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Sounds good, I'll think about it and rethink everything :)
@Wal: It works in SW :) I just didn't think steel was going to be that heavy x) Obviously this is due to the size of the machine, not much about the thickness of the steel. 1300mm Y travel implies at least 1700mm gantry width. Using 100x100x3 profiles will definitely be the key to lightness :)
I would go for a thicker profile say 5mm so that you can tap it ok. I used 60x60x5 profileQuote:
Using 100x100x3 profiles will definitely be the key to lightness
Euri, I'm talking about supporting the rails with 8mm bolts... That just sounds like a really bad idea to me. How are you proposing to make this work without introducing kinks into the rails as you torque them up? Fair enough, if you could guarantee that each and every tapped hole in the plate was IDENTICAL and furthermore the tapped holes in the rails were IDENTICAL then (despite it still being a really bad idea) it probably could work, but why? Why why why..? This is about the silliest way of doing it..! Okay, mounting the rails on blue-tack would be sillier, but not by much. Just think about it for a moment - I'm not trying to disparage, but to me this method makes no sense at all..!!Quote:
Originally Posted by eurikain
Wal.
I have to agree with Wal on this, it really looks like your making life hard for yourself for no other reason than to compromise the integrity of the machine.Quote:
Originally Posted by Wal
It's nice to design somthing totally bespoke, never seen before and so on but I too really would encourage you to look at this from a different perspective, setting aside what the machine will look like cosmetically, I say cosmetically because we really can't see there is advantage to your rail fixture method and it's just going to serve you a handycap.
.Me
Yep, It's not just achieving the consistency in your method that'll give you a problem - the height of the rail will also depend on the torque of the bolts - as such it's going to make measuring for the ball-nut bracket fitment a real pain... You need to be designing around what you know - data that is readily available, not "Oh, I'll just put these rails in using the maddest method I can come up with and then see about my ballnut bracket later.."
Heh, the rails will probably resemble a roller-coaster by the time everything's torqued up anyway. Using this method the ballnut might just move smoothly along a couple of inches of track...
Honestly, don't pursue this inviable method..! It'll be a waste of your time and money. Enough said.
Wal.
Eurikain,
Listen to the sound of bearings moving in this video:
http://www.youtube.com/watch?v=bGbWBDtzydw
It sounds bad.
Very bad.
Very, very bad.
I'm guessing this video or something like it is where you got the idea for DIY supported rails.
It is a bad idea.
Very bad.
Very, very bad.
The reason why everyone is giving you negative feedback is because it is a bad idea, so ditch it and move on. If it helps any, hiwin rails from hobby machines have a good second hand market value. When you outgrow your machine you can recover a lot of the price by selling them on.
PS I'm the resident village idiot, annoying people with my hair-brained ideas, even I figured out that DIY supported rails was a non-starter.
Hi ! Sorry for the late reply, I've been a bit busy :)
I hear you all, and I will take your advice. I know, DIY supported rails are not the way to go. I hear you. Even if this is not going to work, I think that the profile method was going to work, just not with steel, or made differently with short pieces. I think DIY rail is possible, but you need to get the supports milled from ALU or steel and then tap them. What I am just explaining here is that ROUND fully supported rails don't seem efficient to me cost / strength wise. I've run a couple simulations in SW and that confirmed my idea. You could semi-support a round rail with at least 1/2 of the material used in fully supported chinese rails. Of course, getting those parts machined may be expensive, unless you've got a CNC within hand's reach, or know someone that can get them milled.
That said, supporting the rails with bolts is a silly idea, I agree.
@Boyan
I requested a quote from my seller Kevin and from Fred at BST automation for SBR rails.
Kevin asks for $305, Fred for $345 ;)
Now ask fred if he can get any lower or at the least price match ?
.Me
That's an idea :)
I don't know Kevin but Fred is a reliable seller.Quote:
Originally Posted by eurikain
Exactly. i wouldn't trust sb else to pack me a 3m ball screw from China.Quote:
Originally Posted by JoeHarris
You want to know that if something isn't right that they will sort it out. Having bought from China a few times now - Fred has been the most hassle free. One faulty item out of 18 and he sent a replacement a few days later with no quibbles.
The 2m ballscrew was packed very well. It was supported at the bottom with a plywood plank. I know fred puts them in a box. Next time I order I will definitely go with him. Plus, his English is excellent compared to what I've seen on AliExpress so far :D
Good Morning. How is the build coming on.
Just to let you know, I have used the Chinese SBR rail and guide. 1000mm long.
Been in use some 18 months now. Faultless operation, I have had no trouble at all.http://g02.a.alicdn.com/kf/HTB1nvRMI...pg_120x120.jpg
The rail is supported, so why in your drawings is it not?
I have attached a quick photo from an Ali site, just to confirm the style of rail that you are using.
I just happened on this site, and I am curious, as to how you got on.
Cheers,
Mark Needham
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