Worked example · Design Technology · Year 10
DCF: Interacting and collaborating → Storing and sharing
A secure Year 10 response, annotated so you can see which success criterion each part meets. Answer key: body = file 4, DeskTidy_Body.dxf, restored to v2; logo = file 7; pen clip = file 9. Step 6: laser 7 sheets, £29.40; by hand 10 sheets, £42.00; laser time 211 minutes = 3 h 31 min; by hand 1,400 minutes = 23 h 20 min; 3 desk tidies in the 45 minute slot. Show this after pupils have tried the sheet themselves.
| Part | File to use | Why this one | Another file and its problem |
|---|---|---|---|
| Body | 4, DeskTidy_Body.dxf, after restoring v2 | v2 has the 2.9 mm slots that Megan tested: the joints fit tightly because the slots allow for the kerf. It is a DXF in mm, so the laser can read it. | Files 1, 2 and 3 are the same old drawing with 3.0 mm slots, which gave loose joints in the test cut. The word “final” in file 2 is wrong. File 5 is only one panel and is set to inches. |
| Logo | 7, logo_ysgol_outlined.svg | The text has been converted to outlines (paths) with black fill, so it engraves exactly as drawn. Rule 2. | File 6 has live text. The laser computer does not have Megan’s font, so the words would come out in a different font or not at all. |
| Pen clip | 9, penclip_v2.stl | STL is the file type the printer needs, and the 3.2 mm gap has been test printed: “pen clip v2 fits!!” | File 8 has a 2.6 mm gap and “snapped when I pushed it on”. File 10 is the CAD program’s own file, which the printer software cannot open. |
(b) The machine would read 150 as 150 inches: 150 × 25.4 = 3,810 mm. That is more than 6 times longer than the 600 mm bed, so the job would fail or the software would try to scale it. Either way the panel would be wrong. The fix is to set the units to mm and check the size before saving.
Every choice has a reason taken from the dossier, and each rejected file has a specific problem: an old version, the wrong file type, live text or the wrong units. Evidences criteria 1 and 4.
(a) Restore v2. It is the newest version that still has all the finger joints, and it has Megan’s tested 2.9 mm slots. v3 has lost the joints on the top edge of both long sides, so those panels would not fit together. v1 has the loose 3.0 mm slots.
(b) Restoring v2 loses Cai’s close-together layout, so it goes back to 2 desk tidies per sheet. v3 is not deleted: it stays in the version history. Cai can open v3 to see how he fitted 3 on a sheet, then move the v2 parts into the same layout. This time he should delete duplicate lines one at a time and check every edge for joints before saving it as v4.
(c) First, with one file everybody always opens the newest version, while copies leave people guessing: Owen called file 2 “final”, but it was not the newest drawing. Second, version history records who saved each version, when, and a note on what changed, so the team could see exactly when the joints were lost and go back one step. Copies have none of that, and they fill the folder: 3 of the 12 files are the same drawing.
Uses version history as a tool: restores the right version, knows that restoring keeps the newer versions, and has a plan to get the lost change back. Evidences criterion 1.
| Problem | Cause | Fix |
|---|---|---|
| “You need permission” | The link is set to “Restricted: only people added”, and Owen only added Megan and Cai. Mr Howells is not on the list. | Move the folder back to the shared D&T drive, and give Mr Howells “Can view” access. He does not need “Can edit”, so he cannot change the files by mistake. |
| “Location not available” | The shortcut pointed to where the folder used to be. Owen moved the folder into his own storage, so the shortcut now points at nothing. | Put the folder back where it was, or make a new shortcut and a new link on the job sheet. After that, nobody moves the folder: they tidy inside it. |
Separates the two causes: who is allowed to open the file (permissions) and where the file is (location). Evidences criterion 3.
(a) Pattern: DeskTidy_Part_vN_STATUS.type, where STATUS is WIP (work in progress) or CHECKED plus the initials of whoever checked it.
| Old name | New name |
|---|---|
| DeskTidy_Body.dxf (restored v2, then relaid 3 per sheet) | DeskTidy_Body_v4_CHECKED-MJ.dxf |
| logo_ysgol_outlined.svg | DeskTidy_Logo_v2_CHECKED-OP.svg |
| penclip_v2.stl | DeskTidy_PenClip_v2_CHECKED-CE.stl |
(b)
Files 1, 2 and 3 can go because v1 of the body file keeps the same drawing in its version history. Untitled drawing.svg is empty.
(c) 1. Only a file that a second person has checked goes into Ready to cut, and it keeps the checker’s initials in its name. 2. Never save a copy to make a change: edit the one file and write a version note saying what changed. 3. Never move the folder or share from personal storage: give Mr Howells “Can view” on the shared drive.
The pattern answers rule 4 (part, version, checked), the folders make rule 1 easy to follow, and every one of the 12 files has a place. Evidences criterion 2.
(a) Laser: 20 ÷ 3 = 6.67, so 7 sheets. 7 × £4.20 = £29.40. By hand: 20 ÷ 2 = 10 sheets. 10 × £4.20 = £42.00. The laser saves £12.60, which is 30% of the wood cost.
(b) Laser: 10 set-up + (7 × 3) loading + (20 × 9) cutting and engraving = 10 + 21 + 180 = 211 minutes = 3 h 31 min. By hand: 20 × 70 = 1,400 minutes = 23 h 20 min. The laser is about 6.6 times faster.
(c) 45 − 10 set-up = 35 minutes. One sheet takes 3 + (3 × 9) = 30 minutes, which leaves 5 minutes: not enough to load another sheet and make one more (3 + 9 = 12 minutes). So 3 desk tidies. The team will need about 5 slots of 45 minutes for the whole batch.
(d) One advantage of CAD/CAM is speed, which matters in batch production. The laser cutter makes all 20 bodies and logos in about 3 h 31 min, compared with 23 h 20 min by hand, so the batch can be ready for the charity sale. A second advantage is accuracy and repeatability: the laser cuts to about ±0.1 mm, so once the slots are set to 2.9 mm every finger joint in all 20 desk tidies fits the same, whereas hand cutting at ±1 mm would give some loose joints. Because the parts can be nested close together, it also uses 7 sheets instead of 10, saving £12.60. One disadvantage is that the machine copies mistakes as accurately as it copies good work. If Mr Howells had cut v3 of the body file, all 20 desk tidies would have been missing joints, wasting 7 sheets and 3.5 hours of machine time. CAM also depends on one expensive machine and a trained technician: the team only has 45 minute slots, so the batch needs about 5 sessions.
Two developed advantages and one developed disadvantage, each with a figure from the working and linked to batch production and to this product. The disadvantage connects back to the file problem the pupils solved. Evidences criterion 5.