Strengthen TurnTable

[goodallpg]

Hi All,

We have a turntable that we use to load/unload our trimming system. However, we have started to drill into our products which are held at an angle on the table. This drilling action causes the table to bend resulting in the drill hole being in an incorrect position. We are looking into reinforcing the table but as it rotates 180 degrees every cycle it must be an in/out system.
I have attached 3 photos showing the side view of our system. The green arrows show the points where we are drilling and the red arrow shows the movement we are experiencing because of it. The other image shows a potential solution where an extrusion from the table clips into a stand from the base to stop the vertical movement. The clip is blown up in image 3. The blue block on the back of the table will run along the back connecting the table to the back wall for stability. The black arrow shows the pivot of the rotation.
This is my potential solution but I am interested to hear if you think this would work or if you guys have a better solution.

Thanks for your time.

 

[Scuka]

I see two problems here.

First is that the inclined part itself deflects, second is that the structure as a whole deflects. Supporting the structure from below with these blue things solves the second problem, but not the first one.

The members seem rather slender (thin and long), and being made out of aluminum makes the problem worse since it has 1/3 of modulus of elasticity compared to steel.

Other than supporting from below, the only way to manage deflection is to use a stiffer material and add height to members.

 

[goodallpg]

Thanks Scuka,

Yeah the pivots on the corners don't seem too strong but that is what came with it. Maybe adding some supports to this should be my first step. I am not a structural engineer myself so I'm looking to see if we can implement something ourselves before we get in contact with someone to see what they can offer.

Many Thanks

 

[Brad805]

What is the tolerance of the holes you are drilling? If thousandth's, this is a difficult problem. The extrusions appear to be fairly standard parts, so finding the section properties is not difficult. Your thrust bearing or rotating assembly could be a different problem unless it is a manufactured part that that comes with tech specs.

 

[goodallpg]

Thanks Brad,

We are creating a counterbored hole that a bolt can slide in but in our testing, after we create the counterbore and begin to drill through the product, the hole is no longer in the centre because of the movement of the table. The tolerance is relatively high. I'm afraid we don't have any specs on what was provided. This is the first time we are trying this which is why we have found the movement problem.

Thanks again

 

[Brad805]

You will need to carefully watch the drilling operation to see which parts are deflecting during the drilling operation.

Couple of thoughts:
1. The top assembly does not appear to change in shape. That could be re-built without those bolted joints. I have used ITEM extrusions and those joints come in different tolerances/stiffness. If you prefer to stiffen this assembly I would add some vertical members to reduce the span of your top truss member or add a plate to each side.
2. Your turntable support may remove much of the table deflection. You will need to experiment unless you want someone to analyze this.
3. If the turntable support does not stiffen the assembly sufficiently you will need to look at the moving parts of the rotating assembly. If the rotating assembly is made up of loose fitting parts (by loose I mean say +-0.050") that will amplify your problems.
4. The support arm between the rotating point and the top assembly could be another source of the problems as well. You have a cantilever, and if any of the load is applied on the left side of your new turntable support, it may need to be stiffened.
5. Getting your turntable support set correctly will take some trial and error. I expect the turntable may deflect some as it rotates or if parts are moved on/off during the operation. The top plane of the turntable support may need a taper at each end so the arm rides up to the correct elevation for the boring operations.