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Chair feet

Posted by imqqmi 
Chair feet
December 19, 2018 05:17AM
We've got these chairs second hand, I gave them to my sister, she likes them, I, not so much smiling smiley



However during moving them the little feet snapped right off of most of them. The plastic became very brittle apparently. My sister asked me to 3D print them or machine them using the CNC. I started modeling and got pretty close to the correct shape. I sent a test print to my sister. She said the angle was perfect but the diameter that goes into the tube is too small. I designed it to be a snug fit. Something didn't add up. As it turns out Slic3r (any edition) makes the diameter of any cylinder at an angle (I used 20 degrees) smaller than should be in the not angled direction.

Also it appears when printing it with TPC 45 flexible filament the part shrinks a bit. After compensating for this the parts came out really nice. I've chosen TPC as it's a bit like PU, it's very tough and will not damage the floor on its own so it doesn't need felt pads. Inter layer strength is some of the strongest I've ever seen in a 3D print, it's basically as strong layer to layer as in any other direction. While it's flexible it doesn't stretch that much, especially when printed in larger pieces.

The clamping mechanism is interesting. In the picture below you can see the original foot in to the left. There's a nut and a bolt through the middle. Tighten the bolt and the four flanges will expand outward and clamp to the inside of the tube. With TPC flex this isn't working very well. I changed it so that when tightening the bolt (with some extra washers to spread the load) the flexible material will squash and expand. It seems to be working. The filament has a bit of friction so when putting a nut on top without washer it stays put, so a bolt can be tightened on the bottom (since the other end is inside a tube, you can't reach that part to put a wrench or allen key.




Close up. The plastic is slightly mottled due to debris of the previous filament (black abs). Print speed is 40mm/s for perimeters and 83mm/s for infill. The bottom of the part is almost glassy and the plastic flows very well, it hides the extrusion lines. It extrudes transparent but cools with a ivory kind of milky color.
I use 0.25mm thick transparent vinyl sheet. It seems to be the best print surface for this kind of filament. It sticks so well that holes are torn in the vinyl, so it's a one use surface. If I print ABS before it, it releases a little bit easier without coming loose from the surface. I also print relatively quickly for the first layer in an attempt to make it release easier (30mm/s as opposed to 15mm/s normally for abs, PETG and PLA). It prints odorless which is nice.



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Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]
Re: Chair feet
December 19, 2018 08:01AM
I Like your new chair feet.

I made these Chair lifts. Like little stilts too raise the couch up 3 inches. Don't look near as good as your replacement chair feet.

Though you can not see the lifts as they are under the couch skirt. and the purpose was for the elderly to be able to easily get up from the higher chair.

Now that I see your chair feet need to spend more time and design a better looking lifts. Or a complete Foot with the added height.

ChairLift-F.stl
ChairLift-R.stl

Would like to Note: that I have had problems with some Filament bleaching color on to my fiberglass shower stall, this was a soap holder that was 3D Printed using PLA.
To be careful I would use some kind of small moving slide under the feet to prevent this color bleaching, to your hardwood floor surfaces.

Is there a way to know which filaments are color bleaching as to those that do not.

Edited 1 time(s). Last edit at 12/19/2018 08:12AM by Roberts_Clif.


Electronics Technician / Computer Programmer
Re: Chair feet
December 19, 2018 10:34AM
Thanks! Using SolidWorks it was surprising easy, even with the odd angles and curved lines, and my limited SW knowledge. Fusion360 should be equally good to do this.

Do they work well? I can imagine the chair would loose some of its stability and could go sideways breaking the 5mm wall. I've bought heavy impact resistant abs ones for my father at some point, though it couldn't be hidden, these do provide enough stability:


The TPC flex I use is neutral color, no color additive was used. TPC is also very chemically neutral/inert to many chemicals. So using neutral color filaments that resist a wider range of chemicals should be safe. Other than that, if you're not sure, just try it out on something non critical first.


--
Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]
Re: Chair feet
December 19, 2018 12:59PM
We have had 4 Adults on the couch without any trouble. When I first made them was worried about them breaking, though they are holding up nicely.
I added some stick on Felt Pads that were purchased from a dollar store to the to bottom of chair lifts to allow for a smooth side when moving.

Actually did not know they made chair lifts that could be purchased. was told the couch was too low ("Ideal") a couple measurements designed the simple lifts in ThinkerCad.
Exported the STL to my PC, sliced with Cura and Printed in PLA.


Electronics Technician / Computer Programmer
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