[peteeng]

Thanks will look thru those, integrated gearing is useful - I'm thinking of using unitised 4WD front bearings (generation 3 type) drive using the spline. NSK have design data. But they are "thicker" (75mm) than slew bearings so take up more space. I used 2 on a robot I built many years ago.... or "thin" bearings all up in the air at the moment.. But the answer will fall out soon...Peter

[joeavaerage]

Hi peteeng,
I worked as a mechanic for twenty years and have fitted more of those bearings than I care to think about. They are remarkably good, but I'm less sure
about their applicability to CNC.

The bearings are very strong and tough with superb impact resistance but even when fitted they have clearance, not much, but some. As you know meant bearings meant for high speed service have
clearance such that when they heat up they do not run an interference fit. Highly appropriate for automotive wheel bearings.

CNC bearings however run (commonly) preload so there is no movement. This has consequences on service speed and service life but is deemed an acceptable tradeoff.

Do the bearing manufacturers specify the clearance as assembled? Would such clearances be objectionable in a CNC machine?

Craig

[joeavaerage]

Hi peteeng,
as you know I have designed and am building both a fourth and fifth axis.

The height of the fifth axis is critical. The lower the profile of the fifth axis drive the better, it reduces the moment arm of the trunnion table, and thereby reduces the torque required
to just 'plain bloody hard' from 'just plain ridiculous'. To this end every mm shaved off the height of the fifth axis is 'money in the bank'.

Wheel bearings such as you have suggested are pretty good, 75mm stack height.

The worm servo reducer I'm using has two taper bearings, approx 120mm outside diameter. Clearly the rigidity of the axis is increased as the separartion between the bearings
increases, but only at the expense of the profile height. The servos reducer has an overall height of 130mm, which is not bad, and is delightfully rigid, but I wish I could reduce its
stack height, without any reduction in rigidity.

The bearings that Ardenum mentions are very good in that they tend to be very low profile, 20mm or so, and quite big diameter, 150mm or more. Consequently you can get a rigid axis
at reduced profile height. I think the performance benefit (rigidity/profile height) is so strong that it puts automotive wheel bearings out of contention no matter the price advantage.

Craig

[Mr-MaW]

If you need mineral castings.You can contact me, my email:[email protected]
I'm from China,My company has produced a lot of products, small can reach 100KG, large can do 46 tons.
My English is very average and I don't know how to upload photos. Very reason to share my product with you.

[Mr-MaW]

https://grabcad.com/library/new-mate...ral-castings-1

[peteeng]

Hi - I agree slew bearings are the better choice. I like looking for alternatives especially if they are cheaper. I'm now considering linear motors vs ballscrews as well. Various things are up in the air. Peter

[ardenum2]

Hi - I agree slew bearings are the better choice. I like looking for alternatives especially if they are cheaper. I'm now considering linear motors vs ballscrews as well. Various things are up in the air. Peter

if you go with ironcore linear motors, have to go with roller guides, the pull between the stator and the forcer is massive and ball guides would wear out too fast.

SMJ got ironless too, those don't have this problem but ironless have smaller force density so you have to make them bigger. Personally I had issues in cad to make it work geometrically, on one hand you need more thrust but you don't have the space to accommodate a bigger forcer, then if you make the part bigger to accommodate it, you need more force to move a bigger part, would need some work to find a correct method for using ironless.

[joeavaerage]

Hi,

I'm now considering linear motors vs ballscrews as well. Various things are up in the air. Peter

I've been following Ardenums 'Design Concepts' thread and looking at the linear drives he has listed. They are impressive. They are ideally suited to lightweight highspeed machines
that require modest only thrusts to counteract cutting forces. If you are using large face mills and so on then the cutting forces are high, and that where the mechanical advantage of a ballscrew
comes out on top.

The largest currently manufactured by the company that Ardenum linked to was 550N (cont) and 2600N (max). My 750w servo/ballscrew combination has 2800N(cont) and 8400N(max).
So ballscrews still have an advantage in high thrust required machines.

It really comes down to the style of machine you want to build, small, fast and lightweight or larger, heavier more powerful high torque spindles requiring high thrusts.

Craig

[peteeng]

Hi Craig - some high iron content for you Peter

https://youtu.be/mTQonWqiU4w

https://youtu.be/vhZcjBwiy-0

[peteeng]

welding video for those who want to weld machines- Peter

https://youtu.be/vk_3BBx3Uak

[aarggh]

That welding video was brilliant! Very good!

[ardenum2]

looks like we get pushed the same videos, the heller crash video actually showed what the column geometry is, I thought that heller had a different structure.

[Mr-MaW]

Hi,



I've been following Ardenums 'Design Concepts' thread and looking at the linear drives he has listed. They are impressive. They are ideally suited to lightweight highspeed machines
that require modest only thrusts to counteract cutting forces. If you are using large face mills and so on then the cutting forces are high, and that where the mechanical advantage of a ballscrew
comes out on top.

The largest currently manufactured by the company that Ardenum linked to was 550N (cont) and 2600N (max). My 750w servo/ballscrew combination has 2800N(cont) and 8400N(max).
So ballscrews still have an advantage in high thrust required machines.

It really comes down to the style of machine you want to build, small, fast and lightweight or larger, heavier more powerful high torque spindles requiring high thrusts.

Craig

if you go with ironcore linear motors, have to go with roller guides, the pull between the stator and the forcer is massive and ball guides would wear out too fast.

SMJ got ironless too, those don't have this problem but ironless have smaller force density so you have to make them bigger. Personally I had issues in cad to make it work geometrically, on one hand you need more thrust but you don't have the space to accommodate a bigger forcer, then if you make the part bigger to accommodate it, you need more force to move a bigger part, would need some work to find a correct method for using ironless.

Hi - I agree slew bearings are the better choice. I like looking for alternatives especially if they are cheaper. I'm now considering linear motors vs ballscrews as well. Various things are up in the air. Peter

Linear motors are not used much in China, and I have done 7 cases before. But the customer can't upload the drawings confidentially, so I can only take some photos and share them with everyone.

https://grabcad.com/library/ma-miner...inear-motors-1

[peteeng]

Hi All - I've been away for a week so some projects need warming up. I've had a chance to think thru the casting figures and still disappointed. Especially with the ALOX. That was a solid chunk of the stuff and it only got to 18GPa. I don't understand how the european concrete plus alox got so high an E figure with only a small % of alox added. My conclusion is that the compression test figures are biased. So I need to do a flexure test with some grout and call it quits. I'll use the AL, ALOX and steel I have for fillers in parts as I go. So back to designing Milli.... seems grout is the go. Peter

[joeavaerage]

Hi,
to be honest the procedure you laid out for bonding thread inserts and so on in grout sounds like a real hassle.
I would prefer to bond inset in place at the time of casting. This has been done with epoxy granite, but sounds like its not successful with grout.

Despite the low modulus of epoxy-alox unless the geometries become untenably large would still be my material of choice of the composite types.

It would be instructive to do a cost comparison between epoxy-alox and cast iron. Perceived cost advantages of epoxy-alox may not materialise due to the large volume
of epoxy-alox required to meet a stiffness spec....but who knows.

Craig

[peteeng]

Hi Craig - Secondary bonding is not difficult. The grout has 1MPa bond strength the epoxy 20MPa so I go with that. I also use smaller fittings then say Rampf (they use long bent rods which I'm sure aren't going anywhere) The alox is unmachinable and undrillable. If there's something you want to add you'd have to bond it on. Concrete starts at 30GPa so well ahead of the alox...Everyone has their own roadway to make and walk. This also pushes me back to solid aluminum or laminated metal...Peter

[joeavaerage]

Hi peteeng,
solid aluminum is just too pricy, I'd be better off casting iron.....I think....at least its that close. As you know I priced a big lump of 6061 just a fortnight ago
and it worked out at $20NZD/kg (including GST and shipping) whereas cast iron works out about $10NZD/kg (including GST and shipping) a part of a given size
and stiffness requires about 15kg of iron to 20kg of aluminum. Neither is cheap, and other issues like damping and machinability will likely sway the choice one way or other.

I prefer a welded steel construction over laminated metals, even with stress relief I think it would be cost competitive with respect to laminated metals.

Craig

[Mr-MaW]

Hi peteeng.
：“seems grout is the go”

I've done a lot of similar experiments.I don't agree with you.

I suggest you still choose embedded steel plates, segmented。
This is safe and saves money.

My English is not good, hope you understand what I mean. Take a closer look at my pictures（The fifth photo is key）, maybe he can give you some inspiration.

https://grabcad.com/library/ma-miner...inear-motors-1

[peteeng]

Hello Mr - MaW - We'd like you to share some of your experience. Do you have photos of empty moulds with internal features? Do you machine finish your fittings vs casting them in? Some of the photos look like solid granite? are they all cast? Are they epoxy and what filler material? Thanks Peter

[ardenum2]

I suggest you still choose embedded steel plates, segmented? This is safe and saves money.

One of my designs used pre-machined, segmented plates but I came across research that showed that being a bad idea, the shrinkage during curing, albeit small, caused distortion significant enough to ruin the alignment. Machining after curing appears to be the only way to utilize segmentation.

How much do you guys charge for machining with what precision?