimensions.
- Check first-layer bulge.
- Verify flow.
- Print a tolerance test.
- Adjust compensation slowly.
- Save values by printer/material.
What to do after it works
Print a small confirmation part before returning to a long print. Save the working material, temperature, cooling, speed, and support notes in Profile Vault so the same problem does not become a repeat mystery.