21 Replies Latest reply on May 17, 2015 12:39 PM by J. Mather

    How are sheet metal drawings made

    Andi H

      I have never done or worked with sheet metal before. but how are the drawings for sheet metal made. You make drawings for flat pattern then make drawings for the bended model?

        • Re: How are sheet metal drawings made
          Jeremy Feist

          It depends on your requirements. if you (or your company) are doing the bending, you will likely need the flat pattern, and to fully dimension it.

           

          if you are having someone else bend it, all you need is a drawing of the finished part - they should develope the flat based on their processes (the flat can be different depending on HOW you bend it)

          • Re: How are sheet metal drawings made
            J. Mather

            I am confused by what you mean by "drawings", but -

             

            Normally you would model the part in its finished folded up form with the desired finished dimensions. within the modeling environment (*.sldprt).  This is best done using the sheet metal tools (especially for beginners) but any modeling tools can be used as long as you follow sheet metal rules (uniform thickness, perpendicular edges....).

             

            Sometimes it is necessary or easier to use tools other than sheet metal tools and then convert to sheet metal.

             

            Once you have the finished form - SolidWorks should automatically give you the flat pattern that would be required to make the part.  You need to know something about bend allowances, k-factors, bend tables if the part dimensions are close tolerance.

             

            Once the folded part is created by you and the flat pattern is created by SolidWorks, then you can create drawings of both the folded flat pattern states in the drawing (*.slddrw) environment.

             

             

            Usually when modeling it can help to try to reproduce the same techniques used out on the shop floor.  With sheet metal this would drive you crazy.  Very rarely would you try to develop a flat pattern and THEN fold it up.  That just doesn't work very well and requires lots of calculations.  You know what the finished dimensions are that you need - model it in finished form and then work backwards to the flat pattern.  (or let the fabricators figure out what to do from the finished dimensions to get the finished dimesions - that is what the customer pays for)

              • Re: How are sheet metal drawings made
                Andi H

                Thats what I meant for a sheet metal drawings what are required to submit? flat patter bended drawings or both. K factor bend radius metal guage will all be calculated but the guy who does the bending.

                  • Re: How are sheet metal drawings made
                    Jeremy Feist

                    it sounds like you want someone else to do the bending. then you need to supply the finished shape and dimension, along with the material and thickness. they should do the rest.

                    • Re: How are sheet metal drawings made
                      J. Mather

                      Depends on who is doing the work for you and how closely you can work with them.

                       

                      If communication is not ideal - then I would submit only the finished folded form drawings - not the flat pattern.  It is up to the fabricator to figure out how to make the finished part.

                       

                      If communication is good, (especially if in-house) I would communicate with the fabricator supplying them with the SolidWorks created Flat Pattern drawings (in addition to the finished form drawings) as reference.  Working with them you could then elevate the reference flat pattern drawings to controlling documents once the bend allowance parameters are known and tested.  This saves money if you do a lot of this type of work as you (SolidWorks) can figure out the flat patterns rather than having to use production time to figure out.

                       

                      But if communication is not good and you supply the flat pattern and it doesn't return correct folded part - the fabricator is going to blame you.  ("hey, I used your dimensions, I can't help it you don't know what you are doing") Bottom line - the finished form drawings must be the controling document.

                  • Re: How are sheet metal drawings made
                    Glenn Schroeder

                    Andi,

                     

                    I agree with Jeremy.  I've talked to several people who do sheet metal work and they've all said that they just need drawings of the finished product and they'll figure out how to cut and bend it.  If you do want to include a flat pattern as a courtesy I would recommend a big red note across it that says "For Refence Only".

                    • Re: How are sheet metal drawings made
                      Steven Smith

                      Never send a flat pattern to a sub-contractor!!!

                      Best thing to do would be to send a .STEP file along with the drawing, they can import this into Radan/Tops etc.

                       

                      Dimension to intersections

                      Where possible keep to outside dimensions (unless inside is critical)

                      Include angles (for brake press operators to program cnc's)

                       

                      If using PEM inserts specify on the drawing that the sub-contractor ensures hole sizes are correct.

                        • Re: How are sheet metal drawings made
                          Andi H

                          Here is how this works. Companty has no engineers at the moment I am the Industrial Designer so its up to me to do 3d and drawings. I have give my drawings to technical manager he gives them to guy who does the bending and sheet metal work for them. so since I have never done sheet metal work before I wasnt clear on how I should submit the drawings. I guess I will make two seperate sheets and let them decide which to submit

                            • Re: How are sheet metal drawings made
                              Jeff Holliday

                              Follow Glenn's advice. Provide a dimensioned drawing showing the finished (formed) part. If needed, show the dimensioned flat pattern as reference only. Even if someone in your company is making the parts, they will get irritated with you when you tell them how to cut the part and they cannot get the finished size correct. In order for it to be correct you WILL NEED to know the K-factors or bend allowance used by the tools on which it will be formed. The material type (density, temper, etc) will likely make a difference. The differences will be more pronounced if the part is thicker. These are the things that the shop-foreman will know how to adjust for.

                          • Re: How are sheet metal drawings made
                            Josh Killalea

                            Jeff and Anna are right on the money. i was a sheetmetal worker for 10yrs and not even once did we get a flat pattern off an extrenal supplier we could use. don't waste your time. i wouldn't even bother to model it with the sheetmetal features unless you are really familiar with them and can do some things faster that way. just do your part/assembly to look like what you want it to look like and let the fabrcators do the rest.

                             

                            something that every designer should know about sheet metal is that the "k-factor" can change not only from the tooling that is used to make the bend, but from the individual sheet that is used and even change depending on where the part was cut from the sheet depending on the material used and the manufacturing process.  and that doesn't even strat to cover a whole host of other things like availability of sheet and sheet sizes etc. etc. etc.

                             

                            even knowing all the things i do from working in the trade for 10years i don't do it because it can change from shop to shop. so don't try and tell the fabricators how to do what they do. you will NEVER get it right unless by pure chance.

                              • Re: How are sheet metal drawings made
                                Erik Bilello

                                Andi,

                                 

                                Josh is on the money too. I've worked at companies where the sheetmetal was fab'd in house and we did the flat pattern development.  Basic stuff was well established and if we needed to know what bend allowance to use for something unusual, or what sort of clearance was needed for tooling, etc. the answer was just a few steps down the hall, I miss that convenience. Now I'm working for a company where all fabrication is done out of house.  I send a PDF drawing and parasolid of the formed part (the shop we use most is a couple of SW releases behind us) and let them work out the appropriate flat pattern to suit their tooling.  Here, I need a finished part, I really don't care, or need to know, what the flat pattern looks like.  I do go over to the fab' shop (fortunately right next door) and ask what they can and can't easily do, what material is most readily available, etc., that way I don't get too many change requests.

                                I would advise that if you have a chance to get to the sheetmetal shop and see how your parts are made, do so.  The more you understand about how your parts are going to be made the better your designs will be.  And you will have a better understanding of what questions to ask earlier in the design process, I.E. know what you don't know. The shop will appreciate not getting designs that are outside their (or maybe anyone's) capabilities too.

                                So, try and get to know what the shop you're using can do, but let them worry about how to do it.

                              • Re: How are sheet metal drawings made
                                Steve Krause

                                I agree with the others that advise against providing the flat pattern.  At my previous employer we did a lot of designs of sheet metal that had rivets and/or pem nuts and or welds.  Years ago we fully dimensioned the drawings to show every feature on every surface.  Over the years we learned that it wasn't necessary and instead we just gave the important dimensions like the overall size, or critical distances between holes, and then only when in situations where it was really important.  We did not use GD&T (and I wish I had learned a bit about that, as it seems it might be useful sometime). 

                                 

                                It is important to show as many views on the drawing as needed to really help the guy on the shop floor see which way he is bending the metal.  If you find there are too many lines on the drawing and it is confusing to figure out what you are looking at make sure to turn off tangent edges on views.

                                 

                                It is also important to help the guy on the floor by clearly showing the orientation of fasteners so that he doesn't put them in on the wrong side, oriented wrong.  Adding notes like PROTRUDES FAR SIDE or something like that can be helpful when you call out a PEM standoff.

                                • Re: How are sheet metal drawings made
                                  Bernie Daraz

                                  I have been in precision sheet metal for more than 40 years and I feel you should generate a flat pattern. Why, because it might point out issues that will affect fabrication and therefore part cost. If you should 'see' in your flat pattern, overlapping flanges, you will need to design around that or figure on a welded, multiple piece part. Maybe you don't need to design around that though and just leave it up to your fabricator, though with this option you may get unfinished welded corners where you didn't expect them.

                                   

                                  If it isn't detailed don't expect it. Expect different parts when changing fabricators. By different I mean a new fabricator may not provide the level of service you've come to expect from your existing one that likely 'understood' what you wanted or needed.

                                   

                                  For quoting, a flat pattern view with overall dimensions (bounding box) only gives me a quick picture of the material required and allows me to quote faster.

                                  • Re: How are sheet metal drawings made
                                    Dennis Bacon

                                    There is a bunch of good information in this thread. It is unlikely (but possible) that a vendor or in-house fab dept in this day and age would need or want a flat pattern in a drawing. The exception is what Bernie alluded to and that is for quoting purposes. Today most designers do as Anna said. Don't bother with it. The only exception I can think of is if the fab shop is still in the stone age and has to layout a blank for punching setups on single hit, single tool presses. When I began in precision sheet metal 49 years ago there was no cnc or even calculators (yes used a slide rule, trig, and lots of paper). As always, the proper bend deductions for the tooling being used would have to be figured for an accurate part.

                                     

                                    If a flat pattern is required and the shop is going to use it for bending, layout, and inspection, the outside mold lines (virtual sharps - not face to bend intersections) and bend lines should be included and dimensioned accordingly.

                                     

                                    If only model views are shown then dimension fully and to virtual sharps. (O.D.). Inspection most likely will need that information.

                                    As pointed out in an earlier post it is always a good idea to flatten your part to check for errors.