Week 3 Computer-Controlled Cutting
This week the assigment was to design and lasercut joints out of carton. Multiple things should be able to join together, and make different things out of it. This week the next assigment was to also designing something with the vinylcutter. After a long thinking on Thursday and Friday I was walking on Friday afternoon to my car. Like every week I like to design the weekly assignments for my final project. During my walk I came with the idea to search for a leaf font. I found a font called Leaf and I directly get another idea. With this font I could make two things. First I make the joints and second my design for the logo for my leaf robot. The font is perfectly made to cut out with the vinyl cutter
The leaf font, that is taken as a basis of this weeks assignment
In Illustrator I startet to draw 3 different objects. The leaf font is build up from these 3 different objects.
Then 3 files have been saved, for each colour 1 file. I copied the different objects in these separate colour files on a special way. Starting from dark green, to lighter green to yellow. And that repating over the leafbot text.
Together the different objects make the leafbot text. Each colour file is equiped with 4 cirkels for alligment.
On the vinyl cutter the 3 files have been cut.
The settings of the vinyl cutter are:
On the topside of the darker green foil a transfer foil is sticked. Pulling the green sticker material away was a little bit tricky. The vinyl cutter knife could have cut just a littlebit deeper in to the foil. So the objects that should remain on the transfer foil, during the removal of the rest of the sticker material, had to be pushed towards the transfer foil to prevent that they also where pulled off as well. The foil material of the lighter green and yellow foils where removed, so the objects remained.The darker green foil with the transfer foil, was sticked on the window, with the transfer foil side towards the window. After that the other 2 foils where sticked on the transfer foil. After sticking one new colour, the backing material was removed, leaving the objects on the transfer foil.
The transfer foil was removed from the window and an acrylic plate was glued onto the sticky side of the objects. After a ferm pressure the transfer foil was removed leaving the objects on top of the plate.
Some objects where pulled of the acrylic plate and had to be reworked by hand.
The final result
Making of the related file
After the vinyl cutter assigment the leaf font was used to create the carton joints. Goal was to design a part that could easily be changed in dimension. If the thickness of the carton should be changed, then the gaps should also be changed to the new wall thinkness width. In solidworks a square is sketched with a outside dimension of 50 mm
In the sketch the gaps where drawn with sketch lines. With "add relations" the horizontal and vertical lines where related with equal relations.
With "construction geometry" I have added additional lines to add relations.
With "Toggle Equation" the lenght of the lines should get an relationship with the wall thickness of the carton. I tried to add an formula like ='D3'. Solidworks did not give any complains, but it didn't work. I tried several options, but I couldn't make it work. Later on tuesday I did some more research and I managed to get it working. See below.
To be able to make a "circular pattern" a cutting line is created between to planes. The middle of the square sketch is postioned perfect in the origin. Therefor the cutting line of the two planes, can be used as an axis to rotate the circular pattern.
A circular pattern of 4 was added
But I should have known better that this doesn't work, because the whole object was patterned 4 times, closing the gaps off course. It should have only patterned the gaps instead of the whole object. I created the gaps in the first sketch and that was my mistake. It works better if the gaps where created as a separate cutting feature.
I tried to make the width of the object in relation of the width of the gap, by multiplying the width by 8. The result was strange, it was half of the expected width, 12 mm instead of 24 mm.
I doubled the multiplying number and it changed to the right width. But this isn't what I was looking for.
I tried to relate the vertical dimension to the horizontal dimension. This was also not working.
I tried several times to change the formula, but it didn't work. The gap size was changed to different dimensions to check if the outside dimension also changed. But this was not the case
I had a look how equations should be applied. But I couldn't find the right way of appling a line lenght to a other line lenght.
Some errors revealed
A lot of relations where applied.
An 1/4 segment is drawn, that will be circular patterned. Because the width of the gap is 3mm but only the 1/2 of it is drawn, I used a horizontal construction line segment. I attached in the middel of it a new vertical construction line that is related colliniair to the plane. In this way the width of 3 mm can be applied.
The gap dimension was changed to 5 mm to check if the complete model would increase in the right dimension. This test worked fine
After the test the circular pattern was done. Also the other two objects where constructed in this way. But it was not the intended way of how the object should be drawn. In the assembly mode in Solidworks I created a assembly of the complete Leafbot logo/text.
The faces of the letters did get a grass decal. After appliing the decal to the letters I noticed that the connectors also compose the leafbot text
On tuesday I have looked again how the formula in the sketch has to be applied. I changed the formula from ='D3' to ='D3@Sketch1'. Now it worked, which seems to me logical. It is possible to refer to lines in a other sketch as well, which the formula also should refer to. I hadn't done that and therefor it didn't work
Preperation of the cutting files in Illustartor
First open in Adobe Illustrator an new file as custom RGB with the maximum laser cut size dimensions of 730 x 430 mm. The fablab Enschede is equiped with a Trotec Speedy 300 laser.
Then save the 4 different objects in Solidworks as .dxf file
Open the 4 different .dxf files in Illustrator.
The 4 objects have been copied in to the new file. In this new file the files are been preperated for the first set of test I have planned to do. The test is designed to test the amount of clamping force in relation to the gap between the objects.
First test is done by making the gap smaller, starting with a width of 3 mm until to 2 mm. In this test no influence of the laser cutting thickness is considered.
The second test is testing the small detail in the hook shape of the joined part. One is applied with small square hooks, the other with chamfered ones. Both hookes are 0,5 mm in height.
The thirth test is to test the differents in strenght of the carton wave direction.
To be able to make a offset of the objects in Illustrator the lines have to be joined. Each connection piont has to joined separately. This can be done by clicking on the line connection and apply cntr+J
To test the joints a offset is applied. It works ok
The new offset lines are been moved to a new layer. This layer 2 will be the laser cutting file. The layer 1 will not be used for the laser cutting and will be hided
The trotec laser requires special line parameters from Illustartor. The cutting lines must have a width of 0,01 mm and RGB 255,0,0 red. All the objects have to change to these parameters. The joints wil be cut with different offset to test the lasercut width. The laser is cutting exactly over the lines. The Trotec cuts with a width of about 0,1 - 0,2 mm. The results is that the object will be smaller then the Illustrator file. So a test is performed to check the amount off cutting width. These test results will be applied in the final laser objects.
The test samples have been prepared in Illustartor. In each sample the amount of offset and the direction of the wave in the carton, is engraved in the carton.
The settings of the laser cutter
Engraving Power/speed/frequency: 75 / 100 / 500
Cutting Power/speed/frequency: 85 / 3 / 5000
The cutted carton
Testing the different gap width. Each time the matching gaps, sliding in each other. The 3 mm gaps fitted very loose. From a gap of 2,4 mm the pressfit was ok.
The smaller gaps where to small, causing that the carton parts cann't stand in a perpendicular position.
So without an offset applied to the carton a gap, to make a connection, is preferred to be 2,4 mm when the carton wall thickness is 3,0 mm.
Some deep groves pressed in the carton due to the tight fitting
The connection to tight, causing the carton object not to be perpendicular any more.
The 2 different joints. The upper joined applied with chamfered hooks and the lower ones with perpendicular hooks.
Every set of joint is also been cutted with a different carton wave direction
Each square object have the same offset as the 4 joints. So on every square object the 4 different parameters could be testet.
The 0,15 mm offset joint with perpendicular hooks was crushed very fast.
The fitting of test samples with an offset of 0,20 mm had the least movement. The ones with no offset the most. The joints with the
lenghtwise wave where the strongest.
The outside dimensions of the square objects are:
Cad dimension: 52 x 52 mm
No offset: 51,85 x 51,8 mm
0,05 offset: 51,9 x 51,9 mm
0,10 offset: 52,1 x 52,15 mm
0,15 offset: 52,2 x 52,15 mm
0,18 offset: 52,2 x 52,25 mm
0,20 offset: 52,4 x 52,2 mm
Due to the better fitting I decided to cut all the objects with an offset of 0,20 mm
In the rush of the day, because off many customers in the FabLabEnschede, a small mistake happend during the movement of the objects in Illustrator. The inner squares where not selected, so they didn't moved as well, causing this misalignment.
The final result assembelt together. The fitting and the assembly worked very good.