Was about to get a toy- then I did some research...

[JAZZCNC]

The round vs profile rail debate is one that has had me torn the most. Undoubtedly profile are superior in theory, in practice, however, I've been somewhat put off by the many worst case scenarios people have posted about when ordering the Chinese kind (which I strongly suspect is the only kind my budget allows).

This is the problem people only focus on those who have had issues, probably because they shout the loudest, but for everyone that as an issue there are 100's more who haven't and work perfectly fine.
Chinese VFD's and spindles being a classic case, I've lost count of how many sets of VFD/Spindles I've fitted and I've had about 3 failures in 10+yrs and those weren't all due to quality but more user error or wiring issues.
I was probably one of the first in UK to use the Cheap Chinese Linear rails and again I've fitted dozens of sets without any issues, Now I fit Hi-win because the price difference isn't too great, but both come from China so don't be put off. Either of them are far superior to round rail and worth the extra, trust me on this you won't regret buying them.

Second, being a first timer, I was hoping to get slightly more parallel mounting tolerance with the round rails (bc self alignment), and they provide more room for mounting ball screws on the same face (although that could also be achieved by spacers on the profile carriages). I'm curious though, in what way do you find profile to be less of a hassle?

Not quite sure what your meaning by Less hassle.? Less hassle than what.? Compared to using steel it's lot less hassle for obvious reason, try drilling and tapping 150 x M5 holes in steel and you'll understand this quickly.! . .Lol

If you are referring to my comment about using 45x90 because of the slot spacing being less hassle. Then I mean it's less hassle than having to make plates which first bolt to the profile so you can then mount the BK/BF bearings onto. Or having to Drill and tap the profile directly, which don't advise doing because never works out good. Like on this gantry that uses 40mm spaced slots and BK15 bearings with larger hole spacing.

With regards the bk/bf12, I thought bolt spacing was something like 46mm in which case standard t-slot nuts wouldn't work? Or is it merely a case of using good ol' force? .

The holes allow just enough wiggle room so that it works ok.

I long favoured flipping the ball screw and stepper positions, but figured ball screw placement as centrally as possible relative to the gantry rails took precedence over drop plate length.

I find comments you've seen made like these are made mostly by armchair theorists who have probably never built a machine.!
Because in the real world the difference between them is so negligible that you'll never see or notice any difference in how the machine performs. I've built all kinds of machines in all possible configurations and I've yet to see one that stands out to even slightest degree that says that's the best way.

End of the day if it fits your design best to have it raised up a little higher then go with it because you won't notice any difference if struggle on and have it the so-called "Optium" position.
The reason I say move it up is that being shorter it won't vibrate as much, which then goes into the screw, which then goes into the motor etc.
Also because the bracket is actually fastened to the top bearing plate anyway, the so-called optimum center position doesn't apply because the forces are being placed on the top bearing plate, not into the center of the Z-axis rear plate which is considered the Optimum position. So having it short means the forces are moved closer to the actual bearing plate which is what's being moved and makes everything that little bit stiffer.

Again don't stress over this stuff because it's not a game-changer or disastrous if not in the optimum place, you WON'T notice any difference. The little details like being stiffer or better-placed screws, motors, switches, etc make for a better more reliable machine than if a ball-screw isn't quite in the Optimum place.

[Boyan Silyavski]

First off- those are some slick looking machines! Also, I never considered using a cross beam under the frame for dual stepper set-ups.

The round vs profile rail debate is one that has had me torn the most. Undoubtedly profile are superior in theory, in practice, however, I've been somewhat put off by the many worst case scenarios people have posted about when ordering the Chinese kind (which I strongly suspect is the only kind my budget allows). Second, being a first timer, I was hoping to get slightly more parallel mounting tolerance with the round rails (bc self alignment), and they provide more room for mounting ball screws on the same face (although that could also be achieved by spacers on the profile carriages). I'm curious though, in what way do you find profile to be less of a hassle?
.

The square rails for me are may be the most important part of the machine in the long run, so there should not be any doubts about that. In fact better buy a smaller size square rails than round rails. mean 15 instead of 20 size , if machine is not intended for heavy duty use . You can always use one carriage more as they are cheap. rail is heavy hence expensive to ship. You get what i say?

About the Chinese square rails, if you buy from a good factory they are same or very similar quality like the Hiwin. You may need to clean a carriage or similar, but most important is to be from a good place.

I buy from these guys https://es.aliexpress.com/store/822038 12 and 15 size. Have not bought from them 20 size , but their rails are very good quality and price. Custom size also, contact them. make sure to buy the long carriages.

[Juranovich]

This is the problem people only focus on those who have had issues, probably because they shout the loudest, but for everyone that as an issue there are 100's more who haven't and work perfectly fine.

Typical case of selection bias... This is what they warned us about in uni!

Not quite sure what your meaning by Less hassle.?

You said that profile rails are better and less hassle, but I think I got the drift now.

The square rails for me are may be the most important part of the machine in the long run, so there should not be any doubts about that. In fact better buy a smaller size square rails than round rails. mean 15 instead of 20 size , if machine is not intended for heavy duty use . You can always use one carriage more as they are cheap. rail is heavy hence expensive to ship. You get what i say?

[...]

I buy from these guys https://es.aliexpress.com/store/822038 12 and 15 size. Have not bought from them 20 size , but their rails are very good quality and price. Custom size also, contact them. make sure to buy the long carriages.

I hear and thanks for the link (and thanks to everyone who's provided useful links to vendors). Theoretical modelling is one thing, but sourcing good materials is always extra hard when you lack experience. Much appreciated!

[Juranovich]

A quick update:

I did some modelling last night based on profile rails so I now have two options. Next I'll compile a shopping list in order to make a price comparison between the two.

Do any of you have suggestions as I plunge into the endless mass of online stores? Preferably suggestions you have personal experience with...I reckon I can always shop at the european stores for fairly safe choices, but I'd be super interested to hear of specific "chinese" vendors/products which might save me a penny.

Below I've compiled a list of recommended vendors/products I've come across on forums (I'll post these so as to avoid duplicates, but also as reference for others that might come across this thread looking for buying advice).

Extrusions: motedis, kjn

rails/ballscrews: https://es.aliexpress.com/store/822038, BST Motion on Aliexpress, linearmotion on ebay

Steppers: https://www.aliexpress.com/store/190...569f5bd5XOOljj

Motion controllers/BoBs/electronics: CNCDrive

Stepper drives: https://www.ebay.co.uk/itm/2DM860H-2...72.m2749.l2649

Spindles: Teknomotor (price worthy (?) italian brand), Huan Yang Shop on AliExpress

General european cnc related stores: zappautomation, dold mechatronik, sorotec, cnc4you

EDIT: Added Lichuan under steppers, Huan Yang under spindles, cnc4you under general and fixed boken ebay link under stepper drives.

[AndyUK]

You can get a Chinese spindle and VFD kit from BST linear too. As always email directly for a quote, mention this forum.

Steppers, ZappAutomation, Cnc4you, and I think people have used Stepperonline (they advertise on here at least)

Stepper Drivers I got from Zapp, Gary the owner posts on here occasionally with a decent discount code.

KJN also do extrusions.

[Juranovich]

You can get a Chinese spindle and VFD kit from BST linear too. As always email directly for a quote, mention this forum.

Steppers, ZappAutomation, Cnc4you, and I think people have used Stepperonline (they advertise on here at least)

Stepper Drivers I got from Zapp, Gary the owner posts on here occasionally with a decent discount code.

KJN also do extrusions.

Thanks, I'll have a look at those!

[Chaz]

A quick update:

I did some modelling last night based on profile rails so I now have two options. Next I'll compile a shopping list in order to make a price comparison between the two.

Do any of you have suggestions as I plunge into the endless mass of online stores? Preferably suggestions you have personal experience with...I reckon I can always shop at the european stores for fairly safe choices, but I'd be super interested to hear of specific "chinese" vendors/products which might save me a penny.

Below I've compiled a list of recommended vendors/products I've come across on forums (I'll post these so as to avoid duplicates, but also as reference for others that might come across this thread looking for buying advice).

Extrusions: motedis

rails/ballscrews: https://es.aliexpress.com/store/822038, BST Motion on Aliexpress, linearmotion on ebay

Steppers: ??

Motion controllers/BoBs/electronics: CNCDrive

Stepper drives: https://www.ebay.co.uk/itm/2DM860H-2...72.m2749.l2649

Spindles: Teknomotor (price worthy (?) italian brand)

General european cnc related stores: zappautomation, dold mechatronik, sorotec

Certainly the Teknomotor / HSD spindles are good but are pricy. All depends on if you need ATC or want to change tools manually.

[Juranovich]

Certainly the Teknomotor / HSD spindles are good but are pricy. All depends on if you need ATC or want to change tools manually.

Thanks for pointing that out! Among European brands (the few I've come across) I find them to be fairly well priced. But maybe you compare them to Chinese models?

On a side note, I never considered getting any electronics from China out of fear of bad quality, but I'm starting to consider my position.

[Chaz]

Thanks for pointing that out! Among European brands (the few I've come across) I find them to be fairly well priced. But maybe you compare them to Chinese models?

On a side note, I never considered getting any electronics from China out of fear of bad quality, but I'm starting to consider my position.

Yep, compared to the cheaper Chinese stuff where quality can range from 'OK' to bad. Keep in mind, even stuff that we consider good like 'Panasonic etc' is almost always Chinese.

[Chaz]

For info, I currently run a 6.8 KW HSD Spindle on my Concrete mill. If you look up my build thread (search for Thor), you will find it. I started with a 4KW Chinese spindle which worked OK. Low / no torque and ER collets, found a 2nd hand HSD spindle and not looked back.