Sunday, April 14, 2019

Floor Jack Pads: Pushing The Limits of 3D Printed Parts

My 12 year old Audi TT needs new shocks and I am preparing to do the work myself.  I've changed struts on two other cars, so I have most of the tools and a pretty good idea of what to expect.  Now I'm in the process of researching all the correct part numbers to order.

One tool that's been missing from my ever-growing collection is a floor jack.  I fixed that deficiency yesterday with a trip to Harbor Freight Tools where I bought a 3 ton, low profile, steel jack for $89.  I have no illusions about the quality, but it seems sturdily built (it weighs about 80 lbs) and should be fine for my infrequent uses like replacing the struts in my car and rotating the tires once in a while.

The jack did not come with any sort of pad on the saddle, and I don't want to try using it without one, so I did a little research.  Volkswagen Audi Group vehicles use a common lifting point "socket" that is best used with a jack pad that is made to fit.  I looked up commercial offerings and found some for about $8-10, made of polyurethane.  Polyurethane?  I can print that!

One of the jack pad makers was kind enough to provide dimensions:

Audi jack pad dimensions.

I modeled one of the pads in Fusion360 in about 30 seconds.  The commercial pad was only 69 mm in diameter but the saddle on my jack is 93 mm in diameter, so my model has a 90 mm diameter base.

My print used fluorescent green TPU- I won't have any trouble seeing it in the bottom of a drawer or toolbox.


UMMD has a 0.4 mm nozzle, so I used TPU filament in 0.24 mm layers, 0.5 mm line width, 6 perimeters, 8 top and bottom solid layers, and 40% triangular infill.  It used about 101g of filament and took about 5 hours to print at 40 mm/sec.  The print came out beautiful, and like all TPU prints, it's super tough.

Here's the jack with the naked saddle.  You need some sort of pad to protect the car!

Here's the jack with my custom 3D printed pad in the saddle.  The bump on top of the pad fits into the jacking receptacle on the car's frame.
Let's see if it's tough enough:


Well there you go!  TPU is one of the most amazing filaments you can get for a 3D printer!  It's easy to print (220C extruder, 45C bed, 30-40 mm/sec) and produces incredibly tough prints.

A view of the 40% triangular infill looking through the bottom of the Audi floor jack pad.

I used concentric infill for the bottom and top layers.  Other solid fill layers were set to rectilinear.  This nice Moire pattern appears in the bottom of the pad. The black smudge was acquired when I jacked up the car for the video.  Next time I'll take photos before I test a print under load.


Now I'll have to print a jack pad to fit my wife's car...

BMW jack pad dimensions





BMW jack pad printing with 50% infill in fluorescent green TPU.


Done.



The Fusion360 models for Audi and BMW jack pads are here.



6 comments:

  1. I love this! And the color is vibrant! I'm just getting started with TPE/TPU and finding the same as you; it's incredibly tough. I really enjoy your blog. Best regards.

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    1. Thanks! TPU has been one of my favorite materials to print since the first time I used it. I printed a single walled vase with it and took it to a MakerFaire. I had big guys turning red in the face trying to tear it apart. They just couldn't do it.

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  2. Francois BoulangerMay 17, 2019 at 9:10 AM

    Hi Mark,
    What is the shore hardness of the TPU you used ? I am intrigued by your results.
    The TPU I have used in the past from Filaments.ca is semi-rigid (91A), and I have used it for insoles, bumpers, etc.
    I never thought to try it in high stress situations (I go for PETG in these cases).

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    1. The green stuff I used didn't have any hardness spec, but it is quite a bit less rubbery than Ninjaflex. When I print single walled vases with it they can be crushed in your hand or stretched a little and will bounce back to the original shape.

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  3. Dr. Mark,

    Please share a link of where to purchase the filament you used to make the jack pad.
    Thank you and have a most awesome evening!
    Jeff Alessi

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    1. I ordered that filament via Amazon.com about 2 years ago (the stuff seems to have infinite shelf life!). I think just about any TPU filament you find will be about the same. I recently ordered this: https://www.amazon.com/gp/product/B07F1V57BK/ref=ppx_yo_dt_b_asin_title_o09_s01?ie=UTF8&psc=1 and it seems to be about the same as the fluorescent green stuff except for the color.

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