Engineering Change Orders on a Heavy Fabrication Job: Keeping Schedule and Cost Under Control

Almost every fabrication job of any size gets a design change at some point, whether it is a bolt pattern that moved, a material substitution forced by availability, or a tolerance that turned out to be tighter than the design actually needed. The cost of a change is rarely about the change itself. It is about how far into the process the part already was when the change landed.

Why timing decides the cost

A change made before material is cut costs little more than the engineering time to redraw. A change made after material is cut but before welding starts usually means scrapped or reworked plate. A change made after welding has started can mean cutting apart a partially built structure, which is slower and more expensive than starting fresh because the shop has to remove existing welds without damaging adjacent material. A change discovered after machining, when a feature is in the wrong place relative to a now-immovable datum, is close to the most expensive point a change can happen, short of discovering it after the part has shipped.

This is why a shop’s quote for a change order is not really pricing “how much work is the change,” it is pricing “how much of the finished-so-far work has to be undone before the change work can start.”

What a change order should document

A verbal agreement to “just move the hole over” invites disagreement later about what exactly was agreed, who approved it and whether it affects the price or the schedule. A written change order, however brief, should record:

• What is changing, referenced against the specific drawing revision it modifies.
• Why, if it matters for future reference (a design correction is different from a customer-requested feature addition, and shops sometimes price them differently).
• The cost impact, stated as a number, not “to be determined.”
• The schedule impact, stated as a new delivery date, not “slight delay.”
• Who approved it, by name, on both sides.

This does not need to be a formal contract amendment for a small job. It needs to exist in writing, even as a confirmed email, so that six weeks later nobody is relying on memory of a phone call.

Revision control on the drawing

Every change should produce a new drawing revision, clearly marked, and every party working from the drawing should be working from the current revision. A shop building from an outdated PDF because the updated one sat in an email nobody opened is one of the most common and most avoidable causes of a part built to the wrong revision. Revision blocks exist for exactly this reason: a simple table on the drawing showing revision letter, date and what changed, so anyone can confirm at a glance they have the right version.

Negotiating a change without wrecking the schedule

Some practical patterns that keep a change from cascading into a much bigger delay:

• Ask what is already committed before finalizing a change. If material has not been ordered yet, the change is nearly free. If it has, the shop may be able to use it for a different job rather than scrapping it, which reduces the cost impact.
• Batch small changes where the schedule allows, rather than issuing five separate change orders over two weeks, each one interrupting the shop’s plan.
• Separate the urgent from the optional. A change needed for the part to function correctly is not the same priority as a cosmetic preference, and treating them the same in the negotiation slows down the change that actually matters.
• Get the revised schedule in writing at the same time as the cost, not as an afterthought. A change order that only addresses price and leaves the delivery date vague tends to resurface as a dispute closer to the original ship date.

Where this connects to the RFQ

A well-specified RFQ, using something like our RFQ spec template, reduces the number of changes that originate from ambiguity in the original request, which is a different category from changes that come from a genuine design evolution. Fewer avoidable changes means the changes that do happen get handled without the friction of also renegotiating what should have been clear from the start.

Getting a change quoted

If a job already placed through this site needs a change, send the revised drawing and a plain description of what changed to your matched shop directly, copying us if you want a second read on the cost impact. For a new job, send the drawing through the RFQ form and we match it with up to three shops within 24 business hours.