SuperMod Heavy Duty Bar Clamp

DIY clamps for your garage and workshop.  The tougher the filament, the tougher the clamps.  Please remember that these are plastic parts that can violently break apart.  Safety glasses are recommended.

You can find an up-to-date list of SuperMod designs here: https://www.printables.com/@FlyingGyroscope/collections/2284604. 

Key Features

• Metal fasteners for added strength
• Metric and imperial fasteners for easy parts sourcing
• Easily make long or short clamps
• Clamps sit upright on a flat surface
• Swivel mechanism deals with flexing

How Strong?

TLDR: I measured a sustained clamping force of 51 lbs (23 kgs) and a peak force of 67 lbs (30 kgs).  To maximize clamping force:

• Use metal bars
• Use bars and plastic with lots of friction
• Use stiff and durable filaments
• Adjust slicer settings for strength

While testing ASA and PLA clamps with 2020 aluminum extrusion, I noticed two failure modes: (1) clamp jaws losing grip and sliding down the bar, and (2) cracking and excessive flexing.  Losing grip was the most common problem I observed, and this seems to put an upper limit on sustained clamping force.  While it is annoying, losing grip helps to reduce the likelihood of cracking parts.

Which Size Bar?

Clamps fit the following sizes of square bar:

• 15 mm
• 0.75 inch (19.05 mm)
• 20 mm
• 1 inch (25.4 mm)

To print a square bar, load the template into a slicer and scale to a new length.  For long or strong clamps, I recommend using some material off the shelf.  You can repurpose any reasonably strong square bar.

• Square, metal tubes
• Aluminum extrusion (like 1515 or 2020)
• Hardwood scraps 

Printing

I recommend durable and stiff filaments to maximize clamping force and avoid cracking.  ABS and ASA will work well.  PLA will have the most trouble with cracking, and PETG may have issues with reduced friction (less grip) and flexing.

Be sure to use speeds and temperatures that allow good layer adhesion.  I used 5 walls with a 0.4 mm nozzle, 6 top and bottom layers, and 45% cubic infill.  For strong clamps use enough perimeters to make the narrowest wall (between the square bar and knob) completely solid.

The protective screw pad should be printed solid, or nearly solid.  A lot of force concentrates in this single part and it needs to be strong.

The bridge on the sliding locks is completed in 3 steps for better printability.  I recommend organic supports for a clean print.  I increased Branch Density to 30%, XY separation to 100%, and changed Support on build plate only to enabled.

Supplies

All of the screws listed below should be fully threaded – they are supposed to thread into printed knobs to make the connection tight and rigid.  You can use socket head, cap head, machine, or pan head screws.  I recommend hardened steel screws over stainless steel because the threads are more durable.  Note that the screw for the swivel mechanism is not structural.  It is there to keep the part from falling out.

Travel for the adjustment mechanism is less than the length of the large screw.  Subtract 38 mm (1.5 inches) from screw length to determine total travel.  For example, a 2.5 inch screw results in 1 inch of travel.  A 65 mm screw results in 27 mm of travel.

Metric Fasteners

• For the large knob: (1) M5 screw
  • 50 mm minimum 
  • 65+ mm recommended
• (1) M5 hex nut
• For small knobs: (2) M3 screws
  • 25 mm minimum
  • 30+ mm recommended
• (2) M3 hex nuts
• To attach the swivel: (1) M3x25 mm

Imperial Fasteners

• For the large knob: (1) 1/4-20 screw
  • 2 inch minimum 
  • 2.5+ inch recommended
• (1) 1/4-20 hex nut
• For small knobs: (2) 4-40 screws
  • 1 inch minimum
  • 1.25+ inch recommended
• (2) 4-40 hex nuts
• To attach the swivel: (1) 4-40 x 1 inch

Assembly

You need to glue knobs and screws together.  I put glue on/around the screw head and on threads close to the screw head.  Be sure to keep glue off of threads that stick out of a knob.  I used superglue gel for testing prototypes.  Use a generous amount of glue and be sure to let it fully cure.

You also need to glue the protective pad onto the end of the large screw.  This keeps the sharp end of the screw from leaving marks on your projects.  Make sure to glue the pad last!  Try your best to keep it square.  Protip: If the screw is too loose or too tight, use XY Size Compensation to adjust the fit.

When you are ready to insert the square bar, loosen the knob so that the insert can slide all the way to the left (using the orientation in the illustration above).  

Friction and Slide Locks

Clamp jaws are asymmetric, and this differentiates lock and unlock directions.  Note the skewed angle at the bottom and extension that makes one wall thicker.

The locking mechanism that holds the jaws in place creates a significant amount of friction.  This effect can keep clamps frozen in place even when the knob is loose.  It is easily fixed by pushing the knob into the clamp, in the direction of the unlock arrow.

Thanks for visiting, and safely enjoy your new clamps!