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They will help you and others who have similar questions.
| 8.27.08
Mike,
I have a application where a
linear slide is used to position a spray paint nozzle.
The
slide table moves a spray nozzle back & forth a few inches
(but with a high duty cycle). The environment is very dirty,
but that is not the problem. The problem is that customer
occasionally crashes these units which creates a large (they
were unable to quantify) roll moment on the slide table.
This roll moment is causing the aluminum pillow block
housings to open up, which leads to the bushing popping out
of the pillow block housing. The roll moment also causes
the fasteners connecting the ball screw nut bracket to the
top table to shear. One potential solution, obviously, is
to just put a larger slide (customer has plenty of room to
make changes). However, I wanted to see what you would
propose. Steel pillow blocks?
Stroke - 8"
Bellows are desired
NEMA23 motor mounting required
Steve
Steve,
This is the type of slide we are discussing:
I have a few questions.
1. Is the "crash" a linear crash due to over-travel or is
the slide getting hammered from the side by another
operation because it is out of position? It sounds like the
latter.
2. Is the slide driven by a servo? Does the servo have
encoder feedback?
3. Does the slide have any mechanical limit or prox switches
to stop it from over-travel?
IF THE ISSUE IS A LINEAR CRASH
Given the information, I
would suggest ( you said the customer has room to go larger
)
longer shafting so you have some extra inches to accommodate
some over-travel before the slide crashes. I would also, if
not currently employed, use prox switches
to kill power to the slide if it over-travels. Lastly, I
would employ shock absorbers to mitigate any damage due to
crashing - no hard stop.
Bellows are no problem. Just make sure the slide is long
enough to accommodate the collapsed bellow - folds. I would
stay with Teflon Composite bearings because of the dirty
environment. I might go to larger size, possibly 1"
shafting/bearing package.
IF THE CRASH IS FROM THE SIDE
You mentioned roll moments, pried-open aluminum pillow
blocks and sheared screw mounting blocks. If the pillow
blocks are opening, they become so sloppy the screw and nut
assembly take the side load and then it's curtains for them.
I know your customer does not want ball bearings of any kind
because of the dirt and debris. But, this roll moment seems
to be beyond the abilities of our standard open, aluminum
pillow blocks. A profile rail, possibly a SHS 25 caged ball
unit might be a better choice because of its ability to take
high moments. The bellow coupled with the block's seals
might be enough to keep the system up and running.
I do need to properly
characterize the "crash." I need to know what is ramming the
slide from the side and why this is happening.
I look forward to learning more about the application.
Mike |
8.14.08
Mike,I have a high
speed sled which will see 40g's acceleration - Max Speed 700
IPS -
over 3 seconds. What is my initial velocity?
| initial velocity (v0) |
= |
-102.22 |
meter/second
|
Good Luck, Mike |
7.15.08
Mike,My name is Mike
Anderson and I work for Chrysler. We are making dealer show
room
interactive units that will allow customers to move a large
LCD TV type unit along a
wall. Under the TV there will be pictures of our different
model cars. When the customer stops the TV over a particular
model, a video will begin showing a short video on that
model. Since we are in a showroom, I need a linear unit that
will be presentable, support the weight of the LCD, be easy
to move and will work quietly.
We need some suggestions asap. Travel is 15 Feet and the
unit weighs approx 200 pounds.
Mike,
I would use our JET RAIL
linear bearings on supported shafting. For aesthetics I
would use 1060 steel shafting with a thick chrome plating. I
would also black anodize the shaft support rail. I would use
our DPB 16 OPN bearings ( 1" diameter shafting ) with fixed
bearings on one side and floating bearings on the other
side. This will give some ability to compensate for
misaligned shafting. The rollers are quiet and system will
look super.Call me if you have any questions or need further
information.
http://www.lm76.com/jet_rail.htm
Good Luck, Mike |
6.22.08
Mike,
I used MAX Rail bearings on an pusher assembly( like a snow
plow on a hydraulic cylinder ). We are pushing a 500 pound
billet of aluminum onto a conveyor. We did not use the
bearings with the mounting plate, we drilled through the
back of the bearing and tapped the hole. We then used Loc-Tite
so the bolts would not get loose. The bearings keep getting
loose and the system binds. Any ideas?
JaredJared,
I would not fasten the bearings in this manner. It is the
weakest link in your design. I suspect the constant impacts
and misaligned loading will continue to loosen the bearings.
I strongly suggest you use the appropriate mounting flange
plate. The plate
is welded to the bearing and the shear strength is extreme.
Moreover, the force vectors are not concentrated on the bolt
threads. Again, a weak point.
Let me know if you have any further questions.
Good luck, Mike
|
5.27.08
Mike
Do you have shafting that will not become magnetic no matter
what happens to it?Arnie
Arnie,
You might want to take a look
at Nitronic 50 shafting. It will not become magnetic
regardless of how it is work hardened.
see:
http://www.lm76.com/linear_shaft_selector.htm
It is expensive and hard to work with. But it does the job.
Good luck, Mike |
5.20.08
Mike,
Is there a linear
ball bushing that can translate both linear and rotary
motion?
Thanks, Dan
Dan,
 I
only know of one company that makes a linear/rotary linear
ball bushing, Linear Rotary Bearings:http://www.e-lrb.com/index.htm
They are located in Mount Vernon, NY.
Good luck, Mike |
5.18.08
Mike,I need a linear
system for a meat portioning project I am working on. It
will be washdown and caustics will be used. It has to be FDA
approved. Any ideas?
Carmen
Carmen,
 It
is really difficult to buy FDA " Approved"
linear slides. FDA "Compliant" slides are more
available. The Seal Slide is a great product from LM76. It's
pass-through design allows for debris evacuation. It is all
stainless for corrosion resistance.
http://www.lm76.com/seal_slides.htm
Good luck. Mike |
5.7.08
Mike,
I have an application where I need to move a 4000 pound cart 20
feet. It will be driven by cable. There is no precision
required. The mounting surface is flat
( concrete ). Kevin.
Kevin,
 Thanks
for your question. I would suggest a system like
the LM76 MAX Rail. It is a combined bearing which takes
radial and axial loads simultaneously. It can be mounted to your
floor with rails that match each bearing size. You can
easily put together a high load system that is easy to
install and is economical.
http://www.lm76.com/max_rail.htm
Good Luck, Mike |
5.1.08
Mike,
There is a type of ball bushing with balls imbedded in a bronze
sleeve so they
are free to rotate. The balls roll against a precision shaft. What
do you call these
bearings and where can I get them?
Thanks, Rich
Rich,
Thanks for your question. These bearings are Die-Set bushings.
One company you can call is Producto. This is a website you can
reference:
http://www.producto.com/guide-pins-bushings.html.
Good Luck, Mike
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