The Problem with your Hob Gear – Pinch Type extruder
The hob gear – pinch type roller system provides for only a very limited amount of contact surface area between the printing filament and the mechanism providing the driving force. This limits how well you can grip and control the filament.
The hobbed gear is constructed from hard metallic type components which slip easily on polymer and in particular flexible polymer. This limits how well you can grip and control the filament.
The hobbed gear offers some degree of grip however the aggressive nature of the small serrations can easily become clogged with filament debris. This limits how well you can grip and control the filament.
If the hobbed gear is driven too fast the serrations will gouge out and damage the filament profile. This will not only limit how well you can grip and control the filament but damaged filament will ultimately lead to under extrusion or complete print failures.
The fundamental design of the pinch type roller system also makes it difficult to completely contain the filament. The removal of any cavities along the ENTIRE filament path is essential when printing flex. The solution in the past has been to insert a PTFE tube close to the pinch rollers, a simple solution but really not very satisfactory and has many limitations.
One big problem lies in the fact that to produce force with flexible filament the pinch rollers need to squeeze the filament and as the force is localised the pressure distorts the cylindrical profile of the filament, as it leaves the rollers it is elliptical and you can not fit a oval profile into a round PTFE tube without creating excessive friction. To overcome this you need to either limit the amount of pressure exerted on the filament (which limits how well you can grip and control the filament) or you need to leave some space to allow the filament profile to resume the original cylindrical shape before entering the PTFE tubing and as we know – any cavity no matter how small along the filament feed path is bad news for flex.
The solution is the Flex Wheel
The driving force behind the Flex Wheel extruder is unsurprisingly the Flex Wheel itself.
The Flex Wheel comprises a larger diameter drive wheel coupled with two flexible flanges located either side.
These flexible flanges are designed to be folded by external profiles, which then completely enclose and envelope the filament.
As a result the contact surface area between the filament and the drive mechanism is significantly increased, additionally the soft polymer flanges offer an amazing amount of grip on all types of filaments either rigid or flexible.
As the load is spread over a larger area coupled with the flexibility of the flanges, filament profile distortion is significantly reduced, meaning that when the filament leaves the extruder and passes into the tubing system it slides effortlessly, no matter how much force is applied.
The entire drive path of the filament through the extrusion mechanism is completely enclosed, the filament can’t escape – it has nowhere else to go – except straight into the hot end of your printer.
In fact this system works so well that you now have the ability to print flexible filament at a shore hardness softer and more flexible than you could believe is possible – and certainly lower than what is currently commercially available.
You can print flex at the same speed, parameters and print quality as you currently achieve with rigid type filament.
You can increase the overall speed of your extrusion system, as the Flex Wheel has power to burn.
The Flex Wheel – Designed for flex but prints everything the best.
Patent application pending.