Blog · Lessons · 29 Sep 2026 · 3 min read
Seven mistakes AI automation made on our cutting drawings, and the fix for each
An AI agent drafting from a STEP file is fast. It is also fast at repeating the same mistake on every part. The mistakes our AI-driven process made, and the rule each one left behind.
An AI agent does not make fewer mistakes than a person. It makes the same mistake on every part, very quickly, and reports success while doing it. These are the ones our AI-driven process made, and the rule each one left behind. Every rule is now a check the agent must pass, not a note it may forget.
1. Plate thickness taken from the volume
What happened. Thickness was estimated as volume divided by the area of the part's bounding rectangle. On a full rectangular plate that is right. On a plate with cut-outs or an irregular outline, the volume is smaller and the thickness comes out thinner than it is, at values no steel mill sells.
The fix. Thickness is read from the dimensions of the side views on the drawing, and it must match a thickness you can actually buy. Anything else stops the run and gets a question. More in how to get plate thickness from a STEP file.
2. A decimal comma in a spreadsheet
What happened. A thickness written as 10,0 instead of 10.0 in the parts register was read by the drawing rule as one thousand. The drawings came out with an impossible thickness in the title block.
The fix. Numbers in the register are always written with a dot and one decimal, and the register is checked before any drawing is generated. The check is a gate: if it fails, nothing runs.
3. Mirrored parts treated as the same part
What happened. Two plates with the same outline were grouped as one part with quantity two. One of them had its bevel on the opposite face. Turned over, it is not the same plate.
The fix. Parts are grouped only after comparing them in 3D, not only as flat outlines. Mirrored parts get their own left-hand drawing. More in how to find identical and mirrored parts.
4. Bought sections in the nesting
What happened. Angles and bulb flats came through as flat parts and ended up on the nesting sheets, as if they were to be cut.
The fix. Every part is classified first: flat plate, bent plate, bar or bought section. Bought sections never go into the nesting.
5. Two blocks with the same name
What happened. Several DXF drawings were merged into one sheet. Two of them used the same block name for different content. The merged file drew the wrong section in the wrong place, with no error.
The fix. Before merging, blocks, text styles and dimension styles are compared by content, not by name. A name that means two things gets renamed.
6. A counter that said "OK"
What happened. A batch export reported every file done, and every file had a normal size. A few of them still contained the old version of the drawing.
The fix. "Done" is not a message. It is a value read inside the produced file and compared with what should be there.
7. Regenerating a file that was edited by hand
What happened. A drawing was corrected by hand after delivery, then a new run regenerated it and the correction was gone.
The fix. A file edited by hand is the reference, not the script that produced it. Before anything is regenerated, its date is checked and the owner is asked.
What they have in common
None of these threw an error. Every one produced a file that looked normal. That is why every project we deliver goes through checks that read inside the files before it reaches a shop.
Related
- How to check CAD files produced by an AI agent
- How to stop an AI agent repeating the same mistake
- Mistake 5 in full: block names and dimension styles colliding in merged DXF files