Originally posted on Med Device Online
Written by Jon Wenderoth, Lead Mechanical Engineer at Smithwise
Many new companies have a business model based on transitioning their product to high-volume manufacturing and distribution. Unfortunately, this is more complex than breaking out the parts from a working prototype and selecting a manufacturer. Mistakenly thinking the development is wrapped up at this point will cause schedule projections to be significantly off, and seed doubt in knowledgeable investors.
It is important to understand that these steps alone won’t fix the output from a broken development process; a house needs a solid foundation to remain standing. The entire evolution, from thoughtful design through prototypes and iteration, inherently becomes the footing for an efficient transition to manufacture. The five steps discussed within this article identify what to expect, and how to respond as a team to move a well-designed device to volume production.
1. Prepare A Request For Quote Package
When it’s time to start shopping around for vendors, it is important to gather the necessary information into a concise Request for Quote (RFQ) package. Remember that everything is on the table at this point, so if a potential customer appears disorganized, unprepared, or generally unknowledgeable, it sends up a red flag that a project may involve significant hand-holding; prices will be adjusted accordingly. Having a complete, up-to-date database is in your best interest and will pay repeated dividends over the life of a product.
The RFQ package should start with an engineering Bill of Materials (BOM). This is the full parts list, including part descriptions, materials, proposed manufacturing processes for custom components, any secondary processes, quantities, file names, and revision tracking. For a contract manufacturer (CM), a complete BOM is a quick reference for the submitted parts that implies experience and attention to detail. If quoting at individual vendors for specific manufacturing capabilities, segment the data so they aren’t overwhelmed with extraneous information.
Above Image: Zip-Stitch by ZSX Medical (zsxmedical.com).
Vendors also will need part files to know what they are quoting. Stay away from sending any native file formats; in addition to document reference headaches, outside parties are less likely to attempt to modify CAD data without design tree information. Instead, identify which file formats fit a vendor’s process. For instance, two-dimensional process manufacturers (stamping, die cutting, water jetting, etc.) can usually work with 3D part files, but many prefer flat pattern DXFs, as these can feed directly into their machine software. Three-dimensional process manufacturers (molding, casting, multi-axis machining, etc.) need 3D part files, like IGS or STP.
If your project is like most development efforts, time is on short supply and quoting is begun prior to design finalization. This typically is ok, as long as general size and features are included within your files. Ensure some form of revision control is used, so when it is time to hit “go,” the appropriate files can be referenced. To summarize:
- Compile an appropriate, complete package for each vendor.
- Use revision control (dated files, revision numbers, etc.) that can be easily referenced.
- Send the entire package at one time. A barrage of emails to sort through is inconvenient for the recipient and increases the chance that things will be lost.
- Special operations/secondaries can be specified in the BOM. If further granularity is required, 2D control drawings can be generated.
2. Construct A Realistic Timeline
One of the key outputs from the RFQ and vendor selection process is schedule. Formal quotes come with lead times, so be clear on what these lead times mean — when does the timer start, and what is the deliverable when it stops?
Using injection molding as an example, imagine it is May 2nd, and a vendor quoted a five-week timeframe to T1 sample parts. If a purchase order is sent today, the first parts will arrive in early June, giving just enough time for each part to be packaged and sent to representatives at the big east-coast medical design tradeshow later that month. (At this point, if you’ve done this before, you are questioning the validity of this article.)
Unfortunately, this is a common trap new developers fall into when doing the right thing and trying to project into the future. The intent is there, but the data is skewed. In this simplified example, the five weeks are for sample part molding, not including shipping time, and other steps in the process are not considered. A typical timeline for this example part might be as follows, with up to several months added on to the five weeks quoted:
- Final file delivery
- Moldability evaluation1-2 weeks
- Discussion & part modification2-3 weeks
- Final review & tool design approval1 week
- Tool construction & T1 samples5 weeks
- Part evaluation, testing, and file updates2-4 weeks
- Tool grooming and texturing2-3 weeks
- T2 samples delivered1 week
For multi-part assemblies, using varied manufacturing methods, schedules become increasingly complex. It can be helpful to fully understand all the steps in a process and work backwards from a set deliverable date. With this approach, as the project progresses, it is clear what the longest lead time items are, and which milestones need to be met, so they don’t become a gating item.
3. Finalize The Documentation Package
After vendors are selected and the product design is finalized, the documentation process discussed in step one will need to be repeated at a more discrete level. In addition to CAD files, this should include complete engineering drawings in PDF format. If working with a CM, assembly drawings should be included, with all pertinent drawing views and instruction to enable a third party to assemble the product.
This documentation is the engineer’s chance to identify areas that need specific tolerances, with critical dimensions for functionality and inspection dimensions for the vendor to verify. In many cases, a vendor will inspect all drawing dimensions; at the least, values identified as “inspection” will highlight their importance to the physical outcome of a part.
Don’t forget to update and send your BOM with the final files in a complete package. It is critical that vendors have easy access to the most recent documentation to avoid mistakes, and it is wise to include revision numbers on individual file names that can be cross-referenced to the BOM.
4. Manage The Design For Manufacturing (DFM) Process
At this point, the vendors have been sent the information they need, but the job isn’t done yet. There should be some degree of feedback from all manufacturers, but we will continue to use injection molding as our example.
After a few weeks, the vendor will have reviewed the files and provided a moldability evaluation. If a knowledgeable engineer or reviewer has been involved in the development, there shouldn’t be any show-stoppers here. However, if the vendor discovers that a critical feature can’t be molded due to geometric constraints, there may be some late nights ahead. Luckily, the tools haven’t yet been cut and there is room to pivot. Still, a sales team pushing to be first to market won’t appreciate the compromised schedule.
Regardless, expect there to be some feedback to incorporate into the design. Maybe an internal rib is moved to allow for a more convenient gate location, or the draft added to a snap feature isn’t sufficient for appropriate shutoff. When resolving these details, keep in mind that the molder doesn’t know the design intent of your parts, and their first suggestion will likely be the easiest (but not necessarily the correct) solution.
To that end, communication, especially with overseas vendors, can be painful. A phone call to discuss changes directly is often the most productive way of handling this, but this isn’t always possible. Discussion often reverts to “Powerpoint engineering,” where issues are captured and suggestions given within a slide deck. For these situations, we suggest the following:
- Be clear and concise, and don’t forget there may be a language barrier. Label and date all files, as well as all comments.
- Pictures, arrows, & colors: The “1000 words” philosophy applies here, too, and simple sketches often can suffice, rather than investing time in an exploratory CAD change.
- Consolidate. If schedule permits, gather all the DFM feedback together to review instead of assessing it piecemeal. This is more efficient, and makes it easier to track responses. Provide 2D and 3D file updates in the same way (don’t forget to update your BOM with revisions).
Besides design issues, the vendor will be looking for approval of process-specific features, such as gate and ejector pin locations in a mold. Ensure there is an understanding of what approvals are needed and how they are provided; it is frustrating to believe a vendor is spooling up when they are actually waiting for a well-defined approval.
5. Inspect, Evaluate, And Adjust
Regardless of what anyone says, no custom manufacturing parts are going to be perfect immediately — that takes additional work. For this reason, a good development timeline should always build in a period to assemble and evaluate the form, fit, and function of a design. This is the time to find and correct any issues that arose during manufacturing. If schedule is very tight, it is always helpful to have a representative on site for rapid evaluation. Remember that the vendor will need approval prior to any volume orders (or final tool details, like texture application on molded plastic), and it becomes more costly for budget and schedule if changes are requested later on.
- Ask for inspection reports from vendors. For production parts, these should be available and provide direct measurement of critical dimensions identified on engineering drawings.
- Get all parts in-hand (preferably multiple sets). This includes electronics, fasteners, samples from each cavity in family tooling, custom cables, everything. Long lead time parts need to be sourced appropriately so they are all available.
- Assemble and test: Leverage sample parts and inspection reports to assess functionality.
Testing may start as fit checks — ensuring a sheet metal bend is at the correct angle or fastener holes align — and then may progress to a functional assessment. Eliminate variables where possible to focus on the area in question, and don’t be afraid to do some destructive analysis if supplies allow. This is a valid justification for allocating multiple parts to testing; if a problem can’t be seen or understood, it may not be fixed appropriately. Regardless of how many are available, never be cavalier with the approach to sample parts. Identify a plan, and then inspect, measure, and record until all learning opportunities from a part have been exhausted.
Ensure all members of the design team are aligned before implementing any modifications. As with earlier updates, communicate changes in a clear and concise manner, as the cost and risk of change (and therefore mistakes) increase exponentially after vendors have fully tooled up for high-volume production.
These steps should provide some high-level insight into the effort required to transfer a product to manufacturing. While this is by no means a complete list of the challenges involved, hopefully it can equip hardware developers with enough knowledge to avoid the common headaches and get their product into production.