You’re such a tease!
I’m guessing it’s something like this? (Even deeper and shallower).
How many? Just one on each rail, or two?
In other news, I think I’ve just about finalized the Z-axis design: 
I’d appreciate any feedback anyone has. In particular, the “bridge” that the ballscrew goes under is only 4.5mm thick. I figure that should be okay because most of the force should go straight into the rails but does anyone have an opinion?
And I think most importantly, can anyone see any fatal flaws in the design that should prevent me from purchasing the parts?
The parts I ended up selecting are:
- Ballscrew: TBI XSUR1204T3D-FC5-231-P1 (note: C5 rolled ballscrew, not C7)
- Rails: TBI TR15-166-H
- Rail carriages: TBI TRS15VS, precision H, Z1 preload
- Fixed support: SYK FK10
- Floating support: SYX FF10
- Motor bracket: SYK MBA10-C
- Stepper motor: Leadshine 57CM06 (NEMA 23)
- Coupler: HZ HZ8-D20L27-8*6
- Ballscrew nut bracket: DSG12H
Total cost is looking to be ~$280 ex. shipping (which is ~$130).
@Julien, I’d like to talk about and link to the suppliers I went through to get to my final choice of parts and price, is that okay? I thought it might be interesting to compare them.
Yes, it’s ok to provide purchase links (as long as you don’t make any personal profit by doing so, I’m sure it’s not the case but prefer stating it anyway)
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Marvellous, I of course don’t get anything from this.
I went through a loooong process of finding a supplier. I looked at:
TBI Motion distributors:
- TBI Motion directly, they told me to talk to their distributors.
- Tuli, the TBI distributor I talked about earlier: They’re relatively expensive and have a 3 week lead time on ballscrew machining. They do however also sell some of the really nice linear rails if you want them. Service was knowledgeable and helpful, so I feel a bit bad about not ordering from them.
- MEW, one of the distributors TBI recommended. They’re also quite expensive and like Tuli, take 3 weeks. Service was fairly quick and knowledgeable.
- TOPPER, an AliExpress store which was recommended over on the CNCWerk forum. This is the one I’m certain to go with. Their service was super quick and responsive, they answered all my questions on AliExpress’s chat function, usually within seconds to minutes each time. At this point I already knew what I wanted so it was just a matter of asking them what they had. Like Tuli and MEW, they’ll take 3 weeks to get the product to me but they do it at a drastically lower price.
Chinese ballscrew sellers:
- Dold Mechatronik: Reasonably priced, responsive and seems to ship fast. Their linear rails are okay (they’re CPC rails, just with the branding slightly obscured) but their ballscrews are rated with 0.05mm of backlash while TBI claims no axial play at all.
- Kamp & Kötter, a German reseller of Chinese ballscrews. They are cheeeeeap and seem to have really fast processing because all their screws are pre-machined. I found the lack of specs worrying though so decided against them. Didn’t try talking to them.
And Hiwin: They apparently accept orders directly from private customers and their delivery was fast but their quoted prices were sky high. Had to bug them about the quote but the process was painless.
So on price, which I talked about a bit, I’ll compare the cost of the 231mm ballscrew (with machining but not shipping or tax):
- Tuli: 159.93€ for TBI C7
- MEW: Won’t quote the price directly but it was a decent chunk more expensive than Tuli
- Topper: $77 for TBI C7, $91 for TBI C5
- Dold: 59€ for C7
- Kamp & Kötter: 67€ for C7
- Hiwin: >300 CHF for C7
So I think TOPPER stands out here. TBI ballscrews seem fairly reputable and yet I can get them for a price more comparable to Chinese ballscrews.
Another thing I liked about TOPPER is that they stocked every part I needed. They have the screw, nut, rails, supports, coupling, motor mount, mounting block and the motor. The only other store that had everything was Dold.
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The HDZ also has a surprisingly slim bridge to it, so long as you have the ballnut well attached it seems OK.
Here’s an approximately correct HDZ model in Fusion for comparison;
https://drive.google.com/file/d/16-EZjk4Jk4NpZqhM7MJeRXvCLIPw7Skt/view?usp=sharing
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Well I ordered all the parts finally. Here’s the final total:
I’ll finally have covers for the guide rails!
And I found a bit of a solution to the “bridge” problem: SYK has a lower-profile motor mount that gives me an extra 3mm of height back and I can also carve out a little indent in the mounting plate to get everything a little lower still.
And regarding the flat surface for the rails, I can get:
- 5083 locally, with a flatness specification of 0.13mm/m.
- 7075 imported from Germany with a flatness specifiction of 0.25mm/m.
- 7021 imported from Germany with a flatness specification of 0.25mm/m.
For my ~80 mm rail separation, assuming flatness can be roughly extrapolated, I’d be getting 20µm difference with the 7XXX series plates or 10µm with the 5083, so either is plenty good.
The 7XXX series plates are mechanically superior and make my life a bit easier regarding mounting (I can tap threads into them directly) so I’m thinking I’ll go with them, probably the 7021 specifically because it’s a bit easier to obtain (less insane shipping cost).
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