balloons or part numbers on assembly drawings

[BrianE22]

I'm used to seeing balloons with item numbers that link to a table showing the corresponding part number on an assembly drawing. A young lad I hired to do some Solidworks assembly drawings asked why he shouldn't just put the part numbers on the assembly drawing. These days, when it is just as easy to change a CAD drawing as it is to change an Excel spreadsheet, I'm not sure there is any need to use balloons with item numbers over just having the part number on the drawing. Any thoughts?

 

[hydtools]

The table or BOM would indicate how many of each part is used. How will you indicate that is the part number is put on the assembly drawing, I presume near the indicated part?

Ted

 

[MintJulep]

What are your assembly cell and part distribution processes?

Who are your assembly technicians?

 

[desertfox]

On our assembly drawings we use a 4 digit number prefixed with an M so M2304 would indicate a part number for that assembly and the M prefix also tells us that part has a drawing xxx-xxxxx-xx-M2304.

 

[JStephen]

On our drawings, I've seen it both ways. If a purchaser needs a list of items on the drawing, then the bill of materials is useful. If it's a simple drawing, it doesn't much matter. A major issue is doing it "the way we've always done it"- people used to using one type of drawing may stumble at the other.

 

[chicopee]

I believe that the reason for ballons with item numbers is to have a BOM listing not only the drawing number but also to describe the part instead of checking the part drawing for a description. Also with the BOM you may other pieces of information of the part which may be relevant to the assembly drawing.

 

[Sparweb]

No, the item balloons are a system to prevent duplication of information on a drawing. That is meant to prevent errors.

Every time you print the same information TWO times on a drawing, you make it possible for ONE of them to be changed at a future date, and not the OTHER. Who ever issued a drawing without it coming back for revisions later? By printing the part number on a leader beside each part call-out, you refer to it once, but then need a list or BOM somewhere else on the drawing to add material details and total quantity. Unless the drawing is so very very simple that this duplication probably won't get missed, then the system of item balloons makes it much easier to track down the instances of each part. Also cuts down on extra text crowded around the assembly view.

Your new guy should also be using the Solidworks features properly. If it's anything like Inventor (people say Inventor is a lot like SW) then it can automatically itemize the BOM, link the item number to each balloon, and when the item balloon's leader arrow touches an object in a view, the properties of that object are detected and linked to the number/letter in the balloon. I started using Inventor last year and this is one of the features that I'm really pleased to have, now. Saves me time.


STF

 

[jlnsol]

It seems a good idea to put the part numbers on the assembly drawing instead of item numbers. However items are more efficiënt in communication. Think about someone from assebly deptmt calling you about a part. It is a lot easier to find a two or max three digit number on an assembly drawing than a long partnumber.

 

[chicopee]

I suppose that if the assembly drawing is not complex,you could use drawing numbers instead of item numbers; a sub assembly drawing mayfit that bill.

 

[JohnRBaker]

It's a poor practice, period!

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
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To an Engineer, the glass is twice as big as it needs to be.

 

[KiwiME]

Years ago when engineers received small gifts from visiting salesmen, one gave me a list of wise sayings, one of those being "A man with two watches never knows what time it is." That helped me recognise the importance of not duplicating information, as Sparweb said above.

If you have some kind of ERP/MPR (enterprise/manufacturing resource planning) system (and who doesn't) then you should not duplicate information stored in that database. All you should do is reference it.

Ironically, the half-baked system in use where I currently work does not assign item numbers so I have to use simple descriptions on the drawings.

 

[BrianE22]

A lot of good points - thanks. I'm more comfortable with balloons and I'm leaning that way after reading your comments.

These assembly drawings are for the parts manuals that go to the customers. They order parts for repairs from these manuals. Most people that call will give us the part number they need but maybe 3 out of 10 will say they need "item number such-and-such". Then we have to pull out the manual to get the part number.

I played with Solidworks a bit myself yesterday. It does offer an automated ballooning procedure with item numbers. I didn't seen an easy way to write part numbers for each item.

I do like that with a BOM you can add notes to each item number. We don't currently do that but I can see a need for that now.

 

[Sparweb]

Brian,
It's interesting to read how engineers from different backgrounds and businesses can see things so differently. I left school knowing this stuff, so maybe I go around expecting everyone else to know it!

I use parts manuals and IPC's regularly at work, and they are usually itemized, too. If your customer is referring to "item #" then you can ask for which page or figure in the catalogue, and look it up with that. At your end, the sales orders can include the same page, figure and item number so that there's no confusion. Of course I would expect every one of your agents to have a parts catalog handy for reference, and by referring to it during the phone call can initiate a discussion that confirms that the right part/item has been selected. Many parts catalogs also include, among the first pages, an ordering form or checklist, also to help communicate without errors what part is needed.

Speaking from my experience with Inventor again, when you place a parts list on the drawing, and point it to the assembly that is also illustrated on the drawing, then the parts list is filled automatically with all the part numbers involved in the assembly. They also come in with item numbers, also generated automatically, although they may be in a random order. Then the "housekeeping" begins to sort things out. The point, however, is that the part number, and its material properties, sizes, dimensions etc. have only been defined by the designer only ONCE. All subsequent uses of the data and numbers is linked to the original by SW for you. Not that you can't override it...


STF

 

[drawoh]

BrianE22,

How consistent, unique and sortable are the part numbers on your assembly? You need to look at the part on the assembly and reference it to a line on your parts list. SolidWorks is capable of making your part number and your BOM work. I am not sure this is the best way.

In SolidWorks, I like to sort things so that the fastener sits next to the item it attaches, or at least the first item it attaches. A lot of people try to sort the parts list with the fasteners at the bottom. All of this will be impossible if you sort by part number. Perhaps that is okay for you.

--
JHG

 

[ShaggyPE]

One issue with part numbers spattered all over the face of the drawing is that they are easily missed. The person ordering the parts could easily miss an item. If they are organized in a list, it is much more likely to capture all items. In addition to the points above regarding quantities and descriptions.

In my place of business, we have 25 yr old drawings that use part numbers instead of balloon callouts. We have had first hand issues missing parts on more complex assemblies.

-Dustin
Professional Engineer
Pretty good with SolidWorks

 

[KENAT]

OK, so this isn't a typical engineering drawing, it's an illustration from a user manual or similar?

In that case I can see the attraction of putting the actual part number and not having a parts list as such. Total qty for BOM generation may not be particularly relevant. Our cad system can dynamically call out the indicated components part number which minimizes the issues from listing something multiple times.

However, for a true engineering assy drawing I'd tend to stick with balloons.

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[kjoiner]

Hello,

I say go with balloons for several reasons:

1. They are the correct drafting practice
2. Balloons with a single BOM minimizes duplication and chances for errors. My CAD system can call out baloons or part numbers linked to the model, but reason #1 overrides that.
3. The drawing is much cleaner
4. I chain balloons when calling out a part and fasteners. Using part numbers would quickly clutter the drawing
5. Adding quanities under each part number rather than under a baloon creates clutter.
6. If you don't have a dynamic link between the baloons and BOM, it's much easier to see an item number in a balloon to check against the BOM than it is to see part numbers all over the page.


Kyle