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Since I’ve now got enough parts from past upgrades (Minus an extra XController) to build a second CNC, I’m going to start with screws for X and Y, as well as the 6" linear rig for the Z.
I’ve been researching Ball Screws vs. Lead Screws for the X (I’m starting there), and it appears, that Ball screws make more sense for horizontal applications.
I know it’s only been an hour since I posted, but unfortunately I am a serial compulsive… NEVER a good thing when you like to tinker.
I went ahead and ordered the 16mm Ball Screw from Amazon, however I noticed that I can get a 2000mm screw for ~ $16 more, so I bought that one instead, as well as a coupler and ball nut bracket for mounting the ball nut to the back of the gantry.
I figure I can either cut the 2000mm screw into 2 and have a start on one of the two Y axis, or I can increase my X axis length to 1500mm or more since I’m doing a lot of signs lately. I find that Y is about twice what I need, while X is about 300mm short.
Bad news is the coupler and the bracket come from overseas so I’m looking at 3 weeks plus for delivery time. The screw will be here in a day…
I upgraded my gantry to a 1000mm c-beam kit, and doubled the y axis to 2000mm. (Being able to work with precut 2’ x 4’ sheet of MDF is so worth it)
I have been VERY happy with the results, but would like to replace the Y belts with something better.
Unfortunately the 8mm acme screws max out at 1000mm (any longer and you start to have problems with "screw whip). I had original assumed this was a limitation of all screws, though now it seem obvious that thicker diameter screws could probably be longer before excessive flexing becomes and issue.
Keep in mind that you will need to have their ends machined to match whatever bearing blocks you pick.
Unless you have a capable lathe, cutting what you ordered in two lengths and having 4 ends machined might cost more than the screw & nut itself.
In case you need to order some extra lengths, some sellers provide predefined lengths pre-machined for specific bearing block types (i.e. BK12/BF12 for 1605 and 1610 ballscrews) at no extra cost. Some sellers even bundle (pre-machined) screw & nut & nut mount & bearing blocks, which could be more cost effective that sourcing each part independently.
Most of them are “chinese ballscrews”. It depends on the factory, QC …and length.
Regarding (b) I suspect that in many cases items that do not grade well in QC still find their way to the market at lower prices. They might still work for many hobbyist and even pros depending on precision expectations.
Regarding (c) if you care about short lengths, e.g. for a Z axis, you can get away with ridiculous(ly low) prices. Runouts cannot be that bad in short lengths.
I cannot tell about US sources, but in Europe cnc4you.co.uk is a reliable one. This is why:
Very good points. I already have access to a few BK and BF 12 bearing blocks, and a lathe with a bore size large enough to allow me to machine down the ends of the screw, but you’re absolutely right, in most cases it’s cheaper to buy a kit.
I’m hoping to POC an upgrade to X for now, 1000mm or shorter, and if it works reliably, then I’ll rotate my machine 90’ and extend my Y to somewhere around 1750mm or more. I think finding a kit for the shorter length would be cost effective, but the larger would probably prove simpler to machine the screw and source the blocks separately…
So, my 2000mm ball screw showed up yesterday, took nearly 11 days shipped. Initial inspection on a dead-flat surface shows the screw to be flat, no bowing or deflection. Ball screw nut moves freely, no binding or rough spots.
Early next week I’ll be cutting it to length for the X and running it thru the lathe \ mill to turn down both ends. One for the coupler to the Nema 23 (with flat grind) and the other end for a bearing to help with any whip.
Right now, at least as a POC, I’m going to simply cut it long enough for use with the standard 1000mm X axis, so probably 1050mm to 1070mm. Ideally I can find a source for something larger than 1000 but smaller than 2000 next time so I don’t waste any material…
The ball nut mount bracket won’t be here for another 10-12 days, which is fine, given my schedule, so I’ll either wait on it, or create a rough prototype for attachment of the ball nut to the X gantry.
Ball nut bracket showed up, now I just need to cut down the screw and mill the ends to fit the coupler and a bearing bracket. Probably wont get to that until first week of June thanks to work schedule…
