Alignment Issues - Load on Motors

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Low Friction <1 lb even when loaded down

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• Axis alignment becomes an issue with multiple carriages
• Let’s start from first principles:

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• Coefficient of friction of oil filled bronze on steel - Frictional coefficients for bronze alloys against steel range between 0.08 and 0.14. During wear, or when there is absolutely no lubricant present, the frictional coefficient may range from about 0.12 to as high as 0.18 to 0.30. Ref
• Weight of shaft - 2.7 lb/foot.
• Weight for CNC torch table bearing on Y axes - constitutes of weight of X + Z
• Steppers are about 3 lb
• X axis has 20’ of shaft - 50 lb
• Z axis has 4’ of shaft - 10 lb
• 10 lb for 3 motors
• 10 lb balance of system - metal plates, plastic parts, torch, solenoids, igniter
• Total load of about 80 lb is carried on the Z axes
• With proper alignment - this would be 8-24 lb total load

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rod

bushing

bushing

Alignment Issues - Load on Motors

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• Once bushings are connected - they can misalign
• Currently we have 16 bearings on Y axes
• Each should hold 5 lb, and friction on each should be 0.5 lb
• Misalignment changes this

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• Thus question is how to reduce misalignment
• Less bearings
• Stiffer connection

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carriage

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rod

bushing

bushing

Pulleys

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• 9 mm belt - 3 mm pitch. 20 tooth. 0.752” pitch diameter
• HTD style
• 40 in-lb tooth jump torque expected (extrapolated from data for 6 mm 30 tooth version)
• Other options for future: For 15 mm belt - 5 mm pitch - 20 tooth. 15 tooth.

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Belt

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• 9 mm belt, 3 mm pitch
• HTD style
• 40 in-lb tooth jump torque expected (extrapolated from data for 6 mm 30 tooth version)
• 15 mm belt, 5 mm pitch

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Breaking and Elongation - p61 of Gates

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• Point - LL3MGT15 3MGT GT3 3 mm has 150 lb working strength with 20 groove pulley

Going to GT2 3 mm pitch

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• Point: 2mm GT belt does 9 in lb (36 lb at ¼”).
• We have 269 oz in or 68 lb drive at ¼”
• Ie - belt starts skipping readily with 269 oz in Nema 23 motors
• Solution: 3 mm pitch GT belt does 40 in lb tooth jump torque
• That is 160 lb at ¼” - considerably more sufficient
• Could still use 20 groove pulley
• 3 mm pitch does not affect resolution, but larger drive pulley size (30 grooves vs 21) reduces step resolution from 10 micron to 15 micron (still under 1 thousandth step size with 200 steps.) 1.5”/200/16=0.5 thou

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Going to GT2 3 mm pitch

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• Point - 3 mm pitch dosen’t come in more than 7 foot lengths
• Need to go to PowerGrip HTD? No
• LL (long length) exists

Going to GT2 3 mm pitch

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• Point - LL5MGT-015

Tooth Jump Torque

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• Abstract: We are redesigning the 1” Universal Axis for monolithic design as opposed to clamshell design of the original 5/16” (7.92 mm) Universal Axis. This simplifies the design and reduces part count. We design around existing common parts to make this highly reproducible anywhere in the world. There are 3 Universal Axis pieces: motor side, carriage, and idler. Here are the essential features for a minimum viable product of each of the 3 pieces. We consider generative flexibility of connecting the 1” universal axis to other Universal Axes and to frames - to create many geometries.
• Design Guidelines:
• All bolts accessible
• No hidden nuts as in nut catchers - this is in general replaceable by threading into plastic
• To thread into plastic to connect 2 pieces - make one hole oversize, make second hole undersize
• Maintain maximum symmetry
• Since 3D prints take a long time - optimize for minimum printed material
• Allow for as much different interconnection geometry as possible
• Ex - allow X axis to connect to Y - Y to Z, X to Z, etc etc
• Allow X to X, Y to Y, etc
• Allow horizontal + vertical connection
• For connection - use a uniform grid pattern of holes

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Heated Chamber

6’ frame

3’ bed

40”

50”

Heated Chamber

6’ frame

3’ bed

40”

50”

Heat shield can be up to 2.5’x6’

Heated Chamber - 1x2’ shield

6’ frame

3’ bed

40”

50”

Heat shield 12”x24”

Top of heated chamber is covered with 3’x3’ sheet of polycarbonate

Carbon fiber blanket gasket - 6”x12”

Structure

Polycarbonate shell with insulation

Structure

Mount X Axis to Y - Bolt Holes

Ream this larger than thread size. This way, the bolt clamps down and eliminates space, allowing for both bolt strength and clamp force to hold X to Y

X axis piece

Y axis carriage

CNC Torch - Axis mount to Square Tube

End view of axis

4x4 tube

Weld

CNC Torch - Gas Connection

• Bottles
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Gas

Oxygen

CNC Torch - Gas Connection 2

Photo Album

• Bottles
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CNC Torch - Gas Connection 3

Photo Album

Warming: do not follow diagrams online.

center hole: cutting oxygen (triggered by lever in torch handle)

CNC Torch - Gas Control

• Use existing SSR for 1 channel of gas control, add 2 more
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Torch -> Shredder -> Filament Maker

• Easiest design for shredder

3” shaft + square tube

bearing

3” bearing

Double chain coupler

Torch -> Shredder -> Filament Maker

• Easiest for a filament maker
• Extruder
• Tensioner
• Winder
• CAD -

bearing

Motor Coupler to Socket

• Easiest for a filament maker
• Extruder
• Tensioner
• Winder
• CAD -

bearing

Tensioner

bearing

Gas Trigger for Torch

• Problem statement - trigger 3 gases
• Oxygen
• Acetylene
• Cutting oxygen
• Logic
• Turn on acetylene
• light acetylene
• Turn on heating oxygen
• For cutting - turn on cutting oxygen
• RAMPs pinout
• G4 - dwell
• M42 - turn on a pin
• Generate cut file
• DXF to gcode

Wire Preparation - 3

• Now take the Red and Blue pair of wires, and do the same pattern of cutting and soldering
• Treat the Red and Blue pair exactly as you have done to the Black and Green pair
• Follow Steps 1-6 exactly but replacing the Red and Blue pair for the Black and Green
• The final results should look like this, with the current path shown:

Wiring

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1. Wire TB6600
2. Wire Steppers in Series
3. ​

1

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A

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B

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B’

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A’

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A

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A’

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https://docs.google.com/presentation/d/1bByf3PmjpFA3a9bqet27Hjl1LKSI5rf5zeDrFS1tRZc/edit#slide=id.g995140a2a9_0_166

4 motors

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• Wire TB6600
• Wire Steppers in Series
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B

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B’

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A’

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A

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4 motors

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• Wire TB6600
• Wire Steppers in Series

B

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B’

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A’

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A

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Just see this.

Carriage

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Z axis config: holds single rod

• May have one side with autoparallel bushing

Y axis config: vertical hold of X axis

• Idler and motor piece must have outward holes that line up

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Carriage

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Z axis config: holds single rod

• May have one side with autoparallel bushing

Y axis config: vertical hold of X axis

• Idler and motor piece must have outward holes that line up

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Cut List - ¼”x4”x4” angle + Flat + Rods

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1. [4] - 8’4”
2. [4] - 5’4”
3. [4] - 6’
4. [8] - ¼”x4”x4” flat

Solid Rod:

1. [8] 9’

Hollow Rod - no cuts

1. [4] 6’

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9’x6’ frame

Front view

n.b.: 1/2/3 sanity check: 3x[4] adds up to 12

Welding on a table

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• ¼”x4”x4” angle - 9’
• Do large side first

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Welding on a table 2 - Top View

Build 2 of these

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Top View of side panel

flange

6’

9’

¼”x4”x4” plate

Or 6”x6”

Welding on a table 2 - Top View

Build 2 of these

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Top View of side panel

flange

6’

9’

¼”x4”x4” plate

Or 6”x6”

Large Frames

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Axis attachment to frame

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up

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z

z

6’

2’

2’

2’

Front View

9’

solid rods

hollow rods

X and Y attachment

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up

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z

z

Front View

Z attachment

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up

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1. Assemble motor piece
1. Attach pulley
2. Attach motor with 4 bolts to plastic
2. Mount Z motor piece flush with upper edge of steel bottom frame piece
• Rods go all way to floor
3. Assemble idler piece
• Press fit 1 skateboard bearing into plastic on the capped side
• Cut a small shaft - 8 mm rod - 1.8”
• Mount idler pulley (3D printed piece)
• Insert shaft assembly into first bearing
• Add second bearing - press fit it on a vice
4. Assemble carriage piece
• Insert 2 bushings on each side
• Fix the bushings
1. Use a small flanged bearing on outer side, with M6x30 bolt
2. Use a washer on interior side -

Make sure these red distances are equal

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Mount bed at top

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z

z

Front View

4x4x1/2 “

Design

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• Each motor does 50 lb force
• Design of bed weight -
• Build Upon Universal Axis
1. Bronze bushing
• Universal Controller

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Testing - CAD

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Short Carriage

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• 3:25 to print with 0.6 mm layer height -
• 90 mm rod spacing?

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Results - MVP

FIles

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• 5.5” size
• 1 Inch Rod

Idler

FIles

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2hr 12 min

1.2 nozzle

20% 92g

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• 5.5” size
• 94.6 mm rod spacing?

Carriage

FIles

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• 5.5” size across
• 94.6 mm rod spacing?

Next Steps

FIles

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1. Wire up TB6600
1. TB6600 hardware
2. Power supply
3. wires
2. Create attachment of idler to carriage
3. Motor side
4. Reduce carriage size + put in bearing mounts
• Reduce 9 hr print time
5. Add carriage closure
6. Add belt cylinder
7. Add belt clamp
8. Recess bolt heads for 50 mm m6 bolts to get 20 mm of threading

Electronics 1 - Signal Side

See reference

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• Take D3D Universal Controller
• Remove X driver
• Use available X driver slot
• Extract signal from it
• Pump signal into TB6600

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Electronics 2 - Power Side

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• Wire up 24V or 12V power supply
• Power up TB6600
• Connect large stepper to TB6600

L5Features of Motor Piece

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Features of Carriage Piece

Features of Idler Piece

1. Bearings insertion - 4 bearings for 1” rods
2. Belt throughhole
3. Attachment to other axes (but usually not to frame)
1. Keep spacing same as other axes
4. Belt attachment means
5. Carriage closure to keep bearings inside

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Motor Piece

Carriage

Carriage

Idler to Carriage Connection�(X axis idler connecting to 2 Y axis carriages)

Top View

Top View

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Idler x

shaft

MOtor X

Carriage x

Carriage y

Idler x

shaft

MOtor X

Carriage x

Carriage y

Carriage y

shaft

shaft

5.5”

4.5”

Carriage Detail

Carriage y

shaft

shaft

5.5”

4.5”

bearing

bearing

0.125”

0.5”

0.375”

bearing

bearing

2.5”

Diameter = 5.5 mm in CAD

Carriage

Radius = 0.65

Bearing OD is 1.25”

Distance between rods is 3.5” on center

Print Area

Print Area

Alternative to heavy steel bed

https://www.mcmaster.com/garolite-sheet-stock/

CNC Torch Table v21.08 - Review of v19.10

Hangs too far down and is thus unstable

(instability is from torsion of Y axis)

• CAD of v19.10

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v19.10

https://wiki.opensourceecology.org/wiki/CNC_Torch_Table_v19.10

Y axis

X axis

Use a 5 Axis Configuration instead of 4 Axis Configuration

Good stability with 6 axes as in this CNC circuit mill

• But - 6 axes is a bit of overkill
• Instead - use 5 axes as on next page

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https://wiki.opensourceecology.org/wiki/D3D_CNC_Circuit_Mill

5 Axis Configuration - X, X, Y, Y, Z

Good stability with 5 axes.

[1] z axis.

[2] y and x axes.

Torch head file

Good stability with 5 axes.

[1] z axis.

[2] y and x axes.

X axis not shown.

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Y axis

Y axis

Z axis

Idler prototyping

3hrs 35 min print time

139g 17.54m filament

1st iteration

3hrs 48 min print time

151g 19.05m filament

2nd iteration ğ8vggy

- Added bumps for bolts to hold 1” rods

Carriage prototyping

6hrs 4mins print time

232g 29.28m filament

1st iteration

3hrs 55mins print time

151g 19.08m filament

2nd iteration - reduced height of carriage from 4” down to 2.5”

Idler Pulley?