7. Computer-Controlled Machining¶
Group assignment:¶
- Complete your lab’s safety training
- Test runout, alignment, fixturing, speeds, feeds, materials and toolpaths for your machine
- Document your work to the group work page and reflect on your individual page what you learned
Here is th link to the Group Site.
What I Did:¶
Runout¶
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.
Individual project:¶
- Make (design+mill+assemble) something big
Files¶
Downloads¶
Students Who Helped Me¶
What I made?¶
I decided to make something for my mom for valentines day. I asked her what are some things that she would like for me to make and the first options was a bowl for decorations and the second was a side table. I began making the bowl but it was very hard to make so I decided to switch to make a table for her. I went online and found some inspiration. The image below it what I decided to make because it looked like the drawing my mom made for me.
How to make?¶
Once I picked out what I was going to make I began designing it in Fusion360. I decided to make it in inches because thats what the shopbot is in. In fusion I made a mini version but I used parametrices so I can easily change it later. This ended being very helpful when my tabs failed the first time laser cutting.
Base¶
Circles¶
The first step when creating my table was to create the two bases. These were very easy to make because I really only needed to make one then dublicated it.
To make the base I made a circle on the FRONT SIDE. That is very important to do because as first I didn’t have my design on the front side, so it didn’t add into Aspire correctly. So on the front side, I made a circle that was 4 inches in diameter. I used the tool that creates a circle from a center point which is important because that center point will be used later when you pattern the tabs.
To find this circle, first you create a scetch using the button below that is boxed in red.
Then after that button you go to the create tab, then to circle, and then to the one that says Center Diameter Circle as demonstrated below.
Once that tool was selected, I used the orgin (center point of the screen) as the center point of my circle. This made it easier for me. After that was created I could move on to making the tabs.
Tabs Holes¶
The next step were the tabs that I was going to need to make press-fit. This means that you don’t need to use an glue, nails or screws to keep the design together. To create these I measure the width of the practice wood. This is going to be the width of the tabs. Then for the length I did .58 inches.
To create the rectange I used the two point rectangle tool which can be found in the following.
Above is an image of the final dimentions already with the pattern done which is the next step.
Pattern¶
As mentioned the next step is to create the circular pattern for the tabs. To do this I went under the same create tab, then I went down to circular pattern.
This circular pattern takes you to a new tab bar that looks like this.
Once that pops up you can select the object u want to pattern and the center point. The object is all sides of the tab and the center point is the center of the circle or orgin. Then below that is where you select if you want the pattern to go all the way around the circle or not. I chose Full because I want to go all the way around the point. Then the next important thing is the Quantity which I set this to 6 because I planned on having 6 legs on my table. One that was all set up I clicked ok.
The next thing I did was before I finished the sketch, I wanted to make sure the sketch stayed. In order todo this I projected the whole sctech. To do this I clicked “p” on my keyboard. This should bring you to a drop down menu that looks like this.
From here I selected the whole sketch, thne I selected the first option for “Seletion Filter”. The other option is faces, but since this is a sketch, I didnt have any faces to select. Then the projection link box I had selected and I clicked “OK”. This them made the objects look purple which is good because that means that it worked.
Legs¶
Shape¶
The next step in this process was the legs of the table. I first started with curved lines. To create these I made a new sketched. This is necessary when ever you make a new object. Also you want to do this because when you need to go back in time on the time line, it makes it easier for you to make the objects in different sketches.
Once I made the new sketch, I once again went to the create drop down menu and then went to the “Concic Curve”. With this tool, you choose the starting point, then end point and then the vertex. I did a slight angle that said it was -.75 away from zero. This means that the vertex of the curved line is .75 inches away from a straight line.
Once I made that line I dupicated it and then fliped the line 180 degrees so the the angles went towards eachother. This created the shape of the legs I wanted. Then once I created those two lines I connected them with straight lines across. To create a line simple just click L on the keyboard and you will be on the line tool. Then connect it from one node to the other one on both sides to make a closed sketch. After this was done then I moved onto making the tabs on the legs.
Tabs¶
For the tabs I found the center of the line that I created last time. You will now if you at the center when there is a triangle that looks like the image below.
Then from their I made a construction line that went up the width of the wood for testing. This width is also the same width as the the holes for the tabs.
When you are on the line tool, this side bar pops up and the button that is highlighted blue is the construction line option. This makes a line that isn’t see once you finish the sketch.
This is the length of the construction line which is once again the width of the wood I was using.
After the line I made up, I need to make a line to the side. This is because when I make my rectangle, I’m going to use the contruction line point that I made with the side construction line. Below is the image of both lines combined together.
As you can see the up line is the same as the tab holes and the other side line is half the length of the side of the hole for the tab.
To create the rectangle, I
This is what my rectangle looked like with the right measurements.
The next step is to cut out the extra lines on the inside. The first time that I laser cut I forgot to remove those lines which meant that the laser cut out the tabs. I wanted the tabs connected so I went back through and used the following tool to remove those.
Once I removed those, I needed to connect the rectangle to the the two nods on the sides to make sure that was a closed object.
This is the final tab created
The next steps was to repeate the tab process but on the other side. One thing that may be possible is to copy, paste and flip the one side and drag it to the other.
Finishing¶
This is an imgage of my final design. You can download it below. In the downloaded one I have two circles, but in order to make more all that is needed is to copy and paste a bunch of times.
Laser Cutting¶
Exporting¶
Once I finished designing my file in Fusion360, I exported it as a DXF file for the laser cutting. To do this I first went to file and then export.
The export then takes me to this page.
On here you make a name for the file which is important so you know what version and what the file is. The next thing is the type of file. There are many options but we wanted DXF because thats what coreldraw reads and that how we upload to the laser cutter. The final box is the location and its normally set to downloads. Once the settings are set up, click export. Once that’s done I saved that file to google drive so I could open it up on the computer for the laser.
Settings for Laser Cutter¶
I opened my file on the laser cutter computer and downloaded it which brought it into CorelDraw. Here I didn’t need to make any edits and I went ahead and clicked print. This sent the file to set up area for the printer. I went to the settings for material and changed the material to wood and then set it to cut. Once I did that I sent it to the laser and ran through the proces of auto-focusing becasue the one on the laser cutter is broken. After that I clicked print and it began.
Cutting¶
This is an image of all of my pieces laid out.
As I was building it, I noticed that the tabs were a little too big there for I edited them by one millimeter.
This is an image of me recutting the circles out.
This is am image of the legs fitting perfectly in the base circle.
Image of the final mini table put together.
Life Size¶
The next step was to cut out a life size version to make sure that it was 1 meter in size.
The first time that I laser cut it life size, so I thought, it was too small. Therefore, I resized everything and it was tall enough.
Aspire¶
The next step was to turn the fusion file into an Aspire file. TO do this I struggled alot because at first I made my design on the top side. It is very important to make it from the bottom because thats how Aspire reads the files. Since it didn’t work at first, I had to recreat my file but that was very easy todo because I already knew how to make it. Since Aspire reads DXF files, once it was saved it was very easy to import.
Setup¶
First you go to the button that says “Open an existing file”. From here it will allow you to open your file that is alreadt made rather than start a new one.
The next step was the material setup.
Job Type
The first section is job type. I did a single sides so thats what I selected and the rest of our group.
Job Size
The next step it the “Job Size”. This is where you add the size of your wood. We get wood that is almost the same size as the bed therefore I just set the job size as the the X anf Y dimentions of the shopbot. The only thing that needs to be changed is the thickness. Our options were either 3/4 inch or 1/2 inch wood. If we were doing something that you stand or sit on, then you use the thicker 3/4 inch wood. If you do a table ,like me, or shelfs then you choose the 1/2 inch. That is why the thickness is set to .5 inches. This will end up changing later but js to set it up for now, I kept it are .5 inch.
Z Zero Position
For the Z zero position, We need to set off of the machine bed because its already automatically doing that.
XY Datum Position
The XY Datum Position is also known as the orgin. The origin is where the red dot is and to the right is X and the Y is up. This is also home when you home the machine and it shows from what corner you creat your design from. The botton left corner is the orgin for the shopbot. The othr important part of this section is the “Use Offset” box. It is important to keep this off.
After that there is nothing else that needs to be changed and I went ahead and clicked ok.
Dog Bones¶
The next step was to create dog bones. Dog Bones is the fillet tool.
Under the Edit Objects section, it is the following tool selected.
Once you have selected the fillet tool, it opens you to the following side bar above. Here is where you change the fillet/ tool radius and the type. As mentioned before, we do ‘dog bone’ fillet. The other option that can be selected and is about the same is the ‘T-bone’ fillet but I recommend ‘Dog Bone’. Then the tool radius is very straight forward. Depending on the bit you plan to use, you add that. For example, I used the 1/4 straight bit therefore I typed in 0.125 inches.
Dogbones go in the corners because you can’t make sharp cuts. Thats mainly bcause the bit is rounded which means that in order to make the tabs fit, you need to add dog bones.
When using it you know you are in the right spot when you have a tiny check mark. You can’t use this tool on straight edges and only corners. If you would like to undo a dog bone, just hover over the corner until u see a tiny X and the click and it will undo it.
This is an image of my circle witht he dog bones done.
This is an image of the dog bones everywhere. It very hard to see them because they are so small and the quality, but they are there.
Tool Path¶
In the top right hand corner it says “Toolpaths”. This is what you click on to create toolpaths. Once you select that, you selected the type you want and the object you want for that toolpath.
The tool path that I chose was the profile tool path. This one allows you to cut peices out of material. If you’re not making a pocket of any kind, then you are most likely choosing this option.
Parts of Profile
Cutting Depth
The first is the Cutting Depth. This is where you set the start depth an cut depth. The start depth for me was 0 and the cut Depth, not shown in picture, was 0.5 inches.
Tool
The tool section is where you pick your tools. Charlotte Latin’s lab has 9 tools that you can choose from. I chose the 1/4 straigh bit(not picture in image above). The other part of this section is the number of passes. Our teacher recomended 3 for us so i needed to edit passes. Once you click that button it taked you to the following.
The only thing to change on this page is the number of passes at the bottom. Instead of 10 we did 3 then click OK. We did 3 because this makes the feed rate, how much of the bit goes into material, less than .333 each pass.
Machine Vectors
Machine Vectors chooses how the CNC goes over over the shape. For the outside profile, I did Outsie/Right and the tab holes were Inside/ Left. This was recommened by my teacher and it worked.
Do Separate Last Pass
For me, I did not turn this on or change anything in this section.
Tabs
Tabs are a small peice of wood that stays connected to the piece we are creating and the outside.We always create tabs because we want the wood to stay to bed rather than fly everywhere. Here you can change the length and thickness which I kept them at the normal settings. one thing is to never put them in the corners. If you do them they won’t cut right. It is recommended to have at least 4 tabs per object. To change this I went to edit tabs.
Inside that button, it looks like this. This automatically makes tabs for you depending on how many you want.
Ramping
Ramping allows the tool bit to slowly go into the peice of plywood which puts less stress on the tool and makes it gradual. This also helps for a smooth test and it was highly recomennded by our teachers.
Name and Calculate
The last section is where you name your tool path and then you press calculate. I don’t recomend changing anything else. Once you click calculate, the side bar turns into a place where you can watch the toole path you just created to make sure it looks right. If you want to watchit again, you have to like reset all tool paths before hitting play or it won’t do anything.
Repeating As mentioned before, I had 2 tool paths. One for the outside and then one for everything inside the the circles. For the stuff inside the circles, I copied everything the same except for the Machine Vector. For these I did Inside/Left. That is because if I did cut ouside, then it would cut off and extra few .125-.5 inches that you want on in order to make press fit.
After everything was done, I tested everything in the preveiw and it looked good. It cut all the way through and had the tabs in the right spots.
CNC Out¶
The second to last step of this project was to actually CNC the table out. I was very scared it was going to be messed up, but I also felt confident because I had tested the file out so many times before and got the shopbot file checked.
Exporting¶
To save your files, first it’s important to click the button with the green. This re-calculates the tool paths. So if you change your depth to the actually depth of your wood (which I definatly recommend because other wise you might not cut all the way through) or you change the position of your file, then you need to use that button. The other important one is the save button. This is the other button that is highlighted.
When you click that button, something like this will pull up.
This is not my exact one in the picture but an example one I took because I forgot to take that photo
In here ther are a few important parks. The first is the option selected tool path. I recommend saving tool paths seperatly for the air cut. The other important part it the Post Processor. This it where you choose the machine you are using, so for me it was the shopbot. Once that was done, click save and it’s ready to save in goodle drive. If you had more toolpaths, like me, then I had to redo that process for the other one too.
Milling¶
Then once I saved it to goodle drive, I went ahead and went to the shopbot. At the shopbot, I followed [these instructions]. It very simple this way and everything came out perfectly.
Safety¶
To keep the wood down to the bed, we use plastic nail bits from a natil gun. They are very thin and tiny but long enough and stronger enough to keep the wood down. We use these for safty. If the machine bit for some reason goes over one of the nails, then it doesn’t ruin the machine and the machine can just go right through them. Another thing we do for safety in the lab is go over in detail a safety before. This is where we go through everything we need to do like stand behind the yellow and black lines on the floor when the machine is moving and wear face sheilds and ear protection. We aso have an advances vacum system that sucks of any wood chips.
Aircuts¶
When milling, it’s important to do an aircut first. This is important because then you see where you will be milling. The first time I did one, it said I was gonna go off the bed which I fixed but that is why you do aircuts first.
Aircut for the Tabs
Aircut for profile
Actual Cuts¶
video of cutting out tabs
Image of tabs cut out
Image of everything cut out
Post Milling¶
This is an image of all of the pieces out of the wood and laid out
Image of assembling the table
Image of finished assembled table
This is my table being used by my mom. She really liked it and thought this was a great spot for it.
Reflection¶
If I were to redo this table, I would only change a few things. I would have the cut depth to be .005 inches deeper because at the center of the pywood, it was lifted up alot meaning that he bit didn’t cut all the way through. This means that I need to go back through with the handsaw in order to get the wood pieces out. This also meant that I needed to sad alot on the edges due to the extra wood on it. The other thing that I would change, would be the tabs thickness. I notices that some of my tabs weren’t there because they were cut all the way through. Overall, besides though two things, this was very fun to make and I enjoyed making the table for my mom.