A1 at 1:2 reduced to A3: false scale field, hairline lineweights, 72 dpi logo
You must issue the general arrangement of a conveyor frame to a customer portal as an A3 PDF, and to the fabricator as an A1 PDF. Model space is drawn 1:1 in millimetres and the frame is 1600 mm long. The A1 layout (841 × 594) is set to 1:2, which puts the frame at 800 mm on paper, and the title block scale field reads '1:2'. The A3 PDF is produced by ticking 'Fit to paper' on the A1 layout; it comes out with coloured layers (red centre lines, green dimensions), object lines that look like hairlines beside the 0.7 mm border, and a company logo that is visibly pixelated. In the plot dialog 'Plot object lineweights' is off, 'Plot with plot styles' points to a CTB that no longer exists on the server, and the logo was inserted from a 72 dpi PNG. The customer checklist requires legible text at A3 and a stated scale.
1. What scale must the A3 issue state, can the A1 layout simply be fitted to A3, and what is the correct way to produce the A3 sheet?
Read the worked answer
Do the arithmetic first. A1 is 841 × 594, A3 is 420 × 297 - exactly half in each direction, so fitting the A1 layout to A3 gives a 0.5× linear reduction. The frame at 1:2 on A1 is 800 mm on paper; reduced to A3 it becomes 400 mm, and the effective scale is 1:4, not 1:2. Leaving '1:2' in the title block produces a sheet whose stated scale is false - the most serious documentation error here, because a fabricator scaling a dimension off it will be out by a factor of two.
A 1:4 A3 also fails practically: 400 mm of drawing on a 420 mm sheet leaves nothing for margins and border, and every text height halves - 3.5 mm becomes 1.75 mm, below any legible minimum for a working drawing (ISO 3098 practice is 2.5 mm minimum, 3.5 mm preferred).
Correct approach:
- Build a dedicated A3 layout with an A3 border and A3 title block - never 'fit' an A1 sheet.
- Set the viewport to a standard scale that fits and reads clearly, e.g. 1:5 → 320 mm long, which leaves room for a margin and keeps text at 2.5–3.5 mm paper height.
- Update the scale field to '1:5' and issue the A1 at 1:2 separately; both PDFs go to the portal with the scale in the filename.
- If the customer explicitly wants a true half-size copy of the A1, print it at exactly 50% with a stamp 'REDUCED COPY - SCALE 1:4 - DO NOT MEASURE' across the sheet, and still correct the printed scale field. It must be exported at fixed scale, not with fit-to-paper, so the 50% is exact.
2. Diagnose the hairlines and the coloured layers, and list the settings that must be checked before re-issuing both PDFs.
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Both symptoms have the same root cause: the drawing is being plotted with no effective plot style table.
- 'Plot with plot styles' points to a CTB that no longer exists on the server. The plotter falls back to plotting with no style table, so each layer prints in its screen colour and lineweights resolve to the plotter's default rather than the intended 0.35/0.25/0.7 mm hierarchy.
- 'Plot object lineweights' is off, so even correctly assigned object and layer lineweights are discarded. Object lines end up as single-pixel hairlines, while the border looks heavy because its geometry is drawn with a wide polyline away from the lineweight system.
Checklist before re-issuing:
- Restore the CTB to the server and add its folder to the plot-style search path so every seat resolves it; or switch the drawing to monochrome.ctb if the company output is mono.
- Enable 'Plot with plot styles' and 'Plot object lineweights'; confirm the table maps every used colour to the required weight, including centre lines (thin, 0.18–0.25 mm) and dimensions (0.25 mm).
- Verify layer lineweights are assigned, not left at Default, and that no entity carries a per-object lineweight override.
- Check the plot scale is fixed (1:2 on A1, 1:5 on A3), never Fit to paper, for both sheets.
- Plot, then measure the PDF: line thickness relative to the 0.7 mm border, no colour, no missing CTB warning, and text legible at A3.
Screen settings such as 'Show/Hide Lineweight' and model-space lineweight display have no effect on the PDF and must not be used as evidence that the plot is correct.
3. The logo prints pixelated. Specify the resolution needed and the options for fixing it, and note what documentation should accompany the corrected issue.
Read the worked answer
Resolution has to be judged at final printed size, not at the source file's nominal figure. If the logo prints about 40 mm wide, a 72 dpi image supplies roughly 40/25.4 × 72 ≈ 113 pixels across. That is about 0.35 mm per pixel - comfortably visible as stair-stepping on a printed sheet, and worse on the A3 reduction.
Target: at least 300 dpi at final size for the A1 issue, i.e. 40/25.4 × 300 ≈ 470 px wide; 600 dpi (≈ 945 px) is preferable if the sheet may be scanned or reduced.
Options, best first:
- Replace with vector artwork - a DWG block of polylines, or a WMF/SVG/PDF insert. Resolution then stops being a variable at any plot scale, and the logo survives the A1 → A3 reduction cleanly.
- Re-export the PNG at 600 dpi at final print size and re-insert with IMAGEATTACH at 1:1 in millimetres, checking the image's insertion scale rather than eyeballing it.
- Check the PDF plotter's raster settings: if the driver downsamples images (e.g. to 300 dpi or lower), the fix at step 1 or 2 is defeated. Set image downsampling off or to 600 dpi for print output.
Documentation to accompany the re-issue: a revision block entry stating 'A3 issue re-scaled to 1:5; plot style table restored; logo replaced with vector artwork', the same revision letter and date on both the A1 and A3 PDFs, and file names that carry drawing number, revision and scale - for example GA-1042 Rev C A1 1-2.pdf and GA-1042 Rev C A3 1-5.pdf. The customer should be told explicitly that the earlier A3 PDF is superseded and must not be used for measurement.