Help needed checking over some dimensions + sheetmetal info

[Anonymous]

Hi all. 

This is going to be my first time sending sheet metal drawings out to a shop.  I feel like something is off because I should be including bend tables or angles somewhere... but I guess these are very simple parts with all 90* bends and might not need it? Am I good leaving things how they are with the radii, or are they going to take that as milling it out of a solid block and putting the radii in with something like a ball nose mill? 

https://a360.co/2NbFZII

Drawings in question are on sheet 2 and 5. If anybody wants to check over the rest of the dimensions on the other sheets and let me know how I'm doing, that would also be appreciated. 

Thanks!

[TheCADWhisperer]

I see several issues of general aesthetics, but also these issues....

Typically I will ask, "Can't you see these?"

I haven't even opened the file yet and expect to find more issues when I do....

Edit:  Hmm - that is strange.  Issues that I pointed out from the preview I do not see in the actual file?

The angle of this isometric view looked strange to me.

And I would add lead-in chamfer to threads (although - unless these are 3D printed, I would not use modeled threads at all - I would use cosmetic threads for simplified representation in 2D drawing). See Attached file.

[Anonymous]

I have absolutely no idea what's up with the preview of the files... it's not like that at all in my files haha. 

Also, that isometric view is not there either. I seriously have no clue what's up with it. Only the shaded isometric view is there, unless that's what you were talking about and saying that I should use the clear one instead.

Aside from that... are things good? Are the sheet metal parts understandable to a machine shop? I'm not exactly sure what you mean about the threads, but I haven't had any issues in the past. I know I don't need to model them either, I could just use a hole and the callout... but it looks better for the people who aren't CAD designers where I'm working to look at. I could make two sets, one for the shop and one for the people here... but **** yo, I ain't getting paid that much.

Please let me know if there's anything wrong with it that I haven't covered. 

[mbostonsprint]

Not to be snarky, but this looks like design without engineering to my eye --

I would suggest that you read up on alloy selection for forming operations, and also look at what is typically available for thicknesses as stock material for those alloys. Additionally, sending a "sheet metal" shop drawings with dimensional callouts at +/-.0025 on powder coated features is a way to drive your costs through the roof.

[Anonymous]

You are correct. There is not much "engineering" in the part because it does nothing except slightly clamp a hose we have running through a guide. I was told to make it quick and cheap - but so that it looks nice enough for clients as well.

The sheet metal parts should be 3003 alloy IIRC, thanks for the reminder, I'd forgotten to change that from 6061.

The hole locations on the top of the main body drawing probably don't need to be .0025, especially since I'm using slots on the actual attachment mechanism. 

Lastly, as just an intern - I've only been informed that "if the shop has any questions at all, we have a good enough relationship with them that they will ask" - so far, I've had no issues and prices have been quite reasonable. 

For the mounting panel - the .0025 toleranced features seem independent of the tolerances generally though of when forming sheet metal. They can simply locate off of each corner of the stock that I've indicated. Is that not a correct way to think?

For the clamp fastener, I guess I could get rid of .0025 tolerances and make the slots themselves slightly wider.

Does these sound like good ideas to you? Please let me know everything you would change. It's not really my job to put a ton of engineering into this, just to be fast and cheap with it, have it work, and have it look good enough for customer use. (Please not, I'm not trying to say "do my job for me") - I just really thought the tight toleranced portions of the mounting panel would not be affected at all by the bend, given the way they can be located. Total height/width doesn't need to be a tight tolerance at all, and that's what the bend would affect. Maybe I should change those from .005 to .015ish.

Thanks

[mbostonsprint]

There has been a lot of improvement in sheet metal forming technology in the last couple of decades, and with laser-cutting and CNC-gauged forming, things are a lot better (read: more tightly controlled) for bend and feature location than they were before. Nevertheless, +/-.010 is about as tight as would ever specify on a sheet metal part. If your company does indeed have a good working relationship with a shop, then for sure ask them the questions. But, the +/-.0025 is too close no matter what, in my opinion. "Standard" precision tolerance for machined features and hole locations is +/-.005, typically. And the powder coat can certainly be variable enough based on application practice to cause several thousandths variation in a feature with two coated surfaces involved.

Alloy 3003 will be usable for this. I would probably look at 5052 for something like this as a first candidate, but if you have received direction for alloy choice already, so be it. Should work fine.

[Anonymous]

Thank you for your advice. Can I ask why you would choose the 5002 over 3003? This is not a high strength part at all - I thought 3003 was the 'typical use case' and 5002 was for if you have more demanding needs. I do have the final say in what we use - I just know we have used 3003 for a lot of the parts that were here before I came.

Thanks again.

[mbostonsprint]

I suppose my experience is simply that more of the parts I design for forming in aluminum would be higher performance, "high-tech" instrument parts. The 3003 alloy is very widely used, for sure.  The alloy I mentioned is 5052, not 5002, but in any case, there is a cost premium for raw material, about 25% additional for 5052, but on small parts or limited production, that is often inconsequential. The effort for the fabricator is essentially the same.