Commit 603f4249 by Jake Read

Update README.md

parent 73baadfc
......@@ -55,18 +55,41 @@ W/R/T Layout, there are a number of permutations of how to go about adding axis
I tend to 'work out' from the Z-axis, towards the edges - this way I can keep track of where I need extra offsets (length of travel != length of gantry). Here's the layout with the Z-and-X axis group moved around to the extents.
![machine layout extents](https://gitlab.cba.mit.edu/jakeread/machineweek/raw/master/images/layout-extents.jpg "machine layout extents")
![machine layout extents](https://gitlab.cba.mit.edu/jakeread/machineweek/blob/master/images/layout-extents.jpg)
And the layout as representative of a real machine...
![machine layout](https://gitlab.cba.mit.edu/jakeread/machineweek/raw/master/images/layout-machine.jpg "machine layout")
![machine layout](https://gitlab.cba.mit.edu/jakeread/machineweek/blob/master/images/layout-machine.jpg)
This is all just loosely blocked out, in this stage I am really trying to get good numbers for the lengths of all of the axis, etc. Now I'll get into the actual Axis detailing.
## Parametric Axis
- Go Here https://github.com/fellesverkstedet/fabricatable-machines
- Racking (two senses)
- Pinioning
Jens Dyvik is on some [wonderful machine building sprials (link!)](https://github.com/fellesverkstedet/fabricatable-machines) and we're going to put them to work this week. In particular, the [chamferrail system](https://github.com/fellesverkstedet/fabricatable-machines/tree/master/chamferrail). Take a look at his documentation to get an overview of the machines!
I'm using his Chamferrail Generator in Rhino and Grasshopper - included in this repo under /cad/axis-generator/ . Now that I have my axis lengths laid out, I'll generate the axis, and go through the process of milling them. I'll do this first on the X Axis and circle back to make any adjustments to the system I see fit!
![generating the x axis](https://gitlab.cba.mit.edu/jakeread/machineweek/blob/master/images/generate-x-axis.jpg)
Use Grasshopper to adjust the parameters - you'll find them all on the left. Things I adjusted were:
- Make sure 'Output Geometry Type' is set to 3D
- 'Make Hole Pattern at Edges' is Yes (I turned this off for the Z axis, where I'll be drilling different holes for mounting end effectors)
- Milling Bit Diameter: 3.175 (1/8")
- Motor Shaft Diameter: 6.35 (for our 1/4" shaft motors)
- Axis Length: 550mm (X Axis, 850mm Y Axis, 260mm Z Axis)
- Axis Width: 80mm
- Material Thickness: 12.5mm (this is important! Measure your stock!)
- Chamfer Distance: 5mm
- Rack Tooth Height: 6.5mm
- Hole Grid Distance: 48mm
- Hole Diameter: 5.25mm (this means we can use M5 Screws to secure the rails)
- Screw Pocket Diameter: 11mm (an M5 washer is 10mm in diameter)
- Edge Screw Pocket Depth: 6.5mm (an M5 Socket Head Cap Screw<sup>9</sup> is 5mm, a washer is 1.1mm thick)
Now I use the 'bake' command to pull the geometry out of grasshopper and into Rhino.
![generating the x axis](https://gitlab.cba.mit.edu/jakeread/machineweek/blob/master/images/generate-x-axis-bake.jpg)
## Axis Blocks
- Connect ur axis
......@@ -74,6 +97,7 @@ This is all just loosely blocked out, in this stage I am really trying to get go
- It's almost as if I knew about this system while I was doing layout! *~!NONLINEARITYALERT!~*
## Doing the Milling
- Layout and Material Planning in Rhino
- First we go to fusion
- Then we do the milling
......@@ -104,6 +128,7 @@ This is all just loosely blocked out, in this stage I am really trying to get go
6. ~ 305x610mm
7. ~ 127mm
8. So I want an H-style layout, because I want to keep the machine small relative it's total work area. One of the biggest drawbacks with an H-machine is that the two sides of the Y-axis are not always set up parallel. The result is what's called 'racking' - i.e. imagine opening a screen door, and the top or bottom exhibits more friction - the 'jam' that this causes happens in CNC Machines as well. A drawing. By cutting both Y-axis rails out of the same 'frame', Jakob gets around this issue - the parallelness of the two rails is a mirror of the parallelness of the machine which cut them. It makes it a bit bulletproof to novice assemblers. He has also done a really good job of keeping the X-axis loads really close to the Y-axis rails (so, a small structural loop).
9. That's a SHCS
to be linked - dan gelbart
talk about resolution vs. accuracy - repeatability vs absolute accuracty - global vs. local resolutions
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