*Critical Review at the end*. and several posts
*Note* (I apologise to why this post is so long I uploaded my maximum amount of post’s and it would not let me upload the rest the day of the hand in, as they were all saved as drafts.)
After getting my 3D print on during the night I was able to collect it yesterday morning. I was very happy with the quality of the print, the material was smooth their was no cracks in the plastic, so it was fantastic. The insulin pens that Ii have fitted into the 3d print perfectly just the way it should be with no shaking about, so if it works well with the aluminium casting it will be great.
After cleaning all the support material off the print. I then went to class to the presentation that was arranged by Microsoft their was some great ideas and innovative project’s that they had being working on. It was really great to here why they had done what they had done and where they see the technology going in the future.
After lunch I managed to get a couple of hours work in the workshop before the end of the day. This time would let me know what preparation I had to do to get my 3d print aluminium cast.
When the casting is done its called ceramic casting, so what happens is the 3d print has a ceramic shell put on it. Then the aluminium gets pored into the shell but the slots were the insulin pens go in will also be filled with aluminium as the plastic evaporates so it needs to be filled with clay then held in place with small brass pins that are hand made to fit. I had to work out were all of these pints would enter the 3d print so that their was no air bubbles. I then drilled the holes to put them in this keeps them in place as the ceramic joins to the clay via the brass pins. Each pin is held in with a little bit of wax before the ceramic is in place.
The next stage was making the wax form for poring the aluminium in. Once the form has been made it then can be painted on with the ceramic. Then the ceramic is heated up with a blow torch to melt the wax within leaving hollow pipes to allow air bubbles to escape when the aluminium is poured into the ceramic mold.
Ceramic Glazing
After making the parts for the vents and putting the pins in and filling the holes with plaster so that it never took away the slots that i needed the injections put into once the aluminium mould had being made. I had to make a ceramic shell for the whole thing to go in.
The shell then got slurry sprayed on to it then a layer of sand was sprayed on top of that. This had to go on in fin layer after layer. But only one layer could be put on a day so at the moment I probably have another week of adding layers.
Dewaxing
Dewaxing Process 24/03
Today I was able to melt the plastic out of the ceramic mould but before i done this, I had coat all the ceramic with one last layer but this time it was with fibre glass and slurry. All of the fibres helps the mould keep its strength just like carbon fibre. This will allow for the ceramic mould to go through extreme temperatures with out cracking or braking anywhere. I did this at the start of the week. I then had to leave it in the drying room to properly set for a couple of days.
Once this was dry I was then able to melt all of the wax and the 3d print out of the mould.
After this was done the another layer of fibre glass was then added to keep the mould from cracking when the aluminium is added. This layer was added then the mould was put into the kiln and left to set properly. I now have to weight in till other people in the university is ready to do their aluminium cast as its far to much work and resources for just one pour to be done. So I will be able to pour the aluminium next week at some point.
Pouring
Today I was able to do my cast as someone else was ready also. Their was a lot of preparation to do before we could get started so it wasn’t in till the afternoon we was able to cast.
The gas bottles had to get carried from out side of the building into the large workshop next to the extraction fan so that all the fumes could be taken out. We also had to build a small kiln to prepare the moulds in. The reason you build the kiln is that if the ceramic is around the same temperature as the aluminium is more likely to be a successful cast, as the aluminium cools down to quick if the mould is a lot colder and also the ceramic mould might crack due to the liquid aluminium being so hot. So its not really an option not to build a small kiln as if its not done several weeks of work could be wasted for the sake of an hour.
The temperature inside the kiln before the aluminium pour is put up to about 800 degrees. The aluminium gets cast at around 700 degrees.
Once both the kiln and the aluminium was at the right temperature we was able to pour the aluminium into the ceramic mould, this was extremely nerve racking because I was scared it didn’t work and all that work would have being for nothing.
The aluminium seemed to flow into the mould without any bubbles so it looked as if it went well. Then it had to be left to cool for a couple of hours before taking it out of the mould.
The cast was still rather warm so I poured a couple of buckets of water over it this also helps crack the ceramic to brake the cast free. I tapped it gently with a leather hammer and a chisel to try brake the large parts of in one rather than hacking at it.
The cast was a complete success after all of the ceramic was removed but its still not finished yet still another few jobs to do before it will be working on my prototype.
Developed prototype presentation
For the presentation today I have being trying to get my prototype completely finished to show a good representation of what it has to look like. I got the overall form finished but it doesn’t have a lid. The concern that I did have was that the Prototype is to heavy and also to bulky.
So I weighed the prototype with all the components and the weight came in at 900 grams which isn’t heavy at all, but for the size of the prototype you would expect it to be lighter when you pick it up. The weight predominantly comes from the batteries and the aluminium casing that holds the insulin pens.
The presentation went quite well my module leader was happy because it was a working prototype. He also had the same concerns that I had that it may be to large in bulky. The other problem is that it may be to large to hang off a bag with out bumping whilst someone walks, and this could cause discomfort or annoyance.
From the feedback that I received, I started to think about how I could make it smaller and lighter. So I had a look over my research and I realised that almost 80 percent of diabetes only have two injection that they take on a daily basis. One long lasting insulin that they take once or twice a day this can also be referred to as a back ground insulin. The other usually gets taken several times a day and its a fast acting insulin that almost works immediately.
Using Solid works I could take parts away on the model that I would be able to take away on the milling machine then I put the material into the computer and because it was the write dimensions it would let me know exactly what it would way in reality.
From this information I then took to the decision that one of the parts of aluminium for the insulin pens could be removed from the prototype taken away a large amount of the weight and also the overall bulk of the design.
I then decided to rearrange the battery lay out and this also made it thinner and less bulky, I played around making cardboard models to see what worked the best before working with solid works.
3d print
After working on different prototypes and the aesthetics of my design over the last few weeks. I have made many different variations from cardboard to Computer aided design programs such as Solidworks. I have made numerous variations fro different lids to make it easier to attach to bags to easier to hold.
All of the different variations of cad models are in my sketchbooks it also explain why I have changed each part as I went along majority of changes were to accommodate wires and the electrical components in the design
The Solidworks CAD models probably helped me the most with fitting the comportment’s perfectly and also rearranging the to make better use of the space whilst trying to keep it as small as possible.
I tried many different ways in which I could have the lid work best with the electronics withing the 3d printed concept. On the image above the lid slides forward. Their is four holes two on the lid and two on the larger bottom part but when the lid is put in place the holes align together. this is where a two carabiner clips would go through working as two purposes one would lock the lid shut and the other purpose is that is how they would attach to the bag.
After 3d printing the shell for this prototype I started to think about how it would be insulated. I also had a worry of it being stolen of the back of someones back pack whilst travelling in crowded areas abroad.
Also getting the 3d pprint made me realises it could be quite awkward with the way that it has being designed to attach to the bag.
The lid for the final concept was changed several times to fit the button and LCD screen to show how much battery is left.
Working Out Voltage
The concept design has being changed so that it is a lot smaller, to that I had taken away one of the sections for insulin pens. This meant that the four battery’s in a row was wider than the metal component. This left it looking aesthetically wrong. So I had to change the arrangement of the batteries so that they went coincide to the metal component.
I was unsure if this would affect the charging ability or the running capacity time of the battery, or even the voltage.
After a little research found out that it will affect them because theirs two different ways that I can wire them up. The two ways that you can wire them up is parallel and series . The one that i’m going to use is going to be parallel.
The reason for it being paralell is that I checked the voltage out put that I needed for the fan and the peltier element is 1.2 volts and the out put for the parallel is 4 volts and this means it will last longer than series if its series the out put would be 8 volts and this would use the batteries energy up twice as fast.
The only down side of the parallel system is that it also takes twice as long to charge, but that’s OK because the unit would be charged during the night which would give it plenty of time to recharge.
Diagrams below explaing the difference between series and parallel.
Ways to insulate
After 3d printing the last variation of my design I have being working on different ideas to insulate the design. Their was several different ways that I could Insulate the product correctly.
The first way that I looked it was having a space in between all the components inside the concept then have the 3d print the outer shell. The outer shell would be 3d printed at I materialise tha way it would give the outer shell a professional finish and looked like a manufacture product rather than just a prototype.
The second would be 3d printed shell tightly to all components then have a lair of insulation then another lair of 3d print to hide all the insulation. The outer lair would be professionally printed the same as the first option.
The only thing that concerned me about these two processes was it might look like and expensive object hanging of the back of your bag, and could become a target t get stolen in busy tourist areas in different countries from pick pockets and thieves that make a living form this sort of thing in different tourist areas.
So the third option that I came up with seems a lot more possible to work. It would be the same material that cooling bags are made out off. The cooling bag material that is used to insulate food and drinks would be stitched around the 3d print with a zip as the lid making the product simply look like some sort of sandwich bag or drinks cooler. This also means it will be a lot easier to make an attachment for the product to be attached to a bag it could simply be attached on by sewing a strap on. But I also want it to be quite difficult to un attach the product. So I have looked at different carabiner’s with safety attachments to stop them from being unhooked easily in case of pick pockets.
Coding The A T Tiny
During the duration of my project, a lot of the electronics I have used didn’t need arduino or any other sort of programming electronics. The peatier element and the fan were always connected to the same simple switch, negative and positive pins so the electronics have been fairly simple. The only thing that was slightly complex was working out the voltage of the battery’s I had take from a battery pack so that they could be recharged.
First I had to find out what the amps that would be drawn from the peltier element and the fan would be at the same time, I discovered after hooking them both up together that it was 1.2 amps this meant after some calculations that 5200 Millie amps would run for about four hours. So for my design with it being used for day trips this would be far to short, looking at larger battery packs I decided to buy a larger battery pack to take apart to put in side the prototype. This one was 20000 Millie amps, This would keep the device going for around 16 hours which was perfect for what I needed.
After making the first prototype and getting the aluminium cast done I the realised that it was quite heavy and weighed in at 900 grams all together which was heavier that what I wanted it to be as its just a bag attachment. I then took one section from the aluminium cast away to take away some of the weight as it wasn’t really needed anyway. Then I had to take half the battery’s away to completely change the design and make it a lot thinner than it was.
This brings me to the reason I need to program the A T Tiny on the arduino. Now that the battery’s have been cut in half and only have 8 hours instead of sixteen, I realised that this isn’t long enough as the concept is being designed for day trips and sixteen hours will be a lot more suitable. I then went on to looking at ways in which I could make it last longer with a day of experiments I realised with insulation around the design the product would work perfectly if it cut in and out every half hour it would stil stay at the same temperature inside.
I looked into ways in which you can make a switch within a switch to make the electronics turn off for half and hour then turn back on for half an hour, this would give the device 16 hours running time again and be half the weight due to the battery’s being taken away. Their was two options one of them being an analogue timer circuit called a 555 timer witch didn’t work very accurately so I decided to go with the A T Tiny which can be programmed to be put on after the main power supply and also doesn’t take up any space at all really within the design.
Fabric being stitched
The Material choice that I did decide to go with to insulate the prototype was the same material that is used for cooling bags, after a little more research into cooling bags I found that they are typically used to keep what ever is inside the bag between 2 and 8 degrees its around 36 to 46 Farren height.
This also means that the design will look more like a sandwich bag or a drinks cooler rather than something expensive that might get stolen. The colours that will be used will be dark colours something that wont jump out and attract attention the only part that will be plastic will be the part for the fan and this will be matt black.
The thermal cover has to be able to come on and off in case something goes wrong with the wiring inside, the picture above shows it being measured so that this can come off.
The next step is adding the zip in the correct place this is important as if the lid that goes on and its placed to low it will affect the power switch inside the design.
The lid is all stitched up and just needs the top to be added which was quite difficult making it neatly due to how small it was.
This was the last step of the process attaching the strap, the next stage will be putting all the wire back together.
A T Tiny
Working out how to program the A T Tiny has being difficult for me as arduino and anything to do with it I dont particularly like, So I have realised I’m very rusty at doing anything to do with it.
The main thing the arduino or the A T Tiny has to do is keep the aluminium at the write temperature by cutting the fan and the element on and off. The temperature of the out side should not matter so If its in a hot climate or cold climate it should stay the same temperature due to the insulation. Thermal bags are made to stay at a temperature between 2 and 8 degrees .
So after testing the prototype by turning it on and off by hand before programming the a t tiny I realised that a small amount of cold being added to the aluminium makes a significant difference to the inside of the prototype. So the time that the element needs to be on can be reduced to as little as one minute and then turn of for 15 minutes this will roughly give the battery life a 4 day cycle between charges if need be.
So for the coding of the arduino I had to use a basic programming code set that is in the arduino library its just the simple blink its what you use to turn on and off an LED in your circuit.
The arduino works in milliseconds so the I had to work out how many milliseconds was in one minute and 15 minutes. So for one minute its 60 000 milliseconds for 15 minutes is 900 000 milliseconds.
So the code goes as following digitalErite(LED_Button_Low); Delay(900000)
Its the same line of code for on but you replace Low with High.
So the Attiny simply believes that its turning on and of an LED.
The complicated part was putting the circuit together and soldering it to a board because I also needed to attach a Mosfet to the circuit board this stops the Electricity going back into the Attiny and braking the small micro controller.
As you can see the A t tiny fits into extremely small places that is why its the best choice of technology for what I need to do. The offer choice would have been a 555 timer but the delays one them I found after a little research was that they only worked for on off for around 40 seconds which is far to short for my needs.
Small Button
Their will be two button on my design one to control the power supply to my fan and the element that is going to keep the metal cast cold that is with in the design. The other is a small button will be used to activate the LCDscreen that lets the user what percentage they have left in the battery’s. It only needs to be clicked once then it will light up then time out.
The small button will also control an LED that is on the top of the design. The reason that the LED is their is so that night time diabetics can see clearly because at the meetings it was a problem that everyone had ran into at one point or another. It can be difficult to dial up the insulin pens in the dark to ensure that the correct doses are being used, also changing the needle on the top and ensuring its done correctly can also be difficult and if its not done rite it can be dangerous to your health.
So as an extra attachment they all agreed at one of the adult diabetic meetings in Dundee this one is called Circle D Tayside on facebook. That it would be a good idea to have and Led In case they were out a night.
Creating a small button was quite difficult to make it look as if it was meant to be their rather than just stuck on as an after though, so I have being thinking about it for a few weeks. I new I was going to put some small piece of metal onto the lathe but I decided to use a small rivet as the pin goes through the middle part and if I left an edge on both ends of the pin it meant it could be glued in and it would be able to slide back and forward to meet up with the button.
Critical Review
Starting fourth year I didn’t realise how many ups and downs, I would have gone through the duration of the project. I started off feeling excited and quite anxious. As the year went on the anxiousness got worse but the sense of accomplishment also came over me. Medical design has always been an interest for me, especially branching off into diabetes where I have tried to create better product’s and gain a better understanding of medical condition’s, this is mainly due to me being diagnose with diabetes at an early age. Although I am diabetic I have always tried my best to look at the project from a designer’s point of view and try to look at it from an out siders view. This way I won’t design products from my own pre-conceived perceptions as they might be wrong for the needs of the majority.
Up in-till this year I haven’t ever felt as pushed with different skills sets, as this year it has always being in the back of my head to show a good combination of skills to show that I am worthy to work in a medical design firm. The project has enlightened me to understand that I’m not afraid to look into the negatives of diabetes and ask the questions that need to be asked because I am diabetic myself the years before now I have felt that I tried not to know about all the depression and anxiety and negative health affect’s that diabetes can have on someone’s life. The saying “ignorance is bliss” made sudden sense to me about a quarter of the way into the project. The more doctors and people who were in the medical field that I had spoken to this negative feeling that was on me at the start of the project, the feeling that do I really want to know this? Started to fade and I realised this is what I want to do I want to help others for the greater good. Once I had realised this the negativity started to go, and I wanted to know more and more because the more I know the more I can help.
This year has definitely refined my skill set. From my sketching abilities to my prototyping skill’s. Even more importantly I believe is my thought process. It has made me scrutinise each and every one of my decisions, It has made me question everything I do. From adding features to the design is it necessary? what’s more important? The aesthetics or the function for the user. I discovered for my design process that it defiantly was the function, I believe this has led me to create a better design due to my newly found outlook on the design process.
Understanding the user group has probably being one of the biggest challenges for me throughout this project, as I found that designing for diabetes isn’t just creating a product for a specific style or need. Because every single person who suffers from diabetes is different. There is no specific user image. They all have different ages both male and female all whom of course have different aesthetic tastes and lifestyles. But even more importantly I had to understand that they all had diverse ways of treating their condition from medication to routines in using medication even down to things that I thought I would never had to encounter for such as meal times and how they carry their day to day medical equipment. Later on in the project when things started to come together it was a great feeling that I maybe could create a product that is divers as to who uses it.