Introduction
Group assignment:
Complete your lab’s safety training
Test runout, alignment, speeds, feeds, and toolpaths for your machine
Make (design+mill+assemble) something big
Group assignment
Shopbot operation
Overview
The FabLab Amsterdam owns a Shopbot which is prepared to mill sheet material with dimensions of 2440mmx1220mm. The shopbot reised in a separate space in the Fablab.
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Shopbot when entering the room, looking down the negative y-axis |
Shopbot looking at in the positive y-axis |
The rather intimidating machine is driven by a number of large stepper motors. When the machine eventually moves, it moves with a speed and ferocity which you would not expect of a machine this size. We were constantly reminded by our instructor that this was a dangerous machine.
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X-stepper motor 1 |
X-stepper motor2 |
Y-Stepper motor |
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The z-axis and spindle |
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Using a 2-inch router… |
…the sacrificial layer is milled flat with respect to the machine |
Safety
It is very important that safety measures are taken into account when operating the shopbot.
- Loose hair and loose clothing can get stuck in the moving parts of the machine
- Flying debris and broke milling bits can fly of in any direction and hit parts of the machine, or humans.
- The friction of the milling bit can start a fire when it’s moving too slowly
- Sparks can fly in the dust collector and start a fire
- The machine can be obstructed and break.
Some safety precautions:
- No loose hair
- No loose clothing
- Don’t touch the device when it is in operation
- Wear safety goggles
- Wear ear protection
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Before operation, make sure the area next to the shopbot is clear. No material should be leaning against the machine |
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The shopbot dust collection system runs from the mill… |
…to the dustcollector in the back |
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When the mill hits a metal object, sparks might ignite the dust in the dust collector. When this happens stop the machine, loosen the dustcollection bag and check for fire. |
A fire extinguisher is always at hand. |
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In case of fire use the regular exit… |
…or the emergency exit |
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In case of emergency, use the emergency button to cut power to the machine altogether. |
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Keep your hands away from the machine while it’s operating. The machine path can be quit unpredictable. The geared rails on the sides are genuine finger choppers. |
Before the shopbot can operate, you have to prepare the tool path. Already at this stage, safety must be taken into account. A wrong tool-path can hit screws and start fires, or mill too deep and demolish the sacrificial plate or break the machine.
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V-carve is the software used for preparing the toolpath |
It supports a range of vector formats…but no .svg |
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When starting VCarve, you are presented with the opportunity to set up your job. Be sure to set it to mm when not in the USA |
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Always measure the thickness of your sheet material, as it is never the thickness as is advertised. |
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The clearance height is the safe distance above the stock material. |
An error occurs when the milling bit will be at the wrong height |
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Start creating a toolpath for the selected shapes. Select “pocket” toolpath for milling a pocket. |
Enter the depth of the pocket and select the milling bit you want to use. |
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VCarve is mostly based on imperial measures. |
We use a 5mm milling bit. The pass depth is taken as half the milling bit diameter. |
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Select the profile toolpath for shapes that represent the outline of the parts. Be sure to first mill out the inner parts (holes, etc. before milling the outer parts) |
Tabs are little pieces of material that are not being milled out on purpose, to prevent loose parts from flying of and interfering with the milling process.
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Select the dimensions of the tabs. |
You can put tabs in manually or automatically. |
Screws are used to secure the stock material to the sacrificial layer. The mill must absolutely not hit any screws because this might cause a fire in the dust-collection bags. Therefore, the screws have to be part of the toolpath.
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Draw circles (5mm in diameter) to indicate where the screws can go. |
Select a drilling toolpath for the screws. |
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Simulate the toolpath before saving it. |
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Save the toolpaths. Drilling the screws should be in a separate file. The inner paths and outer paths can go in one file. |
Milling
Changing bits
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A 5mm 2-flute endmill is used for all out milling |
Securing the milling bit to the spindle is done with these tools |
The key to start the spindle is attached to one of the tools to secure the milling bit. This way you can’t ever try to change a bit on a spinning spindle.
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The collet is the part that grips on the milling bit. |
The collet is fastened with this nut |
The order of operation of changing a milling bit should be:
- Insert the collet in the nut.
- Insert the tool in the collet
- Screw the collet to the spindle.
Don’t do it the other way around: the collet won;t fit nicely on the spindle and the tool will be skewed.
Before starting the control-software, first start the machine, and secondly, start the dust-collection system using the switch in the back.
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The ShopBot is turned on with the big red switch on it’s side. |
The dust collection system has it’s own power switch |
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The orientation of the operator is important. The display is turned towards the positive y-axis |
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The shop-bot software allows the operator to jog the machine along different axes. To do this, press k . The arrow keys will jog the device: up and down for positive y and negative y, Right and Left for positive x and negative x, PageUp and PageDown |
When jogged towards the lower left corner of your product, set the x- and y-axis of the project to 0.
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Press this button to set y and y to 0 |
Zeroing the z-axis is done by probing |
Tip |
Make a picture of the x and y coordinates before zeroing the x and y axis. You will need this to continue the job after something fails. |
When the right tool is installed, the toolpath is loaded and all axes are set to zero, the milling can begin, but first:
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Turn on the spindle using the key on the tool-change-tool |
Set the spindle to the appropriate speed on the spindle controller, located beneath the machine |
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Start the dust collection using the button at the right of the operator seat |
A checklist before milling:
- Are all axes properly zeroed
- Is the spindle running
- Is the dustcollector running
- Is the machine free of any debris
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Start the milling process in the software |
It mills. |
When the milling is finished, the parts are still stuck to the leftover material. We found the best way to get them out is using a blade of a hacksaw because it’s thin enough to get through small gaps.
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A hacksaw blade does the trick for getting the parts out. |
Group experiment
To get to know the machine a bit more, we milled out two pieces of layered plywood of 20mm thickness. One with the conventional
setting, and one with climb
.
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For climb milling (left), the bit rotates in the same direction of the feed. For conventional milling (right), the milling bit rotates against the direction of the feed. |
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Two pieces were milled, one with conventional milling, the other with climb |
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The conventionally milled piece had more splinters. |
The piece milled out with the climb setting enabled was les splintery. |
Make
For my project I wanted to create a cool looking table/stand to put my instrument on.
Design
I wanted to take the opportunity to learn Grasshopper, a parametric modelling tool in Rhino. Some youtube tutorials led to the aesthetic I quite liked. An organic shape that is built from separate 2d cross-sections. Not knowing beforehand what I wanted to make, I chose to use a plate of plywood, 1220mx2440mm in size and 9mm thick.
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Lots of tutorials to learn how to make a parametric bench in Grasshopper |
However, I din’t have much time to design the product and designing something, making it ready to ill AND learning a new piece of software in one evening was a bit too much. So I decided to still use Rhino, but not make my design parametric.
The design would be a simple loft of closed three curves, which I could use to make cross-sections that could be milled. I planned to assemble the cross-sections by using three broomsticks to connect them.
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The design started with three curves. The center curve was slightly off-center |
The final object when lofted was curved in the xy-plane. The curves were chosen rather randomly but some features were deliberately added. |
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I capped the lateral sides of the design |
Cylinders would cut holes… |
… with a diameter of 23mm (the diameter of a broomstick) |
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To make the coss-sections I used the “array along curve” tool in Rhino to lay out 9 evenly spaced points |
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Using a Rhino plugin called SectionTools it was easy to create cross sections of the design |
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SectionTools also helped with the nesting but eventually I nested the parts by hand because I would be able to make the most of the space I had at my disposal. |
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After rendering the object I could already have seen that the cylinders to keep the object together did not resemble the dimensions of broomsticks. |
Prepare
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I used layers to make it easier to select shapes belonging to a similar toolpath |
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Settings for the “holes” toolpath |
Settings for the “outline” toolpath |
Settings for the “drill” toolpath |
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Make sure to select the metric profile when exporting. Fortunately the Shopbot software warned me for this. |
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Visualizing… |
…and simulating the toolpaths. Everything seemed OK |
Mill
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Before putting down my material I noticed the sacrificial plate was not entirely flat. There was a ridge on the upper y-limit that would lift my material for at least 1mm. I had to take that into account when laying down my sheet |
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Measuring al |
four corners of |
the plate yielded |
different results |
I took the largest plate thickness to plan my toolpath, as not to damage the sacrificial layer.
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For 9mm sheet material I used 3x2.5mm screws to secure the sheet material to the sacrificial layer |
Look out not to break screws but if one breaks, be sure not to leave broken screws in the sacrificial layer.
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By counting all the screws I put in, I was sure to get them all out again |
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Before zeroing the x and y axis, I took a picture of the x and y coordinates |
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After the milling was finished, the screws could be undone |
Assemble
Now the product was just a bunch of loose plates. During the milling process I realized I made a mistake in the design. As I was planning to use broomsticks to hold the pates together I realized I had mistaken the broomstick diameter for the broomstick radius in the design. The holes were now 45mm wide instead of 23. As a replacement I bought 3m of white PVC pipe.
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This wasn’t wide enough to fit in the 45mm hole, so I designed and printed adapter rings. |
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Using OpenSCAD adapter rings were designed |
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The adapter rings appeared to be slightly to small for the holes in the wood and slightly too small for the PVC pipe to fit through |
Eventually I stuck to using these rings as I was out of time to print new ones.
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Because of the measurements ot the rings, assembling the product was quite hard. I will have to print new rings eventually. |
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But overall I’m satisfied with the aesthetic of the final design. |
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