Now that we have an official dual motor Y-axis drive kit, price comparisons are a bit easier:
$58.42 for the https://www.inventables.com/projects/sh ... -drive-kit
To get only the items the two upgrades have in common we subract:
$16.94 Stepper Motor - NEMA 17
$3.00 3 ft. Stepper Motor Cable
$2.50 Terminal Block
(but should also account for a 4th stepper driver, $9.95--$11.95)
We need to set off the motor so as to not lose working area:
$2.00 25285-14 50mm 0.5mm 10 M3
$6.00 25312-08 0.7500 in 10
$2.00 25287-03 Zinc Plated 3.1mm 7mm 10 .45mm - .55mm
Ideally the screws would be 45mm the longer screws will need washers to make up the difference (I used 3 M3 and 5 M5) if one isn't willing to cut them. Nylon spacers would be cheaper, ~$1.60 --- I was able to pick up 4 steel 1.5" 7/32" rolling pins for $1.60. However, this arguably should be done for the motor as well, so as to not lose working area, so we'll call it a wash.
Assuming a 1/4" drive shaft we need to switch out the 5mm pulley for a 1/4"
$6.25 25204-03 .25"
Inventables has 1/4" aluminum rods in the following alloys --- not sure which would be best for a drive shaft. For an 18" length (a stock Shapeoko needs ~17") prices run from
$4.21 24792-30 1/4" 18" (2011)
$10.71 24793-02 1/4" 18" (2024)
$1.21 24794-09 1/4" 18" (6061)
$2.26 24795-02 1/4" 18" (7075)
and Home Depot has ``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
Anyone know the tradeoffs for these alloys? (I went ahead and asked the Inventables folks about this)
We need a shaft coupler --- I was able to find them on eBay quite inexpensively, but I think the perfect solution is to use an over-size one which would connect the drive shaft to the pulley, allowing the belt to move to the outside:
$12.00 6.35mm to 12.7mm Linear Motion Control Couplings 1/4 x 1/2 In Encoder Clamp Shaft Coupler Diameter 25mm Length 30mm at http://www.fscoupling.com/635mm-to-127m ... p-139.html
(Amazon has the same for $13.99)
This essentially makes the dual-purpose pulley--coupling I wished for above.
And we need a flanged bearing:
$6.72 Kilian F-160 1/4" Bore, 13/16" Minor Diameter, 29/32" Flange Diameter, 1/4" Wide Flanged Bearing available at Amazon http://www.amazon.com/Kilian-Diameter-F ... B003XU6QW0
The motor hole will need to be adjusted in size --- a 7/8" tapered reamer should work for that, (though I worry about making such a large hole), or you can make a bearing plate out of HDPE and mount it w/ M3 screws. Or, one could find the proper sized bearing (found by searching on .25 i.d. instead... $6.49, but not a small parts item, http://www.amazon.com/2500-Flange-Flang ... B002HAXAFI
$23.68 (or less) versus $32.39 or ($22.44 if _not_ using a 4th driver)
My build came in at quite a bit less (if I only counted actually used parts) --- the roll pins are a nice savings, the aluminum rod was cheap and I got a 5mm--6.35mm coupler off eBay for $3.97.
The 5mm variant should in theory be cheaper, but it's not, given the parts I can find. For reference:
$10.77 Tool Steel Round Rod, Ground Finish, Grade O1, Annealed, Meets ASTM A681 Specifications, 5millimeters Diameter, 36" Length, Precision Tolerance http://www.amazon.com/Annealed-Specific ... B0050RMUT2
$6.79 F624ZZ Miniature Flanged Ball Bearing 4x13x5 mm Shielded by ESI Bearings http://www.amazon.com/F624ZZ-Miniature- ... B009H6X1TK
plus 8 #4-40 Machine Screws, 1/2" Length, Phillips http://www.pololu.com/catalog/product/1962
(25-pack). $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 http://www.amazon.com/Ruland-PSMR16-5-5 ... B0060M1XLM
(from China on eBay, purchased from Member id bluestone002, this was $2.99 + $1.56 s/h)
The drive shaft is in place, see signature, (though the pulley was a nerve-wrackingly tight fit, despite test fitting in the store), so just need to install the belts, square the machine, bolt it down and tighten things up.
- source a 1/4"--1/2" coupler and move the motor belt to the outside as theorised above
- drill new holes for the idler wheels so the belts can be flipped over and work out suitable mounts / end plates
- organise the above and add it to the wiki, merging w/ Tom Smith's --- I was thinking a table w/ columns for different shaft sizes....
- anything else I forgot....
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets