Custom Part Ordering Checklist: What I Check Before Clicking Buy on Shapeways

Why I Use a Checklist for Custom Part Orders

I'm the office administrator for a 48-person product development team. I don't design parts; I buy them. That means I handle about $350,000 in annual spend on prototypes and short-run parts, mostly through online manufacturing platforms and specialized machine shops. I report to both operations and finance, so I have to keep the engineers happy and the invoices clean. It's a balancing act.

I started using a formal ordering checklist after a mistake in 2023. A new vendor quoted me 18% less than the platform I usually use. I uploaded the file, approved the quote, and didn't look at the line items carefully. When the invoice arrived, it included a setup charge, a minimum-order fee, and a packaging fee that hadn't appeared in the original estimate. The total was 22% higher than the quote. My finance team rejected the expense, the vendor put the account on hold, and the engineer who needed the part came to my desk three times in one day. That was the last time I approved a custom part order without a checklist.

This is the checklist I run through now when I order from Shapeways or any other custom manufacturing service. It won't turn you into an engineer, but it will help you catch the problems that live between a clean quote and a surprise invoice.

1. Start With a Written Part Requirement

Before you click the instant quote button, ask yourself what you actually know about the part. Most mistakes happen because someone uploaded a file and assumed the process would work itself out.

I ask our design team for these details on every request:

• The part name and revision number
• The material and finish they need
• The quantity and whether it's a prototype or final part
• The date the part has to be on a desk, not just the date it has to ship

If they say 'same as last order,' I still ask for a file. Last order may have been modified by another engineer, and nobody tells the buyer. Trust me on that one.

2. Confirm File Format and Units Before Uploading

Online manufacturing platforms usually specify the file formats they accept, and those formats change by process. For 3D printing, .stl and .3mf are common. For CNC machining, .step is usually safer. Shapeways lists what it needs for each process, and I check that before I upload rather than guessing.

I also open the file in a viewer whenever I can. Units are a quiet killer. I once approved a quote for what the engineer called a 6 inch part, but the exported model was in millimeters and the quote came back for a part over 150 mm long. It wasn't the platform's fault. The file was confusing. A 30-second check would have caught it.

3. Read the Quote Like Finance Will Ask About It

Here is the rule I repeat most: don't ask what's included. Ask what's not included.

Custom manufacturing quotes are not all built the same. One quote may include setup, another adds it at the end. One quote may list finishing as a separate step, another hides it in the material price. None of that is necessarily dishonest, but it makes line-by-line reading important.

A quote that shows every fee upfront, even if the total looks higher, usually costs less in the end.

I have come to believe that transparent pricing actually saves money. The vendor who shows the cost of a finish or a setup is giving you useful information. The vendor who shows only a low total is asking you to trust that everything else is included. No one at Finance likes that form of trust.

Per FTC guidance (ftc.gov), marketing claims need to be truthful and not misleading. I am not a lawyer, but I treat an instant quote as a quote that should match the checkout total for the options I selected. If it doesn't, I stop the order and ask why.

On the finance side, I also look at the supplier identity. When I receive an order confirmation from Shapeways, I check that the Shapeways logo, the legal entity name, and the email domain match. That check sounds paranoid, but it has stopped duplicate supplier entries in our accounting system more than once.

4. Understand the Process Before You Approve It

I am not an engineer, but I've learned enough about manufacturing processes to ask the right questions before I buy. You don't need to run a CNC machine. You just need to notice the details that affect cost and lead time.

If the part involves CNC machining, look at the tooling notes. A callout for a 6mm ball nose end mill usually means the design has a contoured surface or an internal radius that has to be machined. If the quote is higher than expected, this is often why. A 6mm ball nose end mill can't cut a sharp internal corner, and the toolpath needed to finish a 3D surface will be longer than a simple drilling job.

Tool holders may also show up in the comments. Atlas Copco tool holder is not the kind of note I would have paid attention to a few years ago. Tool holder type can affect runout and surface finish, especially in aluminum and harder materials. I record the note, paste it into the order comments, and let the engineer decide. Don't remove notes just because you don't understand them.

Laser work has its own vocabulary traps. People see 'infrared' and assume it means fiber laser. For example, the question 'is xtool f1 infrared laser a fiber laser' comes up because the desktop machine is advertised as an infrared laser, but it is not a fiber laser. It uses a diode-pumped solid-state infrared source. That doesn't make it useless; it makes it different. When you order laser marking or cutting, the type of laser matters. I always confirm whether a supplier is using CO2, fiber, or diode because they produce different results, especially on metal.

5. Check Lead Time, Shipping, and the Difference Between Them

When a quote says 10 business days, I ask whether that means production time or delivery time. Many manufacturing quotes show the time needed to make the part, not the time it takes to reach your loading dock. The difference has caused me more than one uncomfortable conversation.

My rule is to plan backward from the date the part is actually needed. If an engineer says a prototype is needed for a Friday customer demo, I don't order on the Tuesday before and expect overnight delivery of a machined part. I ask for a ship date, then add transit time, then add a buffer.

I also confirm whether shipping is included in the quote. Every online manufacturing platform has its own approach. Some add calculated shipping at checkout. Some don't. What matters is that you know the final delivered cost before you submit the order, not after.

6. Save a Complete Audit Trail

I order a lot of parts, and I have learned that verbal approvals and 'sure, we'll send a confirmation later' are not enough. Before payment, I need:

• The current file name and revision
• A quote with an order number
• The selected material, process, finish, and quantity
• A delivery date or ship date
• An invoice template that matches the PO

If a vendor can't provide an invoice with line items, I don't order. It sounds harsh, but I once lost a $740 expense to a rejected reimbursement because a supplier sent a handwritten receipt. I had to pull the cost out of a different budget line to keep the project moving. That may sound like an isolated story, but it happens more often than you'd think.

A Few Mistakes I Still Have to Watch For

This final list is the one I seem to keep re-learning:

• Choosing a process by price alone. The cheapest process is not always the best fit. Sometimes a more expensive process costs less total time and creates fewer headaches.
• Assuming surface finish is included. A quote might be for the part as printed or as machined. Finishing can be a separate line item and it changes both cost and lead time.
• Approving a design change without looking at the new total. If the platform recommends a support structure or a wall thickness change, the price can move. The recommendation may be right, but I still check the revised total before approving.
• Forgetting that quote date and revision matter. I now write the revision number in the PO notes. It sounds small until a different revision is accidentally used.

Bottom Line

Custom manufacturing doesn't have to be nerve-racking. If you know the requirements, confirm file format and process, read the quote line by line, and keep a clean paper trail, you'll avoid the mistakes that wake me up at 2 a.m. I still don't know every machining detail, but I know what to ask for, and I know to get it in writing. That has been enough.