The Engineer Who Starts Every Project from a Blank Assembly
There’s a type of engineer I’ve worked with. Every new machine, they open a new SolidWorks assembly, click “new part,” and start drawing a base plate. By Wednesday they’ve modeled the four levelling feet. By Friday they’ve added the four corner tubes. Two weeks in, they have a frame that looks exactly like the frame they built last quarter, because the last quarter’s frame was also 80×80 tube on four feet.
That engineer is me. It was me on my first three projects. I thought I was being thorough. I was just slow. It took a mentor pointing at the server drive and saying “you already drew that” before I understood what rapid custom machine design actually means. It’s not about working faster. It’s about not drawing the same thing twice.
This article is the system I built after that conversation — the habits, folders, and standards that let me quote a machine in a week and start detailed design on day two instead of day five. It’s not a PDM implementation. It’s the stuff that works without buying software.
What “Rapid Design” Actually Means (and What It Doesn’t)
Rapid design isn’t about skipping steps. It’s about spending your engineering hours on the parts that are actually new. The frame, the guarding, the standard actuator mounting, the safety circuit — those aren’t new. They’re the same as last time. The part handling, the custom gripper, the tricky indexing — those are new, and that’s where your time goes.
The goal isn’t to make machines that look identical. It’s to make the 70% that repeats, repeat without re-engineering. The 30% that’s custom, you design properly.
| Category | Reuse Strategy | Design Time Saved |
|---|---|---|
| Base frame | Standard weldment family, modify footprint | 8–12 hours |
| Station mounting plates | Standard 500×500 plate with hole grid | 3–5 hours per station |
| Guarding | Aluminum extrusion panels, rearrange | 6–8 hours |
| Control panel layout | Copy previous panel, swap components | 4–6 hours |
| HMI screens | Copy template, change titles and tags | 8–10 hours |
| Standard actuators + brackets | From component library | 2–4 hours per actuator |
Add it up and you’ve saved 30–40 hours per machine. That’s a week of engineering time on every project. On a 14-week build, that’s 7% of the schedule. It’s the difference between shipping on time and shipping late.
Building the Reusable Parts Library
A library doesn’t help if nobody uses it. The best library is the one your team actually opens. Here’s how to build one that gets used.
Folder Structure: Organize by Function, Not by Project
The worst folder structure I ever saw was “Project A / 2024 / Machine v3 / Final / Final_rev2.” You can’t find anything. The reusable parts library should be separate from any project. Organize it by function:
Standard_Library/
01_Frames/
Frame_Small_1x1m/
Frame_Medium_2x1.5m/
Frame_Large_3x2m/
02_Stations/
PickPlace_Standard/
Press_Standard/
Indexer_Rotary_Standard/
03_Actuators/
Cylinder_Mounts/
Gripper_Standard/
Linear_Slide_Packs/
04_Guards/
Guard_Panel_500x500/
Guard_Door_Standard/
05_Electrical/
Panel_Layout_Basic/
HMI_Template/
06_Fixtures/
Locator_Pins/
Quick_Change_Plates/
When you start a new project, you don’t browse this folder like a museum. You know what you need. “I need a medium frame” — open Frame_Medium, save a copy into the new project, modify the footprint. Done in 20 minutes instead of a day.
What Makes a Part Reusable (and What Doesn’t)
Not every part from a previous project belongs in the library. A part is reusable if:
- It has no external references to the old project. If the bracket has an in-context reference to a hole in the old machine’s frame, it’s not reusable. Clean the references before saving it to the library.
- The mounting interface is standardized. It bolts onto a standard pattern, not a unique feature of the old machine.
- It’s been proven. It worked on at least one machine without a recall. A part that’s never been built is a design, not a reusable component.
- It has a one-line description. When you’re scrolling the library at 4 PM, you need to know what each folder contains without opening it.
Parts that are project-specific (the customer’s custom tooling, the weird one-off bracket) stay in the project folder. They don’t go in the library. The library is for the stuff that repeats.
Reusing 3D Models Without Copying Problems
Copying an old model is faster than drawing from scratch. It’s also dangerous — you inherit the old model’s mistakes, its broken references, and its assumptions about the old project. Here’s how to reuse without inheriting the baggage.
The “Save As” Discipline
When you copy a library part into a new project:
- Save a copy, don’t reference the original. The library part is a master. The project gets its own working copy. Changes in the project don’t propagate back to the library unless you intentionally update it.
- Break external references. Use the “break reference” command in your CAD software. The library part should be a standalone assembly that doesn’t look back at the old project. If it has an external reference to a sketch in the old machine’s skeleton, you’ll lose that sketch when you open it in the new project.
- Check the mates. A copied assembly might have mates that reference components from the old project. Fix them before you start modifying. A red “missing reference” in the feature tree is a problem you can ignore today and regret tomorrow.
- Rename the file. “MountingPlate_V2_final.sldprt” is not a reusable part. Name it after its function: “Gripper_Mount_80mm.sldprt.” The next engineer (or you, in six months) needs to know what it is from the filename.
The test: Open the copied assembly in a new window. Does it rebuild without errors? If it does, it’s clean. If it shows broken references, clean it now — don’t “fix it later.”
Supplier Catalogs: The Library You Didn’t Have to Build
Every supplier makes 3D CAD models of their products. Use them. This is the fastest way to reuse standard components without modeling them yourself.
What to Download and Keep
- Pneumatic cylinders (SMC, Festo, Parker): Download the exact bore and stroke you use most. Most suppliers have online CAD configurators that generate the exact model you need.
- Linear guides and ball screws (HIWIN, THK, Bosch Rexroth): Download the carriage and rail models. They’re parametric to size. Don’t model a rail from scratch — the supplier already did it better.
- Sensors and switches (Balluff, Sick, Keyence): Every sensor has a CAD model. It saves you from modeling a housing that won’t match the real part.
- Aluminum extrusion (80/20, item, MiniTec): The supplier libraries are accurate and parametric. Use them instead of drawing a profile.
- Fasteners (McMaster-Carr, BoltBase): Standard hardware. Don’t model bolts. Use the supplier model or your CAD software’s built-in hardware library.
The key is to download the model into your library under the supplier’s name and part number. When you need an SMC CDQ2B32-100DZ cylinder, you open the SMC folder, find that part number, and drag it into your assembly. No guessing dimensions, no modeling, no checking the datasheet to see if the mounting holes match.
Standards: The Quiet Productivity Multiplier
Beyond the parts library, the real time saver is standards. A standard is a decision you make once, then never have to make again.
Standards That Save the Most Time
| Standard | What It Specifies | Time Saved |
|---|---|---|
| Mounting hole pattern | Every station plate uses a 50 mm grid, M6 threads | No time deciding hole spacing every project |
| Cylinder mounting | Trunnion or foot mount on a standard bracket | Use library bracket, not new design |
| Cable and tube colors | Air blue, power red, signal black | Electrician and plumber know without asking |
| Datum height | Station top at 850 mm from floor | All stations align by default |
| Sensor mounting | Standard bracket family for photo-eyes and proxes | Drag and drop, not design |
| Fastener grades | M8 socket head class 8.8 everywhere | Purchasing stocks one thing |
A standard isn’t a rule that can never be broken. It’s a default that you override only when there’s a good reason. If every project uses M8 on a 50 mm grid, the designer doesn’t spend an hour deciding hole size and spacing. They spend that hour on the part handling problem.
The Quote-to-Design Handoff
Rapid design starts before the project is won. The engineer who did the quote should hand off more than a footprint and a price. They should hand off:
- The concept layout (even a rough one)
- The list of standard modules used in the quote
- The customer’s “must-have” constraints (cycle time, footprint, utilities)
- The open questions that the customer didn’t answer
If the quote used the medium frame and the standard press station, the design engineer starts with those in the model. They’re not starting from scratch — they’re modifying a known-good starting point. That handoff is what turns a 14-week build into a 12-week build.
Starting Today: A 30-Minute Exercise
If you’re not reusing models yet, here’s a practical starting point that doesn’t require a PDM system or a company-wide initiative:
- Open your last completed machine. Find the frame assembly. Save it to a “Standard Frames” folder with a clear name.
- Clean up the references. Break external links, generalize the mounting holes, save as a generic template.
- Pick one station from that machine. The one that’s most generic (the infeed, the outfeed, a standard pick-and-place). Save it as a station template.
- Write a two-line note for each: what it is, what it fits. Put it in the folder.
- Next project, start from those. Instead of a blank assembly, open the frame template and go from there.
That’s it. You don’t need to catalog everything. You just need to stop drawing the same frame twice. After three projects, you’ll have enough templates that the starting point isn’t a blank screen — it’s a machine that’s 70% built before you start.
The Bottom Line
Rapid custom machine design isn’t about working faster. It’s about making the decisions once, reusing the geometry, and spending your engineering hours on the parts that are actually new. The shops that ship in 14 weeks aren’t staffed by faster CAD operators. They’re staffed by engineers who know what’s already designed and what actually needs to be engineered.
Build the library incrementally, organize by function not by project, download supplier models instead of drawing them, and write down your standards. The next time a customer calls with a new part, you’ll start with a frame that already exists, a station that’s already been built, and an HMI that already works. You’ll spend your week one on the part — not on the plate.
