Xcarve updates and Passive Amplifiers

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passiveAmpIn summer, I went to Woodcraft and grabbed a bunch of blocks of wood to make x-mas presents for some friends. I already had an idea of what I was going to make from a project video I saw on Inventables’s site. I wanted to make Passive Amplifiers that would double as a desk nameplate. Rather than use the pre-made file from Easel, I wanted to do my own in Fusion360 to get more practice.

Machine Upgrades:

Before I had any time to work on this at all, I ended up buying the new beefier gantry makerslide.  I also 3D printed an enclosure for my smoothieboard and an enclosure for my E-stop button, both from thingiverse.

E-stop box         smoothiebox

Literally at this point, I’ve got enough extra makerslide, plates, belts, ACME screw and nut set and gears to build a Shapeoko 2 (missing bolts, nuts, washers, V wheels, bearings, or idler wheels). Leave a comment if you are interested in purchasing my extra parts.

I also had beefed up my gantry motor to a NEMA 23.

Processing the Blocks:

Once I had made the changes to my machine (a never-ending project in itself) I got to work on the passive speakers.  I clamped my handheld belt sander upside down in my workmate bench (I do not condone this stupid behavior). I sanded down all the blocks until you could no longer see the bandsaw marks using 150 grit sand paper. I rolled the edges and ends to get nice rounded edges. This worked for the most part, but sometimes I got inconsistent results along the entire edge of the block which looked bad and wasn’t easy to fix.

blocks

After rough sanding, I hand-sanded the corners to remove the sharp point using 150 paper by hand, then used 220 paper on my orbital sander to remove the traces of the rougher sanding and smoothed out the overall faces. Due to time constraints (I was so busy that I waited until the last minute to do these) I went ahead and hit the blocks with Tung Oil every other day for about a week. This soaks in and if I had done it more would really bring out the luster int he wood. It smells a bit funny so I left the blocks in the garage to air out.  Tung oil is good because it won’t combust spontaneously like a lot of oil-based stains. Heck, the guy that sold it to me said he never even wears gloves and has been using it 20+years. I wore gloves anyway.

After the blocks were processed and thoroughly tunged, I went about using Fusion 360 to design the passive amplifier element. Unlike the inspiration project, I wanted a continuous spiral as my cone. I created a block approximately the size of these blocks, then I created a spring. It took a long time to figure out exactly how to get the spring to have the features and be be the size I wanted. I then had to merge this with a cone shape to create a single solid body that was a helical cone shape. I put it on the block and performed a difference operation to remove the helical cone shape from the block. Then I added the slot for the phone. I used my and Jess’s phones as tests using a block of scrap 2×4 to find a width that fit both of them.

model1

CAM Processing

I can’t say this was intuitive. When I ran simulations of the cut, I kept having weird errors that would break an endmill in the real world. For instance, the bit would circle the perimeter of the helical cone step by step, leaving a huge plug of wood in the middle 40mm high to be cut from the side at the very end of the job. In order to remove this weirdness, I had to get creative with the cuts. Firstly I used a plunge cut to cut the very center of the cone out in several passes. As you can see in the image at the top of this article, there’s a bit of an error at the right side near the top of the helical cone. This is due to the lead-in of the plunge cut. In later iterations, I removed that stupid lead-in. I have no clue why it would generate paths that would defile the user’s design, but it does…

Then I used a contour cut to remove material for the slot and helical cone in multiple passes. The Fusion 360 simulator said it’d take about 5 minutes for the whole shebang, but it took about 3 times longer in reality. I’m not sure how to reconcile this. CAM

Milling:

So I intentionally went against my best judgment on this one. Looking for a cheap engraving bit, I ended up at Harbor Freight. I found a pack of 5 HSS router bits that included an engraver for $8. Since an engraver bit is usually taking a bit more light duty use than other bits, this was a good deal. Other bits were like $25 just for the engraver elsewhere! My mistake happened when I considered using the half-inch  router bit as an endmill. I figured if I take off only 1.5mm at a time, then it couldn’t hurt to use this router bit slightly out of its specified application. So I went ahead.

Surprisingly, this worked beautifully for the first four blocks I milled. The last one had ragged edges though. Since I needed to make about 4 more, I went back and bought another Hazard Fraught bit set. This was enough to cut the bulk of the gifts I was making. I had another 2 blocks to mill, but I had a couple weeks to finish those while these first 8 were needed literally that night at a party.

After I milled them, I had Jess get one of her fancy fonts and make some SVGs of our friend’s names to engrave on the other face of the block so it could be used as a nameplate on their desks. This was easy to do in fusion in a new file. I simply created a block the size of the wood I was using, then imported the SVG onto the face of the block. The Z axis here is still setup so the tool comes from the top (ie. as if the block has been rotated so that the face is pointing upward). Simply go into CAM and do an engrave and it’s done. The results came out beautifully!

The problems started when I moved my CNC machine the garage form the office to avoid the dust. I used one of those half-inch bits and aligned everything and let ‘er rip. I was making a video when the failure happened…

 

I hit the E-stop immediately but it still screwed up stuff. The bit came loose and slipped down as the router continued to spin (likely screwing up my quarter-inch collet) The CNC kept moving for a short time as well until I could hit the E-stop. This  caused the bit itself to break. Luckily no chunks of it came loose or flew off at the 22,000RPM I was running at, but it came close as the pics below show.

bit1     bit2

After this error, I went ahead and redesigned the toolpaths to use a proper 0.25″ endmill and tried cutting another block.  I didn’t get to see the final result, BUt I’m pretty sure the lead-in screwed me on the first plunge cuts I did.  I didn’t finish the part because like a genius I stuck the vacuum cleaner hose in the way of the Z cart and ended usp causing my X axis motor to skip a bunch of steps as it wedged the vacuum hose into the block. I’ve yet to revisit this. even this short amount of exposure to the incredibly fine wood dust made my nose clog up again(even wearing a respirator). I had to go back to work after new years and haven’t had a chance to revisit (or document) and projects until now.

Lessons Learned:

  • Never, ever, ever use tools the wrong way… especially if you get them from Harbor Freight. The half-inch router bit I used was intended only for routing (ie cutting sideways) and not designed for plunge cuts, even 1.5mm shallow ones.
  • Fusion 360 can’t fix stupid part 1. If you delete a shape’s reference, it’ll cause you trouble in Fusion. I don’t know how I did it, but somewhere in my timeline I deleted the helical coil. I get errors all over the place if I try to modify it. Yellows are warnings, reds are errors.
    timeline
  • Fusion 360 can’t fix stupid part duex. If you don’t know what you are doing as far as feeds and speeds, making sure your lead ins and outs don’t screw up your part, and don’t try to cut off too much at once, then there’s nothing Fusion 360 can do to help you.
  • Even with a respirator on during the sanding and milling, I still ingested a lot of dust through my nose (ended up with one hell of a sinus infection requiring a shot on Christmas Eve). It was a loud and dusty process. I need to build an enclosure. The never-ending project continues…

My Humble Telescope Case

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scopeIncase1You can find them for as high as $600 for a hard-shell case or for a soft-shell case, about $300. We’ve had a set of luggage my mother gave us like 10 years ago and I repurposed the largest one to carry my OTA (telescope tube). It’s dimensions were perfect. 13″deep x 18″wide x 28″ tall. I went to a craft store and got some 1.5″ foam, wrapped it in a circle and smushed it into the bag. Then I cut off the excess which left me with enough to do a top and bottom and a sliver to set on the face of the tube after I lay it in there.

insideCase1

I did have to carefully cut a slot and hole in the top piece of foam to make a pathway for the focuser knob on the scope. This is the only thing I really worry about with this setup.

insideCase4

insideCase3

 

To make it look nicer and more finished, I got about 3 yards of shiny-satiny black soft fabric that I thought would be good to use and stuffed it along all the edges of the foam. I made sure to form the fabric into  the slot and hole for the focuser knob. I don’t want that snagging or to have any weight on it at all. There’s no sewing involved, simply tuck in about 1 foot of material around every edge, leaving a long extra piece hanging out the bottom.

insideCase2

Once the tube is set in place, bring this excess fabric up, fold in the sliver of left-over foam and set it on top of the OTA. Then zip up and you are ready to go. The bag has plenty of storage for accessories, although I do not keep my lenses in this bag.

pocket1pocket2

I would like to get a hard-shell case for it, but with the types of luggage available, the hard shell is very thin and I worry that it won’t hold up over time, but something like this looks a little more beefy. I’ve been looking at Ross and TJ Maxx when I happen to go to those stores, but nothing there seems to be big enough.

case1

My Introduction to Astrophotography

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I’ve been interested in astonomy my whole life, and a few years back, I got a second-hand Meade LX-10 telescope. This is a 8″ diameter scope… definitely not a toy. It is great for planetary viewing and can even track the planets as the Earth turns. I have used it from time to time to try to take some pictures of celestial objects, but not very good ones. Astrophotography is a growing interest of mine now and I found the learning curve quite steep. I’m throwing together everything I’ve learned over the past couple of years including links to software and such into a few posts. There are multiple steps involved in this project and it took me a long time, working here and there and amongst about 1000 other projects, to finally get everything together for this.

To take amazing amateur astrophotography images you need to decide whether you want to look at deep space objects (DSO) like galaxies or nebulae, or if you want to focus on planetary viewing (within our own solar system). You don’t really want to zoom very much if you want DSO images because zooming narrows your field of view and most DSOs you want to get are very dim so you don’t want to zoom in to make their light spread out across your eye or camera sensor too much, you want bright pictures. You can take some amazingly cool pictures with just a DSLR and a “barn door” tracker. (This is just a device that rotates counter to the Earth’s rotation so your camera will continue pointing at the same object for minutes or hours at a time, meaning it moves a full 360 degrees in 24 hours).

In my case, I want to do a little of both planetary and DSO. So I have my LX-10 telescope, which has an 8″ diameter mirror, meaning it can collect a lot of light, and it has a tracker so I can point a camera at one point in the sky as long as I want. However, unless you perfectly align the scope with true celestial north, the scope will still drift a bit over the night. This is because it is an open control system. You just point it at a star, turn it on and hope you aligned it well when you started. The best images are taken with closed-loop control systems. That is, they continuously look to see if it is drifting off target, then takes actions to move back on target when needed. This guy has my telescope and has taken some amazing pictures of planets, sunspots, and DSOs. Some are mindlbowingly good!  To be fair, he’s using some reducer lenses like this one to change his F-stop to make it much quicker (for example F/3.75 and F/4.6 in some images), oh and he’s using a 4x Powermate lens  a lot which costs as much as I spent on my entire telescope… But what is great about his site is that he tells all the settings he used for the images. This is similar to Reddit’s astrophotography subreddit.

My scope is what they call “slow,” “long,” or “dark.” This refers to the F-stop number. This is also called the focal ratio or relative aperture. It is a ratio of the len’s focal length and the diameter of the scope. THe focal length of my telescope is 2000mm. And the aperture is 8″ or 203mm. The F-stop of this would be about 2000mm / 200mm = 10. So this means my scope is a F/10 lens. The higher the f-stop number is, the darker the image will be (all other things being equal) when compared to a lens with a smaller f-stop number. For example an F/4 is considered a pretty “fast” telescope. My F/10 number basically means that to take a nice bright picture of Jupiter for instance, I need to play with the “sensitivity” or ISO number of the camera sensor (used to be film) as well as the duration I leave the shutter open on the camera.

You might say, “Well I can just crank up the sensitivity then. Higher sensitivity will make the image come out brighter, right?” The answer is yes and no. You can raise the sensitivity, but then a lot of other things (such as heat) can trigger a pixel to register a value in a digital camera. This will increase the noise in the image, making it staticy.

You might then think “Ok, the other option is to just open the shutter for a long time, exposing the camera sensor to more light over a longer time period.” yeah… not really. This can work as well, however you will increase the overall light pollution in your images and worse, you risk blurring the image. Since the Earth keeps on spinning, objects in a fixed telescope’s field of view move. Without tracking perfectly, long exposures will be blurred.

Even if you can fix all that, there’s blurring you simply cannot fix. This is due to heat inversion in the air column between you and the object you are viewing. The Hubble space telescope was designed to fix this problem… by simply being above all the air on earth orbiting in a pretty high orbital plane (at the farthest reach that the space shuttles could fly). Air at different temperatures has different densities. This acts like a prism to bend the shape of a beam of light. Look at a straw or pencil in a glass of water. Notice how it looks like it’s broken in half at the interface of the water and the air? That’s an example of the different densities acting like a prism. Since air is, well, air… it is gaseous and mixes and moves around a lot. It is in constant motion (unlike the water in your glass compared to the air sitting on top of it.) Hot air rises and cool air falls, making all sorts of weird prism effects in our viewfinder. In the column of air between you and the top of the atmosphere where Hubble is, there’s also a lot of dust. The dust as well as the temperature inversions is what makes starts look like they are twinkling.

Side note: Planets don’t twinkle in the sky when viewed by eye. This is because a star is so far away, you are only seeing it as a point light. This makes it easy for dust or temperature inversion to affect your view of it. But planets are much closer, and their light is spread slightly wider across the retina in your eye. This means there much less of a chance that a mote of dust will block it, or temperature inversion will guide the light too far from your retina.

So how do you fix the problem of having a dark image from the telescope without getting errors from too high of a sensitivity setting or blurring from too long an exposure and temperature inversions? You can thank Woz for the home computer! Using a laptop, I’m going to connect a closed-loop control system to my computer to track the objects I want to image very closely, reducing blur of long exposure images. I’m also going to take multiple images of the same object, then do a process called “stacking” where a computer algorithm will take the sharpest views of different parts of the planet, for instance, and stitch them together into a composite image that is overall much sharper. Then I’ll be able to do some image processing on the composite image to get some great results. Stay tuned for more posts on this theme!

Xcarve and Fusion 360 CAD/CAM

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xcarve2   It has been bout a year now since I last had a chance to play with my CNC machine, so I figured I’d give an update on the progress so far and what I’ve learned.

Hardware:

Firstly, I got the Dewalt 611 router and router mount. This is a huge upgrade from the no-name dremel knock-off I had. After test cutting just once with the old router, the brushes were shot. I sprung for a real tool instead of a toy.  As a bonus, it makes the machine look nicer as well.  In order to fit 1/8″ shank bits, I had to get a 1/8″ collet for the DW611. This wasn’t terribly expensive if you compare the cost to replacing all of my router bits with 1/4″ bits.  I got all of this late summer 2015 and literally had only enough time to attach it all to my machine before life got crazy busy. I never even had a chance to test it until now.

I also recently got the Suck-It from kickstarter. This goes a LONG way into keeping dust to a minimum. A warning, however, I tightened the screw too tightly on my Suck-it and accidentally drove the bottom edge into one of my makerslide rails since I don’t have endstop switches. This  promptly shattered the Suck-it acrylic into incredibly sharp shards.  While you can purchase additional parts from the Suck-it website, I opted to make my own replacements from wood, which is a bit more forgiving.This also gave me a great chance to finally learn some CAD software.

While testing, I finally realized that the ACME screw inventables sent me last year as part of my upgrade kit is warped. It binds in a couple of places when I try to move the Z-axis up all the way.  I thought that I  could fix this by simply getting a stronger motor, so I ordered the NEMA 17 from inventables. This was stronger, but still couldn’t overcome the bend in the screw. The bend also causes the very tip of my bits to wobble ever so slightly. It is almost imperceptible, but makes a big difference when I mill multiple passes of the same shape or try to do PCBs.I contacted Inventables and Mo in customer service worked with me over a couple of weeks to get my Z working great. It turns out that Since I upgraded from Shapeoko1—> Shapeoko2–> Xcarve, I had the wrong spacers on my router mount.  The ones I had were about 2mm too short. Mo helped me get the right length spacers (9.5mm long) and bolts(35mm). My short spacers and bolts were causing the ACME screw to bend back towards the gantry at a significant angle. When installing the new spacers, be sure not to use washers as this will also change the angle of the ACME screw.  With the new spacers installed I can get all but 7mm of my Z axis working perfectly smoothly.  Thanks Mo!

I also bought this clear tube for my suck-it vacuum mount. This was about 63mm in diameter, so I had to same the interior of the acrylic suck-it plate to fit the tube. I also cut it to about 9 or 10 inches in length. At this height, the tube is about the height of the router itself. This gives me more visibility to see what is going on with the business end of my router rather than the black coupling tube that the suck-it came with.

CAD/CAM:

I wanted to learn a real CAD package since my FabAcademy training in 2014.  I only had experience with Sketchup which, while very good for beginners, it doesn’t really follow the same kind of workflow as professional engineering CAD/CAM packages. I wanted to learn something along those lines. I had played with Creo, Solidworks, Antimony, and was looking into Rhino/Grasshopper when I saw Fusion 360. Autodesk has been going crazy buying and building awesome CAD/CAM tools for the hobby market as well as for industry.  Fusion 360 is a complete engineering tool that can start with a 2D sketch or a 3D body and allow a user to create objects, render them realistically, stress test them with finite state analysis, and export 3D print or CNC toolpaths.  Oh, and did I mention that it is free and has a very active community online as well?  So I downloaded it and gave it a try. I am quite pleased with it in all respects!

Having no formal training, I opted to take some free online courses from Udemy.com. Check out my other posts concerning that. Of course, as with anything, beginning is the toughest part. It took me a couple of days to get the hang of the Fusion 360 workflow, but with all the great tutorials and videos online, it is easy to find answers to your questions. If not, you can post to Autodesk’s forum for help.

Moving on, I played with Fusion 360 starting with the 3D sculpt method at first to get some awesome organic shapes, then moved to learning the 2D sketch workflow. I measured my machine and aluminum rails of the Suck-it. I made quite a few mistakes along the way, and had to start over several times, but I finally figured out how to get what I wanted  out of the software. It is still a bit buggy from time to time and crashed a few times when I tried to do certain things, but I think it was partially due to a bad design.  I watched a couple videos and fixed my design and was able to create the toolpaths without further issue.

Fusion 360 can do 2D and 3D milling jobs with ease. There are a lot of options, but videos mentioned in my previous post cover most of what you need to know. I’m running a smoothieBoard on my machine and Fusion 360 has a CAM processor script designed for my board, so I simply select “Smoothie” from the dropdown menu when I go to export my design and I’m good to go.

Sending the job to the machine:

The main software people are using to send jobs to the smoothieboard is Pronterface, which is typically used for 3D printing. It’s all Gcode, so it doesn’t really matter, but for some reason, I didn’t like using a 3D printing software for CNC. Last year I tried using Universal G-code Sender with the smoothie and even played with coding in this ability, but life got too busy for me to continue, so I stuck with using Pronterface. What I like about Pronterface is the ability to create custom buttons. For example, I made buttons to zero the axes, reset the smoothieBoard after I hit the killswitch, etc.  These prevent me from having to manually type the Gcode in the command window. I can even send smoothie console commands using these buttons.

pronterface buttons

You can also run the smoothieboard over ethernet. You can do so through pronterface or by using one of several web interfaces (meaning you can control your 3dprinter or CNC machines over the web). This is useful in my FabLab at work where we have a lot of 3D printers running on a 3D print server. You can run the smoothieboard on this as well. It can host several different web interfaces which I hope to go into later, but one of them is basically a webpage that looks just like pronterface.

I feel like I finally have a good workflow here. You can see my results here. I made replacements of the broken acrylic pieces of my suck-it dust boot that I made in Fusion 360. I used scrap wood, so it had quite a few drill holes going all the way through it already. I also did conventional only, and no climb milling which would have given a nicer finish.  I used a 2-flute straight 1/8″ but as well, no spiral which would have also given me a cleaner result.  Due to my learning curve, I did have to do some manual touch ups to the dimensions of the pocket which explains the nastiness in there you see. suckit

 

 

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