VACUUM FORMED OR DIRECT MILLED
Vacuum Formed manufacture involves vacuum forming a sheet of heated thermoplastic material over the positive cast (usually plaster of paris or a milled positive cast).
This is the traditional method for orthosis manufacture and has been used for decades with excellent results. Vacuum pressing means that the clinician has a little more autonomy over their prescription because each separate component of the orthotic can be easily modified. Another benefit is that a large variety of shell materials can be used; from EVA to carbon fibre.
Vacuum pressing orthoses is a handmade procedure requiring a knowledgeable technician to carry out the process. Some clinicians prefer this because it means that the devices they prescribe are “handmade”, however, it does mean that any repeatability may not be 100% accurate.
Direct Milled manufacturing uses CAD/CAM technology. This abbreviation stands for “Computer-Aided Design and Computer-Aided Manufacture” and is capable of producing high-quality orthoses with a higher level of accuracy than Vacuum Pressed orthoses.
Knowledgeable, highly trained technicians are still needed for Direct Milled manufacture but their role is different. Instead of the hands-on approach seen with Vacuum Pressing, this process requires the technician to design an orthotic on a computer screen and then the device is “milled out” by a milling machine from a solid block of material as part of the whole computer programme.
Direct Milling is very popular, especially amongst the more computer savvy clinicians. Accuracy is the biggest advantage with high repeatability. These devices are also extremely hard-wearing because the heel post can be part of the whole orthotic rather than being glued on (as with Vacuum Pressed). The main disadvantage is that once the device is complete, it’s not as easy as the Vacuum Pressed method to amend. Additionally, certain materials are not compatible with Direct Milling such as carbon fibre.
There is no right or wrong answer regarding which method is best. It may come down to how you prefer to work as a clinician, or you may choose different manufacturing techniques depending on your patient’s diagnosis and management.
- Choose Vacuum Formed if:
- You like a handmade device
- You alter or modify a lot of your orthoses
- Choose Direct Milled if:
- You prefer using computer technology in your practice
- You amend very few prescriptions and order a lot of repeats.