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The front tensioner secures the remaining loose end of the belt and sets the hard limit for the actuator’s stroke. This component includes an adjustable hard limit piece that determines the maximum travel distance of the slide.

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Required Components and Tools

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Components

ComponentCountSpecification / Notes
Front Tensioner Piece1Main tensioner component (installed loosely at this stage)
Belt1The remaining loose end from the rear tensioner installation
M3 Bolt1Sets the stroke hard limit
M3 Nut1For the M3 bolt

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Tools

ToolCountSpecification / Notes
2.5 mm Hex1To fit the M3 bolt
The front tensioner is installed loosely at this stage. You’ll adjust the belt tension and secure the tensioner properly later in the build process after all components are assembled.

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Step-by-Step Assembly

1

Prepare the front tensioner

The front tensioner piece should already be installed loosely on the linear rail from earlier assembly steps.
The front tensioner piece is in place but not yet secured or tensioned.
2

Route the belt

Take the loose end of the belt and route it down into the tensioner piece.Ensure the screw hole is positioned on the left side of the tensioner.
The belt routing determines how the tensioner functions. Make sure the belt follows the path through the tensioner grooves smoothly without kinks or twists.
3

Position the hard limit piece

Place the smaller hard limit piece (which sets the hard limit for the stroke) into the grooves of the main tensioner piece.Align the hole in the hard limit piece with the corresponding hole in the main tensioner piece.
The hard limit piece should sit securely in the grooves with the holes perfectly aligned.
4

Install the hard limit bolt

Insert the M3 bolt through the aligned holes.For maximum stroke (approximately 20 cm on a 350 mm rail), position the bolt all the way to the end of the hard limit piece.
The position of the M3 bolt determines the maximum stroke length. Placing it at the end of the hard limit piece provides the longest possible travel distance.
5

Secure loosely

Place the M3 nut on the bolt from the opposite side.Hold the nut in place while lightly tightening the bolt with the 2.5 mm hex tool.
It is crucial for this assembly to remain loosely attached. You will need to adjust the belt tension later in the build process, and overtightening now will make those adjustments difficult or impossible.
The M3 bolt and nut should be secured but loose enough to allow for future belt tension adjustments. The hard limit piece should be able to move slightly if needed.

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Next Steps

With the front tensioner installed and the hard limit set, the basic tensioner assembly is complete. Proceed to install the OSSM motor head to continue the actuator assembly.