progress on CoreXY doc

UrumbotXY/README.md

@@ -14,17 +14,38 @@ Acceleration:
 
 ## CoreXY
 
-Assembly:
+For a simple coreXY motion system, here is the list of parts you need to make:
+
+<img src=img/doc/corexy_kit.png width=100%><br>
+
+It is advised to 3D print `capstan_motor` and `capstan_pulley`, while all other parts can be machined or laser cut. 3D models files are available under [./files/3d](./files/3d), and dxf files under [./files/2d](./files/2d).
+
+For assembly, you will also need:
+
+- 2x NEMA 17 motors
+- 9x bearings
+- 8x V bearings
+- 4x small bearings
+- M5 screws (structure and bearings)
+- M5 nuts and washers
+- M3 screws (string tensioners)
+- M3 nuts and washers
+
+Here is the main frame after assembly:
 
 <img src=img/corexy.jpg width=100%><br>
 
-CoreXY constant speed:
+Note how the string is inserted on the capstans. The string can be attached to temporary anchor points to provide enough tension during this step. Inside `capstan_pulley`, you should insert a small bearing at the top and bottom. Use appropriate washers to have the correct height; there are 4 levels on `capstan_pulley`, and they should be aligned between each levels of `capstan_motor`.
+
+<img src=img/capstan.jpg width=100%><br>
+
+
+Here is a video of the motion at constant speed:
 
 <img src=video/corexy_linear.mp4 width=100%><br>
 
-Capstan:
 
-<img src=img/capstan.jpg width=100%><br>
+## Pen plotter
 
 Pen:
 

UrumbotXY/code/urumbu_corexy.py

@@ -254,8 +254,10 @@ def parse_arguments():
                         help="COM port for B")
     parser.add_argument("-s", default="COM24",
                         help="COM port for servo")
-    parser.add_argument("-u", "--unit_scale", default=1,
+    parser.add_argument("-u", "--unit_scale", type=float, default=1.0,
                         help="Scaling factor")
+    parser.add_argument("-d", "--dryrun", action="store_true",
+                        help="Perform a dryrun")
     return parser.parse_known_args()
 
 
@@ -295,7 +297,7 @@ def main():
     p1.start()
 
     feedrate = args.feedrate
-    feedrate_homing = 15
+    feedrate_homing = 20
 
     servo_up = ServoAction("servo", 1265, wait=0.5)
     servo_down = ServoAction("servo", 800, wait=0.5)
@@ -307,8 +309,10 @@ def main():
     with open(args.filename, "r") as f:
         for line in f.readlines():
             if line.upper().startswith("UP"):
+                if not args.dryrun:
                     action_queue.put(servo_up)
             elif line.upper().startswith("DOWN"):
+                if not args.dryrun:
                     action_queue.put(servo_down)
             else:
                 action_queue.put(Line([float(x)*args.unit_scale for x in line.strip().split(",")], feedrate))