There’s no shortage of advice on how Design for Manufacturing (DFM) best practices can improve cost and time in CNC machining, so we won’t bore you with that topic.
Well, not today, anyway. DFM is super important—especially for complex machined parts—but there’s another topic you should know about that also has a major impact on cost and lead time.
That’s right, we’re talking about everyone’s favorite subject of discussion. . .
Document control.
Believe it or not, good document control is one of the keys to avoiding manufacturing disasters like missed deadlines, blown budgets, and inaccurate parts. Today, we’re shedding light on 4 disastrous document control mistakes to avoid when you work with a prototype or production machine shop.
4 Disastrous Document Control Mistakes
1. Mismatched models and prints
All too often, machine shops receive mismatched models and prints that make it difficult to tell which features are accurate. These discrepancies frequently take the form of forced or rounded dimensions, which can result in a part that is physically impossible to make.
We often program and machine from solid model files and complete inspections from the print. If they don’t match, it slows us down and costs you more. In addition, it often leaves us with decisions to make about what is actually important. Do you really want your machine shop making critical decisions about part dimensions on your behalf? Of course you don’t! To avoid this disaster, make sure that your model matches your print.
2. Over- or under-dimensioning
When machine shops receive insufficient information about a part, they can’t start manufacturing without additional back-and-forth with the customer. But too much information can lead to the utter chaos of conflicting information. We’re talking things like the same feature dimensioned twice—with two different nominal dimensions and tolerance ranges. Also, if a print is cluttered with unimportant dimensions, important tolerances on critical features can be overlooked.
What’s the sweet spot for this kind of information? We recommend detailing the overall part dimensions, hole/thread specs, and tight tolerance features on your print so we know exactly where to focus our attention. You can throw in some features that are critical for part functionality, but if they only require standard print tolerances, we’ll get them right anyway.
3. No part numbers and poor revision control
Part numbers and proper revision control is so important in manufacturing! A file that is just named “widget” is not very useful if you consider the fact that most machine shops work with many customers making many types of widgets.
File name = part number + revision + name is a good rule of thumb. It ensures that customers and machine shops are speaking the same language and reduces the chances of the shop using the wrong file. An example of one of our file names is: 20211215ACME01_REV_1_widget
In case you are wondering what the heck is up with that long part number, we use date + customer abbreviation + 01, 02, 03, etc. By keeping the date format year, month, day, your files will always be in the order they were created, and unless you make more than 99 files per day (or you wind up in a groundhog day situation), your organization will never run out of unique part numbers. For internal use, you can change customer name to engineer initials or department.
Customers in the engineering or prototype machining phases of the manufacturing process are the biggest culprits of poor revision control. We have heard many excuses for not tracking revisions during prototype machining:
- “We want our first production part to be rev 0.” The purpose of revisions is to track changes, not to make it look like you nailed the design on the first shot.
- “We are tracking the changes internally.” If you send multiple versions with the same part number to your vendors with no revisions, how does your internal tracking help?
- “It isn’t a production part so who cares.” Someone always cares if the part revision is wrong!
If you already have a file numbering system and revision control, WE THANK YOU! We will happily use your part numbers and revisions so it is easy to order and receive your parts. If you don’t, we will fill in the gaps with our internal part numbering system and use the date we received the files for the revision.
4. Design changes during production
Requesting design changes during production almost always results in longer lead times and higher costs. Machine shops have no choice but to pause all machining operations until the design changes are finalized. Then they have to set up the machines all over again. These additional steps can push a currently running job to the end of the schedule or require rush charges to cover overtime.
Here at our Illinois machine shop, we are ISO 9001:2015 and AS9100D certified, and ITAR registered, which means that any time we receive a design change, we have stringent guidelines to follow. Between updating documentation in our ERP system, segregating parts, revising inspection plans, and adjusting programs, lead times inevitably become disrupted.
Document Control at Wagner Machine
The truth is that we’re really good at helping our customers mitigate document-related disasters. If we come across any of these four mistakes, we’re prepared to do whatever it takes to resolve them and move forward. We’ll always get you a high-quality part—and sending us good documents will help us do that as quickly and cost-effectively as possible.
You know and we know that the biggest disaster of all is having to sort through thousands of parts to figure out which ones were made right. When you work with Wagner Machine, we’ll do everything in our power to make sure that never happens.
If you find yourself in the middle of a document control mistake, the best thing you can do is contact us. Together we can develop a plan to prevent a full blown disaster. Request a quote today. We expect to see impeccable documents! 😉