There is a specific kind of dead time that eats product schedules. The design is done Thursday. The quote request goes out Friday. The shop replies Tuesday with questions about a tolerance. You answer Wednesday. Parts ship the following Friday. Eight working days, nothing produced but email. Do that four times in a program and you have lost six weeks to logistics, not engineering.
That is the main argument for hiring an engineering firm that owns machines. Not that parts are cheaper — sometimes they are, sometimes not — but that the loop between "we think this works" and "we know this works" gets much shorter. It is worth knowing where that advantage is real and where it is oversold.
What "in-house manufacturing" actually means
The phrase covers a wide range, and the range matters more than the label. Ask specifically what sits inside the building:
- Additive. FDM and resin printers are close to universal now and prove almost nothing about capability. Industrial SLS, SLA, or metal systems are a real signal.
- Subtractive. A 3-axis mill and a lathe cover a lot of prototype work. A 5-axis machine and a decent CAM programmer cover much more.
- Sheet and profile. Laser cutting, a press brake, waterjet — cheap to access, transformative for enclosure and chassis work.
- Electronics. A reflow oven, stencil printer, and rework station let a firm build and repair boards without a two-week turn at an assembler.
- Assembly and test. Benches, fixtures, and the people who use them. This is the capability firms mention least and that helps most.
A firm with printers only is a design firm with printers. A firm with a machine shop, an SMT line, and a test bench is a genuinely different operation — closer to what you get when a firm also runs its own test lab, where the equipment changes what the team is willing to attempt rather than just where the parts come from.
Iteration speed is the real product
Every design iteration carries a fixed overhead — package the files, request the quote, answer questions, wait, receive, inspect — that often exceeds the actual machining time. When that overhead drops from days to hours, engineers change their behavior. They stop batching risky ideas into one careful revision and start testing three variants on the same afternoon.
That behavioral change is where the value sits. A gasket groove gets cut at four depths and the one that seals is the one that ships. Engineering judgment improves because it is fed by parts instead of assumptions, which is exactly the argument behind running fit and assembly checks with printed parts before tooling.
A rough comparison
| Task | Outsourced | In-house shop |
|---|---|---|
| Machined bracket revision | 5–10 business days | Same day to 2 days |
| Printed housing iteration | 3–7 business days | Overnight |
| Sheet metal chassis change | 7–14 business days | 1–3 days |
| Board rework after a bring-up bug | 1–3 weeks | Hours |
| Custom test fixture | 2–4 weeks | 2–5 days |
These are typical spans, not promises. The outsourced numbers assume a responsive vendor you already have a relationship with; a new vendor is slower.
Accountability when a part fails
When a prototype part cracks under load, a split design-and-build arrangement produces an argument. The designer says the shop deviated from the drawing. The shop says the drawing under-specified the radius. Both are partly right, you are paying for both, and neither is motivated to settle it quickly.
When one organization drew it and cut it, that argument has nowhere to go, and the root cause gets found because finding it is cheaper than deflecting it. It is also why what a manufacturing drawing must include tends to be better understood by teams who machine from their own drawings. Scope disputes get simpler too: you are not managing the boundary described in deciding who is responsible for what between a development firm and a manufacturer, because there is only one boundary and it is with you.
Cost transparency versus the black box
An outside shop quotes a number. You cannot see how much is setup, how much is cycle time, and how much is the fixture they had to build. That opacity makes design-for-cost conversations vague — you know the part costs $340 but not which feature caused it.
A firm running its own machines can tell you: this pocket adds eleven minutes of cycle time, this tolerance forces a second setup, this material is on the shelf and that one is a four-week order. That granularity is what makes designing parts to cut CNC machining cost an engineering exercise instead of guesswork, and you arrive at the volume manufacturer already knowing which features are expensive.
Now the honest downsides
This model has real limits, and a firm that will not name them is selling rather than advising.
Capacity ceilings
An in-house shop is sized for prototypes and small runs. Somewhere between fifty and a few hundred units, depending on the part, it stops making sense — the machines that were a competitive advantage at quantity five become an expensive bottleneck at quantity five hundred. A good firm tells you where that line is for your part and plans the handoff to volume production before you hit it, rather than quietly stretching its own capacity because it can bill for it.
The conflict of interest
This is the one clients raise least and should raise most. A firm that designs the part and then quotes its own shop to make it has a financial reason to design parts its shop is good at. That bias is usually unconscious and it is still real. A design that could have been a $4 injection-molded part may end up as a $60 machined part because machining is what the building does well.
Three practical protections:
- Ask for shop work to be quoted as a separate line item, at a stated rate, not folded into a project fee.
- Retain the right to competitively bid any part, and actually do it once or twice mid-project as a calibration check.
- Require that the process selection be justified in writing at the design review, against volume and unit-cost targets you set.
A firm confident in its shop will agree to all three without friction. Resistance to any of them is the answer to your question. This sits alongside the other things worth probing in comparing quotes from different engineering firms — a bundled quote that hides the shop margin is not comparable to an unbundled one.
Narrower process range
No firm owns every process. A shop with excellent milling may have no experience with die casting, overmolding, or extrusion, and there is a quiet gravity that pulls designs toward the processes on site. The counterweight is a firm that maintains a real external supplier network and uses it without defensiveness — which is also what you need when the program moves to managing overseas manufacturing.
What to ask on the first call
- What equipment is in the building, and who operates it — staff or contractors?
- What percentage of prototype parts on a typical project are made in-house versus bought?
- At what quantity do you stop making the part yourself, and what happens then?
- How is shop time billed, and can I see the rate card?
- Can you show a project where you recommended a process you do not have in-house?
That last question is the useful one. A firm that can point to a case where it sent work out because sending it out was correct has demonstrated the judgment you are buying. Equipment is easy to photograph; the discipline not to use it is what separates a development partner from a job shop with a CAD seat.
Projects House combines engineering design with hands-on build and test capability, and works through a global manufacturing network when a part belongs somewhere else. If you want a candid read on which parts of your product should be made in-house and which should not, reach out through the contact form.