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View Full Version : Mounts; Motors, bearings etc..



mocha
27-09-2011, 07:07 PM
Has anyone used box section metal (suitably machined) for mounting motors etc? Something like 70 x 70 x 4 for example?

Any problems likely? :question:

Lee Roberts
27-09-2011, 08:52 PM
Not seen anything done like that "yet!".

The best method i've seen/used is a solid bar of ali, on the other side of the block is a pocket to recive the leadscrew fixed end bearings, like the floating end round mounts in the other pic, but you use two bearings back to back for the fixed ends.

.Me

mocha
28-09-2011, 02:57 AM
Thanks Lee, They do look pretty!

had a ferret around and found these, but forgot to note where I pulled it from! Apologies to the owner for the borrowing his pic :redface:

I'm toying with the thought of using something similar, but longer.. to help protect the more delicate parts.:naughty:

4646

edit; picture is from pavlo's excellent build log elsewhere on this site.

Web Goblin
28-09-2011, 09:01 AM
Mocha,
do you mean longer between the motor and the ballscrew so that you have more room for the coupling?

Ian

mocha
28-09-2011, 01:40 PM
Hi Ian
It seemed like a really good idea at 3am this morning! lol, but I think I may have screwed up on the numbers.

The distance between the face of the motor and the face of the bearing for the ballscrew nearest it...
I'm working on the shaft of the NEMA 23 being around 20mm long and the coupling in the region of 34mm.

What I can't seem to calculate is the overall distance when it's all fitted together... I think it's around 60mm but that has some "guess" in it! Does it sound reasonable?

Can anyone point me at the right place to look or take a look at their set up and have a quick check for me please?
thanks!

Web Goblin
28-09-2011, 02:12 PM
You would also need to know how much shaft you have sticking out through the bearing to start with would you not? This would let you know where your coupling would sit. If you are going to make them from box section where are you going to mount the shaft bearing?

Ian

mocha
28-09-2011, 03:25 PM
You would also need to know how much shaft you have sticking out through the bearing to start with would you not?Yes, spot on! Which is probably why I'm having trouble figuring it out! :redface:

I'm looking at slicing something like an 80mm length of 70 x 70 x 4 and mounting the motor on one of the "x4" side walls, with the bearing on the opposite side. So, the ID (62mm) of the box section is the space available to fit the coupling and anything else etc.

I'm trying to find out if 70mm square is going to give me enough room inside, or if I need to go to 80mm, or more.. But I want to use the smallest size that is practical.

Web Goblin
28-09-2011, 06:19 PM
Can you fit the coupling to the motor shaft then fit the ballscrew shaft into the coupling. If you fit them loosely you will have a bit of play to guage what length you need on the ballscrew shaft.
The photo below will give you a rough idea of the distance of the motor mount.
4647

Are you using a bought bearing mount for the ballscrew or are you going to make one?

Ian

mocha
28-09-2011, 07:10 PM
Thanks Ian, Thats a big help!


Can you fit the coupling to the motor shaft then fit the ballscrew shaft into the coupling.That's the plan, (theroretical plan!) :)
Mount the motor first, align that with the bearing at the far end, then the coupling loose, bearing, ballscrew. Then make another plan when that doesn't work! lol


Are you using a bought bearing mount for the ballscrew or are you going to make one?


Yes to both parts.. The other side of the steel "box" will be what I bolt the bearing mount to as it were...

Web Goblin
28-09-2011, 09:09 PM
No problem. Post some pictures so we can see what you get done.

Ian

mocha
28-09-2011, 10:16 PM
Thanks Ian, my apologies for not having anything I can use to illustrate this and the other questions I've posed. I'm working on it! I'll certainly be taking lots in the build!

From what I've seen from Ian's picture and the schematics on line for motor mounts, it looks like it will be ok. Of course until I get the parts and the steel in my hand I can't know for sure.

JAZZCNC
28-09-2011, 11:46 PM
Don't think you'll need as much room inside the box section as you think because you only really need say approx 10-12mm more than the length of the coupling because the shafts of both motor and screw go inside the coupling. So the only extra distance required is the thickness of the coupling dampner (If using split type coupling) plus a bit of wiggle room.

Obviously will depend on how you mount the fixed end of the screw IE:bought BK/BF blocks or DIY etc and how much of the screw you let stick thru the steel.

Edit: Drawing or rough sketch of intended frame and screw mounting would help. ;)

mocha
29-09-2011, 12:15 AM
Thanks Jazz, I think it should all fit in.. I'll just do a complete redesign if it doesn't! (so far I'm only wasting paper, not metal!)

Didn't find a bearing to drop in here too but here's a pic! I'm not convinced about the scale being correct.. but it should illustrate what I mean
4648

Lee Roberts
29-09-2011, 12:27 AM
Mocha,

When the mounts got made for my machine (the ones in the pic above) they were designed specifically for the said coupling, months later when I was ready to order my parts the coupling had gone past “end of line” and I couldn’t buy them anymore. It was a real time waster trying to locate a coupling that was the right OD and overall length, so if I was you I would order your couplings as soon as you can.

I’m not sure if you’re buying pre machined ball screws or turning them down yourself, ether way you should be able to order/machine them with the final blank longer then you need it, then once you come to assembly you could trim them to best fit. May save you some time now and allow you to move on.

I don’t know if you can use it or not but attached is a drawing you may find useful while you’re working things out, if you’re like me and do everything “pen to paper” then you could also print this out, finalize it, then use it for machining purpose.

.Me

JAZZCNC
29-09-2011, 12:56 AM
Thanks Jazz, I think it should all fit in.. I'll just do a complete redesign if it doesn't! (so far I'm only wasting paper, not metal!)

Didn't find a bearing to drop in here too but here's a pic! I'm not convinced about the scale being correct.. but it should illustrate what I mean
4648

Ye I get the picture but I already did.!

To me it seems your not accounting enough for the fixed screw bearing mount and how it will mate with your proposed motor mounts, this will be the main determaning factor to length required.
Also like Lee skirts upon the other down side to this way of doing things is the lack of easy adjustabilty if things or needs change.!

mocha
29-09-2011, 01:20 AM
so if I was you I would order your couplings as soon as you can.




Yep, that's the plan... get all the hardware, check it against the estimates I've been using and then tweak the metal work to suit in the design and then order the metal and start the build...


Iím not sure if youíre buying pre machined ball screws or turning them down yourself, Pre machined.

The design is going with me to the shops so I should be able to see if anything is going to cause me any problems before I part with any cash. I'm sure there will still be some surprises.
:naughty:

Jonathan
29-09-2011, 01:25 AM
As Lee has suggested I got the end portion (F) of my screws machined 25mm long to leave plenty of room for pulleys. You could do the same here if necessary.

If you do something a similar size to what I made here it should be fine...if not luke is in trouble! I don't remember spending more than a few seconds deciding the length.

http://www.mycncuk.com/forums/showthread.php/3621-Nema-23-motor-mounts

I can make you some if you like but it would cost more than a piece of box section and you'd almost certainly be much better off investing that money in buying pulleys as I keep saying! So much more versatile...

This may help, if you've not already found equivalent:

http://www.file-vault.us/pdfs/ball_screw_documentation.pdf

mocha
29-09-2011, 03:29 AM
lol, Pulleys will be on the mark 2 version, along with flow alarms, massage chair and coffee maker!! lol

That Pdf is one I haven't seen, most useful! Thanks

luke11cnc
29-09-2011, 07:19 AM
why box ?

why not angle or flat plate ?? then you are clear for wiggling and no mounting trouble of the ballscrew

just a thought

James

mocha
29-09-2011, 11:20 AM
why box ?

why not angle or flat plate ?? then you are clear for wiggling and no mounting trouble of the ballscrew

just a thought

James

Hi James, (I've enjoyed your build log) Why box? Well, my thinking is that in the right circumstances box is stronger than plate or angle, especially if you are expecting the loading to be in multiple directions.

Square section is very efficient shape for this multiple-axis loading as it has uniform geometric and thus uniform strength characteristics along two or more cross-sectional axes.

Having said that, a hexagonal profile made from welded triangular shapes would no doubt be even better :lol: but "£ for lb", box is good value.

This view may well be modified after practical testing! :naughty: