One thing I have been doing for a little while now is creating all of the parts for the Buildlog laser in Google Sketchup – I really must start to learn some other 3D modelling package, but I have become so comfortable with Sketchup that it is still my ‘go-to’ modelling tool.
One thing I don’t like about the design is that despite it using mainly metric dimensions, nuts and screws, the Z axis still uses SAE thread and fittings.
As such for my Sketchup model, I have converted all the items from 1/4″ thread to M6 thread and replaced the bearings, self clinching nuts (PEM nuts), all thread, etc with appropriate alternatives.
Something else I have decided do is to use GT2 belts and pulleys in place of the MXL ones in the original design. GT2 is supposedly backlash free and is virtually the same pitch (2mm vs 2.032mm) plus I also have 50 metres of it that I bought for building 3D printers.
I have reduced the length of the Z belt from 64″ (1625.6mm) to 1524mm as this is the longest standard GT2 belt loop and can be bought from various suppliers, the cheapest I have found being robotdigg at $2.40, the 204mm MXL belt loop can be replaced with a 202mm GT2 belt loop at $0.50 from robotdigg.
The 20 tooth pulleys can be bought from robotdigg for only around $2.00 each or $15.00 for a pack of 10. Most of my nema 17 stepper motors came with GT2 timing pulleys installed anyway.
The only current issue is seeing if I can persuade robotdigg to make a 48 tooth pulley for the Z axis.
I bought a dual axle nema 17 stepper motor from ebay for £9.00 + £3.00 P&P although I have since discovered that I could also have bought this item for $10.10 (about £6.00) from robotdigg.
The one set of items that will tricky to fabricate myself are the various gantry plates, there is someone selling them on the Buildlog forum for $75.00 + shipping, this set comes with Z plates, however I may have some issues with a standard set of these brackets, plus once I add shipping, these start to become a little pricey. So instead I decided to buy an anodised set from Blomker Industries for $49.00 + $29.00 shipping (about £50.00).
These arrived in just a few days and comes with SAE PEM nuts pre-installed for mounting the focusing unit and the energy chain. On searching through my collection of hard disk mounting screws, I find some that are suitable for the #6-32 screws to retain the focusing unit. I have yet to locate some #4-40 screws for the energy chain, although I may simply re-tap these to M3.
The 1/4″ floating PEM nuts for the Z plates require a 0.515″ diameter hole (13.08mm) although this is effectively the same size hole as required for an M6 floating self clinching nut (13.06mm), attempting to find anyone that will sell these in a quantity of less than 1000 is proving difficult.
Pondering this matter a little further, it occurs to me that since this is supposed to be a floating nut rather than a fixed nut, it may also be possible to use an M6 19″ rack mount cage nut instead (I have hundreds of these), the only issue will be the thickness of the material as 3mm aluminium will be too thick, so I may make them out of 2mm aluminium instead, and then cut a suitable square hole for the cage nut.
The hole does not need to be perfectly square, just good enough for the nut to engage correctly.
The cheapest place I have found so far for the V wheels, eccentric nuts, spacers and idler pulleys is the Openbuilds Part Store, which despite being in the USA is cheaper, even after shipping has been added, than buying from AmberSpyGlass (Makerslide UK). I will however be buying a 2m length of Makerslide from AmberSpyGlass for £24.00 + £17.02 P&P. I will most likely add one or two additional 2m lengths as the shipping remains the same, I may also add an M5 spiral flute tap for £8.75.