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Revisions in Weld Fixture or Machine Design
What is a revision in machine design?
It is a change to the production machine or weld fixture that is made after the drawings have been “released”.
When the drawings are released that means the shop can start machining parts and putting the machine together. So any changes to the drawing and design are now being made after the metal is formed. Changes are even made after the machine is on the floor and production has begun.
There are lots of reasons why revisions or changes are made.
Some of them are:
1) The machine was poorly designed and doesn’t work well.
2) Changes to the product have occurred. For example, sometimes, when we are designing production machinery, such as a weld fixture, the product design team is still making final changes to the product design. Sometimes the company is in such a hurry to get the new product into production that the production machine is on the floor or the machine is being built while the product design is still being “tweeked”. Small changes in the product can mean that changes also need to be made to a weld fixture or other production machine.
3) The guys on the floor discover a better way or an additional process that can be done at that one station.
4) A mistake was made while building the machine and modifications were made that need to be documented.
We have found that a step by step process is helpful for reducing errors and time involved in making drawing revision when using 3D CAD.
THINK! Before you begin!
If you dig into revisions without thinking it through or following the steps I am about to give you, you could make major and costly mistakes. Remember, time is money in business. So think before you begin.
Steps Toward Error-Free Machine Design Revisions
1) Save a copy of the original!
Go into the Assembly Drawing. (In Pro/E make sure that the master assembly is active.) And make a back up of the project into a separate electronic file folder. Make sure you get the drawings backed up along with the 3D models.
In Pro/E back up to a new folder while pointing to the master rep.
2) Print out any complex change areas.
If the revisions are many, or are complex, it is good idea to plot out or print the original BOM, Assembly, and parts modified.
3) THINK!!! and PREPARE!!
Think the process through before you begin. For example:
- Remember that the models you are fiddling with exist. So a part that is 3 inches long can NOT be made 4 inches long. You can cut pieces off, but you can’t change the over all dimensions. You can ADD a hole. But you can’t MOVE a hole. If a part gets bigger, you have to create a copy or a new model with a new part number.
- Remember that holes and parts can be dependent on each other in the 3D assembly. Make the holes independent of other parts. We call it “hard coding” the holes.
- Remember parts are sometime dependent on other parts for their location. Make sure to redefine the location of parts that may be affected by the changes you are about to make.
4) Keep a list.
Keep track of what you change as you change it.
Remember every change you make will need to be recorded on the drawing. Make note of each change as you change it. Don’t try to remember it all at the end of the project. So make note of each part you modify, each part you add, each part you delete.
5) Use Sub-assemblies when it makes sense to do so. (To learn more about sub assemblies …) A sub assembly will make it easier for the shop to make the change.
We have touched on 5 steps to reduce errors and time in making revisions to weld fixture and machine designs. And we haven’t even touched on the drawings and revision notes yet!
Learn your company’s or customer’s standards for making revisions. Always ask if you are unsure. And keep this list of steps in your files or your head so you can save time and money in your machine design revisions.
‘Til next time,
The Queen of Lean Machine Design
