I want to DIY.. some questions please!

I know water is great for cutting thick materials; a friend of my Dad works (oops, worked) at an industrial kitchen makers, and they cut 100mm work tops. That said, I've seen some slightly rough edges on water-cut stainless plate I once got done (free of charge admittedly). It almost looked like the contour was plunge cut without enough swathe.

I also just want to say thank you to the people who have contributed to my thread! I keep getting told I need to use stronger, faster, better parts but at least I am also avoiding some big mistakes. I think perhaps part of the problem for me is that I got a CNC3040 and figured it is easy enough to scale up, but most of the things they have done in that machine don't work on a bigger scale. I think I also have a loose wallet as I don't have a set budget and I think of this machine as a business investment since I design and make speakers.

Just curious, how many of you like good stereos? Not to be rude, but most of the machinists I have met don't seem to worry about wearing hearing protection even though they work in very noisy places. Please protect your hearing, it's not girly!

I've just had a quick look and actually steel box section is more pricey than the alu profile, though not including connectors. I was going to buy from this place http://www.valuframe.co.uk/Valuframe...t 27-02-12.pdf

Even more interesting, it is cheaper to cover the entire bed with 30x30mm profile than 16x160mm.

P.S. Would a mod please move this to the DIY section ;)

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Originally Posted by Tenson

I've just had a quick look and actually steel box section is more pricey than the alu profile,

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Rubbish it's no where near the price of profile and I'm not guessing at this as I buy steel all the time. I pay Approx £25 for 50x50x7.5mtr lengths of 3mm box section. Just payed £34 for 80x40x7.5mtr. See your local steel merchant and they may well even cut it for you for a small few.

Water jetting leaves a edge slightly angled so it's no good for pieces that need 90deg joining to others like bearing blocks to gantry sides or the Z axis etc.

Sorry I don't know my local steel merchants. I looked on Google and the first on-line retailer I found sells 30x30mm mild steel box section at £8.30/meter, and the next sells 30x30mm stainless box at £18/meter.

Alu 30x30mm profile is £6.55/meter.

Looking a bit deeper I foun mild steel for £5/meter. Is mild steel suitable or should I be looking for 'engineering steel'?

Thanks for the advice on water-jet. A shame, as most precision engineers seem uninterested in small one off jobs. I worked shortly with a local one who did a bad job and our relationship went bad when I expected them to make it good. I've emailed a few online guys and they tend not to respond for small jobs.

Yes mild steel is what you want and you will find it a lot cheaper if look for a steel stockist. 7.5mtr is standard length for steel section and it's often sold and priced per length.

Post what you want making on here I'm sure someone will help you out, unfortunatly I can't offer as I'm commited to other people and only so many hours in a day.

Digressing just a little.

As steel is more suitable and lower cost than ali profile why don't we see more low end commercial machines made from it? The only ones I know of are these sexy beasts http://translate.googleusercontent.c...Zrb3V7vkmqihcw , looks more like pressed thin sheet than welded box section :( So, is it tooling costs? Assembly and finishing costs? Weight? The price of paint? Or have we all become victims of the profile looks sexy fashion cult?

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Originally Posted by Tenson

Thanks Jonathan. I saw you used steel box section for the frame of your machine. Trouble is I can't weld! I only have a gas bottle torch for doing a bit of plumbing, and I have little experience with it.

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That frame was the first welding I had done. Practices on some scrap first that's all...

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Originally Posted by ecat

Digressing just a little.

As steel is more suitable and lower cost than ali profile why don't we see more low end commercial machines made from it? ... Assembly and finishing costs? Weight? The price of paint? Or have we all become victims of the profile looks sexy fashion cult?

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I reckon it's because it looks fancy and most 'hobby' machine manufacturers are either too lazy or don't know better. They'll probably argue it saves a lot on labour. I got round the price of paint by not painting it - machine not art.

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Originally Posted by ecat

:( So, is it tooling costs? Assembly and finishing costs? Weight? The price of paint? Or have we all become victims of the profile looks sexy fashion cult?

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No it's because lots are into bling and posing. . . . Paint aint expensive just messy.!!!

I'm always suspicious of machines with lots of fat looking plastic covers.!!. . . . Always makes me wonder what there hiding.????

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Originally Posted by Tenson

Just curious, how many of you like good stereos? Not to be rude, but most of the machinists I have met don't seem to worry about wearing hearing protection even though they work in very noisy places. Please protect your hearing, it's not girly!

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I quite like audio ;)

I knew you'd get the bug. The 3020 looks like good training wheels but I'd ignore everything about its construction if your wanting to making a decent machine. They're notoriously shite in general and the principles used are barely suited to its own small frame let alone once scaled up.

I think I already mentioned it to you over on DIYA but I bought a 'commercial' 4x4ft machine from a supplier here in the UK. Its been eventful and to be honest I wish I'd built my own now. Its really not that difficult with that right tools and a helping hand from folks on here. Of course I wanted to be up and running quickly so thought an off the shelf solution would be best. That was December and 4 months on I still haven't cut a single useful part yet. Annoying but around £5.5k lighter in pocket I'm almost ready to go. I hate to think what that money would have bought if I'd DIY'd.

Good luck with the machine. If you listen to the folks like Jazz then you won't go far wrong.

PS. Since your building this can't you go with a larger bed? I'd say 4x4ft is the minimum for cabinet work otherwise you'll be swapping sheets in and out as often as you change undies. 4x4 also has the advantage of taking a standard sheet without cutting. I would have liked an 8x4ft really but that would take up most of the workshop. Interestingly you might want to consider wall mounting or making a vertical frame to get the bed size up and the floor space back.

Don't forget about your choice of spindle too. I know its early days and you haven't even drawn up plans for the construction yet but I'd recommending avoiding regular routers, even the larger one's. I went with one of these types and quickly swapped to a 3hp water cooler spindle with vfd. These are around £250-350(inc del) from china via ebay and can vary in quality depending on the seller. Check out linearmotion_2008, he seems to sell the better models. If you prefer to buy from the UK then CNC4you have the same model for £369

http://www.cnc4you.co.uk/index.php?r...product_id=147

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Originally Posted by ecat

Digressing just a little.

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Moslty fabrication costs/equipment.
Alu profile just needs cut, bolted together with suitable brackets, and with a bit care you have a pretty accurate machine.
Steel needs cut (more expensive/time consuming to do accurately than cutting alu), joined, be that via welding or drilling and brackets, which both take longer than doing similar with alu profile. If welded, you then have to deal with distortion.
Plus alu profile is also more accurate out the box so to speak, as extrusions are usually accurate within a thou, unlike steel which can vary quite a bit.

I've used alu profile for frames before, and cost wise it is more expensive, but takes less time to assemble, and for what I used it for, resulted in a lighter stiffer frame than using steel. Plus it looks cool ;)

Hi Ant,

I knew you got a CNC machine but only after reading about it on here as I haven't been reading DIYA much lately.When I read about your machine I thought 'oh, you too!'.

I'd love to go for a bigger machine but I just can't find the space. I moved a couple months ago and have a smaller workspace. But I did get a wife and a bigger listening room in exchange. I'm going for 2ftx4ft as sheets commonly come in that size, and also they fit in my car so I can collect myself. I thought about vertical mounting too, but I'm worried about the practicality of clamping work pieces in place, and I also want to make a dust/sound cover.

I got the spindle today actually :) I was unsure if I should get the 1.5Kw or 2.2Kw motor, but decided to go for 2.2Kw firstly because it was available from CNC4U at the same price as Chinese sellers, and also because I don't want to limit my cutting speed for the sake of £100.

So what are you doing for a water-pump, and does it need a radiator to cool the water? If so, I thought I might run the water through one of the alu extrusions.

By the way, Mr. ZappAutomation, please don't use the shredded paper for packing my floor is all messy now. At least get a paper shredder that makes long lines of it rather than flakes. :) Other than that thank very much for your great and fast service!

Fudge me, that's a big motor!! I hope my Z-axis can cope with 16mm rails and ballscrew.
http://i608.photobucket.com/albums/t...k/BigMotor.jpg

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Originally Posted by Shinobiwan

The 3020...notoriously shite in general and the principles used are barely suited to its own small frame

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They are notorious for that, but it works superbly!!

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Originally Posted by Tenson

I got the spindle today actually :) I was unsure if I should get the 1.5Kw or 2.2Kw motor, but decided to go for 2.2Kw firstly because it was available from CNC4U at the same price as Chinese sellers, and also because I don't want to limit my cutting speed for the sake of £100.

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You made the right choice, but for the wrong reason! The main reason to get the 2.2KW spindle is that it takes ER20 collets which hold up to 13mm (i.e. 1/2") cutters, whereas the 1.5KW spindles are limited to ER11 which is only 7mm. I'm surprised CNC4YOU was cheaper than china - did that include the VFD?

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Originally Posted by Tenson

So what are you doing for a water-pump, and does it need a radiator to cool the water? If so, I thought I might run the water through one of the alu extrusions.

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Just get a generic brushless submersible pump, something like this one:

http://www.ebay.co.uk/itm/Water-Pump...ht_2757wt_1037

(seach around - you'll find cheaper ones)

No need for a radiator since if you have a decent volume of water the natural heat conduction to the atmosphere is sufficient. Just find a good size (20L ish) tank and ideally use de-ionised water with antifreeze.

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Originally Posted by Tenson

By the way, Mr. ZappAutomation, please don't....

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What did you get from Zapp?

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Originally Posted by Tenson

Fudge me, that's a big motor!! I hope my Z-axis can cope with 16mm rails and ballscrew.

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It will if done right - do post the drawing first.

Mine has an ER16 clamping nut. I guess I can't use ER20 as the part the collet goes into (spindle shaft?) will be too small?

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Originally Posted by Tenson

Mine has an ER16 clamping nut. I guess I can't use ER20 as the part the collet goes into (spindle shaft?) will be too small?

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Yes the dimensions of the taper for ER20 are completely different so you'll have to use ER16, so upto 10mm:

http://www.ebay.co.uk/itm/FULL-ER16-...item231b785020

Has anyone done this before?

Linear bearing - £6

http://i608.photobucket.com/albums/t...earBearing.jpg


Bearing taken out, and Ballnut put in:

http://i608.photobucket.com/albums/t...NutBracket.jpg


http://i608.photobucket.com/albums/t...tBracket-1.jpg


Now it's not quite a perfect fit because the top of the nut is slightly ~0.5mm) taller than the top of the bracket housing. So one could either fit a thin sheet on top of the bracket, or trim the top off the nut if you can figure out how to do it. Or just account for it on the plate you are mounting.

Anyway, seems better than paying ~£35 for a ballnut housing? Isn't it?

Hi Tenson,

I see your cnc endeavours are coming along nicely!

I have toyed about a little with ball nut mounts myself using the "off the shelf" components, what I found with using the SMA units is the mounting holes for the Nut. If memory serves me right only two of the fixing holes could be used.

Your drive nut is properly one of if not the most critical part of an axis, personally I wouldn’t be happy with such a fixing, however I have seen machine’s up and running and only using the same two fixing points. I am guilty of being a perfectionist though with a little OCD topping to add to the flavour :)

In the end I decided to design my own drive nut mounts, I wasn’t able to machine them myself but another member on the forum was able to and did a great job for me. The price wasn’t a lot however they did stress that clamping was an issue due to the shape/design.

I have attached the finished picks for you to view, if you want the part details I am happy to post them for you.

.Me

Thanks Lee! Four of the six screw holes can be used, so I thought that is enough. I also considered putting a bit of lock-tight around the nut before inserting it. Not too much, since it should come out again with a whack.

P.S. your mounts look like a super-charger!

Quote:

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Originally Posted by Tenson

Thanks Lee! Four of the six screw holes can be used, so I thought that is enough. I also considered putting a bit of lock-tight around the nut before inserting it. Not too much, since it should come out again with a whack.

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I wouldn't put lock-tight round it. You'll need a bit of room for adjustment when you first fix everything together to ensure the nut can be set precisely concentric to the screw.

I've made a few ballnut mounts for myself and these for people on the forum:
Attachment 5581Attachment 5582Attachment 5583Attachment 5584Attachment 5585\

I hope you're not intending to use those unsupported rails on this machine?

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Originally Posted by Tenson

Hi Ant,

I knew you got a CNC machine but only after reading about it on here as I haven't been reading DIYA much lately.When I read about your machine I thought 'oh, you too!'.

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Aye. I'd been looking longingly(as you do) at them for years but things fell into place the middle of last year and I suddenly found myself with a decent size workshop.

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But I did get a wife and a bigger listening room in exchange.

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Simon, it seems like we're in the twilight zone here. We've both bought a CNC, we build speakers and now we've both saddled ourselves with partners who moan about all the MDF dust we walk into the house or that the dinning room isn't an assembly area.

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I'm going for 2ftx4ft as sheets commonly come in that size, and also they fit in my car so I can collect myself. I thought about vertical mounting too, but I'm worried about the practicality of clamping work pieces in place, and I also want to make a dust/sound cover.

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You can build in a cover and have it vertical. Its more work in the design stage but can make for a really neat machine when space is an issue(when isn't it?). If I'd DIY'd I'd have likely done something very similar to this:

http://www.denfordata.com/pdfs/produ...cal-router.pdf

Very tidy package that would easily allow for a 4x4ft bed. All the crap falling into a pan at the bottom rather than all over the workpiece or into you rails etc. is another plus. Really there's not many downsides aside from increased build complexity and more awkward clamping. You could add vacuum bed later to solve the latter.

If your spending the sort of money I think you are then its worth considering.

Quote:

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I got the spindle today actually :) I was unsure if I should get the 1.5Kw or 2.2Kw motor, but decided to go for 2.2Kw firstly because it was available from CNC4U at the same price as Chinese sellers, and also because I don't want to limit my cutting speed for the sake of £100.

---

Good stuff but the ER16 collet might be a bit limiting. Can I ask why you choose that over the ER20? I looked around long and hard at cutters and most of the extra long series cutter are 12mm shank. These cutters allow thick(ie. 100mm) baffles to be safely machined.

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So what are you doing for a water-pump, and does it need a radiator to cool the water? If so, I thought I might run the water through one of the alu extrusions.

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Absolutely no need for a radiator/fan setup in this country, maybe the Sahara. I'm going for simple so that means a bucket with about 25ltrs of water, a dash of anti freeze and a regular submersible pump in the bottom. That's all you need and anything else is additional expense and not warranted. The only thing you need to watch out for is the pump head height capacity something like 3m is fine.

Quote:

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By the way, Mr. ZappAutomation, please don't use the shredded paper for packing my floor is all messy now. At least get a paper shredder that makes long lines of it rather than flakes. :) Other than that thank very much for your great and fast service!

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Yep can't say I'm a fan either. No matter how carefully you try to remove things from the box that stuff still goes everywhere. I'm sure Gary is laughing whilst he's packing these things.

Quote:

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Originally Posted by Tenson

Now it's not quite a perfect fit because the top of the nut is slightly ~0.5mm) taller than the top of the bracket housing. So one could either fit a thin sheet on top of the bracket, or trim the top off the nut if you can figure out how to do it.

---

You could use shimming steel to do this, a bench grinder can also be used to take the nut down a little.

Quote:

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Originally Posted by Tenson

Thanks Lee! Four of the six screw holes can be used, so I thought that is enough. I also considered putting a bit of lock-tight around the nut before inserting it.

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Humm are you sure?, the top two holes look as though they would pass through the mounting holes for the SMA unit, the middle two dont look like they would have much material for a thread because of the bore in the unit?

As Jonathan said you may need to jig the nut about to get it concentric to the screw, all sounds a little to "make do" for me when a little creativity is all that is needed. Our right honorable gentleman Jonathan could properly fix you up with some custom mounts for a reasonable price.

Somthing to think about also is machine maintenance in the future, maybe unlikly but what if a ball gets jammed or stuck in the nut and you need to take it apart....smash it out with a hammer ?!?!? Obserred, how dare you :tongue:

:joker:

.Me

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Originally Posted by Jonathan

I wouldn't put lock-tight round it. You'll need a bit of room for adjustment when you first fix everything together to ensure the nut can be set precisely concentric to the screw.

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Do the mounts usually have much room to move? This fits absolutely perfectly and tightly so no room to move at all, although it could rotate a little.

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I've made a few ballnut mounts for myself and these for people on the forum:

*Pictures*

I hope you're not intending to use those unsupported rails on this machine?

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Very nice mounts. If I use your super rotating ballnut systems on the Y and X then I only need a nut-bracket for the Z right?

The unsupported rails are for the 25cm Z axis.

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Originally Posted by Shinobiwan

Simon, it seems like we're in the twilight zone here. We've both bought a CNC, we build speakers and now we've both saddled ourselves with partners who moan about all the MDF dust we walk into the house or that the dinning room isn't an assembly area.

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Eunji doesn't mind too much, she just wants me to sell lots! She is very understanding about hi-fi stuff too since she works in music. Actually she is very helpful in blind testing stuff since she did 3 years of critical listening training.

Just for fun, a quick photo of the table in the living room right now, lol.

http://i608.photobucket.com/albums/t...LivingRoom.jpg

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You can build in a cover and have it vertical. Its more work in the design stage but can make for a really neat machine when space is an issue(when isn't it?). If I'd DIY'd I'd have likely done something very similar to this:

http://www.denfordata.com/pdfs/produ...cal-router.pdf

Very tidy package that would easily allow for a 4x4ft bed. All the crap falling into a pan at the bottom rather than all over the workpiece or into you rails etc. is another plus. Really there's not many downsides aside from increased build complexity and more awkward clamping. You could add vacuum bed later to solve the latter.

If your spending the sort of money I think you are then its worth considering.

---

Ooooh that is nice! I don't think it will save alot of space for me though because the gantry height, plus z-axis motor and machine frame end up about 65cm, and the width is only about 85cm. I think I'd prefer easy clamping. That said, I could easily turn the machine on it's side if I want.

Quote:

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Good stuff but the ER16 collet might be a bit limiting. Can I ask why you choose that over the ER20? I looked around long and hard at cutters and most of the extra long series cutter are 12mm shank. These cutters allow thick(ie. 100mm) baffles to be safely machined.

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All the router bits I have are 6mm shank, and I have a fair bit of money in that. I also thought it was possible to just buy an ER20 collet... nevermind!

So are you doing custom built speakers professionally now?

I still need to have a go with Acourate!

Tenson that looks like my front room, my wife reckons it won't be long till I've got it looking like delboys flat in only fools and horses. Minus the inflatable dolls of course ;-)

I wonder if we should start a thread on "How diverse are the things that we make?" That could be an eye opener! Got a few good ideas of my own.

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Originally Posted by Tenson

Just for fun, a quick photo of the table in the living room right now, lol.

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Looks familiar :)

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Ooooh that is nice! I don't think it will save alot of space for me though because the gantry height, plus z-axis motor and machine frame end up about 65cm, and the width is only about 85cm. I think I'd prefer easy clamping. That said, I could easily turn the machine on it's side if I want.

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The gantry is offset by you being able to go upto 4x4ft. Generally a 4x4 will stick out at least 1400mm from whatever wall its pushed up against. Vertical would be less than half that.

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All the router bits I have are 6mm shank, and I have a fair bit of money in that. I also thought it was possible to just buy an ER20 collet... nevermind!

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When you say router bits do you mean the regular 1/4" collet types with straight flutes? They'll work fine but you might want to consider getting yourself some end mills. These are generally better quality, plunge much better, remove material better and last longer.

Use up what you've got and once they're starting to dull get yourself something like these:

http://www.ebay.co.uk/itm/1405488812...ht_3253wt_1163

They're really cheap for what they are and were recommended to me by folks like Jonathan and Jazz who've used them to cut aluminium. They'll eat MDF and ply for breakfast and last ages.

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So are you doing custom built speakers professionally now?

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Pretty much but nothing official. Its mostly word of mouth but I hope to bring a small lineup of speakers eventually. There's a lot of planning involved before that can happen not to mention prototypes, listening tests, crossover tuning, auditioning. I had hoped to have a floor standing speaker available before the end of this year but I've recently taken on a custom project for Arthur(Ackcheng on DIYA) over in Hong Kong and its scale is very ambitious. A total of 8x 10" drivers, 4x 8", 4x 5" and a pair of ribbons all housed in 2100mm x 320mm x 750mm cabinets. Its the audio equivalent of the Deathstar.

And last year I designed(not built) a huge OB dipole line array with seperate ripole sub stacks for a guy in New York. 8x 21", 18x 8", 16x BG Neo10's and lots of Mundorf AMT's. I believe he's now taken the CAD files to various machine shops in the US and is in the process of having them manufactured. Materials are alu and acrylic and the project is about the cost of a new mid range Benz.

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Originally Posted by Tenson

The unsupported rails are for the 25cm Z axis.

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CAN NOT STRESS ENOUGH. . . . . .DONT DO IT. . . . ABSOLUTLY DONT DO IT.

You will regret using unsupported rail and even more so on the Z Axis.!!

Quote:

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Originally Posted by JAZZCNC

CAN NOT STRESS ENOUGH. . . . . .DONT DO IT. . . . ABSOLUTLY DONT DO IT.

You will regret using unsupported rail and even more so on the Z Axis.!!

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Simon, I'd really listen to this advice. I know you think you know what your letting yourself into here but honestly, you have no idea. I mean that in the nicest way possible.

I had to have my Z-axis rebuilt because it was using unsupported rails and was shit. About +/-1mm of flex at the bit and that means you'll get a crap finish even in MDF with anything like a decent DOC and feedrate. Your parts will be undersized, oversized and generally a mess. And you can forget it if your thinking of aluminium. Plus your using a heavy spindle with heavy 16mm alu plate. That's a bunch of weight right there before you've even got to the cutting forces.

Do your self a massive favour, ditch it and go with supported round rail. It'll add nothing to build complexity and hardly anything to the price. Cannot stress enough how shit round rail is, it should be banned on anything calling itself a decent CNC router.

Listen to the knowledgeable folks on here and save yourself from a world of pain, you'll get you a much better finish, more accurate parts and will let you move up to harder materials like alu, Corian and so on.

I'm trying to stress this because I fell in to the same trap your about to and its costs me a lot of money to put it right. Do it right the first time.

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Originally Posted by Lee Roberts

You could use shimming steel to do this, a bench grinder can also be used to take the nut down a little.

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I'd be very wary of grinding a ballnut since any dust from grinding in the ballnut is a recipy for disaster. You could try and cover it up but I don't think its worthe the risk.

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Originally Posted by Jazz

CAN NOT STRESS ENOUGH. . . . . .DONT DO IT. . . . ABSOLUTLY DONT DO IT.

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+1

When I said earlier that 16mm rail would be fine 'if done right' I was assuming supported rails. You'll be much better off getting some SBR20 (supported) rails.

The 6mm single flute cutters are brilliant...get lots! Although they are much better than most at plunging you shouldn't need to plunge - use spiral toolpaths or ramping. Router cutters with a 1/2Q shank are much much stronger than the 1/4" ones, so well worth the extra.

Quote:

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Originally Posted by Tenson

Very nice mounts. If I use your super rotating ballnut systems on the Y and X then I only need a nut-bracket for the Z right?

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Yes... but how long is the Y-axis screw going to be? It's a bit sledgehammer to crack a nut using a rotating nut on the gantry, althought it would work well.

Don't under estimate the job the ballnut mount does.!!

Ballscrew mounts, alignment and nut holding are crucial to a good working machine, if any one is off the slightest amount the result is friction.
This friction as to be overcome by the motors, the motors lose torque as the speed increase. Has the speed increase's friction heats things up which inturn creates more friction sapping more power end result stalling motors or missed steps at best.!!. . . . Worse case things lock and prematurely wear away often quickly in tight ballnut's case and die suddenly.

Saving a fiver can cost hundred.!!.. . . Is it really worth it.????

Quote:

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Originally Posted by Shinobiwan

I had to have my Z-axis rebuilt because it was using unsupported rails and was shit. About +/-1mm of flex at the bit

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I find that quite surprising. I rather thought with the very short length and least weight of any axis, the Z would be okay running unsupported. If it really is that bad I'll get some supported rails. Building a Z-axis assembly to have opposing supported rails seem quite tricky though at first thought. Any tips / pictures?

Anyone want to buy 2x 30cm unsupported rails? ;)

Quote:

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Originally Posted by Tenson

I find that quite surprising. I rather thought with the very short length and least weight of any axis, the Z would be okay running unsupported. If it really is that bad I'll get some supported rails.

Anyone want to buy 2x 30cm unsupported rails? ;)

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Ask Jazz about it, he came around to help me out with the machine and saw it. Its the cutting forces that will really show this up but even pulling back and forth on the z axis by hand will tell you how sturdy it is. The more rigid the design, the better the finish and accuracy you'll get.

If you do it right you'll be cutting MDF with very tight tolerances and even aluminium won't be an issue. Just keep asking loads of questions on here and tell folks about every design decision your making as they'll be able to advise if its a good one or a bad one. Building a good machine doesn't mean its more expensive but building a bad one will cost you to fix it.

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Originally Posted by Shinobiwan

Building a good machine doesn't mean its more expensive.

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Bloody seems like it! :tongue:

Quote:

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Originally Posted by Tenson

Bloody seems like it! :tongue:

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lol, ok well not that much more expensive. You'll have a really nice machine if you do it right and it'll last you years.

Is there a big advantage in build quality terms using profile rails for the Z-Axis rather than supported round rail?

I must admit I can't see an easy way to use supported rail so that the bearings oppose each other on the Z axis. I have seen Jazz used HiWin rails facing out, not opposing, so is this only okay with profile rail?

Quote:

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Originally Posted by Tenson

Is there a big advantage in build quality terms using profile rails for the Z-Axis rather than supported round rail?

I must admit I can't see an easy way to use supported rail so that the bearings oppose each other on the Z axis. I have seen Jazz used HiWin rails facing out, not opposing, so is this only okay with profile rail?

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The advantage of profiled rails are much tighter bearing tolerences with a smooth action helping to reduce resonance and flex they also last much longer, esp in harsh conditions like a Z axis where it's constantly in the firing line and open to crap from the cutter. They don't really add much more strength than supported round rail if any.!

You can use supported rails just the same as profiled like you have seen me do. Absolutely no difference other than they stick off the Z axis rear plate (which you would call running across X axis, me Y axis) slightly more due to height of supported rail.

The main advantage with profile rails is that they are preloaded. This means there is negative clearance between the bearings and the rail, so there will not be any play. It also makes any deflection linear and crucially, with rails with 4 rows of balls which are the type you should get, the load ratings are equal in all directions. Conversely supported round rails have little if any preload and the load rating varies significantly depending on the direction the force is applied since the open side of the bearing clearly offers less support. Ideally we would mount supported rails so they 'oppose each other' on Z, however as you say it's quite difficult to accomplish rigidly without a somewhat radical gantry design. Hence most people mount them both the same way round. If I measure the deflection when a force is applied to my Z-axis parallel to X the reading varies quite a bit, due to the uneven load rating.
However this is of course all relative - compared to unsupported rails the deflection is tiny. You wont regret using supported or profile rails on the Z-axis - ultimately depends on what you can afford.

Thanks I rather thought it might be the case, though good to know open bearings on supported round rail are not a no-no. The HiWin rail is okay priced but the bearings seem a bit steep. How about other brands? RS Components sell one called IGUS DryLin T which for 300mm is quite affordable (GBP14 rail, GBP16 Carriage, I can't do the pound sign on this Korean computer) but doesn't offer longer rails. There are many other brands too.

Hi Guys,

I got some SBR rail from CNC-4-U with open bearings. The bearings look like they are normal ones that have been cut open. Is this normal? They also have little grub screws in the top that hold the bearing in and when tightened up they close the bearing up on the rail a little. The motion was a little jerky at first but after a quick sanding of the cut endge of the bearing thye are smooth now. They seem a bit home made. Should I be sending them back or are they okay?

http://i608.photobucket.com/albums/t...0120416082.jpg

http://i608.photobucket.com/albums/t...0120416080.jpg

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Originally Posted by Tenson

They seem a bit home made. Should I be sending them back or are they okay?

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That's perfectly normal. Same as you'd get from linearmotionbearings2008 on eBay. I ordered some recently from china (not for myself I hasten to add!) and they came in less than a week. The're essentially the same except the grubscrew is now on the side of the bearings, not on the base.

Thanks for that. I like CNC-4-U. They are UK based so I'm supporting local trade and the prices are not too far from the eBay ones. I got the 2.2KW VFD spindle and 4Nm steppers from them too.

Jonathan, can you link me to some more pictures of your machine? I saw it in the video for the single flute cutters but I'd like to see more detail.