There have been some troubles with the CNC not following Gcode paths exactly and rounding corners.
In this first picture of the Mach4 screen you can see the green lines which are the path the CNC should follow, and the white lines which are the path the CNC actually followed. (ignore the blue lines)
The problem is the CNC is rounding over the outer corners. This is a result of the CNC trying to move faster than it can manage. The max speed of our CNC is 200 inches per minute. In the above picture it is trying to cut at 150 IPM and can not handle that speed on the corners so it rounds them, which can ruin the piece. Even though the CNC can go faster in a straight line it can’t change directions that fast.
The solution is to use a slower feed rate. But this can greatly increase cut times and other issues such as tool dulling and excess heat.
Fusion360 has a solution called “Feed Optimization”. What it will do is reduce the speed in just the corners to 25% of the feed rate. In this example it reduces the corner feed speed to 37.5 IPM.
In this next picture you can see the white line of the actual cut path looks identical to the green Gcode path with Feed Optimization turned on.
The Feed Optimization setting is found on the 4th tab (labelled Passes) of the Operations Dialog when you are in the Manufacture workspace.
In the bottom of this picture you can see the checkbox to turn it on. The defaults should be fine and will reduce your corner speeds to 25%. This only adds a small amount of extra time to the cut.
This project was set to 100 inches per minute so Feed Optimization reduced the corner speed to 25 IPM.
Mouse over each setting for an explanation of what it controls if you would like to fine tune even more from the defaults.
The Art Printing Photobooth aka The Edgy Printacular
At the Bay Area Maker Faire 2018, a team of Ace Monster Toys members created a photobooth where participants could take selfies which were then transformed into line art versions and printed, all initiated by pressing one ‘too-big-to-believe’ red button.
Back in March, AMT folks began prepping for Maker Faire 2018, and had an idea: what if you made a machine that could take a selfie and then generate a line art version of the said selfie, that could then be printed out for participants like you and me?! Thus, the Art Printing Photobooth was born! This project was based on the Edgy Cam project by Ray Alderman. AMT created a special slack channel just for Bay Area Maker Faire 2018 #maker-faire-2018. Then members set about figuring out how exactly to make this art-generating-automaton and Rachel (Crafty) campaigned for having a ‘too-big-to-believe’ push button. They would need many maker skills: CNC routing and file design, woodworking, electronics wiring, and someone to art it all up on the physical piece itself. Bob (Damp Rabbit) quickly volunteered to take on the design and CNC cutting, while Ray (whamodyne) started to chip away at the code that would be used to convert photos to line art.
Then the trouble began. By mid-April, our intrepid troubleshooters were running into all sorts of snags – so much so that the original code needed to be thrown out and rewritten from the ground up! To add additional difficulty (and awesomeness!) the team decided to use a Print on Demand(POD) service to allow participants to have their generated art uploaded and available to be printed on mugs, t-shirts, posters, etc. Soon after, Ray wrote up a new digispark code for the big-red-button to actuate the script and convert and print the line art (code given below) using Python3, opencv library, printer library from https://github.com/python-escpos/python-escpos.
Meanwhile, Crafty Rachel and Bernard were configuring the TV mount that would be the selfie-display of the photobooth and Damp Rabbit was busy CNCing and painting up a storm to create the beautiful finished product – The Edgy Printacular! The EP was a hit and won three blue ribbons at Maker Faire 2018. Another happy ending that speaks to what a few creative makers can do when they put their heads together in a place with all the right equipment, Ace Monster Toys <3
This month AMT turns 8 years old and we are growing! We have rented an additional 1200sqft suite in the building. We have a Work Party Weekend planned June 1-3 to upgrade and reconfigure all of AMT. All the key areas at AMT are getting an upgrade :
CoWorking and Classroom are moving in to the new suite. Rad wifi, chill space away from the big machines, and core office amenities are planned for CoWorking. The new Classroom will be reconfigurable and have double the capacity.
Textiles is moving upstairs into the light. The room will now be a clean fabrication hub with Electronics and 3D Printing both expanding into the space made available. Photo printing may or may not stay upstairs — plans are still forming up.
Metal working, bike parking, and new storage including the old lockers will be moving into the old classroom. But before they move in the room is getting a face lift by returning to the cement floors and the walls will get a new coat of paint.
The CNC room and workshop will then be reconfigured to take advantage of the space Metal vacated. We aren’t sure what that is going to look like beyond more workspace and possibly affordable storage for larger short term projects.
What expansion means to membership
The other thing that happened in May is after 8 years our rent finally went up. It is still affordable enough that we get to expand. Expansion also means increasing membership volume to cover the new rents and to take advantage of all the upgrades. We are looking to add another 30 members by winter. Our total capacity before we hit the cap will be 200 members. We feel that offering more classes and the best bargain in co-working will allow us to do this. Please help get the word out!
The New Suite in the Raw
December 7th we started a new meet up for Fusion 360.
The group brainstormed on tool-path creation and resolved to develop an understanding of multi-stage CAM processes that can be used on the various mills, routers and cutters at AMT.
We had a terrific time at the hangout. Matt our 3D Printing steward and five others attended. All were quite experienced Fusion 360 users, in contrast to most of the previous Fusion meetings which tend to be weighted toward newcomers. I think everyone present was a AMT member.
We opted to pass the projector cord around and look at all of our projects as a group. Another approach might be to break off into twos or threes; maybe we’ll try it that way next time.
- Bob showed us some renderings of cool guitar designs he’s been working on.
- Rachel (aka Dr. Shiney) showed us a guitar body a client of hers needed cut; we struggled together for a while trying to figure out Fusion’s 3D tool-path generation. I think something like this would be a great thing to get Taylor’s input on: A multi-stage CAM process including facing, profiling, and 3D carving.
- Emory gave us a quick look at his own CAM project, which involved re-mounting the workpiece to cut both sides: tricky stuff.
- Chelsea showed us her silicone casting project. She’s come up with a pretty elaborate flask and core to be 3D printed. We’re all anxious to see the results, but those are going to be some long prints! I recommended smaller test pieces to get sizes and clearances right and generally experiment with the process before committing to the final design.
- Matt brought along a bunch of finished projects you’ve probably seen before if you’re a regular at our Thursday meetings; nothing new, but all done in Fusion 360.
The 3D View is “Just for Show”
With most editing tools, the document you’re editing is comprised of the things displayed right in front of you. With a word processor, it’s the words; a spreadsheet, it’s the numbers and formulae; an image editor, it’s the pixels. This is also true of mesh-centric 3D modelers like Blender or SketchUp. When you move edges or faces, bore holes, or perform any other operation, you’re modifying the Mesh: a collection of points, edges and faces in Cartesian 3D space. The mesh itself is the document.
But with Fusion 360, the document is composed of the sequence of things in the history timeline (shown at the bottom of the screen). The 3D view in the center of the screen is the result of executing that sequence of operations. The things in the Browser (the hierarchical object list on the left), are also a product of the history timeline sequence. Think of the timeline as the program code that produces your design. As far as editing is concerned, the Browser and 3D view are just for show!
I’ve always thought that ‘history timeline’ was a misleading name. ‘Operation Sequence’ might be better. In real life we can’t yet travel back in time, so the term ‘history’ suggests that it’s merely an informational record of what already happened. Not so! Items in Fusion 360’s history timeline can be rearranged and edited. Learning how to do so is key to getting the most out of the tool.
To get some practice with the timeline, let’s walk though a (somewhat contrived) example: The corner bracket pictured above.
First create a sketch describing the basic cross section profile.
Then extrude with the push-pull tool to create a solid body.
Now create a sketch on one of the sides to describe mounting hole profiles.
And extrude to bore the holes.
Now, we’ll use some of the modify tools. First, add a large fillet to strengthen the bracket.
Add a chamfer to counter-sink the holes.
A fillet to round over the top corner.
Add another for the other top corner.
Add one more small fillet to break the sharp edges.
Well, it clearly needs some work, but let’s review the timeline to see what we’ve done so far. First, make the sketches visible for clarity’s sake (find the sketches in The browser and click the light bulbs). Then click the home and fit buttons to get this view:
Right click the first item in the history (a sketch) and select Roll history marker here. The body will vanish from the 3D view, and the Browser will display just one object; the sketch. Don’t panic; you haven’t deleted anything! Note that the items in the history are still there; they’re just grayed-out.
You’ve moved the history marker to display the model as it was defined at this point. Remember: the history timeline is your document; the 3D view and Browser are just for show.
Click the next step icon to advance the history marker. With each click, the display will update to reflect another operation. When you reach the end the 3D view will reflect the model as defined so far.
We can give the sketches and features more meaningful names. This is a good practice in any case, but is especially useful when getting familar with the history timeline.
Right click each item in the timeline; click rename and enter the following names:
corner roundover 2
break sharp edges
To see the names you’ve just entered, hover the mouse over each item in the timeline. The names for sketches also appear in the Browser.
While labeling our history items (sketches and features), I remembered that we rounded the outer corners with two seperate features. It makes more sense to use a single feature, since both of these fillets should always be the same size. That way, if we ever want to change the size we need only edit one feature.
Right click the corner roundover 2 feature and delete it. Fusion will warn that the feature is referenced by other features in the timeline. Click Delete anyway!
Now the break sharp edges round-over feature has a yellow background, indicating that something is amiss. Ignore this for now, we’ll come back to it.
Right click the corner roundover fillet and select edit feature (or just doubleclick the feature’s icon). The fillet dialog will be shown, and the 3D view/browser will reflect the model as it was defined at that point in the history.
The fillet dialog indicates that a single edge has been selected. Hold shift and select the other upper edge. Then release shift and click OK.
Notice that the break sharp edges round-over hasn’t been applied to this new fillet. This is due to the same issue that arose when we deleted the corner roundover 2 feature.
So, let’s have a look. First, right click and choose review warning. This displays more detail about what went wrong. In this case it says: “The edge reference is lost, try editing this feature to reselect the lost edge.”
So, let’s try editing as suggested. Double-click the feature to edit.
Even though the model has the same shape as before, the underlying edges that define the body have changed due to our upstream edit. Notice that it now says two edges were selected (originally there was just one chain of edges). If you press shift these edges will be highlighted. You can clearly see a gap where the redefined fillet is.
Click the ‘X’ next to edges in the dialog box to deselect the edges; then reselect the edge. It will select the entire edge chain again. Once saved, the yellow warning background will disappear. Be sure to address all warning issues in your timeline! If ignored, they’ll just cause trouble later.
When editing something in the history, we often have to review and adjust downstream features like this. This can be very frustrating if you aren’t familiar with the timeline. With a little practice it becomes second nature, and is a worthwhile skill to attain sooner rather than later.
So, let’s finish our bracket. We need holes and round-overs on the other tab, and our break edges fillet needs to go around the entire perimeter.
We’d like the hole pattern to be identical on both tabs of the bracket. We could duplicate the sketch and extrude operations that we used on the first tab, but if we ever changed the pattern (maybe to use more holes), we’d have to edit two sketches instead of one, and we’d have to be careful to keep them identical. By using a mirror operation instead, we can use a single hole definition, making for simpler adjustments later.
First we need a reflecting plane. Choose Construct/Plane at angle and select the bottom edge at the apex of the bracket. Enter an angle of -45. Then right-click the feature in the timeline and rename it reflecting plane.
Now, click Create/Mirror. Set the pattern type to Features, then select our holes extrude feature (in the timeline) and click OK.
Right click the mirror feature and rename it duplicate holes.
Turn the construction plane display off now, just for clarity.
We’d like to countersink these new holes too, but if you double-click to edit the countersinks feature, the new holes do not appear for selection!
That’s because the new holes did not exist at the time we created the countersink object. Note that the countersink feature appears before the mirror feature in the timeline. You might be tempted to simply add another countersink feature, but there’s a better way!
To fix, let’s move the reflecting plane and mirror objects to an earlier point in the timeline. Press shift and select both features. Then drag the features to the left. You’ll find you can’t go further left than our holes feature. Release the mouse button to complete the move.
This illustrates an important concept: Any feature that references another must appear after the dependent feature in the timeline. In this case, the duplicate holes mirror feature refers to the holes extrusion feature, so duplicate holes must appear later. This also applies to sketches that contain projected geometry: The edges being projected must be defined before the sketch.
Now double-click the countersinks chamfer feature to edit it. Since it now happens after the mirror feature, we can add the new holes to the set of ‘edges’ this feature affects. Shift-select the additional holes and click OK.
Let’s fix the corner round-over the same way. Double-click to edit, then shift-select to add the other two edges.
Finally let’s fix the break sharp edges feature again. Double-click to edit it. Click the ‘X’ next to the edges button do deselect all. Then reselect the edge. This time it should select the entire perimeter as originally intended.
Notice that we did all that cleanup without adding much to our history timeline. We removed one feature, then added two and adjusted a few.
The more natural thing might have been to add a new sketch and another extrusion for the extra holes; then apply the fillet and chamfer tools again. Resist this temptation! The model might look the same, but the document will be larger than necessary, will be more difficult to edit later, and will slow Fusion down.
With our concise model, edits are a breeze. Here’s the original plus 3 variants. Each variant was made by editing a single value in a single sketch or feature.
Remember: The history timeline is your document. The rest is just for show!
P.S. The document comparison I made here is oversimplified. Some bitmap editors like Microsoft Paint modify pixels directly, but Photoshop and Gimp documents contain layers and other high-level objects. A Blender document is actually a mixture of a mesh and high-level ‘modifier’ objects, among many other things. In Fusion 360, the ‘sculpt’ workspace offers freeform mesh-based editing much like Blender. Also, Fusion does store faces and bodies in the document that don’t appear as distinct items in the history. I simplified in order to illustrate my paradigm. I lied only to more clearly illuminate the truth.
At AMT you are supposed to stand over your CNC machine as it is doing a job and pay attention. Is it hanging up? Is it breaking itself or the bit? It is on fire? These are all important things to know. However sometimes a job takes…forever. When cutting PCBs the job can take over an hour because I have the bit move so very, very slowly. Faster and the bit shatters into tiny little pieces of carbide all over the room. Not good. I’ve noticed for awhile that inexpensive internet webcams are available, think of it as a BabyCam for non baby owners. Turns out this little $30 wonder does a great job. When setting up the PCB to be cut I can put the camera on it, configure it to talk to my phone over the AMT network and I can be upstairs working on say a soldering job of the last PCB while the next one is being made. Very handy.
I would recommend everyone who has long CNC jobs they need to keep an eye on but don’t always want to stand over the device to try out something like this.
We had a packed house for tonight’s Fusion 360 for CNC hands-on class.
Autodesk evangelist, Taylor Stein, walked us through Fusion 360’s workflow for creating the CNC setup and cutting paths. Then we adjourned to the big CNC machine and our own big-CNC steward, James, ran the job we’d just set up. There’s nothing quite so satisfying as seeing an idea become a physical thing.
The project was a fun beer caddy Taylor came up with. James and Taylor met earlier to test out the design; then did the final version with higher-quality material. A big thanks to James for making this happen. Contact James on Slack if you’d like to be certified on the big CNC machine.
We’re finding that folks really prefer this follow-along format. In earlier sessions we’ve used a question-and-answer approach in which Taylor demonstrates the solution while we all watch. While that’s often useful, we seem to retain a lot more when we actually press the buttons and drag the mouse with our own fingers.
So, next time we’ll repeat the hands-on Fusion 360 introductory class. This is an introduction to the modeling workspace, intended for first-time users. Bring your laptop with Fusion 360 already installed.
Click below to RSVP. The follow-along format slows things down a bit, so we have to limit attendance to a reasonable number; twenty is about all we have room for. If you want to come, sign up quickly; this is sure to be a popular class. If you find you can’t make it, please cancel so someone else can attend.
We’re always thinking about how we can improve these classes. If there’s a particular technique or feature you’d like to know more about, please let us know. Slack is the best way to make suggestions.
A general overview of a recent project to make a set of CNC cut and engraved instrumentation panels for use on sailboats.
The gcode emitted by Fusion 360 using the default settings does not work on our big CNC. Rama figured out that manually editing the gcode and removing the first six lines gets around the issue.
I was curious about this and decided to investigate. I reverse-engineered the codes in the preamble, but all seemed to be perfectly valid Mach 3 g-code. Finally, I found the culprit: G28.
It turns out that there’s a simple solution: Click post process to create the gcode. Then open the Properties pane and un-check useG28. This option also controls some related codes at the end of the file.
I do not recommend deleting the entire six-line preamble! It sets up various values in Mach 3’s brain, and omitting them may be give unexpected results. It sets units to Metric or Imperial, for example. If omitted, your job might be unexpectedly scaled to a weird size.
That’s all you really need to know! Read on if you’re interested in the details.
The issue is covered in this article:
Briefly, G28 is used to return the cutter-head to the home position. If your CNC machine has end-stop switches, Mach 3 can be configured to move to the physical limits of its travel, which is often a convenient parking place for the cutter-head at the end of the job. It also resets Mach 3’s zero position in case you have some kind of permanent workpiece mounting arrangement that always positions the workpiece in the same place.
We don’t use the big CNC this way. Instead, we mount workpieces in a variety of ways and manually set the zero position before each the job. The article above makes a case for implementing G28, but I don’t think it’s applicable for us.