A drilling line is a consumption system, not a shopping list. The number of holes a month decides how much entry board and backup board you buy, the hole cost decides whether the cheaper grade is actually cheaper, and the defect rate decides which grade you should have bought in the first place. This page turns the process parameters you already have into a purchase order: hit count and tool life into monthly volume, cost per good hole into a grade decision, and that volume into MOQ, lead time and payment terms. The process parameters themselves are set out in the drilling parameters guide; the material choices are in the backup board buying guide.
Monthly consumption is not a guess, it is the product of four numbers the process side already holds:
Multiplying those four gives the number of boards to buy, and it is the only defensible basis for a purchase order in consumables. The arithmetic is automated rather than typed: the hit count calculator fixes the hit figure, the panel utilization calculator fixes the panels per sheet, and the cost per panel calculator turns the whole thing into a number per good panel. The available hits themselves come from spindle hours rather than from the board, and the spindle utilization calculator turns spindle count, uptime and hit rate into that monthly ceiling.
Buying the wrong grade does not show up in the price comparison; it shows up in the defect report a month later. The process-side evidence for what causes what is set out in the drilling defect prevention guide, and the four failures a buyer can act on directly are these:
| What goes wrong | What drives it | What changes the purchase |
|---|---|---|
| Exit burr and nail-head | Tool wear against the backup surface, and the hardness and flatness of the board under it | A harder backup grade, or the lubricated composite where drill temperature is the constraint |
| Hole-wall roughness and smear | Heat at the drilling interface | Coated or lubricated entry material instead of plain aluminium |
| Inner corner damage | Tool wear amplifying into the breakout, especially on high-aspect-ratio holes | A hit-count limit below the tool failure point, which changes the monthly volume |
| Position deviation | Stack height, panel flatness and fixturing | A stiffer or flatter board, and in some cases a thicker gauge |
The fourth row is the one that changes the order quantity rather than the grade, which is why it belongs on a purchasing page. A hit count held below the failure point is a larger monthly buy of the same board; a grade upgrade is a smaller buy of a better one. The wear-to-defect chain is documented in the exit burr control guide and the ICD risk guide.
This is the calculation that decides between grades, and it is worth stating precisely. Cost per good hole is not the sheet price divided by the holes in a sheet. It is the total cost of everything consumed to produce one acceptable hole:
The result is why a 15% cheaper sheet can be the more expensive material. A board that yields one fewer panel per sheet is 15% more expensive per hole before any defect rate is applied, and a board that raises the burr rate by a fraction of a percent costs more per good hole than most price differences in the range are worth. The grade comparison for backup board is in the material comparison, and the metal-based pricing for aluminium entry material — the SMM spot price plus a conversion charge — is set out in the procurement walkthrough.
Two comparisons decide the buy, and they are not the same comparison. The technical one asks which grade answers the constraint the process actually has — the backup board selection guide covers it by hole size and layer count. The commercial one asks what the grade costs per good hole once the yield and hit count are in the denominator. A grade can win the first and lose the second, and the second is the one that decides the order.
Two consequences are worth writing into the file. First, the comparison must use the same denominators on both sides: the same hole count, the same yield assumption, the same scrap treatment. Second, the price of a coated or lubricated grade sits against a different saving — fewer regrinds, less bit consumption, lower burr rejection — and that saving belongs in the comparison even though it never appears on the invoice.
Once the monthly volume exists, the commercial terms follow from it rather than the other way round. Four points to fix before the first order:
The full specification-locking set and the landed cost sheet it has to sit on are in the the procurement and landed cost walkthrough, and the move from a first order to a standing schedule is in the first-order ramp guide.
Entry board and backup board are bought by different people in most shops — the process engineer specifies the entry material, procurement buys the board — and that split is where consumable purchasing usually leaks. The two arrive in the same drill cycle, so a change to one without the other changes the result. Three arrangements keep them together:
The document set and the sequence in which a supplier is qualified are in the supplier qualification guide, and the grade-level buying rules for each material are in the the backup board buying guide and the back-drill buying guide, the process hub is the PCB drilling techniques guide, and the ramp from first order to stable supply is in the drilling consumables production ramp guide.
Multiply panels per month by holes per panel, divide by the hit count per bit to get the tool count, then apply the yield factor for scrap and rework. That gives the number of boards to buy. The hit count calculator, the panel utilization calculator and the cost per panel calculator each fix one of those inputs rather than leaving them to be estimated.
Because a sheet price ignores how many usable panels it yields, how many holes it survives and what the defect rate does to it. Cost per good hole divides the total consumed cost by acceptable holes, including entry board, backup board, amortised bit cost and scrap. A sheet that is 15% cheaper but yields one fewer panel per sheet is more expensive per hole before any defect rate is applied.
Two separate comparisons. The technical one asks which grade answers the process constraint the line actually has, by hole size and layer count. The commercial one asks what that grade costs per good hole once yield and hit count are in the denominator. A grade can win the technical comparison and still lose the commercial one, and the commercial one decides the order.
They arrive in the same drill cycle, so a change to one without the other changes the result. Running one board face higher than the other is the usual way a board change quietly alters the process window. Keeping them on one consumption plan, one delivery schedule and one document set keeps the qualification evidence covering the whole stack rather than one face of it.
The minimum is set by the press run and the pallet format. Standard formats move first, at 100 sheets for 940 by 1245 mm and 200 sheets for 520 by 620 mm; a format not in running stock has to be scheduled, which raises the minimum. The standard production lead time is about one week and weekly shipping capacity runs to four containers.
Exit burr and nail-head point to tool wear against the backup surface, so a harder backup grade or the lubricated composite. Hole-wall roughness and smear point to heat, so coated or lubricated entry material. Inner corner damage points to wear amplifying into breakout, so a hit-count limit below the failure point, which changes the monthly volume rather than the grade. Position deviation points to stack height and flatness.