Week 4: windlass part 3

Wednesday 7:30 -11:00 am and 9:00 - 10:30 pm

All in all it was a productive day.  I printed out 3 stakes, and 4 modified hub guards.  

As soon as I came in, I was wanting to print those parts.

I modified the stakes because they needed to be just a little bit thinner so that they could fit length-wise into the holes I had constructed for them.  

I modified the hub guards from last time because fit over the rods and the rectangular drum stakes weren't very tight and the hub guards wouldn't have done a very good job at keeping the hub rotating in the hub plate as shown below. 

Even though I had made a test holes and pegs with the dimensions and fit that fit as I wanted, once the test holes and pegs were placed together on a hub guard, it didn't fit as tightly as I wanted it to.  

Theses were the old ones that didn't fit as tightly as I wanted to

So I slightly adjusted the sizes of the half holes and half rectangles to hold on to the drum stakes and rods better.   I did this on Tuesday night, and I had the part as a part and as a DXF. 

My partner was supposed to show up at 7:30 am, to work on our project together but she didn't come, so I spent the entire time working on my project alone.

Here is a drawing of my hub guard, in Corel Draw, just before it was sent to the laser cutter.  

You know, I thought coming here at 7:30 was rather early since no classes start before 8:30, but in fact, the resident machinist, Larry, was already in by the time I got in to the engineering classroom at 7:30.   I helped clean up and set up the laser printer as well as the laser cutting software and the Corel Draw software, which is what opens up the DXF files and sends the cut job over to the laser machine software (called pro-cut) with the correct instructions. 

I started printing at 8, but very early on there were a lot of issues with printing my parts.  

Firstly I learned not to put cutting lines too close to each other or else the heat around two lines close to each other will be so close as to melt the plastic and create an uneven cut that is either smaller or larger than what you might expect.  I'm assuming the detailedness and  is what happened to cause the hub cap's holes not to match up with what I might expect from the original solid works drawings and with individual test cuts.

Secondly, I was told to be very aware of any bending in the plastic, which might cause the focus beam of the laser not to be in the middle of the material where it ought to have been .  

One of the most obnoxious problems was that the laser printer didn't always cut the entire way through.  I mean take a look at this piece,  You're supposed to see a gray line indicating where the laser has cut through and separated the material, but for many of the cuts, the middle piece of the plastic is still attached to the outer piece of plastic.

I

actually, I saw a lot of different things about a laser cutter that could affect the cutting.  

I saw Larry carefully take out the lens and the mirror that focused the super powerful laser and clean it with lens cleaning fluid and special lens paper that doesn't scratch glass.  The mirror was a little cloudy in the center.   This might be soot or something else, but it was cleaned.

Larry also played around with thee speed.  The default speed for Delrin Plastic was 9 at 2000 bursts [of light] per second but we cut the first one at a speed of 4.5, at default  and cut twice.  We also tried some other settings for 3/16 Delrin.  We also tried decreasing the distance from the laser head to the mateiral in order to change the deph in the material at which the laser beam focused.

Eventually, Larry settled on 7.5 at 1000 bursts per second, cutting multiple times .   This made the cleanest cut, but as I had already gotten some serviceable hub plates from the earlier printings, only two of my hub plates had the nice clean cuts of the final cut .  

eh blurry image of the laser cutting bed where the material to be cut rests on.   The bed has metal deep honeycomb screen that holds the hot material, and the hot laser away from the actual bottom so that it doesn't burn it or warp it from the heat. 

All points on the physical bed is directly mapped in to a computer display of the bed in finalcut which is the program that runs the printer. 

Unfortunately, there's often the problem that when you cut delrin, you go over it twice or more to make sure it cut through and sometimes if you've been touching the delrin checking to see if the laser cut all the way through, or if your delrin starts bending on you midway through the laser cutting, then some of your lines will have shifted, and then you get a double cut line, or even a triple cut line and at least one of the cuts is not where you want it to be.

here is an example of a double cut line. There's an extra slip of delrin in between the two cuts that I am lifting away from the main piece so that you can see the double cut.  Thankfully it wasn't in an area or an edge that was integral to any fits.  I can't say that about the other miscut holes in the hub and hubcap (such a pain I say).

After I had all of my pieces printed out finally, I started on putting things together.  

This is sanding residue 

Firstly, I slid the rods on to the hubs and hub caps. Those were rather easy.  Then I tired to put the rectangular stakes into the rectangular holes in the hubs and hub caps and OMFG was that hard.

But here was the result:

This was an interesting way to knock the pegs into the peg holes.  Rather than pounding on the top of a long rod, if I pounded really close to the peg with the aid of a stick, then I could more effectively pound the pegs into the peg holes, because less of the hammer force was wasted on deflecting the plastic.  

I was very disappointed because some of my laser cut holes came out too small.  Even though the measurements were the same across all of the rectangular peg holes in the center hub, somehow, the one pictured below was much smaller than all the others such that when I tried to stick one of the rectangular drum stake

I figured out that I can use clamps to set one side to be in the correct alignment while I whacked away at the other side  to make sure the hubs and hubcaps on the other side were in the correct alignment as well.  

You know I realized something about the design.  I could have dispensed with the central hub all together.  I could have made the drun stakes rest directly on the circular hole and spin in there.   I was considering usin g

I mean I thought, if I could have 11 stakes, then I'd have a shape of constant width like a Canadian Loonie (explanatory video here).  But actually, if you just have the outside surfaces of all of the stakes line up with the inside of the circle, you would effectively have something that could spin circularly but with only however many contact points as you have stakes, which would still be less than an entire circle spinning in a circle.  

In this image you can see that the hub has a tendency to fall out of the hub plate if not properly aligned.  but actually if the hub was completely out of the hole in the hob plate but was still on the stakes holding them in position to be a drum, that could also work.  

in our current design, getting the hub to be both at right angles to all of the stakes and simultaneously flush with the hub plate in order for everything to spin smoothly was challenging.  I spent a lot of time whacking at hubs in order to get them flush with the hub plates. 

Here are some useful tools that I discovered:

Also helpful hint.  Use this table vise.  This is super useful for sanding corners and edges and holding small parts for you while you fidget with some other tools.  Super useful I say.  You can't see this in the image but its actually itself clamped to the table and you can unclamp it and move it to any other table with an overhanging lip and start using it at a better location.  This is what I did, because I wasn't too chuffed about sanding next to the drill press and the vacuum cleaner. 

Also this is a chisel, but its wedge shape is also useful to wedge in between cracks to separate press fitted pieces. Just be careful of its cutting edge.

look it's a small hammer and it fits in through the stakes of my drum just perfectly in order to tap in the middle of my hub, to tap it out!  It is great to have and use tools that fit the job.   I didn't take a picture, but the big hammers wouldn't have been any use at all to me in this endeavor.  Huge hammers are better weapons though, but only if you have that kind of arm strength.  

Alas, I feel bad about mentioning this, but a file with no handle is hard to use, and although whoever stuck the big file in a small handle -- I mean I'm no longer stabbing myself in the guts with a pointy object, but its still hard to use. 

Mechanism

In class we talked about mechanisms.  Mechanisms are ways to transform import forces and movements into desired set of output forces and movements. 

In this blog I would like to talk about this Helical Rack and Pinion Gear Pair

A rack and pinion is one of the most straightforward means of converting rotational motion into linear motion, at a 90 degree angle from the axis of rotation by means of gears on the rack and on the pinion.  Of course, it can also be used the other way around to convert linear motion into rotational motion.  

which is the rack and which is the pinion you ask?  the rack is the rectangle with the linear back and the pinion is the cylinder with the gears. 

This picture example is called a helical rack because notice that the gears don't point exactly in the same direction as the axis of rotation but actually curve around it (kind of like a helix - you should know what a double helix looks like).

It is able to translate motion through the gears, the gears of the first tug at the gears of the other pulling the other gears along as the first moves.   

Obviously it has some limitations.  If you don't want the pinion to roll off of the rack, there is only so much that you can rotate the pinion.  And if you want the rack to move forward and backward, then you'll have to find another way of changing the pinion's direction.  

I can see this mechanism being use in situations where something is moved forward and backwards a certain limited amount.  Places where I could see something moving back and forth like that would be something like an automatic stamper, or some device that automatically puts pizza in an oven and takes it out again after it's cooked, or something that lifts and takes down pop up targets at a shooting range, because all of those have simple back and forth motions, and especially for setting up moving targets, you definitely don't want a person there setting up the movements.  In the other direction from linear motion to spinning motion, I remember a plastic toy that required a plastic line with perforations like zip ties to spin a little plastic helicopter that few off.  I could imagine that being implemented with a plastic rack and a pinion on the shaft of the flying thing such that when the plastic rack was pulled, the flying thing spun really quickly.  In that situation, the rack definitely flew away from the pinion. Actually the pinion was on the flying helicopter thing so it would be more correct to say the pinion flew away from the rack.  

Actually Wikipedia mentions a perfectly logical application of this to raise and lower the gates of a lock (as in a canal).  The gates of a lock only go up so far and only go down so far, and so this system does very well in that situation.  My only worry is corrosion corroding the gears of the rack, but I assume that must not be a big problem if they are using this method.  By a similar logic, a Pinion and Racket is also used in stair lifts for the mobility impaired

.

Another fascinating usage of this is for locomotives to have a third wheel that is actually a pinion, that contacts a length of rack and then pull themselves up, or lower themselves down a very steep incline that it could not climb on two smooth rails and friction alone.   In this case, it is actually desired that the pinion rolls on and off the rack, because when the locomotive is not traveling a steep incline it does not need the strong grip that the pinion and rack provides 

Week 3: windlass and solidworks fun, part 2

Monday

This week we were to continue working on our well windlass design.  On Monday, we completed a working foam mock up of our design.  Initially I was thinking of supports to support the side supports but that would have cost too much building material said the instructor, and so we scrapped that idea, since the side plates were more likely to collapse inward than collapse outward, and our rigid side and top spans should keep the windlass straight and keep the side plates from toppling. 

This was the final resulting foam model. There were two side plates that had holes for the hub of the fat drum (alluded to with pencils) to spin in.  around both sides of the hub were hub guards to make sure the hub did not pop out of the hole that it was supposed to spin in.  The side supports and the top supports were to keep everything at the right angles and keep the side plates from bending in when the force of the water bottle was applied on the center drum.   It looks pretty handsome, but didn't know it it would and we knew that it would use too much building material, and we expected to cut a lot of triangles to decrease the material used. 

Then we started making the parts in Solidworks

Sorry no pictures at this point, see below for the finished Solidworks parts.

Oh, I should say that I am an very proud of my organization.   

FRIDAY

 On Friday, we continued making the parts in Solidworks.

The first thing that I worked on was the support spans that would keep our windlass rigid and at a right angle.  

I discovered two very neat and useful things about Solidworks  as I puzzled over this piece.  

One is that you can draw guidlines, that will only be used for construction. When you draw a line, you can select the option that the line you draw will only be for construction purposes. 

The other neat discovery was that if you ctrl-click on two or more elements, like lines or points, you can add a relation.  

In this manner, I was able to easily create a beautiful X shaped crossbars, shown below.   I made a construction line connecting the edges of the space that I wanted to span.  Then I made non-construction lines next on either side of the construction line.  I selected the three lines, set a parallel relation, and easily noted the distance of each line from the center line.  

This was SO much better than the way that I was originally doing it, which was with with a parrallelogram.  The parallelogram was difficult and obnixious to to line up, and should I ever choose to change the outer dimensions, because of a lack of relations of a free-drawn parrallelgram, the cross bars would fail to line up anymore 

After I created he top supporting span, I created the two supporting support span in solid works in a similar fashion.  The picture below shows the extruded finished copy.

Actually, as I seemed to be pressed for material, I reduced the space material that we used by cutting out the cross to make this instead.  Because it's a rather small piece, removing the cross structs were unlikely to break it. 

IN order to make the drum that holds the string for the windlass, we had to make the rods that made up the skeleton of the drums.   

Since all but one of the rods were meant to be of the same shape, I wanted to make cut them all out of the same piece,   But alas, when I extruded the whole piece that contained all 6 rods, and then tried to make an drawing of the extruded block containing all 6 rods, the lines that were used to create the rods failed to show up in the drawing.  Thus I had to go back and extrude the rods individually and copy them individually into one drawing.  

one of the rods that will be the skeleton of the drum that holds the string for the windlass:   I think they were 18 cm even though I could have just gotten away with 16 cm.  Maybe I'll make another version of them at 16.5 or 17cm, because that would save me some 5 cm^2

After this, all that was left was to do the hub and the side plates.  My partner had been working on the side-plates and the hub since Monday.   However, I was feeling confident and curious and started tackling the problem of creating a hub.  After all I wanted to learn how to arrange things radially in solidworks myself for the future.  

This is the soliworks sketch of  the hub that I made.  The hub is what holds up the skeleton for creating the drum and would spin in the hole in the side plate.  

Oh look all ofthe things are round numbers except for the width of the holes which are about the width of a piece of 3/16in delrin. the .47cm wideth of the holes are actually a little bit smaller than 3/16 in because we wanted a tight fit of the rods into the holes so the rods don't shimmy away as we're pulling the bottle up.   Oh a joy, to be in America and have to deal with inches. 

For comparison, this is the hub that my partner created. She said she somehow deleted all of the relations, and so I can't be sure if the holes are equally apart around the circle, if they are all equal distances from the center, or if they are all perfectly radially oriented.  Additionally, the hub didn't have the pre-specified diameter of 7.5 cm.  

We agreed to use my version which had better dimensions and probably better symmetry.  

From this hub I created easily created the hub cap by increasing the outer circle's radius, and creating another smaller circle inside, and extruding it differently. 

This is the hub cap, the guard that will be used to prevent the hub from popping out of the hole in the side plate in which it needs to stay in to rotate.

This is the drawing of the hub guard as a sketch with the dimensions.  :P

We initially thought of having two different parts for the side plate and the hub, but we were wondering how the hub was going to spin in side the hole of the side plate.  I figured that if I cut the internal hub out of the same material as the side plate, it had to fit inside the hole and spin, and if it didn't, well, it would only require a little sanding.  

Thus, we started to create the side plate piece by adding on to the hub.

This was my partner's side plate.   

my partner's side plate use up too much material, and so I tried making another version with that was as spartan as possible while retaining structural integrity.
I think it looks suspiciously like a Wolkswagen Das Auto award or something.

I used mirroring for the first time to achieve the freehand symmetrical designs 

Here are just a few of the relations that I added to my drawing in order to make it pretty and fast and not change unexpectedly when I change one dimension:   

tangent, perpendicular, parallel, vertical, horizontal(lines and endpoints), co-linearity, 

I should mention that I figured out how to get solidworks to measure the surface area of a piece.  

What I did was I first extruded the piece, and then under tools, measure, and then click on the face of the part that you want to measure and it automatically tells you the surface area of that surface.  Turns out that my design was doing much better on the surface area front.  The entire thing was 167 cm^2 which was much better than the 189 something surface area of just the side plate that my partner designed. 

all in all, I worked on a lot of files on Friday.  Starting from 1:30 all the way until 6:00.

I learned a lot about Solidworks, and in particular about how important and useful relations are!

These are all of the parts and drawings that I worked on during Friday.

Week 2 : Well windlass : part 1

On the very first day we were given an assignment to create a well windlass spanning 12 centimeters and capable of lifting a bottle of water 10 centimeters above the top of the gap with the 10 centimetres being measured from the top of the bottle to the level surface of the gap which was modeled using two tables separated by 12 centimeters. This time I was working with a different partner. The idea is to work of a whole lot of people during the semester, and then find out who you work best with for the final project. You know the funny thing is that I generally just tend to pick partners are sitting next to me and it class during the day that we pick our partners?

Okay, so the first part in designing is to do the brainstorming. My partner and I came up with basically just one idea of something that was kind of bridge like but had a rotating drum in the middle to pull up the bottle faster than just a stick. However we took up a lot of paper in order to describe our ideas to each other. I had to practice a lot of my 3d rendering skills, which weren't always obvious to my partner. She also had a different way of representing the structure which was a front top left right and bottom views of the object all-in-one page, which I wasn't particularly familiar with, and found difficult to imagine three-dimensionality for.
From the beginning we were concerned about the stability of our structure. I wanted side supports. My partner suggested supporting spans that bridge the gap in addition to the drum, and I supported the idea because I expected that the force pulling down on the drum would tend to make the two side plates the two sides of ports collapse into the gap if they weren't being kept apart. 

On Sunday I went for an hour to try and build what are some of the side plates I went pretty detailed into building them I built the side plates with the holes and the fasteners cutting the holes for the tight fit key and hole. Then you know later on on Tuesday, I figured since this is the model I don't actually have to spend all that time and effort going into the details of fastening when I could just use tape and then after that my modeling process just got like infinitely faster.

Week 2 : Bottle opener part 2

  Okay this is where I continued from the last post about the bottle opener. To recap, on Friday we already had a working bottle cap opener. However we wanted to make it better. Thus we made a different version of our bottle cap opener in SolidWorks with the edges rounded. To round the corner is to fillet the corner.

  However that was not the biggest development to our design. New developments happened in our class. Our partner Callie, left us because she got into another class that she wanted more than this class. And in another group, two other people in a 3 group team left the class. Thus, my partner and I, added a third person the leftover person from that group to our group, Marissa. She brought with with her her own team's design design, which was very similar to a design that we have recently considered, but had decided not to pursue.

  Their design was for a c-shaped hook to grab underneath the bottle cap and lift the bottle cap off of the bottle

  We three, the leftovers of two groups of six, decided to combine our two ideas. Their group after all initially thought they were going to have two bottle openers one on each end of their Delran. They decided against it because it would take a lot of time to develop two designs, and you only really needed one bottle cap opener. However since we already had already done much of the work to get to working bottle cap opener, we thought it would be fun to combine the two working models of bottle cap opener

   Thus, began the process of combining our two designs.

   We struggled for a while trying to decide how to combine the two ideas in SolidWorks. Initially we were thinking of just placing one on top of the other in assembly and then exporting it as a DXF file. However we came to the conclusion that since our design both needed to be modified somewhat that it might be easier just to redesign one of the designs to include the other. We decided to use my original team's SolidWorks design extended somewhat and create the combination two ended bottle opener.

   Meba had already made some changes to our design. These designs changes were splines that allowed for curves in the outside structure. They were were added to improve the aesthetics. When we tried incorporating the new design into SolidWorks and then adjusting the width of our design. All of the splines went kind of crazy. We got some really really wacky shapes. This I found out later was because of a lack of constraints.  But one of the shapes that we did get was as lovely curves that we thought looks like a usable bottle cap opener and looks like the beak of an eagle. We decided to keep that in our final design on the same end of Marisa's bottle opener. So strangely enough our bottle cap opener actually has three bottle cap openers. How's that for an ambition?

   We added some changes to Marissa's design. Her design initially was a little too short in its lifting action and so most of the force was actually used in deflecting the bottle cap and changing the shape rather than lifting it up from the bottom.  We decided persuaded Marissa to increase the length of the non hook edge in order that the pivot point be farther away from the center of the bottle and more towards the edge of the bottle. We added those changes to our SolidWorks design as well.

   It should be noticed that we added many of these these changes Thursday night, the night before our final presentation. We had initially planned to meet all together and three people on Wednesday morning at 8:30 a.m. because that was the only time that all three of us could get together on Wednesday. However, only Meba and I showed up on Wednesday which is why we ended up using our design as the base.

  On Thursday we finished designing our piece, but as we were about to print, another group's piece caught fire in the 3D printer.   That was kind of exciting.  I was at the sink where the rags were, and because nobody cried fire, I didn't understand the rush and anxiety of the person ordering me to get her a wet rag,   Then we had to wait at least half an hour to clean up and cool down the laser cutter, before we could print our design, so we spent some time to redesign our piece yet again.
We eventually did get our design printed.

This is the eventual result:

Fastening & Attaching

Today we explored different methods of connecting pieces of Delrin.  Delrin is difficult to glue with most available glues.  Therefore we explored using heat staking and piano wire to connect the two pieces.

Heat Staking
Heat staking is where you stick part of one piece of Delrin through a hole in another and melt the Delrin so that the two pieces are melted together.
It is done on this machine:
heat stake machine

the pieces before melting

the joined piece afterwards

Heat staking makes a really stable and solid connection between two pieces of Delrin.  The connection is permanent which may be a pro or a con in this category.

One can imagine heat staking for a rigid outer wall encasing that you don't want to be rigid, and don't want other people to take apart.

Piano Wire
The idea is to make a hinge and connect the hinge with a piece of piano wire.  The finished product should look like this:
the finished,  joined pieces. 

the component parts

First you drill a hole through both parts

By using different methods of



Tight [and also not very tight] fit using slots or pegs
You can just use friction between two pieces to keep them together.

example of slots in slot holes

example of pegs bushings fitting in the holes of bushings 






pros and cons of fastening

Pros and Cons of Delrin Joining Methods

	Pros	Cons
Heat Staking	permanent  rigid you might not want a bump	permanent (making a mistake means redoing a piece) rigid planning ahead requires heat staking machine
Piano Wire Hinge	Flexible! its a hinge pieces not permanently attached secure attachment is possible	drilling a hole wrong may mean redoing the piece take time and skill to drill proper holes using drill press
Tight Fit	not permanently attached No other machines other than the delrin cutting machine is required	attachment not secure lots of planning beforehand, not only on designs, but on fitting measurements

Obviously for the tight fit method to properly connect two pieces of Delrin, the measurements of the fitted pieces must be really close to each other for there to be a tight fit.

Precise measurements is very important.  For measuring we use calipers.




one might need tight bushings to prevent things from sliding off the end
you might want loose bushings and a loose connection to

Delrin Rod and Bushing

Bushing fit type	lowest measurement	highest measurement
rod	6.34	6.34
press fit	6.23	6.39
tight	6.35	6.40
tight (snu	6.56	6.60

Delrin peg and slots

Bushing fit type	lowest measurement	highest measurement
peg	5.1	9.9
press fit	5.1	9.86
tight
tight (snu

Week 1 : bottlecap opener: Pt 1

Our first task for my engineering class was to design and create a working bottle cap opener.  Final project was to be designed in Solidworks, and laser cut from a sheet of Delrin.

DAY ONE:
Brainstorming Ideas

The first step was to brainstorm ideas for our bottle cap. I don't really have experience with bottles or with bottle caps.  I mean, I only last year even saw a glass coca cola bottle with a cap.  I thought those were history.  And I must not have opened more than 5 bottle caps in my entire life.   That being said, I do remember the action of a bottle cap opener and at least one design of a bottle cap opener.

The general action of a bottle cap opener is thus:  one part(the lifting edge) of a bottle cap opener gets underneath the pleats of the metal bottle cap and pushes up, while another part (the stabilising part) of the bottle cap opener rests on the far side of the metal bottle cap and pushes down.  The lifting edge pushes the bottle cap away from the bottle.  the curve of the bottle rim and the pleats of the cap means that an upward force on the cap is partially translated into outward force that slightly expands the pleats of the cap so that the cap becomes wide enough to pass over the rim of the bottle cap.  The stabilizing part does two things, it provides you with leverage, and it stabilised the cap.     The far side can act as a pivot for the lever that is the bottle cap opener multiplying the force applied on end of the lever away from the pivot so that more force is applied in the middle of the lever where the lever is pushing up on the bottom of the bottle cap.  And the stabilizing part pushes down on the far side while you push up on the near side to your hand, helps even out the translational force so that the cap or the bottle doesn't go up so much, and kind of pins the cap to the bottle rim so that the cap doesn't go flying off as it would if you just jabbed it on the underside.

During the brainstorming session, my partner Meba and I immediately thought of cutting a J shape active area into what would otherwise be a wrench.  While that would have been strong at supporting the stress of opening a metal bottle cap, we both agreed that cutting it out of a thin sheet, and then requiring a person to push and pull on the thin edge to open a bottle cap wouldn't be so pleasant.
So then, we thought of moving that around such that the user could apply comfortably  pressure on the flat end of the material.

This required a replacement of the lifting and stabilization surfaces.  Finally we came up with the idea to have a hole, where one end could get underneath the pleats and the other end would rest on the cap on the far side from where the opener touched the pleats.

If I were to brainstorm again, I would have brainstormed for longer.  I think we only addressed general ideas for 5 minutes before moving on details.  My thought is that we could have afforded to go longer and go crazier.   I know another group that came up with a sleek design that reminded me of a miniaturized batman masquerade mask.

bottle with bottle cap attached

brainstormed rough ideas 

Measuring
Taking into consideration the general action of a bottle opener in mind, it was the most important that we get the distance from the lifting edge and the stabilization correct so that there was enough leverage, so that when the lifting edge was placed under the pleats, the stabilizing end was near the far end of the cap top. It needed to be far enough so as not to interfere with the lifting action, but not so far enough as to miss the cap entirely, which would mean no pivot for our lever action to work against.

Thus, the second step was to measure the width of the bottle cap and guesstimate how big the opening of our bottle cap opener had to be in order for the levering action to work properly.

The diameter of a bottle cap at the top where it is the smallest is 2.5cm.  the diameter of a bottle cap at the bottom where the flaired rills are, is around 3cm.  I figured that since our bottle opener had to span a bottle cap diagonally, where the lifting end is at the rills, and the stabilizing end is

We came up with a circle of diameter 3 cm and a little semicircle protrusion to catch the underside of the bottle cap.


initial dimensions:



Making Model: checking dimensions

We transferred our idea onto some cheap foam to verify that our guesstimated distances correctly spanned the distance and could theoretically lift the bottle cap off the bottle, were the opener not made of flimsy foam.

We first cut the hole, and we never bothered much with the aesthetics of the outside border, saving that consideration for later, after we had reached a working version.

I liked that approach, because we first put most of our effort on the most vital part of a functioning bottle cap opener.

Just checking hole fit.  Not bad





DAY TWO:

On the second day, a third person joined my group.  In addition to Meba, I now counted Callie as a member. As she had not come to the first day of class, she had some catching up to do.  We quickly caught her up on what we had done the on the first day and then we were off.


First SolidWorks Model ever!
what is Solidworks?
Solidworks is a powerful software that allows one to design and test things before building them.  One can design parts, test parts, assemble them together, and convert them in to precisely detailed diagrams that a machinist, or in our case, a laser cutting machine should be able to follow.

To be honest, I think we were supposed to train ourselves on Solidworks parts and drawings before
I was trained and had some experience designing parts (but not assembling them or FEA them) in Autodesk Cad, which is a similar program that tries to do the same thing as SolidWorks.  That was late 2009, or just around 6 years ago.  As I am 20 at the moment, that was 30% of my life ago.  Generally, I knew I had to sketch, specify dimension, and extrude, and beyond that, I didn't really know how SolidWorks worked.

I didn't know where the buttons lived or what exactly the different buttons did, but somehow I managed to whip up a sketch and figure out extrude before my partners(who had also not gone through the tutorial) even had a chance to struggle with Solidworks.

I went through it again more carefully to make sure I understood the steps of sketching, dimensioning, and extruding and where the buttons for those lived.
I also learned about the skins function and how to edit sketches after you've extruded.
I also learned to fillet something that is not fish.

Sadly ,the author does not have pictures of Solidworks in operation at the moment the author is writing this. 

On the second day, as we were really getting ready to finalize the dimensions on our SolidWorks model, we wanted to verify our measurements.  Meba  made a foam version with a diameter of just over 2.5 cm.   That hole proved to be too small. I re-cut the hole to be larger.  We readjusted the hole size and we were ready to go.

After we had a model that we were satisfied with, we created a drawing out of it and saved it into the DXF file format.

selecting material
We were ready to make our bottle opener cutout!
but before we did we needed to select the thickness of Delrin.
What is Delrin?  Delrin is the product name for Polyoxymethylene, otherwise more commonly known as Acetal. It feels like sturdy plastic.  Its milky white with about the opacity of curdled milk.  Its pretty rigid and it has a low coefficient of friction.

We wanted it to be rigid, but not to thick, or otherwise we would have difficulty crowbarring the lifting end under the cap, in the space between the cap and the bottle.
We ended up using3/8ths Delrin which we thought was the best compromise.

Laser Cutting

What is a laser cutter?  Its a machine that precicely directs a powerful, controlled and precise beam of light (laser)  that melts, burns, vaporizes away the material that the laser is pointed at.  Not all materials are suitable for laser cutters.  Those that create toxic fumes when vaporised are not meant for Laser cutters.

We moved the DXF file containing the drawing for our bottle opener, and then our tutor helped us setup and laser cut our piece.

Before the machine could be used, the drawing had to be defined in Corel, so that the machine would know how to use its laser.

video of laser cutter cutting our bottle cap opener

Filing
 because the material was far too thick to fit in between the cap and the bottle at the lift point, we filed down the lifting edge to fit it underneath the cap.


Testing
it works!
Video of our bottle opener opening bottles!

very often the metal cap would easily strip the Delrin,  we were worried that our Delrin wouldn't last prolonged use.
My teammates uncapped 7 bottle caps on the second day.
Thankfully, we did have a bottle capping device to recap bottles so we didn't have to open new bottles wit each time
we did have some concerns:  the edge was sharp.
The bottle opener was 10 cm long by 5 cm wide and was just long enough for me, with my long thumbs to reach around the long end to hold it at stabilization point.

Improvements
Of course, just because we got a working sample, this is not the end.  In the future we will be considering aesthetics and cost of production.  we are thinking of trying out a thinner Delrin, which Delrin, which is expensive, but would require less filing time.  I've already put fillets to smooth out the edges of the bottle opener, and we were considering decorating the bottle opener as an old cell phone.  I'm fascinated by the spline feature in solid works, and