Week 6: Make Something Big

This week we made something big, or around 4 by 8 feet in area. I had a really hard time brainstorming ideas because most of my experience is using very small parts or is all in software. Some ideas I thought about were a table or a bench/chair for my room, but I really don’t need or have the space for more ‘furniture’ in my room. I was thinking of other relatively large objects I had seen recently and I remembered seeing an easel in an art workshop. I thought an easel would be useful and fun to have- either a place to brainstorm in a large, open space, or a place to just draw or paint on and have fun.

I looked up some typical easels and came across a lot of different styles, some super simple and some complex, and ended up emulating the following design:

I made a CAD design in solidworks and had to take the angles and lengths into consideration when assembling and figuring out the angle the easel would sit at. I looked up typical angles for an easel to sit at and found that it’s usually 20 degrees from the vertical so I went with that.

I tilted each easel leg 5 degrees and calculated how much to cut off the bottom so the easel leg would sit flat on the ground.

I figured out proper dimensions for all the other pieces with some basic calculations and some estimating. Then I assembled all the pieces and put them in the same assembly in solidworks.

Then before exporting I had to lay all the pieces flat so they could be cut using the machine.

The next step was to create toolpaths in masterCAM for the easel parts. I exported the solidworks assembly as a part and then as a .dxf and imported that into masterCAM.

I had to ensure my parts were aligned with the origin first:

Here are the masterCAM tool options:

I had to turn off ‘align tools sequentially’ so I could manually enter tools I wanted, specifically numbers 1,3 and 8, which I put in a different order than a sequential order.

I had to make sure the material was on the left of the mill when cutting- which is climb vs conventional milling. I also ensured the parts were centered on the origin of the masterCAM coordinate system.

At first there were some strange u shaped cuts on the edges of my design and it’s because masterCAM used lead in and lead outs to cut the material. In my case, since we were using OSB, we didn’t need lead in and lead outs, but if it were metal it would be important because the mill is not meant to cut straight into the metal but rather spiral in.

First I selected toolpath type of contour, diameter ¹⁄₄” straight bit, feed rate 200 rpm, plunge rate 100rpm, and spindle speed 18000 rpm (depth cuts on). I used these parameters for the internal slots of my pieces.

To make the external cuts, I again selected toolpath type contour, but this time with mill bit size ⁷⁄₁₆”. I used a 200rpm feed rate and spin rate of 16000rpm(better to overestimate because we can control the speed with a knob on the actual machine) select another tooltype- contour- select outside cuts this time. Depth cuts off this time.

I took the masterCAM file to the shop in N51 and was amazed by the size of the onsrud machine…

I used the onsrud interface to take in my file and then cut the OSB.

There’s a hard stop and a soft stop- soft stop will save current job and continue but hard stop will stop all processes and forget everything- important for emergencies.

Before running the machine, I had to turn on the valves which using suction held the OSB material to the surface of the machine…also fascinating.

The machine switches tools automatically by swinging over to a cylinder of tools and changing the mill bit. It’s very impressive.

The onsrud then began cutting, while underneath where the OSB was being held was sliding very quickly to align with where the mill was cutting.

If the machine speed was too slow, it wouldn’t cut properly because it needs to bite into the material- if it’s too slow the cuts would be really bad. On the other hand, too fast means a terrible noise from the onsrud- sometimes during my cut there was a high pitched sound, but it wasn’t terrible. If it gets to a terrible point, the end mill is likely to break and send flying hot pieces and potentially cause a fire. There is a middle balance here ( I used a spin rate of 16000 rpm to stay conservative)

My job took around 5 minutes- super quick, and then I had to use a boxcutter to cut out the actual pieces because since depth cuts were off the mill didn’t cut all the way through (depth cuts were off because it would likely cause the mill bit to break if it went all the way through)

The OSB was pretty difficult to cut with a box cutter cleanly so I had to do a lot of filing to clean it up.

Then I layed the easel parts flat and took measurements of where I should drill holes to assemble pieces.

I marked my holes and drilled holes in necessary pieces:

I then used bolts and nuts to connect pieces, and then wing nuts and bolts for the moving front part of the easel so it would be able to slide up and down the front face.

I also used a hinge so the easel could be folded and stored efficently. I used bolts and nuts again for this for a secure system.

Here is the easel against the wall flat:

I put a canvas on the easel to show what it would look like if you wanted to draw or paint or brainstorm on it!

You can also see the height of the canvas can be adjusted easily just by loosening and tightening the wing nuts on the back of the center piece and shifting it up or down.