A filament guide that guides thermoplastic filament to an object being manufactured. A deposition head comprising the disclosed filament guide provides a filament to the intended deposition point. The filament guide comprises a guide member having a filament groove configured to guide the filament along a path of travel. The groove has an upstream end that is configured to receive the filament from a source and a downstream end that is configured to direct the filament toward the deposition point in the intended direction. A notch at the downstream end of the guide member enables the filament to travel toward the deposition point. The portions of the guide member on either side of the notch act to keep the filament centered laterally. A plate that is transparent to electromagnetic radiation from a heat source covers the groove and permits the electromagnetic radiation to reach the filament while providing added support.