I had researched this a long time ago just out of curiosity - I did not keep any bookmarked pages. I found numerous manufacturers/suppliers that have precision hardened chrome plated hollow shafts in the lengths (probably need 5’ overall) and diameters required. Same was true for the ball screws. I do not believe the specifications are available for the hardware that OF chose (exact type/alloy of steel, hardness, smoothness, diameter tolerances, etc.), so what you buy as replacements may or may not be of better quality/precision. All of these details impacting the price. I am not a machinist, but I imagine like anything it would be a matter of finding that sweet spot between price and quality/performance. From what I remember, these factors impacted price a great deal, as did who manufactured them, with my rough estimate at the time being about $1.5K pre tax/shipping (shafts - $200X6or7, ball screws - $100X3). I am sure other forum members with actual experience will add greater value to this topic.
From a purely machine design standpoint, you could absolutely do that! The tricky part will be finding a good source for reasonably priced parts. I had browsed www.misumi.com and found parts there. But an added cost will be having the screws machined. It would be a whole lot cheaper if you just did the X axis, so you’d only need 3x of the rails and 1 screw.
I wondered also if the 4’ was pushing the limits of this type of system, especially for those upgrading to a heavier 80mm spindle. Not sure what kind of deflection to expect when a 9kg spindle is in the middle XY position with 2’ of unsupported shaft on either side. Would linear rails on a steel frame be better for a CNC build of this larger size?
In the grand scheme of things, I think the linear rails as-is are sufficiently strong to handle what it needs to. Deflection while cutting wood I think would be minimal, and definitely negligible during a light or finish cut. Deflection/accuracy in the realm of a hobby work should be a non-issue.
Saw that in a another forum, absolutely love this idea. Hope they offer an upgrade for easy plug and play in the future. Another battle is getting the software to play nicely
Yeah that was my worry too. I was considering getting a cnc4newbie/avidcnc because aluminum extrusion is a lot easier to customize(4x4 format)? A lot more assembly/disassembly time though
Checking misumi right now, what parts you looking at? Not sure what key dimensions are. Cheers
It would be these rails - 35mm OD, 1500mm Length would give you a 49.5" cutting area in X, and about 46" in Y (not 100% accurate on Y).
Perhaps if we had enough interest, we could organize a group buy. As each of us ordering individually (3-7) would keep the price high, but if we stepped it up to 50, we’d knock off a significant savings.
I’d be interested in facilitating if there were enough interest.
Count me in for 3, potential 7!
Any ideas for the correct lead screw? Ball screw specs would be “Machinist and Woodworker: X/Y are 16mm diameter, 10mm pitch (every turn it moves 10mm).” Ball Screw Specs
It depends on the rails ultimately (deflection) as the ones I’ve linked above have a much higher thickness than the stock ones. So I presume deflection would be less of an issue. With that, the Y motors would be moving a larger mass, so acceleration might need to be tuned lower. But, still within the reasonable expectations of the motors. I don’t run this thing at it’s max capacity anyway.
I remember the volume discounts when I was looking at these earlier, and you are correct, it provides a substantial savings. I also like that you spec’d a more robust shaft than currently on the OF.
I’m interested in 3.
IMO, the shafts are the easy part… finding a source to do the machining on both ends of the ball screws may prove to be tricky. I don’t know if Misumi does end machining on screws, but it will be a real part of the cost.
My knowledge is limited to information from web searches. Is your concern the replacement ball screw not fitting into the existing bearing blocks, or with acceptable tolerances?
Most higher-end sources will actually let you specify how the ends should be processed, if at all. 1/4" is an option via Misumi, at a much higher cost of course than “unfinished”; but alternative sources could result in better pricing.
I could actually process (turn down) those ends myself if needed. I’ve done this to repair a grizzly mill I have already. Not saying I want to do a large batch, but willing to experiment.
In most cases, you’d buy a matching ball screw and nut, and simply replace them as a whole. But so long as the nuts match specs, there’s usually not an issue swapping one lead screw to another.
Do you know of any group buying website we could use? I know there’s massdrop for electronics. We could potentially try getting support from onefinity to help us spec the correct lengths for each component. I would imagine we could just add x amount to the existing distance of both the rail(steel tube) and ball screw and they should just line up naturally.
I would be interested as well.
I would be interested as well, how ever I am starting to suffer from fundsalow.
Lads, they’re selling this now! Let’s go!