Thursday, June 21, 2018

MPCNC Motor Parts Sourcing in China

Build or buy? This was the decision I had to make for MPCNC Parts Sourcing here in Calgary, Alberta.
mpcnc parts sourcing
In addition to providing a detailed Bill of Materials (BOM), the originator of the Mostly Printed CNC machine also makes MPCNC parts sourcing easier by providing a complete hardware kit, shown above. It costs US$ 255, plus shipping to Canada for US$ 46. I wondered whether this was a reasonable deal compared to MPCNC parts sourcing individually. In part, this was because I already had a few of the components (Arduino Mega, Ramps 1.4 board, DRV8825 stepper drivers, power supply) which account for around 15% of the total cost.
For the rest of the parts, I listed them in a worksheet. All of the hardware (nuts, bolts, screws, washers, threaded rod) was available at Home Depot, Lowes or Princess Auto here in Calgary. Prices varied a bit between these stores. The “big ticket” hardware items turned out to be the #6-32 and 5/16 nylon insert stop nuts at around $6 and $10 total, respectively.
The package of 5 NEMA 17 high torque stepper motors costs around US$75 or CDN$99 on  Unfortunately, the vendor, Stepper China, does not ship to Canada through its Amazon offering. However, with a bit of searching I was able to find the same offer from the same vendor on eBay.
There were additional savings to be achieved on eBay. The cost of the 608 2-SRS bearings (60), the M3-10mm screws for mounting the stepper motors (24) and the GT-2 timing belt and pulleys was an order of magnitude cheaper direct from China than local sources.
I did have trouble finding two of the parts locally. One was the 1.75 inch bolt. Hopefully I can substitute something as I go along. The other exclusion was the 7/8 inch long coupling nut for the anti-backlash assembly. I did find this coupling nut online at Canadian suppliers, but all had a minimum order to 50 – which is 49 more than I need.

I was able to find reasonably priced 5/16 threaded rod, but did not buy it yet. I might consider some re-design for the Z-axis using a lead screw or ACME screw for better durability and accuracy. That will no doubt the the final part of my build. (Threaded rod and coupling nut are shown on the far left side of the picture.)

MPCNC Parts Sourcing – Did I save money?

First, let me say that the hardware kit provided by is probably a good deal if you live in the United States (without currency exchange and with cheaper shipping) and if you don’t already have some of the more expensive parts. The total cost would be $US268.
However, for me in Canada, with exchange rates, extra shipping and the costs and potential hassles of custom tariff and brokering, my cost of would been at least CDN$ 425. By sourcing hardware locally and more specialized parts from offshore, I think my final cost will be under $CDN 300. I will do a full accounting when all is said and done. But I think the saving of CDN$125 for doing MPCNC parts sourcing myself was worth the effort. Of course, I am not accounting for my time, waiting for Chinese shipments, and driving around to the big box hardware stores.
Incidentally, I discovered that much of the hardware actually costs less in Canada, even after currency exchange. For example, both types of nylon insert stop nuts were well less than half the price in Canada. compared to the Home Depot US web site. I have no idea why.

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