v groove bearings
v groove bearings
Author :Admin | Publish Date:2013-05-21 08:32:05
Take a close look at the bearings used to guide along the rail (U groove
and V groove bearings work well for this type of linear rail mechanism). I know,
you're saying that this method is used on other CNC machines. Sure, but he is
positioning the bearings and using minimum hardware to serve multiple purposes.
You can see that he is using the same shaft for each pair of [v groove
bearings] . The back bearings (the bearings to the right) glide horizontally
along the y-axis and the front bearings serve the z-axis up and down movement.
This linear motion mechanis for the y and z axes is very clever. Octavio is
currently trying to reduce the gantry weight. He says that the z-axis alone is
50 pounds. He has a goal of 20 pounds by changing the metal to aluminum using
stamped parts.
As you can see in the images, the chain is connected to a bearing that is
driven by the motor on the other side. As I have said in many parts of the
website, backlash can be introduced in a machine at various parts including the
lead nut, couplings, clamps/nuts at the bearings,
gears, and pulley mechanisms. With the use of a chain and a sprocket, the
backlash is minimized as long as there is sufficient tension. Tension is only
required in a chain drive to reduce the backlash in both directions.
GT Series oil film tables are designed with general-purpose V-Groove
bearings, combined with a magnesium or aluminum slip plate. Oil is supplied
through portholes in the granite slab and is dispersed throughout the underside
of the slip plate. The oil film provides a low friction surface, a damping
medium for restraint of resonances, pitch and roll moments. Yaw restraint is
provided by the V-groove guide bearings combined with the armature guidance
system.
GT Series guide skf bearings are primarily
designed for use with ETS Unibase shakers but are available for any existing or
new shaker.
Light weight magnesium slip plate
Economical aluminium slip plate available
Self contained oil reservoir with filter
Yaw restraint provided by V-groove guide bearings combined with the
armature guidance system
Less expensive technique to perform horizontal testing
I don't think the goal is to "eliminate all axial loading" I think the goal
is to eliminate all slop in the axial direction without putting axial loads on
parts that aren't meant to accept axial loads. I think that using a modest axial
preload on the outer race of the v-groove bearings to eliminate that slop is an
reasonable approach, given that V-groove bearings are ostensibly designed to
bear axial loads.
The trick seems to be finding the right flanged sleeve bearings. I didn't
find anything on McMaster available in the sizes we'd need for this particular
job in 5-10 mins of searching. While the quasi-floating shims illustrated in the
original proposal can do the job of coupling the outer races of the koyo bearings, I would prefer a more stable, less
float-y solution, like the one illustrated in my quick-n-dirty illustration
here.
BRING SKF RMS 8 (1 X 2 1/2 X 3/4)
BRING SKF RMS 9 (1 1/8 X 2 13/16 X 13/16)
BRING SKF RMS 10 (1 1/4 X 3 1/8 X 7/8)
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