[Shalecnc]

I'm using the HIWIN LGH 25mm profile rails for my X-axis.

Is there any reason I can't mount them on the bottom of my x-axis extrusion(so under the table), rather than on the sides or top of the x-axis extrusion?

I'm thinking that putting them on the bottom gets them out of the way of dust & debris, and also would allow for a modestly thinner table (putting them on the sides adds about 80mm to the width of my project.

I know you can't do this with the SBR-type round rail.

Thoughts?

[robe_uk]

You would need to know the spec of your rails as some profile rails dont like being upside down either.

Rob

[louieatienza]

If they're 4-way rails and blocks then it should be fine. As for the round rails, that's exactly the configuration used in the DataCut plans, and there are a few people here who built them successfully... I should say that the Thomson round rails are spec'd out, and probalby have a higher load rating than the Chinese stuff.

[Shalecnc]

The technical info on Automation Overstock claims the LG series has equal loading capacity in all four directions: Hiwin LG linear bearings from Automation Overstock, LGH Hiwin linear bearings, LGW linear bearings & rail from HIWIN

So is there any other reasons not to do this? It seems most put the profile rails on the sides or top of the x-axis extrusion.

[PaulRowntree]

So is there any other reasons not to do this? It seems most put the profile rails on the sides or top of the x-axis extrusion.

Does the larger distance from the underside rails to the dynamic load introduce an excessive torque?

[louieatienza]

Does the larger distance from the underside rails to the dynamic load introduce an excessive torque?

I believe these have a dymaic load rating of over 1600kgf each, so unless he's building something very heavy, and cantilevering it a significant distance, he should be fine... Not completed yet, I built a machine exactly this way, and looking back, it seems my HSR30 rails with C0 preload look to be gross overkill....

[johnmac]

When I built mine, I chose to not "hang" the gantry and rails. I felt the rail mounting screws were a bit small for such a task. My gantry sits on top of the bearing blocks and the rails sit on their supports.

John

[Pplug]

On my techno lc4896 the x axis are mounted upside down underneath the table. They stay a lot cleaner that way. As long as you space out the bearings on each side, you should not encounter any cantilevering effects from the spindle.

It's an old picture and I've made many modifications to it but you can see the x rails mounted under the table along with the central ballscrew.

[johnmac]

On my techno lc4896 the x axis are mounted upside down underneath the table. They stay a lot cleaner that way. As long as you space out the bearings on each side, you should not encounter any cantilevering effects from the spindle.

It's an old picture and I've made many modifications to it but you can see the x rails mounted under the table along with the central ballscrew.

Under the table does look nice. I have a separate support for my rails, under the table.

Those guys are professionals. They build prototypes and test them until they get it right.

Us amateurs usually can't afford remakes. :drowning: We have to get it right the first time.

John

[Pplug]

I have to say the rails mounted underneath are great when you have to mount a full sheet of 3/4" ply by yourself! The one I made in school is a bit more difficult but it does keep down the dust as it hits the sides of the router.