7. Computer Controlled Cutting - Girls¶
Overview¶
| Assignment | Name |
|---|---|
| Safety training | Angel Fang |
| Runout | Elle Hahn |
| Alignment | Angel Fang |
| Fixturing | Zaina Gibrine |
| Speeds and Feeds | Amalia Bordoloi |
| Materials | Jenna Chebaro |
| Toolpaths | Kathryn Wu |
| Thickness Gauge | Angel Fang and Kathryn Wu |
Resource Links¶
Materials - Jenna¶
We use 1/2 inch and 3/4 inch wood for the Shopbot. 1/2 inch is standard for structures that are smaller and/or require less reliability. One would use 3/4 inch for a steadier structure that one typically sits or stands on. Shopbots can also mill plastic, aluminum, foam, as well as composite materials. The material must be flat and aligned, and the bit must be changed accordingly.
Safety Training – Angel Fang¶
Mr. Dubick and Dr. Taylor did a serious safety training with us at the beginning of the week. They told us we MUST wear goggles and earmuffs when we go into the wood working room. They also told us there are two warning lines around the ShopBot CNC machine, we must not across it when we do the wood cutting. For the big ShopBot, they told us we need to disengage the spindle if we are not using it. They also asked us to have atleast two people in the room while we are using the CNC machine. In case the wood would accidentally fly in the air, they told us to wear a face shield when we are cutting.
Speeds and Feeds – Amalia¶
Speeds and feeds in CNC machining determine the cutting tool’s performance, efficiency, and longevity.
Spindle speed (RPM) refers to how fast the tool or workpiece rotates and is based off the tool diameter and material-specific surface speed (SFM).
Feed rate (IPM or mm/min) determines how quickly the tool moves through the material and depends on chip load, tool flutes, and RPM.
Material can play a role in the best setting to use. Harder materials like steel require lower speeds and higher torque, while softer materials like aluminum allow for higher speeds. Small tools typically need higher RPM, unlike larger tools which operate at lower speeds to manage heat buildup.
Pen Turning¶
1. Saw¶
I started out with a long stick of wood that I needed to shorten to the length of the brass tube in the pen kit. I needed to cut two pieces that were the same length. I used a table saw to shorten the wood pieces.
2. Lathe: Making the Hole¶
Next, I needed to use the lathe to do wood turning and create a hole in the middle of each of the wood pieces.
1.Mark the centers of the wood pieces using the diagonal line method. 2.Wear a face shield whenever near the machine. Headphones are optional. 3.Use the lathe chuck key to loosen the area that holds the wood.
4.Place the wood leaving some room between the wood and the edge and tighten it. Make sure to remove the lathe chuck key after tightening.
5.Turn the silver handle until the number reads 0.
6.Move the machine to the desired position and then move the silver handle in the back to lock the machine in place. I moved the machine so that the end of the metal tip was barely touching the front of the wood piece.
7.Turn the machine on by flipping the switch
8.Turn the silver wheel until you can see the metal tip poking out the other side of the wood.
9.Turn the machine off. Turn the silver wheel until the number reads 0 and the metal tip is completely out of the wood.
10.Use the lathe chuck key to loosen the wood holder and gently pull it out. Ensure the hole goes all the way through the wood piece.
3. Sand Brass¶
We needed to sand the brass tubes, ensuring that the outside was rough. The lower the grade of sandpaper, the easier it was to roughen the tubes, so I found it was best to use sandpaper with 60 and 80 roughness. I struggled with sanding the brass enough because I started out using sandpaper that was not rough enough. After switching to 80, it became much easier, and the sanding was much more efficient, and then once I switched to 60, I finished quickly.
This is the kit we used to make the pen.
This is the sandpaper with the brass tubes.
These are the final sanded brass tubes.
4. Gluing the Brass Tubes¶
I used super glue to glue the brass tube in the wood and then used activator to speed up the drying process. I tried to be careful to not use too much glue because the brass tube needed to be fully clear in order to continue and use the lathe again.
5. Drill Hole¶
I still managed to use too much glue, so I needed to drill through the brass tube to clear it out enough for the mandrel to go through it.
I used this drill:
I used this tool to hold the wood piece in place while I drilled:
6. Lathe: Rounding the Wood¶
1.Wear a face mask and face shield anywhere near a running machine because the wood pieces can go flying, and you do not want to inhale wood dust.
2.Place 1 baron, 1 piece of wood, 1 baron, 1 piece of wood, 1 baron and then the gold disc on the metal pole that goes into the lathe.
3.Use a wrench to tighten the metal pole in place until it will not turn anymore.
4.Turn the lathe on.
5.Use the square screwdriver to get rid of the excess wood around the outside. Keep using the square screwdriver until the wood piece gets to be slightly greater than the size you want it to be. Rest your left pointer finger in the finger slot while holding the metal part of the screwdriver with your left hand and the end of the screwdriver with your right hand. Slowly move the screwdriver back and forth horizontally, tilting the metal tip slightly upwards. Try to move the screwdriver evenly across and make the wood roughly the same size for each piece.
6.Switch to the circle screwdriver. This will help round the edges of the wood and create a smoother, rounder look. Rest your left pointer finger in the finger slot while holding the metal part of the screwdriver with your left hand and the end of the screwdriver with your right hand.Slowly move the screwdriver back and forth horizontally, tilting the metal tip slightly upwards. Try to move the screwdriver evenly across and make the wood roughly the same size for each piece. Once the pieces are roughly the same size, you can choose to round the edges making the front and back ends of one piece rounded inwards creating a classic front-of-pen look.
7.Once you have the desired shape, select around 5 pieces of sandpaper ranging from 300 grit to 2000 grit. In increasing order, hold each piece of sandpaper on each of the wood pieces for around 20 seconds, sliding it slowly back and forth horizontally. Make sure to sand the ends too, and sand each piece evenly. I had used the lathe to make my wood pieces pretty thin, so I had to make sure not to use too rough sandpaper for too long because that would make my wood pieces too thin and possibly break.
8.After the wood feels even and smooth, pour around a teaspoon of wood polish on a paper towel and rub the paper towel back and forth horizontally across both pieces of wood for around 20 seconds, making sure to cover all spots. I recommend folding the paper towel in half and making it smaller so that it does not get caught in the lathe.
9.Turn the lathe off. Use the wrench to unscrew the metal pole and gently remove the barons, gold disc, and wood pieces.
Here are my final sanded and polished wood pieces:
6. Assembling the Pen Kit/Using Pen Press¶
1.I used the Rockler Gold Slimline Pen Kit to make my pen. With the wood pieces and the remaining kit materials, I used a pen press machine to assemble the pen. The pen press pushes the materials securely together.
2.To assemble the front half of the pen, align the cone-shaped tip with the thicker wood piece that you want at the front. Place the cone-shaped tip into the small circle in the white part of the pen press and push gently to hold it in place. Once aligned and correctly positioned, push the pen press and then pull it away. Make sure that the tip is firmly pressed into the wood.
3.Take the silver tube and push the gold end into the front wood piece until the wood barely touches the black line. Once you think it is touching the black line, take the ink tube and place it through the tube to make sure the pen tip is out enough to write with.
4.Set the front half of the pen off to the side.
5.Take the cap and clip and place that into the other wood piece. Push these components together to make up the back part of the pen. I struggled with lining the pieces up correctly for these pieces, but after pushing it in a little, my teacher was able to help me align it enough to continue pressing it all the way.
This is my final pen back half:
6.Use the pen press to press the front half of the pen, the center ring, and the back half of the pen together.
Runout - Elle¶
About¶
Runout is a rotation inaccuracy which occurs when the tool is no longer aligned with the main axis. In drilling applications, this can result in a bore diameter that is actually larger than the drill’s nominal diameter.
Spindle Runout, or Tool Runout, as it can also be called, is the inaccuracies that cause a tool (in a mill) or workpiece (in a lathe) to spin off the ideal axis. It’s very bad for tool life, so it’s good to know more about it.
Runout is the tendency to spin the tool around a centerpoint that is not the tool’s center. It makes the tool wobble instead of spinning cleanly and increases chip loads.
There are a few different types of runouts with include radial runout and axial runout. Radial unout is when the tool moves slightly up and down along its axis, leading to inconsistent cutting depths. And a axial runout is when the tool moves slightly side to side as it spins, affecting precision and causing uneven cuts.
Reasons for Runout:¶
A common cause of runout is when machining debris, dirt, chips, etc. enter the spindle and cause interference when the tool is clamped. Furthermore, dirt and damage collets can lead to runout inaccuracy. Lastly, damaged bits and shanks can cause iffuses too. CNC spindle runout can decrease tool life and increase the rate of machining defective parts.
Other Reasons: - Misalignment: The tool or holder isn’t installed correctly. - Worn-out Components: Bearings, collets, or tool holders degrade over time. - Bent or Poor-Quality Tools: A slightly bent tool or low-quality tool holder can introduce runout.
Why a problem¶
Runout can cause: - Uneven Surfaces: Runout leaves behind uneven or wavy surfaces and this can require extra finishing steps like sanding or polishing, increasing production time. - Poor Accuracy:If the tool doesn’t rotate perfectly, cuts won’t be precise. This means that parts may not meet tight tolerances, leading to defects or rejected workpieces. - Increased Tool Wear and Breakage:If there are alot of renout it will put uneven stress on the tool edges. This can cause tools to wear out faster or even break unexpectedly. - Inefficient Cutting Performance:The machine might need to run at slower speeds to compensate for runout. Poor cutting efficiency means longer machining times and higher costs.
Our Machine¶
Tyler Russel taught and helped me set up the runout machine that we using in our lab.
This is our first set up of the runout. This was an incorrect way of setting it up because the ball on the end isn’t touching the the bit. Therefore, to fix this we needed to rotate the device to make sure it was touching the bit fully.
This is the fixed setup. It is important to make sure the dial is set to zero because it its not then the measure ment will be wrong.
To measure the runout, we took a video of us spinning the bit with our hand. It is imprtant to make sure that the machine is disengaged for saftey reasons. Then we slow down the video later to see what it reached. Once I did that the runout we got was around 3 as the runout for the machine. Once we were done it was important to clean up the device we used. This is a very detailed explanation of the tool.
Thickness Gauge - Kathryn and Angel¶
Design¶
I (Kathryn) designed the 0.252-0.27 inch gauge on Fusion360.
I (Angel) designed the 0.492-0.510 inch gauge on Fusion 360. However, because of plan change, boy group and us switched the gauge design. At last, we printed the 0.742-0.760 gauge and 0.252-0.270 gauge.
I exported the drawing as a .dxf file and tried to add dogbone fillets, but the check mark did not show up for certain corners. I realized it was probably because of gaps in the design and Angel let me know that I could solve it easily with the join vectors tool.
And then it worked. But having 0.1 in radius fillets did not fit on both sides, so I went down to 0.075 in. I also added the number labels as text.
For the text, we were planning to use a v-bit to engrave it, but we were worried the woodpiece was too small, so we ended up using a laser cutter to engrave the numbers.
I changed the rest of the settings, but for ramp I wasn’t sure if I should go with the default or not. Chat told me a good ramp distance is 2x to 5x the tool diameter and I’m using the ⅜ compression bit, so I went with 1.8 inches.
I then simulated the toolpath and it looked good.
Milling¶
When we got to the ShopBot stage, we decided to use the smaller desktop ShopBot because our print would not be too large. We followed this workflow to operate the machine.
These were the windows we used to jog z and zero it to do an air cut.
When it started, we needed to make sure the machine was operating at the right hertz.
Before the final cut, we also did a bit tap off.
These are the finished gauges.
Toolpaths - Kathryn¶
For the design, I started with 3 1.5 in squares.
After exporting it to Aspire, I changed the toolpath in the toolpath settings. The options were outside, going along the outer edge of the line; on, with the extra width equally on either side of the line; and in, going along the inner edge of the line.
I did the toolpath simulation for these pockets and they seemed good.
The rest of the cutting process was done along with the gauges, so the previous documentation applies. These were the final products of this test.
It turned out how I expected it to, with the outer toolpath setting resulting in the largest square, then on being second largest and inside resulting in the smallest.
Alignment – Angel Fang¶
The definition of alignment for CNC machining refers to the process that ensures the correct positioning and orientation of the machine’s axes, the workpiece, and the tool in relation to each other to achieve accurate and precise machining operations.
Since our teachers are smart and considerate, they already set up a C3 command for alignment. The C3 command is used to home the machine and reset the z-zero height to the machine bed. So there is no need for us to do alignment manually.
Fixuring¶
In our lab we used plastic brads to fasten are material to the shopbot board.
What are brads?¶
Brads are small, thin nails typically used in woodworking, and they can be useful for ShopBots in specific applications. Here’s how they might be used:
Workpiece Hold-Down: When cutting thin or flexible materials on a ShopBot, brads can help secure the workpiece to the spoil board, preventing movement during milling.
Temporary Fixturing: In cases where clamps are impractical, brads can be used to track down material temporarily. This is especially useful for cutting small parts that might move.
Registration and Alignment: Brads can serve as alignment pins to ensure the accurate placement of multiple workpieces or layers in a project.
Holding Onion-Skinned Pieces – When using an “onion skin” technique (leaving a thin layer of material uncut), brads can prevent pieces from breaking free before the final pass.
How do you install a brad?¶
Here is a step-by-step tutorial from our instructor to install a brad Put on eye and ear protection. 1. Close the doors. 2. Secure your material to the machine spoil board using the composite nail gun (and teacher’s help) if this has not already been done for you.
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Please be sure that the red air compressor tank valve is closed (see image)
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Turn on the red air compressor (see image). Please be sure to allow the tank to fill completely, so that your brad nails will fully drive into the material.
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Retrieve the brad nailer from under the computer in the cabinet.
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Attach the neon yellow air compressor hose to the nailer’s air inlet (see images).
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Set the compressor to the appropriate PSI (see a teacher for the recommended pressure).
- Load the brad nailer by opening the magazine by locating the magazine latch, releasing it, and sliding the magazine open.
- Place the appropriate length brad nails into the magazine with the pointed ends facing outwards.
- Close the magazine by sliding it back until it locks securely.
- Position the nailer by placing the safety tip flat against the work surface where you want the nail.
- Hold Firmly and grip the handle with one hand, ensuring a firm and steady hold.
- Fire the nail by squeezing the trigger while keeping the safety tip pressed against the surface.
- Check the nail placement and confirm that the nail is driven to the correct depth.
- With a teacher If the nail does not go in far enough, increase the PSI by using the depth adjustment dial on the tank to ensure nails sit flush with the surface.