Engineer & Entertain

Ideas I grapple with

Archive for the tag “CNC”

Spiraling into control

I am building a table for my Handibot as one of my biggest challenges thus far is registering the machine in the same spot when I move it to change bits. The table will have dog holes bored every 3 inches. The Handibot will have a fence and work pieces will be clamped against the fence via offset clamps.

The screw does not go through the center of the circle. It is offset so the circle rotates like a cam.

Rather than cut circles and mount them offset, I decide to make cams based on the Fibonacci spiral. I am not sure if there is any advantage or disadvantage to this. My reasoning was that a spiral would have a smoother transition in clamping. We’ll see how this works in practice.

I laid out a rectangle and spiral based on the Fibonacci numbers with a pair of dividers. Alternatives to using dividers/compass include:

  1. Multiplication – the 3″x3″ square is effectively the number 8 square in the picture below. To make the 5 square, multiply 3 by 5/8ths. The 5 square is 1.875″ x 1.875″. To make the 3 square multiply 3″ by 3/8ths and you will find the 3 square is 1.125″ x 1.125″
  2. Print a spiral. Adhere the paper to your work piece with spray adhesive and cut it out.

I laid out a 3″ x 3″ square on a scrap of 3/4″ thick plywood. I set my dividers to divide the square into 8ths.

The 3″x3″ square can effectively be thought of as the 8 square

From the outer corner of the 3″ x 3″ square I paced out five spaces. This is the corner for my 5 square.

Five little steps and I made the 5 square

I repeated this process to create the 3 square, 2 square, and 1 squares.

I used a compass with a pencil to trace the arc in each square. The compass legs are spaced the length of a side of a square.

Then I cut out a small rectangle from the 8 square. This provides a handle for me to grip when tightening the clamp.

Cut with a handsaw.

Next I used my fret saw to cut the spiral. I used a sander to sand down to the line.

Golden

I drilled a 3/4″ diameter hole in the spiral for a dowel. The dowel is 1.5″ long and glued in place.

Looks like a duck

The clamp does hold pieces against a fence, but I am unsure if it will be strong enough while using a CNC router. I’ll report back with those results eventually.

Tooling Around

After running Shopbot’s hello world, my first project was Shopbot’s accessory holder. The project takes you through the basics of designing in VCarve Pro, creating tools paths, and running the file with a CNC.

Tooling around

So as to get more practice, I made some revisions to the tool holder to store the accessories I received with my Handibot. I removed the three large holes which hold spare collets, three of the 1/4″ bit holders, and reduced the rectangular recess. I added six 3/16″ holes at the top to hold allen keys and a second slot to hold a 7mm wrench.

Tooling around

The 3/16″ holes were milled first with a 1/8″ single fluted bit. I marked the location of the Handibot by tracing around it. I switched out the 1/8″ bit for a 1/4″ upcut spiral bit. The rest of the tool holder was milled and cut out.

The redesign worked well in that it gave me more practice, but admittedly it is not how I prefer to store tools and accessories. Even though I thought I was thorough in realigning the Handibot with the pencil tracings when switching out the bits, I was still off. Thankfully the design had loose enough tolerances to accommodate a less than perfect alignment.

I CNC what you did there

I make it a point to not purchase a new tool or material unless it is truly needed. The basis for this rule:

  • I do not want to buy a tool that I will not use frequently enough to justify its cost.
  • Often I can use a tool I already have or build a jig to allow the necessary process to occur.
  • Having a limited set of tools puts constraints on my work and constraint breeds creativity.

Recently though I made a purchase which violates this very rule.

I have no need for a robot which can perform routing, engraving, cutting, and milling operations. But I have wanted one since I used a computer numerical controlled mill in my high school engineering class. Creating with a CNC machine provides an abundance of possibilities. The Handibot has an astronomical amount of potential.

My main attraction to the Handibot was twofold. First, I did not have to assemble it. There are many plans and DIY kits to assemble your own CNC for far less than purchasing a ready-made machine. Knowing that accuracy would be paramount in a DIY kit I opted to not go that route. I know others have built their CNC machines accurately and easily, but I do not have the patience to do so.

My second draw to the Handibot was its size. CNC mills range in size from small enough to fit on your desk to large enough to handle a 4 feet by 8 feet sheet of plywood. You bring the machine to the workpiece with a Handibot. While its cutting area is 6 x 8 inches I can move the Handibot anywhere on the workpiece and run a process. I am not sure how often I will mill on a sheet of plywood, but it is nice having the ability without having to dedicate the space to a large machine.

Setup

The software installation was fairly straightforward; I followed the dialog boxes as directed. I did have a run time error when I tried to run ShopBot 3 because it tried to divide by zero. Turns out I was supposed to run ShopBot_PRSDesktop2418.

It comes with VCarve Pro which is the design and layout software. PartWorks 3D is CAM software. These two bits of software can either be downloaded and installed from a zip file or with the included flash drive. The flash drive also has ShopBot Design (communicates between the device and computer) and ShopBot Editor (reads and edits the ShopBot files).

Use

After installing the software, I zeroed the XYZ axes as directed. I then ran Shopbot’s version of “Hello World”.

The Handibot carves Shopbot’s logo with a 90 degree V bit. It provides fairly clean edges, but the detail will be dependent on the sharpness of the bit and the material being cut.

All of the fuzzy wood chips could be brushed away with an old toothbrush.

Cutting the birch plywood produced very little dust. I ran the sample twice – once with a shop vac attached to the dust port and once without. In both cases there was no observable airborne wood chips or dust. Regardless, you should always wear respiratory protection, but I am not concerned about my computer being near a router.

With and without a shop vac for dust collection.

On Deck

The main limiting reagent is my lack of knowledge of VCarve Pro. The last time I used CAD, CAM, CNC, or any other engineering software my roommates were my parents. Thankfully Vectric provides resources on how to use the software and there are other tutorials on YouTube and Instructables. My attempts at making some other logos and text in plywood were met with failure. I am sure I will figure it out in due time. Or I will become so incredibly frustrated with it I will sell it on Craigslist. Either way.

I am not sure what projects I will attempt with my new tool. Suggestions are always welcome. I love the promise and bright future it offers.

Post Navigation