If you are designing weld and assembly fixtures, sometimes you will be approached by someone in production who might say, “Your fixture was working just fine, but now it doesn’t work.”

Or you might be approached by someone to design a fixture when nothing on the production part has a tight tolerance you need to hold. That is fine and good.

However, just know that the person, machine, or company that is producing the product parts that your fixture will hold MUST make them all the same or very closely the same (tight tolerance variance). If there is too much variation, your fixture just won’t work.

So besides having products designed for manufacture-ability, they have to be manufactured consistently.

I interviewed Rentapen‘s founder, George Straley, on this topic. See what he said.


George says “No”, you can’t design a fixture for inconsistent parts. I am a believer that nothing is impossible. Impossible just takes more time and money to accomplish. And there is the problem. Manufacturers are in a race to get things done fast and for less costs.

Do YOU have a way to do this? Maybe with slides that tighten and release? If YOU have figured it out, please let me know. I will put my email in code, here so the spam-bots don’t find me. news at rentapen

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Have a wonderful holiday.

The Queen

One Response to “Weld and Assembly Fixture Design – Production Part Tolerancing and Consistency”

  1. rentapenblog says:

    This comment came to me from Barry Payne: Part consistency was a big issue back when I was doing new customer integration for Fanuc welding robots. Helping someone with their first welding robot is a steep learning curve. Parts +/- .125″, crooked, not to size hot roll shapes, different spring back in formed parts, different tape measures……ect. In the end they had a much higher quality part and good production but it was a chore.

    We used to do our own welding automation for varying sizes of parts by measuring the part when the robot grabbed it. Usually the edge to be welded would be against two know surfaces. When the servos felt the part they could compare actual position to nominal and offset home or zero to adjust the weld path in the welding robot as needed. We used Delta Tau which could easily several multi axis robots/machines/fixtures so data was easy to share.

    In the past it was difficult to interface with off the shelf welding robots like Fanuc. But I have not programmed one in many years. If you had some measurement feedback on a clamp in a weld fixture there might now be an easy way to get the data into a off the shelf robot like Fanuc, Motoman…ect.

    A smart welding fixture that measures parts and tells the robot to adjust the weld path.