Archive for the ‘Engineering’ Category

Chocolate Candy Cups

Thursday, September 7th, 2017

As a young person, I was quite enamored with Reese’s peanut butter cups. Those were one of my favorite candies to eat during the holidays. It’s now been over 5 years since I have tasted them. This isn’t due to amazing will power and good dieting, it’s due to the fact that those candies are lethal to my son. Yet, I still long for those treats.

I decided to make my own that would be safe for my family. I figured I’d be able to find a candy mold for just such a project, but was unable to find any. I was able to make an approximation of a Reese’s peanut butter cup by using cup cake holders, but I still felt that having the correct type of mold would yield better results.

I devised a plan for how I would do it, and then modeled the geometry in Autocad Inventor. The idea is to model the geometry I want (a positive) and use a CNC machine to carve this geometry. From the positive CNC generated shape, I will create a negative mold using a food-grade silicone rubber. Then, finally, I can make the chocolate treats using the silicone mold.

Modeling

Modeling the shape was pretty easy. I figured out the basic dimensions I wanted and modeled accordingly. The final shape should be about 2 inches in diameter and .5 inches tall. Even though I have no intention of wrapping these in paper, I did some careful math to make sure the ridges were appropriately shaped to allow a circular piece of wrapping to be applied. This was done by making sure the perimeter of the ridged top was equal to the circumference of a circle whose radius is equal to the bottom’s radius plus the length of the side.

The goal is to have a void in the chocolate where anything can be put inside.

CNCing

With the model looking okay, I CNCed the geometry out of some scrap hardwood left over from another project.

After CNCing, I removed the positive geometry, and sanded and filled the wood as best I could.

I then put 4 of the positive carvings in a void made out of particle board. Once glued, the whole thing was coated with black enamel to fill the gaps and hopefully make the silicone not stick.

Casting

I ordered a small supply of silicone casting (Smooth-Sil 945) from Smooth-On. This particular product is food-safe, and is activated using a 50:50 mixture of A and B parts, so it’s really easy to use.

Using some simple geometry, I figured out exactly how much material I would need. I poured the correct amounts into disposable bowls and mixed thoroughly, then poured the material into my mold. 6 hours later, I was able to pull the mold out. It turned out very well!

Chocolate

The next step was to take chocolate, and lightly melt it. I used Guittard chocolate, which is nut-safe. I tried different types, but liked the more milky flavors the best (Milk Chocolate 30% Cacoa). Not being a chocolateer, I have a bit to learn. From what I understand, the key to successfully making chocolate treats is to temper the chocolate by melting it at about 115 degrees, then letting it cool slowly at a temperature of 75 degrees. I could be wrong, but it did seem to work.

I was left with things that look like Reese’s, but have an opening and a void on the bottom!

Soy Butter

The delicious insides is a combination of Wowbutter brand soy butter, butter, brown sugar, and powdered sugar. The butter and soy butter are heated, then sugars are added, and then cooled.

It ends up as a dough that isn’t as sticky as the soy butter began. This allows it to be put into the chocolate shells rather easily.

Finishing it up

Now upside-down, additional chocolate is poured to cover the opening and seal in the delicious center.

Conclusion

The result was very tasty, and completely satisfactory. It’s time intensive. The chocolate takes a LONG time to harden. 4-6 hours at room temperature. This can be sped up by placing the chocolate int he refrigerator or the freezer, but cooling the chocolate too quickly can have negative results.

The Reese’s company (Mars) clearly doesn’t make their cups in this manner. Since the paper liner appears to be the actual mold for the chocolate, I suspect they do it in the opposite fashion. They pour the chocolate into the cup with a removable core that leaves a void when removed. The insides get inserted via extrusion, and then the cup gets topped off with chocolate and packaged once solidified. Empty cups that popup online from time to time seem to confirm this theory.

No matter what, I am happy with the result, and my son can now know of the exquisiteness that is a Reese’s cup.

CNC’d Relief Carving

Friday, August 4th, 2017

I was tasked by a friend to create a relief carving based on a low resolution photo. The subject matter is a baby hand holding onto the daddy’s finger.

I’ve never needed to do any sort of relief carving like this, and I’m not real handy with a chisel, so I decided the best way to do it would be to generate a depth map and feed it into a CAM program that would generate the g-code to carve the relief. A depth map (also known as height map and bump map, depending on the program) is a grayscale image where each pixel represents a height based on it’s brightness; white being highest, and black being lowest.

There were a few ways I could go about making the depth map. I thought that the path of least resistance would be to bring the photo into Photoshop and manually paint a depth map over the image. Here is a gif of some of my iterations.

DepthMap

It took about 18 or so revisions before it got accurate enough that the final result was acceptable. In the CAM program many imperfections are readily noticeable, however the final product often looks better due to the maximum effective resolution of of a ball-nose cutter for a given size on wood.

MeshCamI looked at quite a few programs to decide which would handle the depth map the best, and ended up using MeshCAM. MeshCAM was the most straight forward of the software I tried, and it also is available on the Mac. All I had to do was import the image, specify the wood dimensions, and the maximum cut depth, then adjust the speeds and feeds. The smallest bit I have for the CNC machine is a 1/8th inch ball nose.

Here is the final result. My friend said it was perfect for what he needed.

In retrospect, it might have been easier to import the image into Blender and model the hand and fingers in 3D space. The results might have been better, however the method I chose was an enjoyable challenge and not too time consuming.

Bed Frame

Thursday, January 12th, 2017

It recently became apparent that my son was too big for his toddler bed. As we searched for a twin bed at popular stores for children, I found that beds are grossly over priced. The bed my wife liked was over $600, not including the mattress!

We decided that I could make a better quality bed for much less than that, so I did!

Planning

I started out by drawing some hand sketches with rough measurements. I went through the process a few times, each time refining the plan so that it was more complete, and had more accurate dimensions. I also tried to simplify the material selection so there was as little variety in the lumber required as possible.

Bed Plans 2Bed Plans 1

We chose to paint the bed, rather than stain it. This allowed me to choose multiple types of woods which helped cut costs. Here is what was purchased:

Item Usage Quantity Item Price Total Price
4×4, 16ft (Redwood) Bed Posts 2 $13.97  $27.94
1×6, 24 ft Lower Bed Rails 3 $5.91  $17.73
1×4, 8 ft (Spruce) Head/foot board upper rail 1 $1.84  $1.84
1×1, 16ft (Poplar) Mattress Flange 2 $3.50 $7.00
4×8 3/4″ Plywood Mattress support 1 $38.27 $38.27
4×8 1/8″ Plywood Head/foot board material 1 $7.50 $7.50
1″ Slats (molding) Head/foot board decoration 40 Feet $.36 $14.45
Zinsser Primer/Sealer Prime 1 Gallon $19.98 $19.98
Blue Semi Gloss Paint Paint 1 Gallon $26.97 $26.97
Total Cost: $161.68

Total cost after tax: $175.90

Bed Posts

BedPostsThe bedposts are made from 4x4s meant for framing, which come in 8 foot lengths. The posts for the headboard are 4 feet tall, and the posts for the foot board are about 3 feet tall, so there was plenty of wood to get the posts from the 2 lengths that were purchased.

Obviously, the 4×4’s are way too fat for posts on a child’s bed, so I cut them down to 2.7 x 2.7 using a band saw. Next, I sanded them down to 2.5 x 2.5 by taking off .05 inches on each side using a reciprocating drum sander.

The whole bed was designed to be put together using mortise and tenon joints. The next thing I had to do is put in the mortises. For this, I used a mortise and tenon jig that my dad had. I used the largest setting for all of the mortise and tenons I had to do, which made set up pretty easy since I only had to do it once.

With the mortises all cut, I then needed to add a slot for the 1/8″ sheet of wood that will serve as the head and foot boards. I set up the router with the 1/8″ bit, and a depth of .25 inches, and centered it on the mortises, and made made a groove between the upper and lower mortises on all four posts.

Next, I took the hard edge off the corners by running them each through the router, using a small 1/8 inch quarter round bit.

I designed the bed posts to have a decorative groove near the top. The posts will protrude above the upper rail 2.5 inches, so that the protrusion is a perfect, symmetrical cube of material. I used the golden ratio to decide where to put the groove. The groove was made with the table saw, and is just a single kirf width.

Rails

BedRailsThe lower rails for the bed frame are made from the 1×6 planks of wood, and the upper rails for the head and foot boards are made from the 1×4 planks of wood.

The rails will be supported primarily by the mortise and tenons. I set the tenon jig to cut to a depth of 1 inch, so for the final measurement of the wood, one needs to add 2 inches to account for the tenon.

With the rails all cut to length, and complete with tenons, I routed the corners with the same 1/8″ quarter round that was used on the bed posts.

The shorter of the rails which will be used on the head and foot board require a groove for the head and foot board material. I used the same 1/8″ bit that was used on the posts, and added the groove on one side of all 4 rails at a depth of .25 inches.

Finally, some light sanding, and they are ready for paint.

Head and Foot Boards

The head and foot boards are made up of a 1/8 inch sheet of wood that is inset into the bedposts and rails. This will then be covered with decorative slats.

All I had to do was measure the opening, and add 1/2 an inch to account for the groves in which the wood will be set.

Once cut down to the proper sizes, the head board and foot boards can be assembled. This is done by placing one post down on the table with the mortises face up. The upper and lower rails receive some glue on the tenons which are then inserted to the mortises of the posts, and lightly hammered into place.

IMG_3719Glue is applied to the exposed grooves. The headboard material is then slid down from the top until it is seated in the groove on the post. Finally, glue is applied to the other end of the rail’s tenons, as well as the end of the headboard sheet, and the other post is tapped into place. The whole thing is clamped for a few hours until the completed headboard is dry.

IMG_3720I followed this same procedure for the foot board.

IMG_3722Lastly, slats are added. I took the 1 x 1/4 material and cut it down to the proper length to match the height of the inset area on the headboard. I also used extra material to make spacing jigs to help me distribute the slats evenly across the head and foot boards. They were glued in place. In addition to adding visual interest, the slats add a significant amount of stiffness to the otherwise flimsy 1/4″ material.

Painting

IMG_4014The whole bed was dry-fit together and painted all at once. I masked off a strip on the inner side of the long rails where I planned to put in the flanges that will support the mattress board.

IMG_4016I applied one coat of primer using a gravity fed spraying apparatus for the air compressor. This ended up taking forever due to the small amount of paint that the nozzle delivered. It took about an hour, but was reasonably evenly covered.

IMG_4021I let the primer dry completely, and then began applying coats of the blue paint using an airless sprayer. The airless sprayer delivered a much thicker coat, and after 3-4 coats of paint, I had used the whole gallon! It looked pretty good though.

Final Touches

Next, I cut the 1×1″ poplar to length, then glued and screwed it to the interior side of the long rails that had been masked off. This will serve as the flange upon which the mattress board will sit, and carry all the weight.

The very last detail before assembly is to drill the holes in the rails that will hold the headboard and foot board together. I used an angled countersink jig to put 2 shallow-angled holes on either end of both rails that will allow screws to hold it tightly to the posts.

With all the pieces reader to go, the bed frame could be assembled. The rails were lightly hammered into the head board posts, then screwed in place.

The foot board posts are then hammered into place on the rails and screwed in.

The mattress board was then cut to snugly fit between the rails, and then laid on top of the flange with the mattress placed on top.

Just add a pillow and some sheets, and the bed is completely finished!

Results

IMG_0238_e

The bed turned out great. It is super-sturdy. No rocking or creaking. The price was also exceptional. The paint has a few minor blemishes due to my inexperience with painting, but looks pretty good overall.

My son loves his new bed, and it’s sturdy enough for all the antics of a toddler.