SketchUp Model to Cutting Plan: Import a .skp File

A hobby woodworker in the US who built a closet-sized built-in from a SketchUp model told us the job came to 105 parts on ten sheets. The model knew every one of those parts; the cutting plan only existed once the parts met an optimizer. That used to mean an extension, a spreadsheet and a paste. CutOptim now opens the .skp file itself. This guide follows the path on a small invented closet, so every number below is what the app printed for that stand-in model, and the page carries the made-up-data badge.

A SketchUp cut list is the list of the parts of the model with their cut sizes, quantities and material; a cutting plan is what an optimizer makes of that list on the sheets you buy. The import produces the first, one click later you have the second, and the model stays behind the list, so the same file also feeds the assembly drawing and the labels.

What does CutOptim read from a SketchUp file?

The geometry of the components and groups, their names, their material names and where each one sits in the model. For every component that has flat faces of its own, the import measures the box of its geometry, takes the smallest side as the thickness and reports the two larger sides as the cut size. SketchUp stores everything in inches whatever it displays, so the sizes are converted exactly and then shown in the unit the job is set to.

The file is read in your browser, in a separate worker, and it is never uploaded. Files up to 50 MB are accepted, a reading that takes more than 20 seconds is stopped, and a model whose assembly data would not fit the roughly 500 KB a project can hold is imported as a cut list only, with a warning from about 400 KB. Two more rules matter to a woodworker. The import needs you to be signed in, and a guest is asked to sign up first. And it does not count as an optimization run, so it does not touch the monthly count of a free account.

The import works in 2D mode, because a cut list from a model is a list of sheet parts. Linear and wood modes keep their own tables.

How do you import the model?

1. Name the components in SketchUp

   Give every panel a clear component name, make identical panels copies of one component and keep hardware on components of its own. The name becomes the part name and, with it, the label text.

2. Open the import window

   In 2D mode click SketchUp in the header of the Parts (2D) section (the same import is also in the CSV menu). Pick the file. The window reads it and shows a preview; nothing in your job has changed yet.

3. Read the preview

   It gives the number of cut-list rows and pieces, the notes of the reader, the components that are not sheet parts and the rows with their sizes in your unit. Check the front, described below.

4. Import and answer the material question

   Click Import. When the file names several materials or thicknesses, the app asks whether to cut them separately by material, because parts of different materials cannot share a sheet.

5. Enter the sheet size and run

   Type the size of the sheet you buy in the Stock section and the kerf in Settings, then click Run optimizer. Cancel in the preview changes nothing at all.

If the job already has an assembly model, the import asks first. The default answer replaces the old model and removes the Parts rows that were bound to it, so no orphan row stays; the rows you typed yourself stay. If you say no, the preview stays open and the job is untouched.

How does the import tell a board from hardware?

By a short list of rules, applied in order, and every part it does not take as a board is listed with its reason, so the decision stays yours. A component thicker than 50 mm is not a sheet part. A part in a material such as glass, steel, fabric or leather is not. A board-sized thin sheet, with its longest side at least 150 mm and at least ten times its thickness, is a panel whatever it is called. A part whose name contains a hardware word such as hinge, knob or screw, in any of the ten app languages, is not. A rod or stick, a long part with a squarish cross-section, is not a panel either; the closet’s clothes rod is one. A small, thin sheet is a panel, and a small chunky solid is not, unless its thickness is one the model’s own sheet parts use, which is how a small plywood rod support stays in the cut list.

Same name, same size to 0.1 mm and same material make one row with a quantity, so ten copies of a drawer side are one row and one part number. A SketchUp library texture such as a bamboo look is a look, not a board: the preview reads the thickness instead. Your own material names, such as Baltic Birch, are kept.

Some things never become parts, and the preview counts each of them instead of dropping it silently: hidden items, loose faces at the top level, images, scale figures and geometry thinner than half a millimetre. A part rotated off the axes still goes into the cut list with its own size, but it stays out of the assembly drawing, which works with axis-aligned boxes, and the notes say so.

How is the front of the furniture found?

The assembly drawing and the labels use words such as left, right, front and back, and SketchUp does not say which side of a closet is the front. The import reads it from the model. It looks first for a wall or plane named Front or Back, hidden ones included, in the ten app languages, then for the large, thin, standing back panels, whose opposite side is the front. If neither is conclusive, it marks its guess as not confident and asks you to pick the SketchUp view that shows the front: Front, Right, Back or Left. The file is then read again with your choice.

In the invented closet the front is found from a hidden wall named Front Wall, and it faces SketchUp’s Right view. Without that, a side panel would be called the back and a drawer front the right side. It is the one thing in the preview worth a second look every time.

What does the invented closet give?

The stand-in model has a tall cabinet with a clothes rod, two book shelf units and two drawers. The preview shows 12 sheet-part rows with 29 pieces, one rod kept out of the cut list with the note that it is a rod or a stick and not a sheet part, and a note that 3 hidden items were skipped. The 30 parts, rod included, sit in five groups: the cabinet with 11 parts, the book shelf units with 5 and 4, and the two drawers with 5 each. The file lists four materials and thicknesses, 19 mm, 12.7 mm, 6.4 mm and Baltic Birch at 19 mm, which is why the material question comes up.

To keep the example plain, the run below puts all 12 rows on one board, which is the answer to the material question that does not split them. Run with a 3 mm kerf and parts allowed to turn, the optimizer places all 29 pieces on 3 sheets of 2440 × 1220 mm and uses 73.5% of the board. A real job would split by material and thickness first. The button loads the same rows if you want to see the layout.

A stand-in is only a stand-in, so here is a real one. In our measurement of a hobbyist’s built-in, about a hundred parts in three cabinets drawn in inches, a 426 KB file was read in 42 ms and every size matched the builder’s own drawing to within 0.1 mm. The hidden walls and the ceiling did not come in as parts, and the Model check found two real mistakes in the model: a back panel that overhung and an insert that floated.

What do you get after the import?

The model stays with the job, and three things read it. The first is the cutting plan you already know. The second is the Assembly view: under the results a switch changes from Cutting plan to Assembly, and the parts are drawn exploded in groups, each with its number and, where several parts share a number, a place letter such as 3b. The guide on the exploded view drawing for furniture walks through it. The third is the Build Pack PDF in the Export menu, with the overview, one page per group, the material list and the parts table. It needs an account and does not use a run.

The Model check lists what it finds, errors first. Its findings are an overlap of two parts, a part or group that does not touch the rest, a part that sticks out of its group, a small overlap that is probably a joint, and a part that differs from its identical siblings. On the invented closet it gives nine entries: six about parts or groups that do not touch the rest of the model, two odd ones out among the shelf parts and one overlap to check as a joint. That is what a loosely modelled stand-in earns. Clicking a finding highlights its parts in the drawing and in the cutting plan. The Steps view orders the build: five steps here, the cabinet, the two book shelf units and the two drawers.

The labels use the same model. A label can carry a line such as Carcass · left and the visible edges whenever the job has a model, and the place letter joins the part number when the part number is on. The guide on labelling furniture parts for assembly covers them.

What goes wrong between the model and the plan?

• Unnamed or badly named components. Every part named Group becomes the same row. Name by what the part is, and give different parts different names.
• Hardware modelled as a board. A hinge named Part 12 looks like a small thin sheet. Check the notes and the rows of the preview against the model.
• Skewed parts. A rotated part is cut from its own size but is not drawn in the assembly, and the notes count it.
• Nesting deeper than one level. The assembly model keeps one level of groups; the full SketchUp path is kept in the preview.
• Hidden tags. Hidden components are skipped. Hidden tags in files saved by SketchUp 2021 and newer are not resolved, so hide the components themselves.
• An old, very large file. If the reader refuses it, save the model again from a recent SketchUp.
• Importing twice. The second import replaces the model and its bound rows, and the numbers follow the table, so reprint the labels after it.

What if you prefer a parts list?

The older route still works, and it is the right one when the list comes from somewhere other than a model, or when you want to edit it first. The Parts List of the free OpenCutList extension can be exported as CSV or copied to the clipboard, and CutOptim reads its Designation as the name, the raw cutting size from Length - raw and Width - raw, and Material name. The Importing Data page describes the headers, decimals and units. A list carries no model, so the assembly drawing, the Model check and the place letters are not available from it. For a small job with no model at all, the furniture templates produce the cut list and the assembly model from a few dimensions.