Tony and I should meet up and open the box from Misumi later today. Hopefully, I'll have more to post on that later on.
Meanwhile, I've been going through the MTW Build Guide with a fine tooth comb, trying to sort through the Parts Overview and create a rational Bill of Materials for our builds. I'm finding the organization of the existing parts lists/BOM to be somewhat, um, disorderly. There is little consideration given to the sequence in which these parts need to be ordered, which I believe is because the Build Guide is geared to the MTW MendelMax kits. There are also very few actual supplier part numbers given, nor, for that matter, is a list of suppliers evident in any detail.
Since it is my aim to source as many parts as I can myself and only buy kit parts for what I can't find or make myself, my BOM (in its final form) will be organized a bit differently to permit taking advantage of economies of scale and quantity purchasing to contain build cost.
Just as an example of how a well-organized BOM can make a difference, take the case of M5 X 10 mm SHCS (Socket Head Cap Screws). These are used in many different areas of the build, and knowing how many are needed for all phases of the build, one may buy them in bulk from a low-cost supplier to get a better deal.
Pricing from several sources, I have so far found a better price for these in quantities per 100 than I have in smaller quantities. This quantity jibes well with the number needed for the build, too. I have been as yet unable to find a local supplier who keeps these on the shelf in large quantities, and so will have to order and have them shipped, adding to the cost of purchase.
There are significant variations in price for M5 x 10 mm SHCS at different suppliers. The highest price I found per 100 is about $30, while the lowest is nearer $9, and I'm not done looking, because every penny off the unit price of a fastener at this quantity saves a dollar on the total cost. Prices of fasteners, in particular, can have a real force-multiplying effect on the cost of a build if not researched carefully prior to purchase.
As assembly phases are completed, I will be posting the relevant as-built BOMs. Then, after the printer is fully assembled and in debug phase, an as-built Master BOM will be published. Why am I waiting until I have an as-built? This is to prevent my mistakes from becoming yours. I'll talk about mistakes made and pitfalls encountered along the way plenty in this blog, but not in the BOM. That document is intended to become an accurate reference for this build, and to be useful to anyone who might be following along.
It is my intent to use a numbering system for items which organizes parts in order of build phases, and further by function. It goes something like XXX-XXX where the first group is an assembly group, and the last is the item number in that group. A partial list of assembly group numbers might run like this:
000 - Common Parts/Fasteners - used in nearly all phases.
010 - Fasteners
020 - Printed Plastic Parts
090 - Calibration & Debug Common Parts
100 - Frame Components - used in constructing the Frame
110 - Specialty Fasteners for Frame Assembly
120 - Frame Assembly Printed Parts
180 - Aluminum Extrusion Frame Members
190 - Frame Debug & Calibration
200 - Y-Axis
210 - Y-Axis Specialty Hardware
220 - Y-Axis Printed Parts
230 - Y-Axis Drive Components.
290 - Y-Axis Debug and Calibration
Note the skip between 120 and 180, 230 and 290. There's room in there for other functional groups as needed. A lot of this will be echoed in further Assembly Groups, e.g., something ending in "20" will always be a Printed Part.
Yeah... I'm somewhat of a detail freak for stuff like this.
Boring stuff until you need to know what's used when and where. I'll develop this more as we go along, integrating it into the as-built BOMs. Meanwhile, I hope to have some photos of the Misumi unboxing in the next entry.
Ciao for Now!
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