Ball Screw replacement for wearing thread nuts

I would be interested in details of how you achieved this modification if you progressed it.

It's something worth looking in to but I presume would require bespoke housings to be made to hold the ballscrew.

DOug

It will be a great idea and also for Stepcraft to upgrade to ball screw system.

What would be ideal would be to replace the nuts on the leadscrew with ball nuts - trouble is that these are really expensive items!! They would not be justified unless the leadscrew bearings were made to guarantee minimum end play ( < 0.001" say ) as well.

Peter

I mentioned this to Rory in a recent e-mail and he commented that ballscrews are a "different ball game" in terms of integration. Sadly, I don't think that this is a simple matter of making or sourcing a small ballscrew unit that can just slot into the existing mount. Look at the small clearance between the brass nut and the track rollers. This would likely be showstopper on its own sadly.

Doug

Well, we have had continual y axis jams as a result of the bushing system. And attempted, I think 8-9 large 3d prints with around 6 rolls of pla.... none of them have finished. We have sourced a balls crew relatively cheaply compared to the machine price, they should be on there standard for a machine of this cost !

Well, we have had continual y axis jams as a result of the bushing system. And attempted, I think 8-9 large 3d prints with around 6 rolls of pla.... none of them have finished. We have sourced a balls crew relatively cheaply compared to the machine price, they should be on there standard for a machine of this cost !

Y axis problems are difficult to resolve unless "tuning" is meticulous. I spent days getting mine right. I even went to the lengths of measuring the torque required to move it over the whole range of positions - very tedious but worthwhile, I've never had a a suspicion of jam fortunately.

There are many potential sources of friction, and you'll have to identify and rectify each in turn. In particular the adjustable rollers on the Y axis must be very carefully adjusted to just, and only just remove free play after the X-axis is finally adjusted.

Kinematically speaking this is a poor design with 16 potential contact points when only 5 are needed, but all machines of this type have this problem to a greater or lesser extent.

On top of that it is vital to ensure that when the gantry is at the opposite end to the drive, the end bearings line up exactly with the leadscrew. I had to relieve the bearing seats to achieve this on mine - only by a fraction of a mm, but it made a huge difference to the driving torque required.

Overall it is not a five minute quick tweak to get it all correct - patience is well rewarded.

It is not the ball screws where the major cost lies, but in the recirculating ball nuts. A set of four would probably add 25% or more to the kit price, quite apart from changes necessary to mount them and adjust the machine correctly. A whole new ball park if you will forgive the pun!

Peter

Agreed, the biggest cause of error by far we found, was the brass bushings wearing loose with use, by the end we could move the gantry by .5 to 1mm with y axis screws stationary.

I just had a quote for 4 ball screws ( 1.5, 1.5, 1,and .35 meters with 4 ballscrews, bearing blocks and couplers, 6x20 mm linear rails, with 12 linear blocks with grease nipples for $550 posted. We paid over 3000 for our machine. I think we've paid 200 pounds for the custom balk screws to replace the y, x, and z screws.

Saw this, could be a solution.

Stepcraft ballscrew nut holder

Now if I could just find a supplier in the US 🙂

Hi

Wow!! A solution at last perhaps. I wonder if the original Stepcraft ballscrews can be retained or if they would need to be replaced - hopefully not.

I found this catalogue for the manufacturing company - lots of mouth watering goodies there.

The adaptor looks to be pretty simple - if enough interest could be raised on this forum then I'm sure they could be manufactured commercially at a sensible cost. Is it possible to put together a list of interested parties on this forum??

I for one would be interested in doing this modification.

Peter

I'd be interested, but I'm also interested to know how much the ball screw nuts cost since they want you to call for the price. That may be a deal breaker for me. I have a brand new machine I haven't even been able to use yet because I'm waiting for missing parts, one of which happens to be a ball screw nut 🙂 Would rather do this from the start than disassemble everthing, but I don't think I can wait any longer.

Moore International FGR 10x3 Carry Ball Screws NUT

Hi,

I'd just found Moore myself - looks promising.

I'll fire off an email to Moore expressing potential interest and see what they can offer in the way of price breaks. It wouldn't surprise me if thay are talking £50 + for small quantities. The adapter should be more reasonable - I would guess < £5 once setup costs have been absorbed. Incidentally, unless I am mistaken and read the catalogue incorrectly, the tap required for the adapter thread is M18x1 not M20x1

The thing that grates with me is that the originator suggested cutting a flat on the ball nut to make it fit - ughh!! Milling a shallow recess in the mounting plate would seem a more rational engineering solution - more difficult though I agree. You'd need your Stepcraft to be working if another mill isn't available.

Quoted backlash appears to be 0.06mm ( 0.0024") but apparently this can be bettered if matched screws and nuts are supplied. Expect to need a mortgage for these!!

Peter

Peter

We purchased our Miniature ballscrew from the Uk, we had a mount like that one shown, 3dprinted out of nylon which arrived, and looks great, and fits.

The stepcraft screw, is not designed to have balls in it, so you gonna have to fork out ~200 pounds for a set of 3 custom ballscrews, and then do some DIY to get them mounted

I can post pics of our one, once we have all the bits

Hi Finch

So Stepcraft use a non-standard lead screw - that's a bummer!! It looks just like the Eichenberger ones too.

I guess any new screws would need the appropriate end treatment to get them to match the existing - at least there is minimal machining required - turn to size and grind a flat at one end after annealing?

Do you have a note of any of the critical dimensions such as lead screw length etc, and center height above the mounting plate? The ball nut adapter looks fairly straight forward to DIY in aluminium or brass and would require the purchase of an appropriate M18x1 tap. I've a mini-lathe and mini-mill that would make that very straightforward.

Do please post some pics - I've wanted to ball nut the machine for ages, using backlash correction doesn't always seem to do the business when I'm milling pcb's.

Peter

Pete, it's pretty easy.

I'm not too sure about the compatability, but I believe, you need a ballscrew to install a ballnut. Goodluck trying to figure out what sized ballnuts will work with a leadscrew. I understand that leadscrews use bushings only and are never intended to have bearings running up the thread.

Remove one of your existing Y screws, measure up the threaded length, and measure the end diameter, the ballscrew shops machine most ends to whatever you like.

Our initial plan, is just replace old leadscrew, with new ballscrew machined so the ends match, so we can use the rest of the machine as is.