[Shalecnc]

I'm trying to decide between profile rails (LGR20) and round-supported shaft (SBR20). When I priced out my build (about 36"x56", using 80/20 1530 and 1545) I can save about $370 using the round linear supported shaft. Here's the lowest respective prices I found:

Round Supported Linear Shaft:
- 2x SBR20 (1500mm) + 4x SBR20UU bearing blocks = $170 (probotix for the rails, Keiling for the blocks)
- 2x SBR20 (1000mm) + 4x SBR20UU bearing blocks = $167 (Keiling)

Profile Rails:
- 2x LGR20 Hiwin rails (1400mm) + 4x LGW20HAZ0H/E1 Bearing blocks = $384 (Automation Overstock)
- 2x LGR20 Hiwin Rails (1000mm) + 4x LGW20HAZ0H/E1 Bearing blocks = $322

So that's a savings of about $370. I'm estimating the total build will come out to around $4500, so I'm already in for a bundle and trying to save where possible.

- Would I get more bang-for-the-buck spending that money on other components?
- How much more accurate are the profile rails going to be?
- I've heard they are much more sensitive to racking, is this true? (I'll be using a single ballscrew under the table for the X-axis.) WouldI need two ballscrews if I go with the profile rails?

Thanks

[Falcon69]

well, I got my profile rails a couple weeks ago. I had ordered and planned to use the round rails. But when those round rails came in, I can feel slop in them from just moving them with my hands. The profile rails I can't move them side to side. I feel no slop.

Are they worth it? Well, depends on your budget. My rails set me back $1700. I could have gotten the round rails and pillow blocks for like maybe $400.

It depends on your budget and accuracy you won't from your machine. But for me, I don't plan on building or upgrading my machine. I plan on doing it right the first time. Sure, it's taking me longer to get it built because of funds, but, I won't me kickin my own arse later if I had built it cheaply.

[Falcon69]

oh, fyi, for a cnc machine using profile rails, you want your preload at Z1 or better. Overstostock doesn't have much left for preload Z1 in their LG series. For a DIY cnc machine, you should be fine with the AG series. They have plenty of those in stock with the Z1 pre-load.

[louieatienza]

The profile rails are far better than the round rails, but they're only as good as you install them and the application being used. They can withstand forces probably 10 times greater than the round rail if not more. They can be far stiffer and accurate than the round rails. However they take more care to install and adjust.

If you don't however see anywhere near the forces that the round rails can withstands (I believe about 300lbf for 20mm) then they might not be worht the extra cash.... For ost hobby needs and for some commercial needs round rails are jsut fine...

[Shalecnc]

Thanks for the tip on the Z1 preloading.

So the LG series are single bearing race, which is the discontinued model. The more expensive EG series has 4 bearing races. How much "better" are the EG series? Any practical difference?

also, what are some other good places to get profile rail for less cost?

[Falcon69]

Unless your gantry weighs like 3000 lbs. I don't think you need a 4 bearing race. For the size of machine you're doing, I can't see the gantry weighing more than 300. My gantry with the spindle and z-axis will weigh in at nearly 600lbs, so I ordered my X-Axis rails at 30mm. Overkill? Just alittle.

As far as other places to order? Other than Ebay, I don't think you'll find anything cheaper than Automation-Overstock. But, like you said, they sell the discountinued model. On their other site, Automation4Less, they sell the new series, but you're going to pay 2-3 times more the money for them.

[thefu]

i use profile rails for every axis on a cnc plasma table i own, way worth the money.

[steve123]

I believe you should seriously consider profile rails for you Z axis. Dynamic forces on the Z can be at the limits of round/supported rails, particularly if the blocks are close together. See the important "D2" vs "D7" distance here: Building a CNC Router Step 4: The Z-axis assembly
I looked at the price difference for the relatively short Z axis and found that the profile rails/cars were not very much more than the Glacern rails for the short length of the Z. That caused me to start down the slippery slope, and now I am planning to use profile rails and Nook .001"/Ft. ball screws for everything.

-Steve

[DonFrambach]

I had ordered and planned to use the round rails. But when those round rails came in, I can feel slop in them from just moving them with my hands.

Did you have a preload adjustment on your round rails? The ones I bought from Glacern do and have worked well with no discernable "slop". I use SBR 20 round rails on one axis of my small router (14" x 14") and keep the cutting forces low. I've used the router to make many detailed carvings in wood and a few in aluminum and one in brass with excellent results.

[LazyMan]

I used to be a fan of round rails, but I don't think I will ever use them again. I guess it really depends on how serious you are about CNC routers and your financial situation but after spending hours on your project, even an extra $1000 will seem like a small price to pay for the dramatic performance gains from profile rails. It will be unlikely you will take full advantage of the potential accuracy of linear rails, but you can certainly take advantage of of rigidity and longevity.

[Shalecnc]

I'm leaning towards the overstock site's LY20 rails+bearing combos. Good price at $334 for 1040mm rail + 4 LY20 bearing blocks (z1 preload), which will be great for the Y-Axis.

Unfortunately that's not enough for my X-axis, and I can't find any other reasonable source for extended length (looking for 56") NSK rails.

So it looks like the HIWIN LG20 is my alternative -- which comes out to about $400 for 4 bearings (LGW20HAZ1H) + 1400+ mm rail.


Question -- Does anyone have any more info on the LG20 and LGS20 profile rails available at homeshopcnc.com? I couldn't tell if those were also HIWIN or not. http://www.homeshopcnc.com/index.php...id=10&Itemid=1

[ger21]

Question -- Does anyone have any more info on the LG20 and LGS20 profile rails available at homeshopcnc.com? I couldn't tell if those were also HIWIN or not.

I doubt it, as all the Hiwin's I've seen are green and red, and those are black.

[abs1nth3]

Newbie question here, what's better?

Profile rails like the Hiwin rails you're talking about, or something like the 1018 flat steel with carriages, like the CNC router parts kits?

Advantages/disadvantages between the two?

[Dylwad]

Newbie question here, what's better?

Profile rails like the Hiwin rails you're talking about, or something like the 1018 flat steel with carriages, like the CNC router parts kits?

Advantages/disadvantages between the two?

If price doesnt matter, hands down, without question profile rails are better.

Profile rails are more precise, sealed from dust (for the most part) and can handle higher loads.

The skate bearing/1018 steel rails work great for the price but you need to keep them clean and adjusted properly, and your machine is only as straight as the rails, which is usually close enough for woodworking.

I have a machine with cncrp blocks and rails and its awesome, couldnt afford profile rails when I built it, but have started collecting IKO profile rails (ebay)to replace the cncrp bits.

That said, I am surprised how good the cncrp stuff has held up, and tolerances arent an issue on most of what I cut.

[abs1nth3]

If price doesnt matter, hands down, without question profile rails are better.

Profile rails are more precise, sealed from dust (for the most part) and can handle higher loads.

The skate bearing/1018 steel rails work great for the price but you need to keep them clean and adjusted properly, and your machine is only as straight as the rails, which is usually close enough for woodworking.

I have a machine with cncrp blocks and rails and its awesome, couldnt afford profile rails when I built it, but have started collecting IKO profile rails (ebay)to replace the cncrp bits.

That said, I am surprised how good the cncrp stuff has held up, and tolerances arent an issue on most of what I cut.

Thanks for the info. This is the route I am going as well, and like you, I will save up/collect the more precise rails over time.

[SSN Vet]

I'm going to resurect this old thread to add a comment....

I'm planning a home router build, but I program for CNC routers at work and train the operators. We have a CNT Motion systems 900 series machine now, and previously had a circa 1990 DT Tool Meta Machine. These are both industrial machines with robust custome AL extrusions, and both of them use V-Bearings riding on steal v-rails imbeded in AL extrusions.

But this requires custom machined mounts with adjustability built in.... so there is a level of expertise and machining required.

I'm curious about all the references to using profile rail on home/hobby machines. It seams the recommendations make for hobby machines built better than the industrial ones I'm familiar with.

I'm doing research to make my own home/hobby machine (probably a hybrid to cut cost) and am investigating using the SBR20 fully supported rails.

We have a corrugated sample cutter (gantry robot with tangential control oscillating knife and crease wheals) at work that used 16mm round rails, but they have they doubled up (two parrallel rows) on each side of the table.

[ger21]

Profile rails are far superior to V bearings. Most people either pick up used ones from Ebay, or older surplus. There are also chinese imports available now at reasonable prices. If your building a decent size machine (4x4 or larger), you're probably going to be spending $3000-$4000 or more. An additional $500 for profile rails is worth every penny.


I'm not a fan of round rails, as they're not nearly as strong, and often have a bit of slop in them.


I don't consider routers with V-Bearings "industrial" machines. The industrial routers I've been using for the last 15 years are made of large steel tubing with profile rails, and typically cost $150,000 or more. V-bearing machines aren't in the same class.

[Spk64]

+1 there is really no comparison with profile rails and other methods. Look at any industrial machine made for accuracy and rigidity.
Also if you check out the load ratings and accuracy classes you will see why they are used.


Sent from my iPad using Tapatalk HD

[louieatienza]

It's going to depend on your application. Not all profile rail are created equal. Some are made for horzontal flat use only. These usually have bearing blocks that are not easily removed. Many are made for 4-way equal loading, giving you more options as far as mounting is concerned. Profile rail can be up to 10 times or more stiffer than the equivalent sized supported round rail, even more if you consider those made with roller bearings. The downside is that to take advantage of them they must be installed with greater accuracy than round rail.

[pippin88]

I've got round rails (the standard chinese ones). Sure they are cheap, but by nature they allow rotation in a plane that isn't desired. I also recently found one of the ground rails was loose on the aluminium support. It was hard to pick up, but added to inaccuracy.