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Stages of 3D-Production of Orthopedic Insoles

Oct 20, 2020

Stages of 3D-Production of Orthopedic Insoles

 

General Information about Orthopedic Insoles

Shoe manufacturers are trying to find the best form of insoles and lasts for making shoes, but each person’s foot is unique. Standard shoes fit well for people with no abnormalities in the structure of their feet, but they may also need to adjust the position of the foot in the shoe.

If longitudinal or transverse flat feet, Halus Valgus, diseases or injuries of the spine are present, then standard shoes will cause discomfort, and each step can bring significant pain. With age, unpleasant and painful sensations without treatment can only increase.

There are orthopedic insoles designed to reduce the level of discomfort and compensate for the position of the foot in the shoe. Some of them are sold ready-made, and, as previously mentioned, are designed for an average foot with one deviation or another, while others can be made individually.

You can find orthopedic insoles in orthopedic salons and shops in your city at a price of 500 to 3000 rubles. In some cases, the insole can help achieve the required comfort and even relieve or redistribute the load from certain areas of the foot. But this is still a standardized product and you should not expect a miracle from them.

The next step on the path to walking and wearing shoes comfort are thermoformed insoles. They are represented by various companies and manufacturers, but the main point of it all comes down to thermal forming of the initial blank with subsequent addition of standard elements and substrates in the required places to achieve the desired result.

 

Examples of customized thermoformed insoles. Image source: https://system-med.ru/uslugi-i-ceny/ortopedicheskie-stelki/izgotovlenie-individualnykh-stelek-po-sis…

 

Insoles of this type are produced in the presence of the client in around 20-60 minutes. Forming can occur in various ways, but one way or another, it will follow the contour of the foot.

The indisputable advantage of these insoles is that they are made individually for the patient’s foot, and the wearing comfort will be noticeable immediately after the insole is inserted into the shoe.

Since the insole follows the contour of the foot, adjustments for future treatment can be problematic.

Such insoles are widely used in orthopedic salons and among orthopedists due to the simplicity and speed of manufacture, and among patients since the comfort of wearing is felt immediately after the start of their use. The cost of insoles is much higher than common ones – from 3000 to 15000 rubles, depending on the manufacturer and the specific case. Under the pressure of the foot, a workpiece or plastic mass can follow its pathologically incorrect position and shape, which means that the corrective effect may not be achieved.

And the most progressive today are individually made insoles, based on a three-dimensional scan of the patient’s foot. This technology is still rare on the market due to the fact that the manufacturing process required expensive equipment for a long time, and the doctor must master the software to create a model of the insole based on data from a 3D scanner for orthopedics.

A 3D printed insole with and without a topcoat is shown on the photo

 

This technology, in addition to creating proper and comfortable insoles, allows for proper treatment and making insoles that have a corrective effect to compensate for a foot defect. The manufacturing process is not fast – first the patient will come in for a 3D scan, and after a couple of days, for the finished insoles. It is rather difficult to determine the cost of making an insole for a client here, because first you need an orthopedic doctor, who will later be engaged in creating for you a model of an insole for treatment. But in general, you can focus on the cost of manufacturing a thermoformed insole, i.e., 3000-15000 rubles.

INSOLES MANUFACTURING PROCESS

Now let’s take a closer look at the process of making insoles using 3D technologies. The whole process can be divided into 4 stages: 3D scanning, 3D modelling in specialized software, 3D printing, and finishing.

 

The First Stage – 3D Scanning

The patient visits a clinic or orthopedic salon, where a 3D scan of the leg takes place.

The participation of a doctor at this moment is not required, scanning can be carried out by the staff of the orthopedic salon in accordance with instructions. There is nothing complicated in this procedure – the patient first places one leg on the scanner, the operator controls the correct placement and presses the “Start” button, and then the patient changes their leg and the process repeats. The procedure takes no more than 5 minutes for both feet.

The photo shows the scanning process on the orthopedic 3D scanner ScanPod3D UPOD-S

 

For this stage, we recommend using ScanPod3D 3D scanners, since they are fully automated and specially prepared for 3D scanning of feet. There are a number of models in this line of devices, and you can choose the optimal solution for each task.

In this case, it will be enough to purchase a junior model – the ScanPod3D USOL Orthopedic 3D scanner, to scan the foot only for the insoles. And if, in addition to the insoles, there are plans to scan the whole foot for the future manufacture of a shoe, then the best choice is the ScanPod3D UPOD-S Orthopedic 3D scanner, since the height of the scanned area of ​​the model mentioned at the beginning is 80 mm, and this is only enough for scanning the sole.

On the left photo is an orthopedic 3D scanner ScanPod3D UPOD-S, on the right is an orthopedic 3D scanner ScanPod3D USOL.

 

After scanning, the program will write a scan report, as well create as two STL files and photos of the left and right legs and send them all to a specified location.

 

 

 

 

 

Above is an example of a report generated by a 3D scanner after scanning the patient’s left and right foot. After the scan is completed and the files are created, the patient’s presence is not required, and we proceed to create a CAD model for the future insole.

 

The Second Stage – 3D Modelling of the Insole

The files obtained during the first stage are received by the doctor, and in accordance with the treatment plan, we proceed to modelling the future insole.

Screenshot of IsoleCAD program for creating insoles

First, the left and right foot files are loaded into the STL software, then the joint bend line and centre points are adjusted. Then we start modelling the insole.

 

When modelling, it is necessary to set such basic parameters as the thickness and width of the insole, as well as its height. It mainly depends on the type of shoe for which the insole is designed. There is no universal solution, there should be one insole for sports shoes, and another for classic shoes.

 

 

The screenshot of the IsoleCAD program shows an assessment of the fit of the insole on the foot in cross section. On the right side of the screen, the blue line is the section of the insole, the red line is the foot.

Many functions of the program are automated, but at the same time it remains possible to manually adjust the parameters of the insole according to the vision of the attending doctor. When creating an insole, the doctor can assess the position of the foot on the insole and its fit to it at any time, as well as make any necessary adjustments and corrections.

 

In the screenshot of the IsoleCAD program, the intersection for the fingers and the pad is being created.

 

The simulation process takes 10 to 60 minutes. At the end of the simulation, the program will generate an STL file of the insole, which is suitable for subsequent 3D printing or 3D milling.

The screenshot shows the STL files of the created models of the left and right foot insoles.

 

Now we turn to the production of the insole, i.e. to print it on a 3D printer.

The Third Stage – 3D Printing

For printing insoles, we recommend using thermoplastic polyurethane – TPU (TPU). This material belongs to the class of elastomers, substances with increased elasticity. It is twice as elastic as rubber, and at the same time, it is able retain its properties and geometry over a long period of use.

This material is produced by many companies, but we recommend the ESUN eTPU material, since it has maximum stability from batch to batch and does not pose additional problems for owners of 3D printers.
A 3D printer for printing insoles must meet the following requirements: FDM printing technology; a Direct type extruder; and a printable area corresponding to the maximum foot size. If we consider a budget solution, then one of these printers is Raise3D E2.

General view of the Raise3D E2 3D printer

The process of printing insoles on a 3D printer Raise3D E2

 

Depending on the desire and the required finish of the insole, you can set the filling, as well as choosing whether or not to fill the first and last layers. This affects print speed and also improves surface adhesion when using some heavy top insole materials.

A set of insoles printed without filling the first and last layers. Printing time is 1 hour 30 minutes.

 

A set of insoles printed with the filling of the first and last layers. Printing time is 6 hours 40 minutes.

 

The visible gaps in the print are the boundaries of the areas of the layers, since the closure occurs in only one layer. This is not a defect and will be hidden under the topcoat.

As you can see, the full filling of the first and last layers significantly increases the printing time, and it is perfectly possible to use various materials for finishing the upper part of the insole, such as genuine leather, various natural or synthetic fabrics, or polyurethane with memory effect, as well as EVA (foamed ethylene vinyl acetate). We consider that full filling is only necessary for heavy materials that require a large contact area for adequate adhesion with glue.

The printer is able to work around the clock, including being able to function without the operator’s supervision, but since 2 insoles are placed on the working platform, printing jobs that require full filling of the first and last layers are most effective when printing overnight. Printing jobs without filling are best done during the day. This will allow you to combine tasks and make the most of your equipment and working hours.

 

The Fourth Stage – Processing and Finishing

Immediately after printing on a 3D printer, the insoles are ready for finishing. If during printing extra fuses appear or you need to remove transitions between layers and sectors, they can be removed mechanically.

You can offer different options for the top layer of the insole – they are available in different colors that can be found on the market. The cover is sold as pre-cut along the contour of the insole, and it remains to be glued to the printed model, with the parts protruding from the insole cut off or rolled in. They also come with or without an applied adhesive layer.

Pre-cut insoles with an adhesive layer.

 

On average, the cost of EVA material for a set of insoles is 40 rubles, when using the material in a roll without an adhesive layer. It is 170 rubles when using a preformed blank with applied glue.

Ready-to-use insoles with different options of upper finishing

 

The insoles are now ready and can be handed over to the client.

 

Description of the Insole Manufacturing Solution and its Benefits

We offer a turnkey solution for the production of orthopedic insoles, which consists of a 3D scanner, IsoleCAD software and a 3D printer with a set of consumables and a profile for them. The software is licensed perpetually and has no additional fees for the number of insoles created or projects downloaded.

Features and benefits of the solution:

Flexibility. If, in addition to the insoles, you plan to take measurements and make the scan of the foot for the last, we will change the 3D scanner, and it will have that extra advanced functionality. We recommend using a 3D printer for making the insoles, as it is faster, cleaner and more accurate. But if desired, a CNC machine can be used.

Easy scaling. By purchasing a solution, you acquire a great development potential. The bottleneck of the solution is a 3D printer – its performance is lower than that of the scanner and software. Thus, when scaling up, first you will start building a 3D farm from identical 3D printers, increasing the potential volume of insoles produced with each new device. The scanner can work continuously, and the time spent on one patient is 5 minutes. The software is licensed for one workplace, while it is possible to organize remote access within the company to the workplace where it is installed for consistent work of doctors from different locations. The second point for scaling will be to increase the number of 3D scanners to create more coverage for your city or region.

The ability to distribute production to the most efficient locations. You can put the 3D scanner in a place that will be convenient for the client to visit – orthopedic salons, sports shoe stores or a doctor’s office. The first stage of scanning does not require a large area and special requirements for the room – an area of ​​1 sq. meter and personal computer. Thanks to cloud technologies and high data transfer rates, the creation of an insole in a CAD program by a doctor can take place at any location where there is a computer and access to the network, while printing can take place in a third location. Thus, you can organize comfortable and customer-friendly places for scanning, a convenient pattern and place of work for a doctor, and an efficient and inexpensive room for printing and production, combining al these locations using cloud technologies, and delivering finished products to pick-up points or courier services.

 

Calculation of Cost and Time of Production

Scanning the patient’s feet and preparing for a new scan – 10 minutes

Modelling in CAD program – takes an average of 35 minutes

The cost of 1 kilogram of material (eTPU-95A Esun filament, 1.75 mm, 1 kg) is 3300 rubles. With an average insole weight of 44 grams, we can count on 10 ready-made sets of insoles, which is 330 rubles per pair. (10% was spent on cleaning the extruder, printing mat and other printer operations). Print time is 90 minutes + 10 minutes per job change.

 

The finishing layer of the insole will be considered at the maximum cost – 170 rubles per pair, and the time for gluing, finishing and trimming is considered as 20 minutes.

The total production time for one set is 165 minutes, or 2 hours 45 minutes.

All equipment, including a computer, has an energy consumption of about 500 W, which means that during this time the electricity will be spent: 5.46 rub / kW * (165 minutes * 500 W) / 60 minutes = 7.50 rubles.

We do not take into account the cost of work, rental and depreciation of equipment, since this would have to be calculated case-by-case.

The cost of making a set of insoles is: 330 rubles + 170 rubles + 7.50 = 507.5 rubles.

The number of sets produced per working day – 3 (8 hour working day with a lunch break, excluding night printing)

It is worth noting that in this calculation we do all the operations sequentially, in serial production – operations must be performed in parallel, such as printing and the post-processing of insoles printed earlier. But we will not go deeper, since we want to show the effectiveness of this method even with rough and overstated calculation.

With the cost of a pair of insoles at 10,000 rubles, the offset for the cost of equipment will occur with 159 pairs of insoles, the production of which will take 53 work shifts.

With this calculation, we want to show the efficiency and feasibility of using a 3D printer for the production of insoles for both private doctors and for the creation of large-scale centres for the production of orthopedic insoles, including federal ones, since scaling significantly reduces both the production time of each pair of insoles and the overall cost.

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