DIY Custom 3D Printed TPU Insoles: Generate, Print, Finish, and Iterate

Most custom insoles are made through a slow traditional workflow: foot assessment, plaster or foam molds, lab work, manual finishing, and a long wait. This project shows a simpler DIY workflow using Ergono3D: generate a custom insole STL, print it in TPU, finish it with a top cover, wear test it, and refine the design if needed.

The goal is not to replace professional care. This is a maker-focused comfort and support project for people who want to explore functional 3D printing with flexible TPU.

With Ergono3D, the design starts from a guided profile: daily use, activity type, arch type, shoe wear pattern, discomfort areas, shoe type, and support priority. The system then generates a printable insole model with adjustable parameters such as arch height, heel cup depth, posting, flange height, skive, thickness, and scaling.

The workflow is simple:

Generate the STL → Adjust parameters → Scale for fit → Print in TPU → Add a top cover → Wear test → Iterate

The useful part is the iteration. If the arch feels too high, the heel cup rubs, the insole feels too stiff, or the shoe fit is too tight, you can go back, adjust the model, and print a better version.

Ergono3d.com

1. FDM 3D printer capable of printing TPU
2. TPU filament
3. TPU 85A for softer comfort-focused use
4. TPU 90A for balanced daily use
5. TPU 95A for firmer support and stability
6. Slicer software such as Bambu Studio, OrcaSlicer, PrusaSlicer, or Cura
7. Ergono3D-generated STL file
8. Shoes with removable insoles
9. Scissors or a trimming knife
10. Sandpaper for edge finishing
11. Optional: EVA, Poron, fabric, leather, or another top cover material
12. Optional: flexible adhesive for bonding the top cover
13. Optional: measuring tape, ruler, or calipers
14. Optional: printed foot outline or measurement sheet

Recommended starting TPU settings

1. Nozzle temperature: 230–240°C
2. Bed temperature: 50–60°C
3. Print speed: 25–50 mm/s
4. Infill: 15–25% gyroid
5. Retraction: low or disabled, depending on your extruder
6. Walls: 2–3 perimeters

Start by creating a basic profile for the insole.

In Ergono3D, choose your daily routine, sub-category, arch type, and shoe wear pattern. These choices help define the first version of the insole shell.

For example, a daily walking insole does not need the same structure as a court-sport or running insole. A flat arch, high arch, medial wear pattern, or lateral wear pattern can all lead to different starting parameters.

In this step, select:

1. Daily routine
2. Main movement category
3. Arch type
4. Shoe sole wear pattern

This gives the system a first understanding of how the insole will be used.

Next, describe where you feel discomfort and how you plan to use the insoles.

You can select discomfort areas such as the heel, arch, forefoot, ankle, knee, or lower back. Then choose the main usage scenario, such as running, standing, walking, hiking, court sports, or dancing.

Also choose your top priority:

1. Comfort
2. Support
3. Performance
4. Correction

Finally, select the shoe type. This matters because sneakers, boots, dress shoes, and open shoes have very different space limits.

A thick insole may feel fine in a sneaker but too tight in a dress shoe. This is why shoe type should be part of the design process from the beginning.

After the profile is complete, Ergono3D generates an initial 3D insole model.

This is not just a static STL. You can still adjust the advanced parameters before printing. The left and right sides can be tuned separately when needed.

Common adjustable parameters include:

1. Arch height
2. Arch length
3. Medial flange height
4. Lateral flange height
5. Heel cup depth
6. Rearfoot varus or valgus posting
7. Forefoot varus or valgus posting
8. Medial or lateral heel skive
9. Metatarsal pad option
10. Overall thickness
11. Midsole recess

Start with the default settings first. Then only change one or two parameters if you have a clear reason. This makes it easier to understand what changed after the next wear test.

Before printing, check the final insole size.

Use the scaling adjustment screen to fine-tune length, width, and height. This is useful when the STL shape is correct but the shoe fit needs small adjustments.

You can adjust:

1. Length scale
2. Width scale
3. Height scale

The final dimensions are shown below the preview. Once the fit looks right, download the STL and prepare it for slicing.

This step is especially useful when moving between different shoes. Even the same foot size can need different insole scaling depending on the shoe shape and internal volume.

This step is optional, but it can help improve fit accuracy.

Trace your foot outline on paper or use a measurement reference image. Mark the top, heel, left, and right points of the foot. This helps you understand the real length and width of your foot before scaling the STL.

This is especially helpful if:

1. You are between shoe sizes
2. Your left and right feet are different
3. Your shoes have limited internal space
4. The first printed version feels too long, too wide, or too narrow

Use the measurement as a fit reference.

Import the STL into your slicer and use slow, TPU-friendly settings.

A reliable starting point is:

1. Nozzle: around 235°C
2. Bed: around 55°C
3. Speed: 25–50 mm/s
4. Infill: 20% gyroid
5. Retraction: off or very low
6. Cooling: moderate to high, depending on your TPU and printer

TPU is flexible, so printing too fast can cause poor extrusion, stringing, or weak layers. If you are using a Bowden extruder, go slower. Direct-drive printers usually handle TPU more easily.

For the first print, do not chase speed. A clean first print is more useful than a fast failed print.

Print the insoles in TPU and let them cool before removing them from the build plate.

After printing:

1. Trim any brim or excess material.
2. Lightly round sharp edges with scissors or sandpaper.
3. Test the shell inside the shoe.
4. Add a top cover if you plan to wear it for real use.

The TPU shell is the structural part of the insole. The top cover is the part your foot actually touches. It improves comfort, reduces friction, helps with sweat management, and can add cushioning or rebound depending on the material.

For top cover material:

1. EVA is the easiest all-round choice
2. Poron is better for rebound and athletic use
3. Thin supercritical foam can work if available
4. Leather is suitable for dress shoes

A common EVA starting point is about 2–3 mm thick and around 25–40 Shore C.

Use flexible adhesive, not super glue. Bond from the heel cup forward, then trim the excess around the edge.

Do a short wear test before using the insoles for a full day or a long activity.

Check:

1. Does the arch feel too high or too low?
2. Does the heel cup rub?
3. Is the insole sliding inside the shoe?
4. Does the forefoot feel too firm?
5. Is the shoe too tight after adding the insole?
6. Does one foot feel different from the other?

Use the feedback to adjust the next version.

Examples:

1. Arch feels too high → reduce arch height
2. Arch feels unsupported → increase arch height slightly
3. Heel edge rubs → reduce heel cup depth or round the edge
4. Insole feels too stiff → use softer TPU or lower infill
5. Insole feels too soft → use firmer TPU or higher infill
6. Shoe feels too tight → reduce thickness or adjust scaling

This is the main advantage of the workflow: the first print does not have to be the final version. You can adjust, regenerate, reprint, and improve the fit over time.