add n17

README.md

@@ -36,41 +36,33 @@ Make sure to change 'type' to .step, and check the 'save to my computer' box. No
 
 ## Gantry for NEMA17 Motor, 0.25" ALU
 
-~ ongoing ~
-
-- last rites before building a machine is to 3dp a new set of blocks and re-build that gantry on your desk. test it w/ new circuits and invent cable management that works real good. 
-
-![n17sofar](images/n17-blocks.jpg)
-
 ![n17sofar](images/n17-assem.jpg)
 
-### BOM for N17 
-
-625ZZ bearings are 5x16x5mm [VXB 20](https://www.vxb.com/20-625ZZ-5x16x5-Metal-5mm-Bore-Miniature-p/kit250.htm)
-Bearing Shims are 5x10x0.5mm (McMaster, 18-8)
-Shoulder Bolts are 5x6xM4 mostly and 5x10xM4 at the pulleys.
-Pulleys are 10mm GT2 (try to find steel-core GT2)
-Belt Pinion is 20T (speed!) or 12T (resolution!)
-Uses many Heat-Set Tapered Inserts, M3 (94180A331) and M4 (94180A351).
+Smaller Gantries. Uses 45* bearings in 3DP blocks, with one set riding on flexures for smooth preloaded motion. Cut rail on WJ with high cut quality.
 
-### Notes from the First Build 
-Increased preload from 0.2 to 0.4mm 
-A few fitting things ... motor mounts get lots more clearance
-Increased sizes for heat-set inserts to make overflow smaller. 
+![n17sofar](images/n17-with-n23.jpg)
 
-Overall, pretty good. Could do with some more allowance around the 'reachover' ... recall the M4 Heat-Set Insert for the 'vertical' constraining bearing pushes PLA into the through-hole for its 'option-retaining' shcs.
+Ostensibly easy to cut on a laser with 1/4" Acrylic for very-easy machine-making. 
 
-Might want to replace all M3 Heat-Set Inserts with Plastic Hardware.
+This is ready to be applied in the [Little Rascal](http://gitlab.cba.mit.edu/jakeread/littlerascal) [(see also)](https://en.wikipedia.org/wiki/List_of_spacecraft_in_the_Culture_series) project. My last thoughts are:
+- could abandond servo-belt type, not enough motor torque to overcome friction at this size. re-up on that for N23, with steel belts, for milling and other higher force applications.
+- in abandoning this, belt tensioning becomes easy: make simple, small stops and apply tension at the motor. become smaller. 
+- I would be interested in a motor-hanging-from-end-of-plate flying belt type at this size, for very fast applications (lasers). 
 
-Mounting Blocks-Into-Plate wants a 3.5mm M3 through hole, and counter-sinks. Flat heads into countersunk holes helps overconstrain the finnicky plastic blocks. 10mm length black-oxide seems best.
-
-Plastic is heavy. 
-
-Added 1mm more space between the two blocks to try to eliminate the backlash I found in the planar direction. (i.e. in displacements not-normal to the rail). 
-
-It seems to run pretty well, wants to be pre-loaded into the 0.5mm range. 
+### BOM for N17 
 
-At the end of the day, they're not a *whole lot* smaller than the N23s.
+Type | Size | QTY | Where Used | Vendor | PN
+--- | --- | --- | --- | --- | --- 
+Flat Head Thread-Forming | No. 6, 1/2" | 20 | - | McMaster | 95893A255
+Bearing Shims | 5x10x0.5mm | 22 | - | McMaster | 98089A375
+Shoulder Bolts | 5x10xM4 | 2 | Pulleys | McMaster | 92981A030 
+Shoulder Bolts | 5x6xM4 | 8 | Rollers | McMaster | 92981A146
+Heat-Set M4 Tapered Inserts | M4 | 10 | - | McMaster | 94180A351
+Heat-Set M3 Tapered Insert | M3 | 1 | - | McMaster | 94180A331
+Various M3 SHCS | - | 5 | - | - | - 
+625ZZ Bearings | 5x16x5mm | 12 | - | VXB | [link](https://www.vxb.com/20-625ZZ-5x16x5-Metal-5mm-Bore-Miniature-p/kit250.htm) or McMaster 6153K113
+20T or 16T GT2 Pulley | 10mm or Wider, 5mm Bore | 1 | - | Amazon or SDP/SI | [Amazon Link](https://www.amazon.com/uxcell-Aluminum-Timing-Synchronous-Printer/dp/B072M2CM1W/)
+10mm (or 9mm) Wide GT2 Belt | Find Steel-Core for Stiffness! | 1 | - | Amazon or SDP/SI | [Amazon Link](https://www.amazon.com/BALITENSEN-Black-Timing-Printer-Machine/dp/B07F2X236H/)
 
 ## Gantry for NEMA23 Motor, 0.375" HDPE