[SatanKlawz]

I am putting together my machine and I have the x axis rails and bearings installed. They are HIWIN LG series 20mm rails and blocks. The bearings that I bought have a p/n designation that says they have a "light preload". I have 2 on each side of the machine for a total of 4. When I move them back and fourth by hand there is a noticable amount of resistance. Not a ton but a decent amount. They run smooth but are just stiff. Will these wear in and be easier to move or should I have bought the non preload version? My machine will be moved by steppers and I am wondering if this will affect the machine in any way?

[hemsworthlad]

Hi,
No this is quite normal so long has it's not too excessive and is even all along the rails length.
If you give them an average push they should slide for a short distance the stop gently IE not in a harsh abrupt gerky stop.

They will free off slightly under use but not too much, they will feel smoother when they have weight on them as well.

My rails did this also and it worried me too.!!. . . . But worrie not.

[louieatienza]

hemsworthlad hit on something that I found out tuning my x axis - the key is having an even feel thoughout. Definitely don't want it tight, then free, then tight or such. Between the steppers and leadscrews, they can output a lot of force, more than one may realize....

[SatanKlawz]

The resistance is even along the rail. However you can not just give it an average shove and have it coast for a bit, it will stop almost immediately. There seems to be a little bit more resistance than what I was expecting but at the same time it does not feel excessive or like something is in a bind. Its feels almost like there is a set screw that adjust the tension that is set just a tiny bit too tight.

[CarbonKevin]

I wonder if the rails were coated with some sort of heavy grease to keep them from rusting? That would certainly slow up your movement. Give that a good wipe with some solvent on a rag...wear gloves and a respirator, though!

[SatanKlawz]

Yeah they do have a super heavy coat of grease on them. Its not real thick but it is there.

[hemsworthlad]

Yes this may be causing it, do what CK says and clean it off but only the rails the bearings obviously need to be greased.

I think you'll find they will be fine and so long as there is no obvious binding or sticking then you wont have a problem.
When i say a short distance i do mean only 6 or 8 inch and not 2-3 feet.!!

I,ve just been and tested some rails that i have here for another project, not hi-win but equivelents and if i line the end of the bearing with a hole on the rail and flick the bearing hard with my index finger on the edge thats lined with the hole then it travels between 3 and 4 holes the holes have 60mm centers.

Hope this helps.

[madtownrob]

Same issue here. I ordered the LG "light" preload because the light and very-light were said to be negligible in the felt difference. I went from V-rail and bearings to LG 20 series and you just can't push the blocks and have them move freely. I have tried to clean the rail and it feels better than it was, however still no free movement.

[hemsworthlad]

Same issue here. I ordered the LG "light" preload because the light and very-light were said to be negligible in the felt difference. I went from V-rail and bearings to LG 20 series and you just can't push the blocks and have them move freely. I have tried to clean the rail and it feels better than it was, however still no free movement.

You'll be surpised just how free they slide when you have the full weight of the gantry etc mounted onto them.!!

If they are still very stiff when the gantry etc is attached then i would be concerned and start looking to see if the rails are mounted correctly and straight, it doesn't take much missalignment to cause them to bhind.

[arizonavideo]

The new cart wiper seals will have a lot of drag when new but will smooth out in time.

If you want to feel how they will roll after break in just remove the wiper seals and give them a roll.

I am running the 35mm rails and they were a bit stiff when new but not any more.

These rails have been stored for a few years now so the plastic parts may be getting a bit hard.