Engineering

Herold Precision Metals engineers bring years of sheet metal fabricating experience to bear on even the most complex problems. With the ability to anticipate and resolve manufacturing challenges even before the process is begun, we insure the development of products that can be manufactured easily and cost-effectively.

For engineering support contact: Jim Gaffke - Director of Program Management at jgaffke@heroldprecision.com

Product Development Support

During the product development cycle, Herold Precision Metals collaborates with customers from product designing to rapid prototyping to manufacturing. During the initial phases of development, HPM engineers serve as a resource to our client's own design staffs, which is especially critical to clients who have been forced to downsize their own product development operations. By providing design and engineering services, we help improve speed to market. HPM also offers manufacturing expertise, helping designers translate ideas from the drawing board to the assembly line. By applying DFM principles throughout the development process, we can ensure that a product are manufactured efficiently while maintaining its aesthetic and functional purposes.

Value engineering

Our expertise can also help OEMs with their existing products. Using a process known as value engineering, our team evaluates a customer's product looking for ways to reduce manufacturing costs and to simplify assembly (DFMA). Value engineering delivers parts at a lower cost that are easier to assemble.

Engineering Software

(6) Seats - SolidWorks
(3) Seats - Pro/ENGINEER (Wildfire)
(1) Seat - CADKEY

Sheetmetal Specific Machine Programming Software

• Amada FabriWIN
• Amada Bend Cam

Sending electronic files to Herold Precision Metals:

• Via e-mail, send to Jim Gaffke – Director of Program Management at jgaffke@heroldprecision.com
• Via e-mail send HPM your company FTP site access information
• Contact HPM and we will set up an FTP site for you
• Mail a CD, DVD disk to: Herold Precision Metals 1370 Hammond Rd, White Bear Township, MN 55110     Attn: Jim Gaffke - Director of Program Management

Best practices for sending files

12 things you can provide to expedite service and get the most accurate parts. All CAD files should have an attached file or notes providing the following information:

1. Provide a point of contact for technical questions. Include: name, phone, and email address.
2. A revision level must be included in the filename.
3. We have the capability to read most native file formats including SolidWorks, Pro E, and AutoCAD. SolidWorks with sheet metal is the preferred file format. 3-D files other than those mentioned should be sent in STEP or IGES format. IGES files should be sent as a solid whenever possible.
4. 2-D files, such as prints, should be sent in .DXF format. SolidWorks drawing files (.slddrw) are preferred, and the part file(.prt) must accompany the drawing file.
5. If arcs are drawn for bends, they must be tangent to flange planes. Unless there is a need for bend radii to be different, all bends should have the same radius. Bend radii not specified will be .03 or .130 depending upon material thickness. Bend relief not shown on CAD files will be left to our discretion.
6. Material thickness, material type and specification. I.E. 0.050 thick 5052-h32 aluminum.
7. Hardware type, manufacturer, location, and installation direction. Hardware drawn in the CAD file is preferred. Holes for hardware should be drawn to the spec that the hardware manufacturer recommends.
8. A parts list for assemblies including file name, part number and revision, and description.
9. If assembly is required, a 3-D file specifying which parts are to be assembled and by what method. I.E. rivet, spot weld, etc.
10. If rivets are to be used, what type (pop rivet, flathead, etc.) and installation side.
11. Part Marking specification and location.
12. Finish requirements. Paint or powder specifications, anodize, plating, etc.

Sheet Metal Fabrication Tolerances

Best Practices in Tolerance Specification

Although the machinery and tooling will repeat within .004", it is a mistake to simply engineer all mating parts expecting +/-.005" accuracy. Such over kill forces additional labor in sorting and inspection. The result of tolerances that are too tight is simply higher cost and lower productivity. Correctly toleranced parts will still have excellent fit and function, with the added benefit of manufacturing efficiency.

Click the Image to Download HPM's Recommended Tolerance Document

Hole Sizes
Forcing a punch tool through the sheet metal in order to rip out a slug produces holes. When the punch retracts the slug remains stuck in the die tool and a hole is left in the sheet metal. The size and shape of the punch and die tooling determine the size and shape of the hole. A minimum hole or relief size is determined by the thickness of stock to be used, for best results the punched feature can be no less than the material being punched. The die tool is slightly larger than the punch to minimize tooling wear and to reduce the pressure required to punch the hole. Generally speaking 10% of the material thickness is used for most applications. For example, the material is .100 aluminum and the punch diameter is 1.000”, the die diameter would be 1.010”. The size of the hole on the punch side will be the same size as the punch tool. The size of the hole on the die side will be the same size as the die tool. Except for tooling wear, there is very little variation from one hole to the next. Herold Precision Metals has an extensive library of tooling, but we do not stock all possible tool sizes. This is why we look to the designers, engineers and draftsmen to give us a tolerance range that allows us some flexibility in using tooling that we have in house. When that is not possible, a capital investment in new tooling is required. Generally speaking, +/-.003” is a reasonable and functional tolerance.

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Hole to Hole

Accuracy of the distance from one hole to another is dependent primarily upon the machinery used to process the sheet. Herold Precision Metals has equipment that will hold better than +/-.005” with little difficulty. However, all holes and features punched through the sheet can introduce stress into the sheet metal. If the part has a closely spaced perforated pattern or formed features such as dimples or counter sinks the result can cause the sheet to warp and distort -- this can cause unwanted variation between holes or features. If this condition exists, a greater tolerance should be applied to certain areas surrounding this characteristic.

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Hole to Edge

Part profiles are punched just like any other feature except when using a machine with shearing capabilities; these dimensions should be considered the same as hole-to-hole. When punching close to an edge (less than double the material thickness) the edge can be pushed out by the stress of punching the metal. This edge movement can introduce variables in the accuracy of the hole location in relation to the edge. There are techniques to minimize this problem but whenever possible, engineers should allow +/-.010” hole-to-edge. Tolerances of +/-.005” should be used only when absolutely necessary.

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Hole to Bend

Several factors have been introduced leading up to this stage in the fabrication process. Features and parts have been punched on a CNC turret press, line sanded or tumbled to remove burrs, and now is being formed on a press brake. The deburring process may remove .003” when cosmetic appearance is a priority. Precision press brakes will position and repeat within the +/- .002” range. Skilled brake operators are able to load the parts for forming consistently from bend to bend. Nevertheless, consideration must be given to the natural variation in material thickness (5% of nominal thickness), the +/-.005” from the turret press, the effects of cosmetic sanding, and the variation introduced by the press brake. A tolerance of +/-.015” hole-to-bend is functionally reasonable for most applications. Resort to +/-.010” only when absolutely necessary.

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Bend to Bend

Considering the variables that effect "hole to bend" tolerances, now multiple material surfaces and thickness are introduced. Whenever possible, engineers should allow +/-.020” bend-to-bend. Resort to +/.010” only when absolutely necessary.

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