Acrylic letters nested for a sign shop
Two shop fascias, forty one pieces, and a sheet of acrylic that costs more than most people expect. The shop had been laying each sign out on its own sheet because that is how the job arrives in your head. Both signs fit on one sheet.
The job
Two units in the same parade, both refitting at the same time, both wanting flat cut letters on the fascia. Five millimetre opal acrylic, cut on the shop's router from 3050 by 2030 sheets.
The first fascia is a 450 mm cap height, twenty two letters. The second is 300 mm cap height, seventeen letters. Two 520 mm roundels go above the doors. Grouped by the rectangle each letter sits inside, the list is:
- 3 wide letters at 400 by 450, and 14 standard at 310 by 450, and 5 narrow at 150 by 450
- 2 wide letters at 268 by 300, and 11 standard at 208 by 300, and 4 narrow at 100 by 300
- 2 roundels at 520 by 520
41 pieces, 4.3 square metres of rectangle. A sheet is 6.191 square metres.
How they were cutting it before
One sign, one sheet. The letters were dragged around inside the drawing until they looked about right, then the toolpath was generated and the sheet was cut. Two signs meant two sheets, and the second sheet came off the router about a third used.
It is not carelessness. When you are drawing a fascia you are thinking about the fascia, and the sheet is just the thing underneath it. The two jobs were quoted separately, invoiced separately, and so they were cut separately.
Two sheets against 4.3 square metres of letters is 65.0 per cent waste. Acrylic is not chipboard. That hurts.
What changed
Both sign's letters went into one parts list, with a note in the label column saying which fascia each piece belonged to so they could be sorted at the bench afterwards. The kerf was set to 6 mm, which is the cutter diameter rather than a saw blade thickness, and the trim to 12 mm because the sheets come with masking that lifts at the edges. Acrylic has no grain, so everything was free to turn.
It came back on one sheet with a usable piece left over.
Job sheet
- Material5 mm opal acrylic
- Sheet size3050 x 2030
- Sheet area6.191 m2
- Pieces41
- Piece area4.3 m2
- Kerf6.0 mm cutter
- Edge trim12 mm
- GrainNot applicable
- Sheets before2
- Sheets after1
The layout
Both fascias on one sheet. The 450 letters run along the top in two bands, the 300 letters fill underneath, and the roundels take the corner that nothing else wanted.
The result
One sheet instead of two. Waste down from 65.0 per cent to 29.9 per cent. The shop was paying about 210 dollars a sheet for 5 mm opal at the time, so the saving on this pair of signs was one sheet, and the leftover piece was big enough to hold the next set of house numbers.
The wider point is that a sign shop almost never cuts one job. There are usually three or four small jobs sitting in the queue that are all the same material and thickness. Putting them on one sheet is not clever, it is just something nobody has time to do by hand.
What it does not do
This is the honest limit of the tool and it matters most in this trade. Cut Solver nests the rectangle a letter sits in. It does not nest the letter outline.
An L, a T or a Y leaves a large amount of perfectly good acrylic inside its own bounding box, and a true shape nester would tuck a smaller letter into that space. We do not do that, and we are not planning to. If your work is mostly large open letterforms, a dedicated shape nester will beat this layout and you should use one.
Where rectangles are the right model, which is most panel work and a surprising amount of sign work once you count the trays, backs and packers, it does the job in one pass.
How long it took
Measuring and typing the bounding boxes for thirty nine letters took about twenty minutes, which is the slowest part and always will be. The shop now reads the bounding box straight off the drawing bounds in their design software and types the two numbers in.
The layout ran in under a second. Checking it, deciding they wanted the roundels moved so the masking peel started on a clean edge, and re-running took another three minutes. Then it printed and went on the wall by the router.
Sorting after the cut
Forty one letters from two different signs come off one sheet mixed together. The label printed on each piece in the diagram is what keeps them apart, which is covered in reading a cutting diagram.
Cutter diameter, not blade thickness
On a router the gap between parts is the cutter diameter, and it is usually far bigger than a saw kerf. Putting 3 mm in that box because it looks like a saw number will cost you every part on the sheet. See kerf.
The other five examples
Every job here is written up the same way, with the sheet count before, the sheet count after and the time it took.
- Eighteen kitchen carcasses from melamineKitchen fitting. 108 parts, 13 sheets down to 11.
- A sideboard cut with the grain running one wayFurniture making. 14 grain locked parts, 4 sheets down to 3.
- A term of plywood for a school workshopEducation. 216 parts for 36 pupils, 6 sheets down to 4.
- Marine ply for a small launchBoatbuilding. Scarfed hull pieces, 10 sheets down to 6.
- Engineered oak floor cut from lengthsFlooring. 81 pieces from 2200 mm boards, 64 down to 58.
Read on
The settings behind this job, and how to price the next one.