Aidan Williamson Log

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Old Logs:

Feb 25, 2019

I made a new tube builder when I heard mine wasn't working in FreeCad 0.16 on Ubuntu.
The new file is based on the Sketcher, Draft, and Part workbenches whereas the original file was based on the Sketcher and Part Design workbenches.

File:Alternative Universal Tube Builder.fcstd

Here is a video explaining the new file approach

Feb 23, 2019

Video showing making of a spreadsheet parametrized cad file.

Feb 22, 2019

Made a video about the tube generator and improved the file by adding HoleSpacing parameter to spreadsheet.

Nov 20, 2018

Here is a version uploaded to the OSE Wiki. It should work but may have design flaws. I'm using an O-ring to seal the cylinder in the cap trepan groove. This is questionable.
File:Universal Cylinder Builder ADW.FCStd


I've been working on a cad file for the Open Source Cylinder. Here is a link to the alpha stage of the file. DROPBOX The end-caps are square with a trepan machined for the tube to seat. The caps could potentially be parted so that a welding operation replaces a machining operation for the tube seat. The Rod is welded to the Piston in my version.

Like the universal tube builder, I'm trying to make it parameterized from a spreadsheet. Here is what the parameters look like right now:

Name	Input (Inches)	Output (mm)	Note
Cap Side Length	4	50.8	
Cap Thickness	1	25.4	
Tube OD	3	38.1	
Tube Wall Thickness	0.25	6.35	
Piston Thickness	1	25.4	
Piston Seal Inner, Height	0.3125	7.9375	
Piston Seal Inner, ID	2.125	26.9875	
Piston Seal Inner, OD	2.5	31.75	
Piston Seal Outer, Height	0.25	6.35	
Piston Seal Outer, ID	2.125	26.9875	
Piston Seal Outer, OD	2.5	31.75	
Stroke	12	304.8	
Rod OD	1.5	19.05	
Rod Stickout	2.5	63.5	
Cap Seal Outer, Height	0.25	6.35	
Cap Seal Outer, OD	2	25.4	
Cap Seal Outer, ID	1.495	18.9865	
Cap Seal Inner, Height	0.25	6.35	
Cap Seal Inner, OD	2	25.4	
Cap Seal Inner, ID	1.495	18.9865	

Need to add a few parameters like tie-rod diameter. I think the model may need to be scrapped. Especially if one looks at the dependency graph lol. I didn't take as intentional an approach to modeling it as I could have.

I believe it is a worthwhile effort, though. A user could generate the CAD for a cylinder of different sizes by simply entering data into a spreadsheet.



Left

Notes

The caps as I have drawn can be easily made on a lathe and mill. How i would make this: Cut the plate to size and machine square. Surface grind for extra credit. Put the four tie rod holes in but make them half inch reams. Using shoulder bolts, attach the plate to a lathe jig or 2 bolts and 2 dowel pins. To make the lathe jig, press fit a piece of 4" or similar crs into a thick plate with the bolt pattern on it and weld. Face the jig on the lathe after welding. The bolt pattern should be put in after the welding operation. Use custom vise jaws and maybe a small bore for picking up the center. For the rod end cap, drill and bore the rod hole then bore internal grooves. Then cut trepan groove. For the base, it's just a trepan. Make those in half a day including making the jig.

As an alternative, I was imagining "slicing" the caps into layers, like 3d printing, and then welding the slices together.

For plastic cylinders, I would start with pvc or abs pipe as the tube. I'd go down that road before I started messing with a metal prototype.

I'll keep thinking about it.


Aidan

Nov 5, 2018

Here is a file that might be helpful for y'all. Open the Universal Tube Builder file and use the spreadsheet to create tubing with all dimensions parametrized. Holes will automatically be set to 4" spacing. I can change that if you want. You can define the standoff for the first hole.

File:Universal Tube Builder ADW.FCstd

FreeCAD expressions for constraint solver