Drive Shaft

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General Overview

Initial discussion in the old Google Groups at: http://groups.google.com/group/shapeoko/browse_thread/thread/6981bc9713c79f38/6dd76af64a02fc2b?lnk=gst&q=shaft#6dd76af64a02fc2b and continuing on Dual Drive Setup (with driveshaft) (link in that to dual_drive_gantry_driveshaft.zip). Further discussion here.

Note: Best paired with a Double Makerslide X-Axis, which moves the Z-axis out as seems to be needed to clear the driveshaft. If the X-axis is a single Makerslide, longer bolts and various spacers may be necessary. Alternately, one could drill holes for double Makerslide, shift the one piece over and have the driveshaft under the extrusion. Negatives: this changes the balance of the gantry and reduces working area along the Y-axis. Also, it become even more important to have belt anchors which do not reduce the working area --- if using the old style mounts, at least the second, new belt should be moved to the outside so as to avoid doubling the work area lost to them.

Bill of Materials

The following table's columns each provide a different version of this upgrade, along w/ notes. Parts which are common to multiple upgrades span the appropriate columns.

Part 5mm drive shaft w/ NEMA 17 (5mm shaft) Belts on the outside 1/4" drive shaft w/ NEMA 17 (5mm shaft) 1/4" drive shaft w/ NEMA 17 (5mm shaft) Belts on the outside 1/4" drive shaft w/ NEMA 23 (1/4" shaft) Belts on the outside
Status Tested [1] [2] Tested [3] Tested [4] Tested [5]
Drive Shaft 5mm steel rod (length must match X-axis, plus space for couplers and pulleys) - some hardware stores carry this, (available from Amazon or Amazon, McMaster-Carr --- check tolerance of latter) 1/4" aluminum rod is available at most hardware stores (“Everbilt 1/4 in. x 36 in. Aluminum Round Rod” for $4.21 and True Value hardware stores stock K&S Engineering 1/4x36 ALU RND Rod for $3.49 and Inventables has 1/4" rod in various lengths in 2011, 2024, 6061 and 7075 --- which is more suitable is unknown) --- other alternatives are stainless steel, precision drill rod or actual drive shafts. Unless purchasing a rod w/ a guaranteed dimensional tolerance, try out components for size before purchase if possible --- only 1 out of 3 in-stock pieces allowed all components to fit when purchasing recently.

N.B. music wire in 36" lengths is available at hardware stores and hobby shops and is inexpensive, but due to how it is manufactured will tend to be larger than the nominal diameter --- do not purchase unless you’re confident of making things properly fit.

Pulley-Drive Shaft 5mm bore Inventables 25204-02 OpenBuilds 1/4" bore Inventables 25204-03 1/4" bore Inventables 25204-03
Pulley-Motor 5mm bore (re-use the original) 1/4" bore Inventables 25204-03 (the pulley is placed on the drive shaft) 1/4" bore (re-use the original)
Coupler 1 5mm Shaft coupler pololu Sparkfun

4 #4 screws for coupler - hardware store

See also $23.11 Ruland PSMR16-5-5-A Set Screw Beam Coupling, Polished Aluminum, Metric, 5mm Bore A Diameter, 5mm Bore B Diameter, 15.9mm OD, 20.3mm Length, 1.36 Nm Nominal Torque Amazon (from China on eBay, purchased from Member id bluestone002, this was $2.99 + $1.56 s/h)

5mm--1/4" coupler 1/4"--1/4" coupler McMaster-Carr
Motor Mount Spacers At least 1.5" of spacing will be needed to stand the motor off the plate to make room for the coupler (and possibly pulley) - Hardware store, DIY, Inventables, aluminum or other metal, nylon will also work.
8 3/4 inch spacers aluminum 7/32" 1.5" roll pins 4 x 7/32" 1.5" roll pins and 4 x #8 bore 1/2" aluminum spacers, 12 M3 washers, 5 M5 washers, motor rotated 45 degrees, which facilitates using the NEMA 23 holes for the belt idlers --- A negative on this is the screw heads are hidden by the Makerslide. M5 nuts [6].
Motor Mount Bolts 4 M3 45mm capscrews - hardware store if lucky, but you might need to do some hunting for these (electronics supply store?). Some people have used brass circuit board standoffs, this might be easier to find. 4 M3 50mm screws (required padding w/ washers) 4 M3 60mm SCH screws --- Purchased via Ship to store from Home Depot[7] M5 bolts
Idler Spacers 2 1/2 inch spacers (a stack of washers can be used here instead - these are to act as standoffs for the idler pulleys on the motor side to account for the extra space used by the couplers) 2 1/4" nylon spacers 4 x #10 5/16" 1/4" spacers, 2 stacks of ~ 4 M5 washers (would be better to use 10 1/4" spacers, 2 per axis for idler wheels, 4 for Z-axis V-wheels)
Drive Shaft Bearing/Bushing 5mm bearing [8] or use HDPE Cutting board, or other material to act as drive shaft bushing, the harder the better. 1/4" Bore bearing: Amazon: Kilian F-160 1/4" Bore, 13/16" Minor Diameter, 29/32" Flange Diameter, 1/4" Wide Flanged Bearing (a sealed bearing would be better), Sparkfun: Ball Bearing - Flanged (1/4" Bore, 1/2" OD)

The motor hole may need to be adjusted in size --- a tapered reamer can be used to enlarge the hole, or you can make a bearing plate out of HDPE and mount it w/ M3 screws (if making a bearing plate a normal bearing can be used: Inventables: Sealed Bearing - 1/4" x 5/8" x 0.196". Or, one could find the proper sized bearing (found by searching on .25 i.d. instead... $6.49, but not a small parts item Amazon). N.B. Hole size varies w/ batch, measure before ordering. Probably best to use a pair of them, one for each motor mount carriage plate.

1/4" bore bearing McMaster-Carr]
The following parts are in-common with the Dual Motor upgrade (in addition to the pulley and spacers above)
2 Idler Pulleys https://www.inventables.com/technologies/smooth-idler-wheel-kit
Bolts or other axle for Idlers 2 M5 16mm capscrews, 2 M5 nuts, M5 washers - hardware store M5?
Belting note that you will need more than 50cm if you have lengthened your X-axis Inventables
Belt Anchors Standard zip tie belt anchors w/ eye bolts 1 1/4" steel bar, drilled for holes, 1/4" aluminum rod, shelf standards cut down w/ zip ties and eye bolts
Right hand side view
Left hand side view.

Shaft Supports

User wlanfox had issues w/ the shaft flexing, so added supports as documented in Re: Shapeoko #0735, mods evolution... (at least my version)

Homing

This is simply done --- just loosen the set screw on one pulley, gently move the carriage in each direction, then tighten the screw.

Troubleshooting

It is important that the two belts for the axis have the same tension --- adjust tension as needed until it is adequate and equal.[9]

Having two pulleys on the drive shaft creates the possibility that one will slip while the other will continue to drive the machine --- any instance of slippage should be investigated by checking the set screws on the pulleys.

Other implementations

Discussion

Theoretical implementation

1/4" drive shaft w/ NEMA 17 (5mm shaft) Belts on the outside using mounting plate and pulley on motor shaft

1/2"--1/4" coupler, connecting it to the pulley mounted on the motor shaft (one concern over doing this is it becomes impossible to check/tighten the pulley set screw) 6.35mm to 12.7mm Linear Motion Control Couplings 1/4 x 1/2 In Encoder Clamp Shaft Coupler Diameter 25mm Length 30mm FS Coupling (Amazon has the same for $13.99).

Alternately, use longer bolts and place the pulley so that the set screw end is on the other side of the gantry plate --- this would allow use of the 5mm--1/4" coupler listed above.

Sleeve the M3 screw used for a motor mount w/ 3/16" or 5mm steel tubing (K & S Precision Metals 3/16" stainless steel available @ True Value, other hardware stores and some hobby stores), alternately, rotate the motor 45 degrees.

K & S Precision Metals stainless steel tubes @ True Value 1/4" cut to length (fits over the 3/16" above) (available @ True Value, other hardware stores and some hobby stores)