Sheet Metal Prototyping Done Right
To avoid common pitfalls of sheet metal prototyping, follow these tips
Your company has just designed a great product, and it’s your responsibility to take it from the drawing board to a working prototype in sheet metal. You need a prototype fast, and you need it done right. You’d prefer to use the same vendor from prototype through final production. To increase the chances of your project’s success, here are key steps to take when selecting and working with a sheet metal fabrication vendor.
Check Their credentials – Not all shops are created equal. Check to see that it is SO 9000 certified, and if your product is a medical device, find out if they have ISO 13485 certification.
Tour The Shop – Is the facility clean and orderly? Is the manufacturing equipment up to snuff and is the work flow smooth and efficient? Check the quality of their finished products. Ask about past and current customers and projects. Have they ever manufactured a product like yours? Can their current workload and schedule accommodate your project and deadline? Do they use the latest 3-D solid-modeling software to verify form, fit and function of devices?
Get To Know The Engineering Team – A good, collaborative engineering team is worth its weight in . . . a perfectly produced product, if not gold! The shop’s engineers should act like a part of your team. They should be responsive and eager to share ideas with you, able to find mistakes and suggest improvements to your design.
Take A Tool Inventory – Once you’ve selected a shop, research its tool inventory and try to use the tools they have to avoid the time and expense of having to order special tools for your project. For example, my company Airtronics’ Web site features a “tool library” so design engineers can see what tools we have and utilize them in their models. Provide A Good, Clean Model (supported by drawings that match) – Production houses rely more heavily on models than on drawings to produce parts, but you can expedite the process by providing them with drawings that specify, at minimum, the following information:
- Material type and thickness.
- Overall size of part, and length of all flanges.
- Any hardware.
- Threaded holes.
- Any dimensions more critical than +/- .005 per bend, and +.003/-.000 on through holes.
If you really don’t have time to make a drawing, but you provide the shop with a good model and all of the above information, they can make the drawing for you, but it may slow them down.
A few things to keep in mind when designing for sheet metal:
- Sheet metal thicknesses vary: by as much as ±.004 (and usually come in on the minus side), so if your project calls for countersinking in thin sheet metal, check to ensure that the countersink you call for is achievable within the actual material’s thickness. Do not specify countersink depths all the way to the theoretical bottom of the material. Do specify the major diameter at the countersink rather than at the through hole.
- Bend radiuses and deductions are routinely changed: by the engineers at production houses. For this reason, avoid constraining any features to a bend radius, because if the bend radius is changed, the feature will move. Your best practice is to tie the feature’s location to an outside edge.