I am about to start building my large (60x50x50 high) 3d printer. The last thing I need is the linear rail for the X axis. I have 2 x HiWin HGR20 rails for the Y axis which are H precision and V0 preload.
I want to get a HGR15 from these guys
[my-eshop.info]
which are made by CPC which I believe is South Korean. I will get the H precision grade but they offer the following preloads:
preload:
VC: Play 2μm - 13μm
V0: transition area; Play (4μm) - preload (0.02 C)
V1: preload (0.08 C)
V2: preload (0.13 C)

I am considering the V1 preload but I have no idea how stiff it will be! The axis is powered by a 0.9 degree stepper with 42N holding torque and 2.2N detent torque. Moving mass is about 300 grams.

Should I go for V0 or V1?

your best bet is to contact the supplier by email with what you are using it for and they will set that or advise you. With linear bearings it is best not to remove the block from the rails

Quote
Roger123D
your best bet is to contact the supplier by email with what you are using it for and they will set that or advise you. With linear bearings it is best not to remove the block from the rails

Blocks are quite easy to safely remove from the rails for cleaning and replacing balls. You just need to remove the rails from blocks, not the blocks from the rails.

You want V0. Preload doesn't make sense on a belt driven axis. Even VC would be more appropriate than V1 because any resistance to motion will degrade motion in the timing belt, motors, and frame.

Even at VC, 13um of play in the rail (averaged across 2 rails and 4 blocks?) is basically irrelevant. Timing belts will deflect more than 13um if you blow on them.

You might also consider one of the miniature variants of linear rail to save costs because a 3d printer X aixs doesn't really need two rows of balls.

Edited 1 time(s). Last edit at 02/11/2018 06:59PM by 691175002.

Thanks for that - I tend to agree with you and will be getting the V0 grade. Actually it is only 1 block and rail as it is the x axis, and I am also
only using 1 block per rail for the Y axis - the pair of blocks are rigidly connected via the x axis so I dont anticipate any problems,
especially as the Y axis is being driven by 2 belts one on each side.
Surprisingly the 15 and 20mm HGR rails/blocks are the same price or less than the mini rails and move more easily and most
importantly provide a larger and more stable mount than the tiny blocks on the mini rails.
I will check the quality of the Romani rails and I they are as good as they seem I will post a thread on here as many people are looking for high spec reasonably priced
linear rails and they have a huge range!