The problem: quantities hide inside levels
A machine BOM is rarely flat. A bracket assembly holds 5 screws, the bracket assembly is used 8 times on the frame, and the same screw also appears in the guarding. The indented BOM shows "5" next to the screw, but the number purchasing needs is much larger.
If someone orders from the indented list line by line, the result is a shortage on the day assembly starts. If they add it up by hand, it works until the design changes.
Do the math once: 5 screws × 8 assemblies = 40
The rule is simple: multiply each part's quantity by the quantity of every assembly above it, then add up every place the same part number appears. In the example, 5 screws × 8 bracket assemblies = 40 screws. If the guarding uses another 12 of the same screw, the purchase quantity is 52.
Doing this by hand in a spreadsheet is slow and easy to get wrong, especially with three or four levels.
Let your CAD system total it: the "Parts only" BOM
Most CAD systems can produce a flat BOM that already contains the totals. In SolidWorks this is the BOM type Parts only: it lists each part once, with its total quantity for the whole assembly, and leaves out the subassembly rows. Other CAD systems call it a flat or parts-only BOM.
In general:
- Open or insert the BOM table of the top-level assembly.
- Set the BOM type to Parts only (or flat).
- Save the table as an Excel or CSV file.
For the exact steps in your CAD version, use its official help pages.
Check the flat BOM before purchasing
- Spot-check two or three parts by hand against the assembly.
- Look for the same part under two part numbers (for example a catalog number and an internal number) and fix it in CAD.
- Decide how you treat spares and consumables, and add them as separate rows so the design quantity stays clean.
Where AssembleFlow fits
AssembleFlow does not roll up subassembly quantities itself, and it does not merge the same part number from several rows into one purchase order line. That is why the flat BOM matters: import the Parts only file and each part arrives once, with its total.
From there, AssembleFlow takes over the purchasing work: the Import BOM wizard reads CSV, XLSX, XLSM and XLS files and keeps your part numbers exactly as written, Qty per machine is multiplied by the number of machines in the project, and you can send quote requests and purchase orders to each supplier straight from the parts list. Stock is shared across all your jobs, so you see what is already on the shelf before you order it again.
If you design in SolidWorks, see From a SolidWorks BOM to purchase orders. To try it on one of your own builds, start a 14-day free trial or ask for the three-month pilot.
SolidWorks is a trademark of Dassault Systèmes. AssembleFlow is not affiliated with or endorsed by Dassault Systèmes.