How to optimize this part for production

[omarmorocci]

I would like to produce the 3mm thick sheet metal steel part shown bellow but I have a few questions.

I have my doubts about the whether the bending of the top right part (with the holes) will work. The 5 mm spacing has to be there as the tool will be inserted into a 3 mm surface

Feel free to add any other comments

 

[JBA]

Since you have provided the required notches on both sides of the top plate the bending of that plate should not be a problem, it will simply require the mechanic to use a top blade that cut to the inside width of the formed channel to make that bend and center bend as well.

Just as a note, I cannot tell from the drawing what bend radius you are using for your bends but for best results the inside radius should be no less than 1 1/2 x the material thickness

 

[omarmorocci]

Since you have provided the required notches on both sides of the top plate the bending of that plate should not be a problem, it will simply require the mechanic to use a top blade that cut to the inside width of the formed channel to make that bend and center bend as well.

Just as a note, I cannot tell from the drawing what bend radius you are using for your bends but for best results the inside radius should be no less than 1 1/2 x the material thickness

Thank you for your feedback.
The bending radius I am using is equal to the thickness of the material as that is what they use in the workshop.

I have some other questions in mind regarding this tool:
1) How long should the leg be relative to the base/web for maximum stiffness in the plane perpendicular to the legs

2) How can I increase the stiffness of the tool in the plane perpendicular to the legs without adding additional parts.

Thank you in advance

 

[JBA]

The web, not the legs is what provides stiffness for loads perpendicular to the legs. The legs are what prevent warping of the web due to that loading. I cannot give you a specific answer to your length vs leg height but you can calculate area moment of the channel and the deflection under load in the plane of of the web using a standard channel beam stress and deflection analysis. As for the best leg height to channel web width, as a guide to practical ratios I recommend you take a look at the dimensions of standard commercial structural "C" channels.

One caution about using channel shapes for lateral loading, the the load must be applied directly transverse in line with the web face of the channel. Any load that creates a torque on the channel, for example, a force applied to the face of the extension you have on one leg of the bottom arm of your fixture will easily twist that arm; and the same problem applies to the vertical arm of your fixture. Any lateral load applied to your horizontal arm is going to easily twist that vertical arm. (As I pointed out in my post to your earlier Physics Forum thread about this fixture design)

 

[omarmorocci]

The web, not the legs is what provides stiffness for loads perpendicular to the legs. The legs are what prevent warping of the web due to that loading. I cannot give you a specific answer to your length vs leg height but you can calculate area moment of the channel and the deflection under load in the plane of of the web using a standard channel beam stress and deflection analysis. As for the best leg height to channel web width, as a guide to practical ratios I recommend you take a look at the dimensions of standard commercial structural "C" channels.

I followed you advice but instead of calculating it I figured it would be better to simulate it in solidworks. I simulated a force of 5 N on the leg of the tool.

I got a maximum deflection of 10 mm, which I think is pretty big for such a small force

Bellow is the top view of the deflection

 

[JBA]

That is no surprise to me, as I have already explained, channel type beams are very easy to twist when subjected to a torque.

 

[omarmorocci]

That is no surprise to me, as I have already explained, channel type beams are very easy to twist when subjected to a torque.

Well, what are the possible adjustments/ alternative that could be used to minimize this twisting ?

 

[JBA]

The main issue is that you apparently have a very limited space width for the mounting of your fixture and apparently nothing to connect to for restraining the end of the horizontal arm. Using a rectangular tube shape for the vertical leg will substantially increase the torque resistance of that leg; (You can run a FEA analysis to see how much improvement that will provide) but, that is going to require either using rectangular tubing for that section and welding or bolting the top connection plate and horizontal leg to that member; or possibly making a second channel that can be fitted into or around your current channel from the open side and welded to form a rectangular tube shape.

Beyond that, without seeing an overall picture of the item on which this fixture is be mounted it is impossible to know what other alternatives might be possible.

 

[RogueOne]

Well, what are the possible adjustments/ alternative that could be used to minimize this twisting ?

Have you considered a cross-brake on the mid-sections of the channels? Have you considered any other deformation features such as gussets on the bends on the sheet metal?

I think that scrolling through this page will help spark some ideas about deformation features that you could use on this structure to increase stiffness. Try them in your FEA. Try a few different ones and put them in different areas. http://www.soliddna.com/SEHelp/ST6/EN/create_sheet_metal_part/shtpls1a.htm