Filament accumulator or tensioning assembly

A filament accumulator for absorbing a speed mismatch between filament provided from a filament source and filament used at a filament deposition head comprising:

• a continuous filament forming a filament loop;
• a filament inlet for receiving the continuous filament from a filament source;
• a filament outlet for receiving the continuous filament from the filament inlet, the filament loop being a loop in the continuous filament between the continuous filament exiting the filament inlet and entering the filament outlet;
• and
• a filament track defining at least part of an inner boundary and an outer boundary of a circuitous filament route between the filament inlet and the filament outlet, the filament loop being bound by the filament track;
• wherein the filament loop has a diameter that varies across a range of potential diameters within the filament track;
• wherein the filament deposition head draws the continuous filament from the filament outlet at a first speed;
• wherein the filament inlet receives the continuous filament from the filament source at a second speed, and
• wherein a mismatch between the first speed and the second speed results in a change in the diameter of the filament loop.