Here's an idea for a cheap bellows style ballscrew cover

[DR-Motion]

This has definitely been a sticky problem for me for a while... how do you keep the swarf out of the ballnuts.

Wood dust does not cause a big problem but when machining aluminum or thermoforming plastics (like Lexan)... the hard bits of swarf get carried along the ballscrews into the ballnuts where it causes binding, lost steps and !@#!-@#up cuts... usually towards the finish of a job.

I've tried using 3" flexible vinyl dryer duct with some success... but it looks ugly, (smells funny too). And we all know how expensive "real" bellows screw covers are...

So I've got an idea of using *really* inexpensive ( can you say $0.33 CAN each) plastic toy 'Slinky' springs covered with little girls tights.

Well I've finally found a bountiful source of the 1 3/16" ID plastic Slinkys at the local PartyPackagers, where they are sold as party favours... now if I can just get my wife to let me have a pair of my little daughter's old tights... I'm ready to try it out.

wish me luck, Gary

[DR-Motion]

Well wifey came through and said I can use whatever I can find... swell ol' girl.

Initial impression is " not bad "... but the stocking material is a bit baggy after stretching... so I've tried painting on a coat of latex. This should tighten up the fabric a touch and give me a waterproof coating ( for repelling coolant ).

Before, I mentioned that the flex ducting looked ugly... well the stretched out, latex coated contraption in front of me... resembles a ribbed condom for a donkey and liquid latex smells real bad.

But let's see how it works after a couple of hours, when the latex has dried and cured a bit.

Come to think of it... do you think a condom would make a usable cover for the springs? Have to buy some... don't use 'em since the operation

[sendkeys]

ahh sounds cool do yo have any pics?

[samualt]

Hmmm, not being married w/children I just can't see myself walking into a store and asking for "Little girl's tights". Egads man! Not going to happen! Bahahaha.

Condoms? I don't think so...(obligatory "Size" joke deleted).

Why don't you like the cool looking black vinyl flex duct? You can get it at Home Depot in assorted sizes. Very "machine" like. Also, you can find accordian style metal flex duct also, it's bright and shiney silver, but I don't know how well that would really work. The metal flex duct isn't made to keep compressing and uncompressing repeatedly.
I think the black vinyl stuff is the best.

[DR-Motion]

So, the latex is cured and the result looks like bellows cover... convolutions and all...but...

The compressibility ratio has decreased substantially... initially... with the uncoated "stocking" material... it was 1 1/2" compressed and would stretch to 16" easily... now with the cured latex coating... the compressed length is 4"... extended length is 15".

This is about the same as the oft recommended "Flexaust"... not suitable for this application because too much travel is lost to the bellows... with the compresion ratio being about 4:1.

The vinyl flex ducting has about a 6:1 compression ratio... available only in white at my local Home Depot. If this were available in a smaller diameter ( and cool looking black ) it would certainly be more usable... but 3" is the smallest I've found.

Commercial bellows have a 10:1 or better compression ratio.

So... if I can find, perhaps, a lycra version of a small girls tights, ( yeah, I know far too much about ladies undergarments... what can I say...I'm an engineer and like to understand everything ) and can live without the water resistant latex coating... this idea may still work out.

I hope some of you guys try a few experiments with this approach and together we can work out some of the kinks.

[DR-Motion]

Here's a comparison of the different styles of bellows so far...

• the plain spring is 1 1/2 " long closed... >24" open

• the uncoated stocking wrapped spring is 2" closed... 16" open

• the latex coated bellows is 3 1/2 " compressed... 13" open

• the 3" diam vinyl coated dryer vent is 2" compressed... 12" open

[samualt]

How long does it have to be?

Just a thought...I bought a rubber boot for my C-band satellite dish actuator. It is accordian style and covers the arm that expands and contracts. It costs $20. That is probably much cheaper than CNC companies sell them. I'm sure there are other sizes available. I've had one outside on my BUD (big ugly dish) for almost 10 years and it's still perfect. So I know they hold up over time. Do you think that might work?

In fact, try:
Daves Web shop - 18" Satellite Boot
Daves Web Shop - 24" Satellite Boot
Accordian Bellows Boot For Satellite - 18, 24, 36, 52 Inch!

Also, always check out manufacturers at Thomas Register. Sometimes they will sell direct to you. But they usually want to sell you a large quantity. One I found that looked promissing is: Mino Rubber.



P.S. Sorry I keep editing this darn thing!

[DR-Motion]

Samualt,

Thanks for the link. I checked it out... $17 for the 18" and $20 for the 24"... cheaper than most suppliers and longer than automotive shock boots. (right now they say they're out of stock)

So... if you need 18" of travel on your router you would need two 18" boots... one to cover each end of the exposed ballscrew. Probably one 18" coulld be cut in half to cover a Z axis screw... so it still adds up to $51 plus shipping for a smaller 18" x 18" x 6" travel router... I'm in Canada so add 7% GST, customs processing and increased shipping... about $125 CAN.

Is it possible for you to (somehow) measure the compressed length of the boot on your BUD... so we can figure out the compression ratio. If it is better than 8:1 we may have a good alternative to commercial bellows.

Thanks again, Gary

[whiteriver]

I've got a 10' screw 1 1/4" dia. Need a bellows for it. Got any ideas for something that long. 4.5' travel on each side.

Donny

[sendkeys]

Originally Posted by samualt How long does it have to be? Just a thought...I bought a rubber boot for my C-band satellite dish actuator. It is accordian style and covers the arm that expands and contracts. It costs $20. That is probably much cheaper than CNC companies sell them

man thats a good price check out mcmaster.com search for "way covers" it comes up with 65.00 bucks for same thing



Thank you doc for the pictures make sure to tell us how they work out

[samualt]

DR-Motion:
Sorry, I'd have to remove the boot from the actuator, which means taking the actuator off. Then I'd have to realign the dish and all. I don't dare...it works at the moment! But I can say it smushes down and expands real good. You might try Fry's or a local satellite store.

I really think, in the end, it would be much cheaper just contacting a manufacturer and buying a 100 feet or so (See my message above). But then you would have all that excess to get rid of. It might make a good business for someone here to sell the stuff. Just an idea.

[hook'em]

I've had similar same thoughts for my linear ways, which might work for your ball screws (and round ways) as well. Mind you these are just thoughts at this point but 'seem like it should work'. Go to a good fabric store ( mainly for selection of material ) and get a yard or so ( or however long you might need ) of medium weight nylon fabric. After determining the circumference of your item to be 'surrounded and sealed', cut a length of the cloth equal to that of the required travel ( plus a little, just 'cuz ) and width about 1/4" to 1/2" wider ( allows for the 'gather' of the fabric ) than the circumference of screw/linear way. Sew, or get it sewn, along the length of the piece, creating a long tubing of fabric. Now you just need to determine how to attach to your machine (tacks, staples cyano, etc...) And you can even 'Scotchgard' it for water repellancy(sp). The gathering of a thin fabric ought to be able to give a really high ratio of compression with little loss of travel. Others have thought on this method? Only downside I can see is for screws, for keeping it out of the nut, but there are probably several ways to do that, and cheaply.
Vance