Parametric CupMax: Expand Your Auto Cupholder Capacity

CupMax is a dual material, cup holder expander designed to solve a common problem: most car cup holders are just too small for large bottles like Nalgene, Hydro Flask, or Stanley styles.

This 3D printable design provides a compliant, adaptable fit that lets you hold larger bottles, even in smaller cup holders. It uses a rigid shell printed in ABS, ASA, or PC for strength and heat resistance, paired with a TPU part(s) that compress gently to hold bottles of various diameters snugly in place — without rattling, binding, or scratching your gear.

The result is a smart insert that lets you safely stow your favorite oversized bottle, travel mug, or tumbler in your car.

My example/default print here is with grey Bambu PC (shell) + Overture high speed TPU (yellow parts in picture above) for the flex part on top and the insert. The flat center insert could is optional entirely and you can adjust the inner shelf size angle in this case (ShelfOverhangAngle), I just did it for “bottom feel” when i land my cup.  I glued the insert in place after placing it with a couple of dabs of superglue.

This thing is designed and tested to fit my Audi Q4 and my friend's Audi SQ6.  Likely to fit other cars as-is, but I would encourage you to measure and look at the dimensions of your cup-holder (depth, diameter at opening on top and diameter at bottom) and adjust before printing if needed.

The key variables to adjust here for fit into your existing cupholder are:

• InsertHeight - The depth from the bottom of your holder to the top surface where it's starts to curve out.  Highlighted blue here:

• InsertBottomWidth - the outer diameter of the insert at the bottom of the blue highlighted section above
• insertTopWidth - The outer diameter of the insert at the top of the blue highlighted section above
• insertWallThickness - thickness of the thin wall portions (3 mm by default)
• ShelfOverhangAngle - determines how wide the internal conical shelf is in terms of shelf angle relative to horizontal.  It is 40° by default, which gives a (90-40)=50° print overhang, which should work fine for most people in most filaments.  Recommend values of ~40-90° depending on desired support shelf size and if you're using an insert or not.  With my insert I did a straight 90° to save filament on the part and it worked fine.

Finer tuning the fit, reference this picture:

• insertFlushWidth - the width at the top of the highlighted blue portion, to help match the curve/bump out of of your cup holder above the top (85 mm by default)
• insertTopToFlushDistance - the height of this blue portion (13 mm by default)
• holderTargetMaxWidth - outer diameter of the top most cylindrical section in picture above (inner diameter depends on wall width)
• holderPortionHeight - height of top cylinder section in picture above

The following parameters control the TPU flaps as shown in yellow in this pic:

• flapInset - how much the flaps reach inwards from the outside, 12.25 mm by default.
• flapArcDegrees - how much arc-space each flap takes (10° each by default)
• flapNumber - how many flaps there are, 18 by default.
• flapThickness - how thick the flaps are from top downward (1.2 mm by default), recommend max of 2.0 mm.

Lastly, there's an optional BottomExtraInteriorWidth , which merely creates a thicker printing solid base area that tapers to help print adhesion of the main part.  By default I set this to a conservative 2 mm, although I ran my print without it at all and just used an aggressive brim.  If you want effectively no extra bed helper thickness set it to a very small non-zero value like 0.01 mm.  At 2 mm adds a little extra “foot” at the bottom of the part like this picture below.

Can be customized fully in the Fusion360 file included or in Makerworld's customizer for certain defined parameters above.

3MF, and STEP also included.  Bambu Slicer file for the default settings included for Polycarbonate and TPU print.