OmioCNC report

[zeeflyboy]

Do bear in mind that the carriages and nuts shouldn’t be packed completely full, they need a little space to allow the balls to rotate correctly. 3 or 4 balls “missing” on a carriage is a little excessive but it’s normal to look like one or two are missing. I was surprised how few balls are actually in a ball screw too, lots of empty space on my TBI ones with 3 circuits.

[Mmpie]

Do bear in mind that the carriages and nuts shouldn’t be packed completely full, they need a little space to allow the balls to rotate correctly. 3 or 4 balls “missing” on a carriage is a little excessive but it’s normal to look like one or two are missing. I was surprised how few balls are actually in a ball screw too, lots of empty space on my TBI ones with 3 circuits.

Yes I noticed that, but one side of one of the carriages was only half full no matter how much I ran the balls round the track and shook it about. Regardless there doesn't seem to be any play when it's on the rail and runs up and down ok, although it is a smidgen stiffer than the others, but not a significant amount.

Just need to get the gantry level now. Sod's law would have to make it the cable chain side that needs shimming, not only do I hate taking that flipping thing off, it's also on the 'blind side' in my cabinet so I have to lean in and reach round to work on that side, which is obviously the side I find all the problems


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[Mmpie]

Whilst I've got my spindle mount off I thought I'd send a pic with what I think is a big problem with keeping the spindle pointing down straight. You can see the three contact points inside which is the only area actually holding the spindle. I think a two part mount with a slightly undersized bore forced to stretch around the spindle would give far more contact area and a much firmer hold.



In other news a strip down and clean of the X along with a bit of realignment and less torque on each end of the screw has made a massive difference. It now feels far smoother to turn by hand and runs a lot more quietly. So it was a worthwhile few hours spent.


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[dharmic]

Nekminnit Mmpie "My spindle caught fire because the rotor was rubbing the windings after I crushed the case, it were only a little bit!!"

Regarding the ball nut - remember that the Y ballnut is sitting under the leaky gap between the bed planks. So any coolant (be it alcohol, WD-40 or whatever) you happen to be spraying on top is going to drip down and rinse the lube from that nut. Reminds me, I need to give mine a bit of lubricity lovin...

[Mmpie]

Nekminnit Mmpie "My spindle caught fire because the rotor was rubbing the windings after I crushed the case, it were only a little bit!!"

Regarding the ball nut - remember that the Y ballnut is sitting under the leaky gap between the bed planks. So any coolant (be it alcohol, WD-40 or whatever) you happen to be spraying on top is going to drip down and rinse the lube from that nut. Reminds me, I need to give mine a bit of lubricity lovin...

Haha, point taken but I was thinking probably 0.1mm diameter undersized, just enough to force the clamp around the spindle and gain some proper surface contact.

With regards the ball nut, it was the X nut. What do you lube yours with? I don't have a grease gun so I've been using a healthy amount of silicone lube on each rail and screw and running the axis up and down to hopefully work it in.


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[RCaffin]

Hi all

Some thoughts
An oversize mount for the spindle might be fixed with two wraps of aluminium cooking foil, or the side of a Coke can. It would not be the first time. :-)

Stripping ball nuts is not that big a deal. Just as long as you do it over a bucket!


Cheers
Roger

[dharmic]

Sorry, didn't notice properly which one it was Mmpie, I was distracted by the pretty bed and OH MY GOD HAS HE SMASHED IT WITH A CUTTER ALREADY? :

I just give mine a spray with Inox (lanolin spray) every now and then along the length of the screws and rails.

[Mmpie]

I was wondering what you were on about then... that's the liquid line to my mister that looks like a big gouge. I haven't machined anything on the bed yet I'm still farting about trying to get it as square as possible. I've rolled a DTI over most the working area, there are some high spots, the biggest is 0.15mm, but mostly the whole working range is under 0.1 and a good chunk of it within 0.05. I think that'll do me


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[dharmic]

I blame the iphone smaller screen and a lack of glasses at the time, can see it now on the computer but I shed a tear thinking it was a gouge before.

Sounds pretty good, I think the bed's biggest advantage is not so much flatness as stiffness and they're only going to do so much on a lightweight machine.

[Mmpie]

I'm with you there, stiffness is the reason I bought it. It was obvious in theory how big a difference it was going to make but having it in my hands and mounted on the frame, wow. I might actually be able to face mill things down to somewhere around the size I want them to be now


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[extent]

My split mount works fine, yours is just in really bad shape. It's a shame it's integrated with the Z carriage, otherwise they're really easy to find replacements.

[zeeflyboy]

yeah the spindle mount is just extruded so it's never going to be amazing tbh...

This is the spindle mount for the new machine... could probably work out a way to make such a thing work on the X6 if you make a new nut/carriage mount plate... only complication is that the stock plate is integrated with the nut mount, but it would be simple enough to make a new plate that works with an HD16 ball nut mount. (or maybe even just re-drill if lucky). Quality is great and fit is spot on as it's milled from a block rather than extruded.

[Mmpie]

That is exactly what I had in mind zee, albeit I was thinking about trying to make my own slightly smaller version.

Trying to get my X and Y square today, it was absolutely miles out. By drilling out the gantry sides mounting holes to 9mm (8mm for the ones on the side which also hold the cable chain) I got it to 1.14mm across the 355mm span of the X, no amount of forcing it into position will change that. I think the gantry side arms might just be twisting now and the ball screw/rails are holding firm in their position? Any ideas anyone?

Can't believe I never noticed how far it was out before. Measured some bigger panels I cut early days and they are indeed parallelograms rather than squares and rectangles.

Must have been a new guy made my machine. It really is a piece of ****.


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[zeeflyboy]

You need to take it apart and get the beam that spans the carriages square first... I would suggest using a machinist square to check if the front piece is square to the Y-rails, then if that looks good you can use the front plate as your square reference - loosen up the carriage screws and clamp the cross beam to the front plate. Re-tighten the carriage screws (also worth doing the ball nut btw) and then release the clamp.

You can then do the finer adjustment like I showed in a previous post by tapping the gantry with the bolts at the base loosened. Once you've squared up that bottom beam it should be relatively small adjustments required for the gantry - I didn't need to enlarge any holes.

[Mmpie]

Not what I wanted to hear... hoped to avoid doing that, it took ages to get the bed shimmed

Is there plenty of wiggle room in those holes in the lower beam? Or a case of opening them up? I've had it off once before but I can't recall. I do remember it having milled pockets underneath for the carriages and ball nut to sit in. Not sure they will have room to make up over 1mm difference, from memory they were quite a snug fit.


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[zeeflyboy]

Pockets are over sized iirc, I had no issues squaring it up without messing around opening up bolt holes etc.

Biggest issue in squaring it for me was how bendy the gantry is.

[Mmpie]

You need to take it apart and get the beam that spans the carriages square first... I would suggest using a machinist square to check if the front piece is square to the Y-rails, then if that looks good you can use the front plate as your square reference - loosen up the carriage screws and clamp the cross beam to the front plate. Re-tighten the carriage screws (also worth doing the ball nut btw) and then release the clamp.

You can then do the finer adjustment like I showed in a previous post by tapping the gantry with the bolts at the base loosened. Once you've squared up that bottom beam it should be relatively small adjustments required for the gantry - I didn't need to enlarge any holes.

I did as you suggested today, thankfully the y rails are both perfectly square to the front and back plates. Used a bit of tooling plate as a flat surface to space the gap between the back plate and the beam, clamped and rebolted (12nm on every carriage bolt with the torque wrench) easily enough. The beam was skewed considerably over the 300mm length of the tooling plate to start with, around 1.5mm. Results at first looked perfect but after half hour or so it had sprung back out by 0.28mm. Leaving it til morning to see how far it goes. I'm thinking tomorrow to shim the side which is closer to the back plate by the distance of whatever the gap is and repeat? Or possibly even further, as if it does go beyond there's plenty of movement on the side arm connections to correct. Is this what you'd do?

As I mentioned yesterday I think I've reached the max movement at the gantry sides in the current direction it's out to correct it there.



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[zeeflyboy]

I must admit, I don't quite get how it springs back!

Do you perhaps need to enlarge the holes slightly? Did you re-seat the ball screw nut as well as the carriages?

[Mmpie]

I must admit, I don't quite get how it springs back!

Do you perhaps need to enlarge the holes slightly? Did you re-seat the ball screw nut as well as the carriages?

Yes I reseated the lot. Probably could do with opening the holes up a bit, most the bolts still dropped straight through and turned easily, but one or two were rubbing a bit. Although that was true for both sides of the beam and one end stayed put (or at least to within 0.04mm), it was only the side that I was trying to force into place that sprang back.


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[Mmpie]

I managed to get it just about square today. Got the beam sorted, I couldn't get the drill in to the bolts at the edge without removing the gantry, which meant removing the spindle and cable chain (again). Not difficult but I opted to try the lazy route first by shimming out one side and it worked a treat, the other side sprung back 0.28mm again and another half hour later they were still perfectly level so I carried on.

One thing I kicked myself for not thinking of, and would probably recommend for anyone thinking about getting a bed like this, is having a slot milled away from the work area in the X and Y which you can use to indicate off to tram it all in. The dowels are a super tight to-size-need-a-dead-blow-to-get-them-in fit but I found they still left room for error and a flat edge would yield different results on the same axis depending on which row of dowels i pushed it up against. The edge of a slot takes that error away. My bed is going back on the machine soon to be finished so I'll ask him to put some slots in at the same time for whenever it all needs doing again in the future.

As it is, I think I'm close enough to square to be able to start making fixtures and have the holes match those on the bed. I'm no more than 0.1mm out over 300mm in either direction which I think will hopefully be good enough.

Surprised by the positional accuracy, assuming my indicator is accurate, every single move was on point. My 3D printer cost as much as the X6 and it doesn't move as accurately. Although I did measure 0.01mm of backlash.


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