From 603f4249d6e31bfebd13b5293bf59a893b2b0c4a Mon Sep 17 00:00:00 2001 From: Jake Read <jake.read@cba.mit.edu> Date: Thu, 26 Oct 2017 20:54:52 -0400 Subject: [PATCH] Update README.md --- README.md | 35 ++++++++++++++++++++++++++++++----- 1 file changed, 30 insertions(+), 5 deletions(-) diff --git a/README.md b/README.md index f539f9a..5b9f650 100644 --- a/README.md +++ b/README.md @@ -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. - + And the layout as representative of a real machine... - + 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! + + + +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. + + + ## 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 \ No newline at end of file -- GitLab