SOLIDWORKS Tech Tip – Using DFMXpress

DFMXpress is the smaller brother of the full blown version DFMPro by HCL Technologies, LTD and is included in each level of SOLIDWORKS. DFM stands for Design For Manufacturability. This is a tool we can use to improve our designs by ferreting out those difficult, impossible or expensive to manufacture features we add to our designs. DFMXpress also helps us conform not only to good manufacturing guidelines but also company standards for best machining practices.

I certainly could have used a tool like DFMXpress when I started my career as a design engineer at Xerox. During the prototype stages of the product design process we had parts made in the Model Shop. The Model Shop was manned by a dozen or so Journeymen who knew how to make parts. Every now and then one of the Model Makers would appear at my desk and ask me “son, how would you make this part?” When that happened you wanted to crawl under your desk because the next thing you heard was all the reasons why my beautifully design part couldn’t be made in the shop and some exotic expensive process like EDM had to be used to make it. I took those episodes as learning experiences because there’s nothing like learning from a highly experienced model maker on how to design and manufacture parts.

DFMXpress uses a set of rules we establish for the following types of machining:

1)     Drill Rules for various types of holes.

Hole Diameters

Holes with flat bottoms

Hole entry and exit surfaces

Holes intersecting cavities

Partial holes

Linear and angular tolerances

Standard drill or punch size check

 

 

2)     Mill Rules for general types of milling operations such as:

Deep pockets and slots

Inaccessible features

Sharp internal corners

Fillets on outside edges

 

 

3)     Turn Rules

Minimum corner radii

Bore relief

 

 

4)     Sheet Metal Rules

Hole diameter to thickness ratio

Hole to edge distance

Hole spacing

Bend radii

i.     For most materials the bend radius should be at least equal to the material thickness

 

5)     Injection Molding Rules

Minimum and Maximum wall thickness

 

Let’s go through setting up rules in DFMXpress to check these parts:

This is the setup page for Mill/Drill processes. We’ll use the defaults for our example.

Here are the results. As you can see there are a number of problems with this part. 2 holes violate the hole depth to diameter ratio, there are internal sharp corners in the rectangular slot, a hole with flat bottom, fillets on the outside edge, deep pockets and so on. These violations drive up the cost of the part. Removing these violations the part can be made cheaper and faster.

The sheet metal part faired a bit better than the machined part. Most of the violations have to do with hole to edge and standard hole size violations.

As you can see DFMXpress is a handy tool to use to make sure your designs can be easily machined at the lowest cost possible.

Mike Sabocheck
Mike Sabocheck is a Technical Sales Director with Dassault Systemes SOLIDWORKS. Mike has been with DS SOLIDWORKS for 21 years. Prior to SOLIDWORKS he worked for Xerox for 17 years and then for Intergraph. His specialties are applying SOLIDWORKS to different design and manufacturing processes.
Mike Sabocheck

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