Opinions/Comments on Linear Slide With Ecentric Lift Point
Opinions/Comments on Linear Slide With Ecentric Lift Point
(OP)
I am designing a lifting mechanism for a large glass panel approximately 3500lbs 8ft tall x 17ft wide. Two large columns will support the two linear rail slides mounted to each side of the glass. Two Carriages per side. Lifting the panel vertically.
The question is, I would ideally like to use one ball screw jack on one side of the frame to lift the glass. The screw has the capacity to for the weight, but the loading point is obviously not on center/centroid of any axes due to tight packaging requirements. I am wondering if there will be any significant moment created by the loading point and cause a binding in the linear slides. I have spec'd the track size and screw via calculations and the applications engineers with the manufacturers. I am also discussing possible options with them as well.
Thanks!
The question is, I would ideally like to use one ball screw jack on one side of the frame to lift the glass. The screw has the capacity to for the weight, but the loading point is obviously not on center/centroid of any axes due to tight packaging requirements. I am wondering if there will be any significant moment created by the loading point and cause a binding in the linear slides. I have spec'd the track size and screw via calculations and the applications engineers with the manufacturers. I am also discussing possible options with them as well.
Thanks!





RE: Opinions/Comments on Linear Slide With Ecentric Lift Point
Thanks
RE: Opinions/Comments on Linear Slide With Ecentric Lift Point
If this is a one-off unit then lift it from both sides. If you are building a hundred of them then it may be worth investigating the mechanics in detail, to ecomise of the number of ball screws, but I note that the only roughly similar systems I can think of (vehicle hoists, fork lifts) use a screw in each 'leg' or drive the load from the centre.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Opinions/Comments on Linear Slide With Ecentric Lift Point
RE: Opinions/Comments on Linear Slide With Ecentric Lift Point
More suggestions are welcome!
RE: Opinions/Comments on Linear Slide With Ecentric Lift Point
Thanks
RE: Opinions/Comments on Linear Slide With Ecentric Lift Point
Running two leadscrew systems together is difficult. There will be a lot of set-up to ensure that they travel together. Make sure you leave enough adjustability, such that whoever is assembling the systema cen ensure that the axes of travel are as parallel to each other over the full travel as possible. A very good idea, after the systems have been set up to their running position is to have independant set-up blocks (can be as simple as a block with slots) that can be added to the mechanism that 'record' the X-Y (and Z if required) positions of the slides so that they can be dis-assembled at some future date and put back to their original position.
Re the nut, make sure that the leadscrew nuts are anti-backlash, and bronze is generally the preferred material (depending on the application this may be nylon)
Hope this helps
Kevin Hammond
Mechanical Design Engineer
Derbyshire, UK
RE: Opinions/Comments on Linear Slide With Ecentric Lift Point
Just another thing that came to me last night....
When it comes to choosing the slide itself, because you have (as far as I can see) two pretty stringent design requirements (1. The material you are lifting is glass and 2. the load is high) I would recommend you use GUIDED slides. There are many on the market, but you will need to concentrate on two main specification criteria. Be very careful that the slide system is repeatable (wrt to travel) and that it can take the moment that the glass plate (+ whatever metal you add). From this point of view, it is the guiding that will be of utmost importance. Look at guides that have bearings/cam followers running on machined surfaces. Some companies that Ihave used before and found very good are
Thomson Slides (www.danahermotion.com)[Personally, the best option]
Origa (www.hoerbigeroriga.com)
Good luck.
Kevin Hammond
Mechanical Design Engineer
Derbyshire, UK
RE: Opinions/Comments on Linear Slide With Ecentric Lift Point