How to reduce CNC routing costs

November 14, 2017

Your biggest cost driver for any CNC machining project is almost always the time it takes to machine the part. Materials, set-up time, and custom finishes can factor in. But the time it takes to actually route the part typically exceeds these.

So with that fact in mind, here’s what you can do to cut your CNC routing costs nearly immediately:

Use a Length to Diameter Ratio of 3:1 Or Less for Inside Corners

The wider the radius of your inside corners, the fewer the passes it takes to make them. That leads to lesser routing costs.

In some cases, with a narrower radius, you even have to change your tool to get your inside corners right. So if you can, and wherever possible, make sure you have a length to diameter ratio of 3:1 or less.

In an ideal world, all your inside corner radii have the same ratio so you don’t have to do any tool changes.

Avoid Parts With Deep Internal Cavities

When it comes to cost, deep internal cavities are not your friend. They require fragile tools that break with some frequency.

To work around that potential pitfall, you have to step an end mill down in smaller increments until you reach what your customer requires.

If you stay with parts with lengths up to 4 times their depth, you’ll generally be okay. Anything more than that significantly boosts your manufacturing time.

Only Assign Numerical Values to Critical Features

The more features with numerical callouts that your part has, the more time it takes to manufacture.

However, if the part works fine with a standard tolerance set by the model, that takes far less time.

If you can, define just a single datum, and then create all your other dimensions based on that.

Every step counts.

Thin Part Walls Should Have a Minimum of 1/32” Thickness

When your part walls go below 1/32”, they tend to create chatter. To compensate, you have to slow your routing speed.

This can also lead to distortion of the part. Both factors increase your costs.

If you have to go thinner than 1/32”, sheet metal fabrication may make more sense for you and your customer.

And there you have it. 4 simple ways you can use to cut your CNC routing costs nearly immediately.

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