Initial Concept

First we take multiple measurements of the plywood sheet. For me, I got the following values: 17.17, 17.50, 17.22, 17.46, 17.28, 17.67. Average value is 17.383. The I test if a rough shape of my final design for a standing desk would fit in the 8x4 feet of plywood.

Once I was condfident it would fit, I eperimented with different shapes but I was not satisfied so I rethought my design taking inspiration from an already existing design.

Sketch is made in such a way to waste as less material as possible

I made the first version of my standing desk.

Iterations

Based on feedback from my instructor Mufeed, there were many issues with my design that need to be corrected

• The number of slots will take too much time to be machined. A couple of slots at the top for standing position and a couple of gaps near the bottom for the sitting position only are required.
• There are weak points in the structural members of the desk, an easy fix is to add a large fillet to all of them (~15 mm)
• Slot joints can be added to the table top itself to reduce the total length of the gaps in the side pieces. Also, it helps to ensure that the table top is always pressed into the right position.
• Finger joints can be added to the structural supports
• A T shaped key can be added to lock the horizontal support in place
• To avoid wobbling at the front, a board can be near the front with slot joints on the board and the corresponding slots can be added into the side panels itself

Designing

Instead of slots, I was inspired by this design by Rahul (FA 2017, Fab Lab Trivandrum) and wanted to incroporate his saw tooth mechanism to be able to adjust the height.

Things were not working the way I imagined so I started from scratch

While using Rectangular pattern, one has to make sure that each copy touches each other and the corresponding points are coincident, otherwise you wont be able to extrude the profile.

It's also important to check your design is parametric from time to time by changing the scale. In my case, the curve of the leg kept changing when the scaling factor was changed because it is linked to 'Depth' parameter which was not parametric. Similarly, the steps were not changing in proportion with the rest of the body, so I relinked it with the height parameter instead of the depth parameter.

Finally, I was done with the design, but unfortunately it was not parametric, so I went back to the initial sketches to correct the issue

Laser Cut Mockup

Error with peg, will be cut out in Laser cutter

How it looks in SVG for laser cutting

This is how my model prototype looks like in cardboard

Problems:

• Since the peg and the load bearing joint I made is too small and because the engraving was too shallow, I was not able to get the table top to move like I had designed.
• I did not remove the stroke in the steps of the sides, so the laser cutter completely removed the portion which should have been engraved.Solution: Use two cardboard layers for the thickness in the side, one layer where only half the thickness is required.
• The peg should fit in here to control the direction in which you can pull the tabletop.

• The entire table sits at a minimum height of ~90 cm, which is close to the height I need for a standing table (ie. close to the maximum possible height). This means that the table cannot be used for sitting position, which is why I wanted the adjustable concept in the first place

Change shape of peg to rectangle and make the vertical step parallel to the height adjustment

Modifications

Redefining and revising parameters

Too many parameters and my final model is not completely parametric, in the process of simplifying while modifying original design

A round peg is required to allow the top desk to be rotated back and pulled onto the next step. So I cannot change that feature into something more rectangular.

The vertical steps are kept at an angle instead of vertical to allow for easier height adjustment.

To avoid screwing the peg, I made the peg is made of two parts. The first part is a semcircular shape that will 'lock' into place in the pocket of the side leg, making a tight fit that does not require screws

A useful trick to understand which which parts of a sketch is underconstrained is to use text commandsand zoom into the highlighted section

I created a minimum distance constraint between the steps and the circle using this tutorial

But later I got an error in my sketch due to too many constraints. After deleting and relinking each overconstrained dimension to see which dimension is causing the error, I was able to determine that the cause of the error was the dimension I added for the gap between the last step and the peg.

Based off this tutorialI experimented with making the number of steps a parameter also with a minimum length equal to the thickness of the stock material, but I was not able to get it to work so I went with sketching like I did before

Sketch referencing lost, deleted it and got a red coloured face as a result. Ignored. and late it went away after I changed everything

Forgot about extending the extrusion beyond the width of the lower stand to be able to touch the the steps of the upper table portion. Used Press-pull to correct it

I then arranged all of them.

Because my model was not completely parametric, I took some advice from Ancy & Akash in order to be able to scale my model down without affecting thickness and kerf. What I did was scale down my model according to the ratio between plywood thickness and cardboard thickness in Fusion using the command (not my parameter) and I would multiply both kerf and offset by the inverse of this ratio; then subtract the sum from the material thickness (plywood)to get corrected value for cardboard slots. I would now replace all the dimensions of slot width with this new value, called 'SlotW'

Since I was not able to scale it in Fusion the exact way I wanted to and because I needed to use Inkscape anyway for lasercutting, I went to Inkscape to scale it down according to the ratio of the Cardboard thickness to Plywood thickness

Some unwanted sketches were also imported which I then proceeded to delete. All of the construction lines also got imported as black lines which had to be deleted.

To engrave, first I remove the stroke of the shape of the steps, fill it black and use the cut operation to remove the overlapping strokes in the shape below it hierarchically. This did not work, so in the interest of time, I just removed the portions to be engraved.

CNC Cutting

Finishing

Once I cut all the pieces, the next step is to remove the, from the bed and perform some post processing. I use the chisel to remove bit of wood chips and tabs left behind, then I use the sanding machine to smooth out the surface and remove any burs at the edges. Then I use the file to sand the edges.

Assembling

Since the pegs were so small, one of them snapped in half while machining. I then used glue to stick them

Then I need to assemble the pieces together using a Hammer. In places where I was not able to fit the plywood peices in the slots I made some chamfers using a chisel