Acrylic Tubing Cost

For the past couple of weeks I've been looking for sources of plastic tubing that could be used to fabricate the rather large number of cylindrical components that building a Chopper Droid requires. An early search revealed that there are a bewildering number of different plastics available. Cost and machineability are dominant factors and I've settled on using Extruded Acrylic tubing. Acrylic tubing also comes in Cast form, but as the table illustrates, it's anywhere from 9-10 times the cost of extruded tubing. Go to  http://www.eplastics.com/Plastic/extruded-plexiglass-acrylic-tubing/Cast-vs-Extruded-Plexiglass-Acrylic-tubing-and-rod if you want to know why.

This table is the result of those searches. I'm only showing prices for a representative number of Internet suppliers. There are lots more suppliers, many who don't offer acrylic tubing in the sizes I need. Pricing is shown in both $/ft and $/buy to the minimum length purchase (varies among suppliers) The purpose of this discussion is the 2.625 in OD column.

OD Size inches


0.625

1.000

1.250

1.500

2.250

2.500

2.625

2.750

3.000



ID Size inches


0.375

0.750

1.000

1.250

2.000

2.250

2.375

2.500

2.750
















supplier

# of ft










Cost/ft

notes












Cost/buy


McMaster Carr













petg

1

$2.30

$3.88

$4.66

$7.74

$8.09

$8.64


$9.56

10.48

$/ft



6,1

$13.80

$23.28

$27.96

$7.74

$8.09

$8.64


$9.56

10.48

$/buy

6ft 1st 3,then 1ft

clear extruded acrylic

1

$1.48

$2.51

$3.06






$7.34

$/ft



6

$8.90

$15.03

$18.35






$44.05

$/6ft


clear cast acrylic

1




$35.42

$38.42

$39.83


$40.04

$40.47

$/ft

Buy 1,3,5














ePlastics













clear extruded acrylic

1

$1.70

$2.37

$3.83

$4.31

$7.23

$8.09


$10.73

$9.78

$/ft q1



6

10.18

14.24

22.97

25.85

43.36

48.51


64.38

58.69

$/6ft

Buy 1


6

$7.90

$11.06

$17.83

$20.07

$33.66

$37.65


$49.97

$45.55

$/6ft

Buy 2+

clear cast acrylic

1 2



$37.55

$38.51

$41.44

$43.03

$43.13

$43.27

$43.84

$/ft

Buy 1-2 ft


3 5



$35.53

$36.43

$39.20

$40.70

$40.80

$40.93

$41.47

$/ft

Buy 3-5 ft














nationwide













clear extruded acrylic

1


$0.96

$1.70

$2.25

$1.80

$3.42


$5.39

$3.95

$/ft



6


$5.76

$10.20

$13.50

$10.80

$20.52


$32.34

$23.70

$/6ft















US Plastics Corp













clear extruded acrylic

1

0.81

1.44

1.83

2.22

3.43

3.68


4.25

4.65

$/ft



6

4.86

8.64

10.98

13.32

20.58

22.08


25.5

27.9

$/6ft


clear cast acrylic

1




25.07


28.05


28.22

28.51

$/ft



5




125.35


140.25


141.1

142.55

$/5ft



And the painful observation that it's only available from one supplier and only in Cast Acrylic. It's used in Chopper's Battery Boxes, and given their size (12in long) you'll need 2 ft of tubing for the curved ends of the Battery Box. So you are looking at $81.60 upfront cost for the tubing. OUCH! I prefer lower-cost designs because the costs add up no matter what you do. What's a builder to do?

Consider the following:
Do you see any obvious difference? I know it's hard to tell from this presentation, If you want to compare for yourself, you can download larger size images and .stp 3D designs of the 3 battery box & foot assemblies here.

Scroll Down






Scroll Down (some more)





So as to not hold you in suspense, the center image uses the original 2.625 in diameter battery box. the left is 2.75 in diameter and the right is 2.5 in diameter. How could you tell, I was lazy, the circular access port in the end of the battery box is the same size in all 3 pictures. In my opinion, any of the 3 would work just fine for a Chopper build. If I were building, I'd be inclined to use the 2.75 dia tubing to give more room for Chopper's drive motors.

Yes, as some have done, you can fabricate 2.625 cylinders using a 3D printer. My experience printing R2 battery boxes, however, says that it would be painful. I currently do it for R2's battery box ends. They measure 3in diameter and 7.5in tall. A single, half cylinder, end takes 6 hours (closed) or 5.5 hours (with hole). A set of 4 takes 23 hours, not counting setup time between prints. [Aside, yes I could reduce the print time by using a larger extruder nozzle, but it would still be a long print.] A Chopper battery box is 12.25 in long, actually just beyond the print range of my 3d printer even if I wanted to try a 10 hour print! 

What do you think?
If you've built your own Chopper, and didn't 3D print the Battery Boxes, let me know what you used for the Curved Ends of your Battery Boxes.
While I'm primarily focused on styrene building methods, I'm open to alternatives.
Send comments to: fpirz (at) media (dash) conversions (dot) net
Thanks!

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