When developing sheet metal parts, the first thing that often comes to mind is the prototype: Does the part fit? Does the design work? Can it be manufactured? In mass production, however, these questions determine costs, delivery reliability, and the complaint rate.
Those are the right questions, but they aren’t enough for mass production. A production run of 500 or 5,000 parts places different demands on tolerance specifications, material selection, ramp-up planning, and delivery flexibility. What may be considered an isolated incident with a prototype becomes a systematic problem in series production. And systematic problems get expensive. Learn where the critical decisions are made at BVS and what designers, buyers, and planners need to know before the first production run begins.
Planning a production project? Have the design and production launch reviewed from a technical standpoint in advance.
The most costly mistakes occur before production begins
The most costly mistakes in sheet metal production don’t happen at the machine. They happen at the desk, often weeks before the first order.
The most common and costly error in mass production is an unrecognized tolerance issue. During the design phase, a nominal dimension is specified first. The actual desired, asymmetric tolerance is then noted separately, without adjusting the nominal dimension itself. The manufacturing facility adopts the CAD value and produces parts based on it. The result becomes apparent in practice: The designer intended 399.7 mm, but the part was manufactured to 400.0 mm. During assembly, the parts do not fit together. The order is complete, inspected, and perhaps already delivered. Now the discussions begin about who will bear the additional costs. The principle that prevents such situations is simple: Tolerances must be specified centered on the nominal dimension. If you need 399.7 mm, draw 399.7 mm.
Feasibility questions also belong in this early phase. Whether a bend can be achieved in the planned form, whether a bending radius is compatible with the material, and whether the intended joining technique is suitable for the design—all of this can be clarified before mass production begins in a brief technical discussion. Once mass production has begun, corrective measures are either impossible or so expensive that they throw off the cost estimate for the entire order. A feasibility study before the first order is therefore the most cost-effective way to prevent errors.
The start of series production determines the success of the entire production process
A scenario that plays out time and again: A buyer signs the production order and expects production to begin within a few days. The delivery deadline is tight, and the pressure is high. Two weeks later, the first part still hasn’t been produced—not because production is slow, but because production runs require preparation.
The answer is not that anyone is working too slowly. In the first few days after an order is received, we verify whether the quantities, prices, and delivery dates actually match the quote. Within a maximum of three days, the customer receives a binding order confirmation. Production itself usually begins one to two weeks later, as this time is needed to prepare tools, set production parameters, and organize the supply of materials. Anyone who cuts this phase short under time pressure risks startup problems that will carry over into the entire production run. For buyers, this has a simple implication: If you want realistic delivery times, you must factor in the lead time from the very beginning. If you ignore it, you create pressure that will eventually manifest elsewhere.
Consistent quality throughout the entire series
The greatest quality risk in mass production lies not in the first part, but in the last one. Process variations that build up over the course of a long production run are invisible at the beginning and only become noticeable once a large number of parts have already been affected.
Reliable quality assurance therefore begins and ends at both ends of the production run: The first and last parts of a series are inspected on the measuring machine. In between, measurements are taken throughout the production run so that deviations can be detected before they affect a larger number of parts.
One particularly underestimated variable is the raw material itself. Sheet metal varies from batch to batch, and these variations are not trivial. Even a 0.03 mm deviation in sheet thickness can cause an angle error of one degree during bending. Parts from two different batches can therefore yield different bending results, even though the machine is set identically. The solution is consistent batch separation: sheets from different delivery batches are not mixed. This maintains process stability, and any variations that occur can be clearly traced to a specific cause.
Flexibility in the current series
No order schedule can fully withstand the test of reality. Sometimes a customer places more orders than agreed upon, and sometimes fewer. How a manufacturing company handles this situation determines its ability to deliver.
Annual contracts or framework agreements have proven effective, as they allow for forward-looking production—typically about one month’s worth of inventory, which is held in the warehouse as a buffer. If demand increases on short notice, shipments are made from this buffer. If demand is lower, the buffer is replenished during the next production run. The inventory is thus not a cost center, but rather a reserve of flexibility that benefits both parties: The customer enjoys shorter response times, and the manufacturing company can utilize its capacity more evenly.
Reduce Costs and Effort with Assemblies
Whether a manufacturing company supplies individual parts or assembled subassemblies sounds like a logistical decision. In fact, it is a matter of total cost.
If you purchase five sheet metal parts as individual items, you’ll have five goods receipts, five storage locations, five part numbers, and the responsibility to check the fit and function yourself. Anyone who purchases the same five parts as a fully assembled and tested subassembly has a single delivery line item. If something is wrong, it is corrected before shipment, not at the customer’s assembly line.
The argument that assemblies are only worthwhile once they reach a certain level of complexity falls short. Even with simple parts, the savings in handling costs and the reduced likelihood of errors on the customer’s end are real. The question is not whether an assembly is worthwhile. The question is why it hasn’t been implemented for delivery yet.
Mass Production as an Overall Process
A sheet metal production run that goes smoothly looks unspectacular from the outside. No rework, no discussions about tolerances, no delivery delays. What lies behind this is no coincidence, but rather the result of decisions made long before the first part was manufactured. Anyone who views mass production as a holistic process—rather than a sequence of individual order transactions—will eventually realize that the most costly problems are the ones that never arise in the first place.
Have your series production evaluated from a technical standpoint now. No obligation—drawing and process review
FAQ
Why is a centrally specified tolerance range so important?
Manufacturers use the nominal dimension from the CAD data, not a separately noted tolerance based on a drawing. If you need a part to be 399.7 mm, you must specify 399.7 mm in the drawing. If the drawing specifies 400 mm with an asymmetric tolerance without a corresponding correction to the nominal dimension, the part will be manufactured to 400 mm. The result is parts that do not fit together during assembly.
How do material variations affect an ongoing production run?
Even a 0.03 mm variation in sheet metal thickness can cause a one-degree angle error during bending. As a result, parts from different material batches may yield different bending results, even though the machine settings are identical. Consistent batch separation reliably prevents such variations.
When is it more cost-effective to purchase a pre-assembled unit rather than individual parts?
Basically, always. If you source individual parts separately, you have to manage multiple part numbers, coordinate multiple shipments, and verify the fit yourself. A fully assembled subassembly reduces this to a single delivery item, where functionality and fit have already been verified.
How long does it take from the time an order is received until production begins?
During the first 48 to 72 hours, we verify that the quantities, prices, and delivery dates match those in the quote. A binding order confirmation is issued within three days. Production typically begins one to two weeks later, as tools, production parameters, and material supplies must be prepared.
How can short-term fluctuations in customer demand be accommodated?
Through proactive inventory production under annual contracts or framework agreements. The manufacturing facility produces approximately one month’s worth of product in advance and stores it as a buffer. If the customer orders more than planned, the product is shipped from inventory. This stabilizes delivery times for the customer and enables a more even utilization of production capacity.
