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The First Project: A Cat Tree for a Senior Cat

My 9 year-old cat Amelia.

About a year ago now, we took our cat Amelia to the vet. The vet let us know that she was beginning to show the signs of early Arthritis and that she would start to show signs of being lethargic and not jumping as much as she did in the past. We still wanted to give her a good rest of her years, so we tried to find ways to make the house more accessible to her. We outfitted the bed with a set of stairs, we got a food bowl where she wouldn’t have to bend down to eat, and we mix her joint medication into her food twice a day. The biggest problem, is that there are not many cat trees designed for senior cats. The ones we were able to find, were only about 3 feet high, which is just barely enough for her to see out of the window. I found one cat tree that I was sure would work. It had ramps for her to use to get from one level to another, and seemed perfect. After and ordering snafu, it arrived at our house and I put it together for the kitties.

“Senior Cat Tree” in middle

The problem with it became clear when I was putting it together. The ramps were only secured at the top leaving it to wobble around at the bottom. The steep incline, between 45 and 60 degrees, of the ramps made them too hard for Amelia to traverse. She started to use the cat tree less and less. We now have to help her up and down by picking her up.

The goal of this project will be to make a cat tree that is tall enough for both cats, while also allowing greater mobility between the different sections. The biggest simulation of failure will be a 20+ pound cat jumping from the top level, and not creating a large displacement at the bottom, aka no tipping. The joints must also hold a 20+ pound cat for long periods of time. The catch of all this, is that all materials and production equipment has to be from what is commonly available at a local hardware store. This means no lathes or drill presses, and no fancy woods or carpeting.

Let’s get to the initial designing, and I’ll see you next week!

Engineering and Covid-19

I’m going to take a break from trying to build cat trees for a bit to talk about how flexible the world will need you to be. Sometimes, you have to be prepared for your whole life to switch around and your focus devoted to a new topic. My current day job is to make sure life safety systems work correctly and will do what they need to the instant something happens. I knew things were going to get bad, and at sometime I was going to have to switch concentrations even if it would be in my off time.

After a few months of saving, I finally bought my first 3D printer, a Sovol 01.

My Sovol 01 3D Printer

A lot of printing groups have joined together to print personal protective equipment (PPE) for emergency personnel around the world. However, these groups weren’t really in my area, nor did they focus on more rural areas who don’t have the liquid funds to enter a price war for the necessary PPE. I knew this is where i needed to focus.

I contacted my dad who runs a local EMS service in a rural area around Atlanta, and asked if they needed any kind of PPE. They needed face shields, and 20 of them.

I started looking through all of the models available, and what was available in out local stores. Unfortunately, there isn’t really any elastic in our area, so that ruled out any designs that required any elastic bands, cords, or straps. This lead me to the 3D Verkstan model. This model was light, required no elastic, and would save on print time and plastic.

3D Verkstan Visor
Credit: https://3dverkstan.se/protective-visor/protective-visor-versions/

Now it was time to pick a material. First, I looked at PLA. PLA would be nice and light, save me in cost, and be flexible enough to go around any size head. However, PLA is not chemical resistant, can be very brittle, and doesn’t do well with UV exposure. I want these to be cleaned and reused, to that material won’t work.

The next material was ABS. ABS is chemical resistant, relatively flexible, and a good bit tougher than PLA. However, ABS requires a higher temperature from both the nozzle and print bed. Our house is being run cold to combat the temperature coming from 2 computers running 2 people telecommuting. I could order an enclosure to keep the heat in, but then I would have to wait several days for delivery. Time is important here, so lets see what can be printed ASAP.

Since we need a lower-temperature but chemical resistant material, the next choice is PETG. This plastic prints at a lower temperature than ABS, but stills has the great qualities of both ABS and PLA. The biggest downside is that it doesn’t do well with UV exposure. However, the time in UV light is minimal for this use application.

Once I got the plastic and the printer together, it was time for a test print in order to dial in the settings. My first print with the PETG is an XYZ cube. Reviewing the manufacturer’s recommended settings on the spool, I used a nozzle temperature of 240°C and a bed temperature of 80°C.

Test Print: XYZ Cube

When printing the inner portions of the cube, the plastic looked like it was leaving strings behind. This means that the nozzle temperature is too high. I lowered the nozzle temperature to 235°C, and that greatly reduced the stringing. Now it was time to print the first model.

3D Printed Face Shield Visor

Even though there is still stringing, it can be easily removed by pulling them off when the part is fully cooled. Now that this test looks good, we can start printing more. For the transparent sheet that makes up the actual shield, you can use either transparency sheets, or clear document covers. I had bought a pack of 100 transparency sheets from our local office supply store.

Completed Face Shield

If you want to join the effort in providing 3D printed PPE, please use the “Get in Touch” button on the About page. At the time I’m writing this article, the Georgia Emergency Management Agency (GEMA) is noting the difficulties of optaining PPE, especially for the more rural areas of Georgia. The help is needed now more than ever. https://www.gwinnettdailypost.com/local/obtaining-ppe-continues-to-be-a-struggle-in-georgia/article_5080975e-8013-11ea-b24e-97662101a1a4.html

If you want to know more about 3D printed PPE and other medical devices, you can use the following link for FDA guidelines: https://www.fda.gov/medical-devices/products-and-medical-procedures/3d-printing-medical-devices

For more information on the 3D Verkstan face shield, please use the following link to their information page: https://3dverkstan.se/protective-visor/protective-visor-versions/

A Cat Tree for Senior Cats: Initial Designs

Considering the build parameters set before, I believe a tiered cat tree will be the best option. I will be listing the pros and cons for each design, then combining the base aspects into a single design.

Design 1: Front View
Design 1: Top View

Pros:

  • Landings provide good mobility between levels
  • Square cat beds are easy to build
  • Not many specialty tools would be required
  • Would take less time to manufacture

Cons:

  • Height isn’t much higher than what is already on the market
  • Length is larger than the height
  • The one-foot by one-foot cat bed may be a bit small for larger cats
Design 2: Front View
Design 2: Partial Top View

Pros:

  • Multiple landings between levels give the easiest mobility

Cons:

  • The one-foot by one-foot cat bed may be a bit small for larger cats
  • The large amount of space required for all the landings puts each cat bed at around 4 feet apart
  • Height isn’t better than what is already on the market

After starting on the Top View of this drawing, I could tell this design was going to be way too large for most people’s homes and I decided to leave it and move on.

Design 3: Front View
Design 3: Top View

Pros:

  • Octagonal cat beds offer a cozy spot for kitties to curl up, and increases the area per bed
  • Length is not too large

Cons:

  • Landings and ramps will be difficult and time consuming to manufacture
  • Height isn’t much better than what is already on the market

After taking some time to think out all the pros and cons, and talking with a few cat owners, we can combine some of the best aspects and fix some of the cons.

Pre-Testing Design Concept: Front View
Pre-Testing Design Concept: Side View Without Ramps and Landings
Pre-Testing Design Concept: Top View of Cat Bed Layout

Pros:

  • Octagonal Cat beds give the cats more room
  • Layering the cat beds in a criss-cross pattern adds design appeal and reduces the overall length
  • Height between levels can be adjusted to lower the overall height

Cons:

  • Uneven landing layout may increase tipping
  • Octagonal beds will take longer to produce than square or rectangle ones
  • Increased height will move the center of gravity upwards, increasing the risk of tipping

Our next step will be to get the design concept into SolidWorks, and run the simulations to see what, if any, design changes will need to be made to make this a safe cat tree for both cats and humans. This will mean following any and all design requirements set by local and national organizations. Upon initial investigation, this appears to be the ISO (International Organization for Standardization) and the IBC (International Building Code) in my area.

A Cat Tree for Senior Cats: Initial Planning

Since the challenge of this project was to use as many materials from my local home improvement store as possible, I decided to take a trip to my local store and see what they had. I took pictures of the types of materials, their sizes, and the price. Even though we could over-design this for a higher price, I’d like to keep it at a more accessible budget. As I was looking through materials, I was trying to think about someone who only makes around $50,000 per year being able to do this in their spare time. What materials at my local prices would be accessible to them? How much would their budget be? What kind of room might they have to work on this project? Would they need to take advantage of the large-material cutting services that my local store offered? What other obstacles might they encounter?

Thankfully, my recent experience in the construction industry can help in this instance. The average price for materials should be around $200 as much as possible. The base of the tree needs to be a maximum of 3 feet (0.9 m) wide to clear through a door frame, and a height of between 6 and 7 feet (1.83-2.13 m)because most home ceilings are 8-10 feet high. The weight of the overall tree needs to be where no more that 2 people can carry it, so about 100 pounds (45.4 kg).

Now, let’s see what we have to work with.

First we look at the wood. There are multiple sizes to work with. I’m thinking of making a walkway between the levels from a few sections of 2×18 inch (0.79×7.09 cm) planks of wood. I can use a sheet of plywood to form the base and the bottoms of the beds for the cats to sleep in. I can use the smaller 1×8 inch (0.4×3.15 cm) planks for the sides of the beds.

Carpeting and Supports

The next big thing to look at is the supports. Using PVC piping would be the cheaper route and the lightest option. However, to get the same sturdiness, we would have to increase the diameter of the pipe. The metal piping would be the sturdiest option, and save space on the width requirement. However, the metal would add a significant weight to the overall design and increase the overall price.

My cats love carpet cat trees, so I would need to cover this in as much carpet as possible. Buying a large rug with a pretty pattern and cutting pieces out like you would sheet metal is one option, but it would be rather expensive with the largest option of 80 square feet costing around $150. The other option is to buy the carpet by the square foot, and again cut out what you need. This would bring our cost down to $52 for the same 80 square feet.

Now let’s see how we can turn the larger materials into pieces we can assemble into the cat tree. These have a variety of uses, and can thankfully give me a few options on how to design the tree.

Lastly, there are the fasteners. The deck screws would be really good for joining the base and the feet for the cat beds. I can use the regular screws for some of the other connections as well. I’m not sure what I could use the joiners for, but they could be useful. I didn’t see any biscuit joiners at our local store, but it is a smaller store than some of the others in our area. I’ll have to keep that in mind when doing my initial designs.

Next time: Initial Design Concepts