composite_tensioner_jig_onshapeDuring the production review meeting yesterday, October 22nd, one of the issues raised was that the composite spool tensioners were being irregularly aligned in new Mark One composite 3D printers. This doesn’t degrade the performance of the printer but does significantly impact the aesthetics. Like Steve Jobs, we believe every component matters even the invisible or infrequently seen parts.

Carl Calabria decided it would be easy to create a jig for aligning the tensioners. As the Mark One is the best tool, jig and fixture printer on the market it follow that we would design and print our own tensioner alignment jig.

Carl used OnShape to CAD the holder. It was imported into Eiger, the MarkForged software, and continuous carbon fiber reinforcement was added. This would provide stiffness and strength for the inevitable drops and bumps that were sure to impact the jig in the production facility.


  • The need was identified, a model created in CAD and a first iteration was created on Thursday.
  • The model was updated and a second iteration was printed on Friday
  • It will be at the factory, in use next Monday

Modeled by Carl Calabria, MarkForged Sr. Application Engineer

You can download the Tensioner STL and MFP files on Thingiverse.


Composite Spool Tensioner Jig
Size 144.44mm x 79.88mm x 4mm
Estimated Print Time ~3h 33m
Nylon Cost ~$3.16
Carbon Fiber Cost ~$3.45
STL Download MarkForged_Carl_Calabrias_Tensioner_Jig.stl () 
MFP Download French Horn Case Study – PRT ()