round rails

[TrickyCNC]

I just wouldn't like someone to be put off, because all of a sudden it got too expensive !.MDF is 'almost' free LOL and a great way to learn. Major components can be re-used later if neccesary

[JAZZCNC]

I just wouldn't like someone to be put off, because all of a sudden it got too expensive !.MDF is 'almost' free LOL and a great way to learn. Major components can be re-used later if neccesary

Yep I get your point.! . . . Respectfully thou I don't agree.!!. . . And here's why.?

Steel box section is relatively cheap and 50mmx3mmx7.5mtr lengths compares roughly around the same price has 25mm 8x4 Mdf sheet, I pay £26 per length of steel.
For a small machine then it would probably take a full sheet MDF. One 7.5mtr length steel will build the same small machine.

The sundries involved IE Screws, nut's & bolts etc both need. Steel doesn't have to welded and can be bolted thou for sake of £50 a welder makes slight work of it.
Just because something looks expensive or hard to do doesn't mean it is.?
The difference in performance and longevity are night and day and it's a one time affair still with lots of learning and enjoyment.!! . . . The fun just last's longer.!

Well that's my take on it anyway.!!

[TrickyCNC]

I found steel to be more than that in 1 off's, it came down a bit if you bought 2 or 3 lengths.Maybe I'll shop around a bit, as I have nothing against steel except it's price for a 1st timer. I was pricing up for an 8x4 machine though, so was looking at a lot more steel and larger sections. Even then, I've heard of 2x3" steel box gantry's need beefing up because they were flexing when cutting wood.

Most people that build a machine, use it for a while and want to change it or make it bigger. So it doesn't necessarily need to last

Oh, and I built mine out of 12mm MDF LOL, it gets 3 or 4 hours use most days for the last 6 months ... the parts come out the correct size and everything !

[Tenson]

I got my steel from 'The Metal Store' who do some smaller lengths like 1.5M and 3m and also offer a free cutting service at the checkout stage (cutting not 100% accurate but that doesn't stop you putting your screw holes in the right place).

[martin54]

Sorry hope I'm not hijacking this thread but I was looking for some info on rails & wasn't sure where to look being new to all this. Is there some sort of guide as to what diameter rail should be used when looking to build a machine. Realise there are probably a lot of factors to take in to account but just a very general guide that maybe gives some sort of idea what size rail to use for different length or width tables.

[JAZZCNC]

Sorry hope I'm not hijacking this thread but I was looking for some info on rails & wasn't sure where to look being new to all this. Is there some sort of guide as to what diameter rail should be used when looking to build a machine. Realise there are probably a lot of factors to take in to account but just a very general guide that maybe gives some sort of idea what size rail to use for different length or width tables.

Think Jonathan posted a long head aching thread some where on round rails.? Do a search if you want your brain numbing.!!

Really thou it's not rocket science and it will ultimately boil down to a few factors like Budget and machine size/use. Here's a quick run down for typical DIY use.
Stay away from unsupported round rails unless short lengths =<400mm and even then 20mm or more.

My rule of thumb with Supported round rail is 16mm for small light duty machines =< 600mm. 20mm =< 1500mm 25mm => 1500mm
If Profiled linear rail then it's a completely different and 15mm will be more than most DIY users need in terms of load capacity's but maybe not physical size so 20mm tends to get used often has the bearings sizes etc suit better. It also tends to be more common second hand has it's common size in industry.

hope this helps.

[TrickyCNC]

Also, depending on budget, and how much "DIY" you want to do, there are lots of other home made options, like angle and skate bearings, or steel tube, or steel plate and bearing tucks etc. etc.

[JAZZCNC]

Also, depending on budget, and how much "DIY" you want to do, there are lots of other home made options, like angle and skate bearings, or steel tube, or steel plate and bearing tucks etc. etc.

With all due respect but in my experience thru helping others it 90% of the time leads back to the same thing.? Wasted time and money.!!
If they do get them working they are high maintenance and usually lacking in precision. I think I have helped folks who have used just about all the available options and all of them regretted it.
I know what your probably going to say " It's a cheap entry to CNC" BUT IMO it's also a good way to drive newcomers away has well when they try fail and give it up has a bad job.!! . . If they only knew before hand that for not lots of money and far less time they could have real rails and bearings that are far more accurate and reliable I know for sure they surely would have taken that route on hind sight.

Yes I know there are some very capable machines running DIY setups and someone you've mentioned earlier Gerry(Ger21) who I know quite well runs a very nice machine but think even he'll tell you it's not a simple affair and takes very good design, patience and care to get it right. . . . Do-able Yes, easily No, success rate Low, frustration levels high.!!

My advice save up and save the stress.!!

[Ger21]

Yes I know there are some very capable machines running DIY setups and someone you've mentioned earlier Gerry(Ger21) who I know quite well runs a very nice machine but think even he'll tell you it's not a simple affair and takes very good design, patience and care to get it right. . . . Do-able Yes, easily No, success rate Low, frustration levels high.!!

My advice save up and save the stress.!!

Did I miss something here?

My current machine is wood with skate bearings. I designed it 9 years ago, when DIY CNC was in it's infancy, and the only linear rails available were used from Ebay. While it's probably quite a bit better than most similar machines, the bearings are the main limitation.

Today, I strongly encourage anyone to use supported round rails at a minimum. With the inexpensive rails from China, it really doesn't make sense to go with anything less. If you're on a really tight budget, sure, you can use cheaper methods, but don't expect great performance, or quality cuts. If you have the skill to make the cheapest method work well, you probably wouldn't be using them in the first place.

As far as wood goes, I'm a big proponent of wood construction. But, as Jazzy eluded to, not your basic MDF design.

I'm currently building a (mostly) wood machine, with the goal of outperforming most of the extrusion machines I see. Both in speed, and strength and rigidity. It'll have HiWin linear bearings on all axis, and belt drive X and Y. Not your typical belt drive, though. I've designed a stepper version of the Servobelt

Building a high quality wood machine requires some high tech construction techniques (IMO). Anywhere that metal parts are fastened to wood, I have aluminum or phenolic "mounting pads". This keeps the wood from being crushed and maintains precision.
Most of the wood parts I use are made up of laminations to increase rigidity and stability. In addition, everything is sealed in epoxy to minimize moisture absorption, and subsequent movement. Whenever possible, torsion box construction is employed to again maximize strength and stability.

I am using some aluminum for mounting the linear bearing blocks, but in some cases it's bonded to baltic birch plywood, which let's me use thinner panels.

Oh. It's going to have two spindles.

Today I cut the parts for my gantry beam. It's about 1700mm long, made of MDF. Front and back of the beam are 1" thick, made up of a lamination of 4 layers of 1/4", glued with plastic resin glue in a vacuum press. Phenolic mounting pads for the linear rails were epoxied on.
My day job is in a cabinet shop, so I have access to a 5x12 Morbidelli router. This is what I ended up with. Sorry if this is off topic. If anyone's interested, I've been documenting the evolving design at CNC Zone for the last 5 years.

Start of a New Design - CNCzone.com-The Largest Machinist Community on the net!


New Machine Build Z² - CNCzone.com-The Largest Machinist Community on the net!

[TrickyCNC]

Did I miss something here?

Hi Gerry

I mentioned you on another thread, where a member here was convinced MDF was too bendy and metal is the ONLY way to get accuracy . I made mine
from MDF torsion box/beam sections and was trying to explain that MDF can be made to not bend, and that you , - definately not a newbie - choose MDF to build your new machine.

As for rails ...

I agree that supported precision rails are the best, but a lot of people would be perfectly happy with the results from DIY supported pipe and skate bearing trucks, for example. or for a bit more, steel plate and CNCRP type trucks like CarveOne uses.

There are even people out there very happily using drawer runners and allthread screws, and it does everything they ever wanted ! or, they use it to make parts for a second machine , etc.

On the other hand, Microcarve has extremely accurate machines with unsupported round rails - used to their limits - and made from MDF and plastic pipe ! LOL .