What we did this week:

This week, we mainly focused on our biggest design problem and potential change to the current design; the heated table. One of the requirements we have is to get the table to 100 degrees Celsius, but we need to make sure it doesn't interfere with the other design requirements (cost, weight, etc.) We have broken it down into three major possibilities, which actually apply to the three different methods of heat transfer; conduction, convection, and radiation.


Design 1:
Conduction: Heating Resistant Coil
Essentially running a coil through the bottom of the plate and running an electric charge through it to generate heat. This would be similar to a electric stove or an electric water heater. 
Pros: Hooks into power source, (don't have to use external power source), air resistance is negligible, cheap
Cons: Involves redesigning the table

Design 2:
Convection: Heat gun ("Blow dryer")
A heat gun basically blows hot air out to heat anything. Differences in model have to do with temperature output, and air flow volume. 
Pros:  Can be easily placed anywhere in the design
Cons: Dependent on air resistances, doesn't heat evenly, better models are expensive, would most likely need to be plugged into an external power source (if not modified) 

Design 3:
Radiation: Heat lamp
A lamp that emits heat.
Pros: Easy to implement into the design, 
Cons: Would have to paint the table black so it can benefit from the table easier, can be relatively more expensive that conduction, 


Not completed: It would be best for us to run simulations of all 3 methods, but we only had time for the radiation simulation:


Work in progress:

We were able to run a simulation of the radiation problem in SolidWorks. We changed to wattage of the bulb to figure out what temperature the table would be at steady state conditions. 

link to our google docs for heat transfer design (work in progress)

What we did this week:
Since we are practically finished with the assembly of the project, we decided to take time to discuss the differences in our design compared to what was given to us. 

Heated bed:
• Transfer electricity via slip ring if you could manufacture/procure
one cheaply enough (Basically Hamel's recommendation)
• Wireless inductive heating like how they do for stovetops.
• Paint the bottom black with something heat resistant and blast it with
IR from a heat gun or heat lamp.
• Just use a wire and have the software prevent winding too many times
in one direction.
• Have stationary heater underneath, and plate spins on top of it.
• Have another plate underneath that it rubs against. Spin really fast.
Friction heating.

Electronics placement :
In our senior design, we came across many different obstacles in improving our 
customer’s design while maintaining functionality. Our first problem was placement of
the electronics that support our 3D printer. We had different options of either extending 
our frame or building a separate compartment to house the decapede controller and the 
rest of the electronics. Through our design process, we came to the conclusion that 
building a separate compartment that can be bolted on the side would be better for our 
group in terms of cost. The compartment will be either of wood or aluminum; a final 
decision hasn’t been made yet. 

Tension belt:
The second challenge our group encountered was the rubber belt was sliding up 
and down on the cogs. This problem didn’t allow the platter to move up and down 
efficiently. First we replaced the 3D printed cogs with brand new plastic cogs that our 
group found online. Our group still ran into the same problem, but the movement of the 
belt was vastly improved. Finally we came up with the idea of adding tensioners. The 
tensioners were made by stacking a bolt with washers along the frame and running the 
belt through them to add tension. This idea solved the belt tension problem, and did so 
without spending too much money on it.

For safety purpose, each frame will be covered by a panel. The panels will be designed to have holes for the heat to escape; also to be easy to mount or dismount whenever machine maintenance needed or printed object needs to be removed. 

Ventilation system:
Original design has the top of the machine open. We decided to add and design a lid which function as a ventilation system, so that the heat and toxic fume will be removed from the inside. There will be holes on that top panel for air to blow through; underneath, 120-mm computer case fan will be attached to the top panel to suck the heat and fume out.

 The initial design consisted of a table made out of wood. It is a good material since it has a low density, but other characteristics of wood did not meet our requirements. With alternating heat temperatures, wood tends to deform; therefore, the flatness of our table would vary over time. In addition, it is necessary to maintain a constant temperature on the table during operation in order to reduce the rate of heat transfer of the object being printed. This helps print the object with better precision. To meet these requirements, we decided to use an Aluminum alloy. Aluminum has a high thermal conductivity; therefore, it will heat up faster and help maintain the heat generated by a heating element. In addition, it will retain a tighter flatness tolerance than wood. With a density of 2.70 g/cm^3 and a Volume of 305.80 cm^3, the total mass of the table will be about 835.65 g or 1.82 lbm. Light enough for the motor to run efficiently.

 Motor Size:
Having limiting space for the 4-extruder arms to swing about a fixed axis, we minimized the size of the motors. This helps give enough clearance between extruders to avoid collision. When one extruder is at its maximum angle ( 90 deg or at center of table) , clearance is needed between the operating motor and the stationary extruder motor to the left. 

The initial design of the cogs were made from 3D printed parts. On paper it seemed like it would work fine, but after assembly, we noticed the belt was slipping on the bottom. We decided to order new cogs that would hold the belt better and have better teeth. They also had parts on the top and bottom that would prevent the belt from slipping off. This keeps t inline to ensure it wont slip off.

What we need to do next week:
We need to figure out what to do about our decapede situation. After that, it's simply just electronics and coding. 

What we did this week:

We essentially finished assembly of the device with the parts we had(new cogs and aluminum table). We decided after many calculations and cost analysis, that using the plywood frame would be best. It is possible to reinforce the frame if needed, but after some initial tests, the frame is sturdy enough to handle one extruder arm moving at maximum velocity.

To see new video and pictures : MEDIA

One of the major problems we realized yesterday was heating the table. After doing basic heat transfer calculations, it was determined that about 73.3W of power would be needed to heat the bed to 100C after 15 minutes. We initially thought of a design to add a battery to the bottom the table to avoid a coil getting wrapped around the table, but the 73.3W is too much for a battery to handle. Our other option to is to figure out about electric coupling (which 5 Mechanical Engineers know very little about) to have it plug into our power source. The other option is to NOT heat the bed, which Tyler said would be okay.

What we plan to do this week:
Since we decided on the frame the way it is, we are going to just have to put the electronics outside of the 3D printer, possible in a type of computer case with fans to keep it cool. This shouldn't be too difficult. All we have left to do is some redesign for the extruder fans and limit switches.  We need to test the new bed on the current rollers to see if it fixed our wobbling problem. If it does still wobble, we will need to redesign the rollers. 

What we really want to do is plug this thing up and test out all the motors to see what could be fixed or changed. It's a brash way of doing things, but there are some things we can't account for that can only be seen by actually trying it out

http://i.imgur.com/eeUvaTz.jpg [Gantt chart as of 10-9-13]
What we did this week:
We took a trip to the machine shop after our meeting last week to see what material we could dig up to use on our project.  We found some potential sheet metal for a frame that we could use, and also a square slab of aluminum for the table. We decided to only take the square slab (for the purposes of not looking too greedy with all that metal) and machined it into a new table.

Gantt Chart as of 10/07/2013

We also worked on a new draft of the Gantt chart, which will tie in everything we need to do starting today till the end of the semester. The only foreseeable problems are still the decapede and the coding of the firmware.

(A direct link of the Gantt file can be found in the FILES page)

Higher Res img: http://i.imgur.com/eeUvaTz.jpg
What we did this week:

I uploaded a lot of pictures and videos to the Media page to show our progress on project, as well as our recent trip to get parts laser cut. MEDIA

It's apparent that I didn't really keep the blog up to date on things we were doing in terms of ordering the parts, assembly, and other things blog-worthy. So I will recap all the major points of the project, essentially starting from the end of last semester.

The initial design was completed around the time of the final last semester. After that, we began producing all the 3-D parts needed for the project. This was essentially free and could be done at any point because Tyler already had a 3-D printer available. 

                First meeting: (07/01/2013)
  • Had the 3-D printed parts completed. However, they were 'messy' so we had to clean them up by removing excess material to allow for the other components to fit
  • Began ordering other parts for the physical model; rods, fasteners, frame 

              Second meeting: (7/29/2013)
  • Began basic assembly of the 3-D parts with the rods and fasteners and other materials acquired recently.
  • Ordered extruder and extruder parts

SCHOOL STARTS (8/29/2013)
            Third meeting: (9/1/2013)
  • Continued work on the assembly , mainly the frame. Realized the frame was kind of weak and considered new design.
  • Essentially finished the physical part of the project with the parts we had

          Fourth meeting: (9/8/2013)
  • Began testing the electronics/motors 
  • Was told to consider redesigning certain aspects of project to fit needs better

       Fifth meeting: (9/15/2013)
  • Ordered more parts (aluminum cogs) because the 3-D printer ones didn't work as expected
  • Stress analysis of the frame for redesigning purposed

     Sixth meeting: (9/30/2013)
  • Aluminum table redesign/concept are starting
  • The Decapede problem

What we plan to do this week.

We still need to finish redesigning the problems we stated in the previous week's blog. We looked at getting the aluminum frame, but to machine it to the exact specifications of the current design are costly. The reason we would want to keep the design the same is because the 3D printed parts would already fit it. If we make the frame different for easier manufacturing, we would have to redesign the 3D printed parts that fit to it and redo those(which aren't costly to print out)