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Cutting foam sheets... with a needle!

Jason, thanks for making the video. It has been several months since I used my mpcnc, and all the little tricks are easy to forget. I printed all the new parts and have the machine almost back together. I considered making it bigger since HD is selling fan-fold again, but I think the extra 18" would be unwieldy. I made a basic needle cutter using the new mount that I will post after I verify it works.
 

jhitesma

Some guy in the desert
Mentor
Glad to hear it helps moebeast! I haven't seen any fan-fold at my HD yet...but I wouldn't go any larger...even at 36"x48" I feel my machine is too big and have considered making it a bit smaller. I really miss being able to do more milling on it but at this size it just doesn't have the stiffness. Really thinking that I need to bite the bullet and dig in on printing the latest design in PLA and order up some stainless tubes. Maybe then I'll be able to get better cuts with the router again. Though I also suspect that the hicwic mount is a big part of the issues I have with the router - it was enough to hold my dremel (just barely) but the extra weight of the 660 is just too much for it and it's not stiff enough. So moving to the new style mount is really appealing to me.

I got tied up with family stuff this weekend and wasn't able to find time to sit down and edit the start to finish cutting video - just going to take some time since I have to actually watch through the whole thing and find the spots between me talking to speed up. But knowing me I'll never get around to that so figured I may as well just put it up for anyone who has the tolerance to watch it uncut:


I'd suggest muting it once the needle starts...but I do talk quite a bit while it's running. Not that I add much useful information doing so :D
 
How do you set the default document size in Inkscape? From what I've found is that you open Inkscape, configure your settings and save it as default.svg to a templates folder. Which one? There seems to be a conflict.

While my initial document upon starting Inkscape is the size I want (20x30), but when I open a PDF, it does it in a new window and not the default size that I've set.
 

jhitesma

Some guy in the desert
Mentor
How do you set the default document size in Inkscape? From what I've found is that you open Inkscape, configure your settings and save it as default.svg to a templates folder. Which one? There seems to be a conflict.

While my initial document upon starting Inkscape is the size I want (20x30), but when I open a PDF, it does it in a new window and not the default size that I've set.
Sounds like you're setting the default right - the exact location of the default folder changes from mac to pc to linux which is why I didn't want to get into it in my video.

I think what you're doing wrong is opening the PDF instead of importing it. Opening it opens it as sized as it is in it's own document. Importing it lets you load one page of it into the current document which is what I do.
 
Finally got my mpcnc put back together with the new parts. The X-Y is much stiffer and therefore stays square better. Here is my new simple cutter mount.

Needle cutter.jpg

I will try to load it to Thingiverse tomorrow, but FFE17 preps take priority.
 
Sounds like you're setting the default right - the exact location of the default folder changes from mac to pc to linux which is why I didn't want to get into it in my video.

I think what you're doing wrong is opening the PDF instead of importing it. Opening it opens it as sized as it is in it's own document. Importing it lets you load one page of it into the current document which is what I do.
Thank you, that makes perfect sense. Always good to have someone point out the obvious when you're in tunnel vision.
 

jhitesma

Some guy in the desert
Mentor
Well twice in the past week or two I've been burned by a shortcut I took. I never extended my Z stepper wires, which wasn't a huge deal until I added the shower curtain hangers as cable management to solve the problem of running the needle over my Z wires. The shower hooks have worked wonderful for cable management, the wires stay up off my work surface perfectly now.

However that has resulted in less effective length on those wires. If you watched my recent cutting video you probably noticed (and I mentioned) the way that this means my RAMPS board now gets dragged around while cutting. Not good.

And twice now I've ruined a sheet of foam because the RAMPS getting dragged around caused one of my stepper connections to get pulled loose (The Y both times oddly enough.) The first time it happened in the first 5 minutes of the cut and was just a sheet of DTFB - no big loss.

But last night it happened to me about 70% of the way into cutting a sheet of FT water resistant foam :mad: I only have a dozen sheets of that stuff and the cub with floats is going to take 4 of them...I can't waste it! I still want to have enough to make an airboat of some kind...(a sea duck would be great too but I don't think I've got enough foam to pull that off.)

So finally bit the bullet and extended the Z stepper wires Used the same basic method I did for the other steppers - took some ethernet cable and soldered the pairs together to make 4 higher current conductors out of 8 lower current conductors. Then added a set of pins on one end and a socket on the other so it's a nice extension cord. Zip tied it into the wiring harness...and all works great now. The RAMPS stays put and the machine can move full coverage over the entire work surface without it's wires touching the worksurface or risking getting itself tangled in them!

However, my needle is not super happy now either. I was afraid that the bearings may be going, but it seems it's actually just the mount. I really don't like these bayonet style mounts, think I may order a different motor with a more solid mount to replace it. The two set screws were still tight but the motor was loose in its mount. Took it out and could see that the set screws have worn divots into the aluminum shaft, turned it about 15 degrees to get fresh metal under the set screws and it's much quieter and more stable now. But it's only a matter of time before it wears again.

I tried running it while holding it by the shaft with just the crank on it..and there's a decent amount of imbalance. I could try adding some material to balance it...but with the needle on that will change. I don't think there's really a great way to eliminate all of the vibration on this simple setup. I may finally bite the bullet and try the counterweight setup...Just need to find a suitable bearing for the needle and come up with a way to weight things since my scale doesn't go grains or anything else that accurate.
 
Finally got my mpcnc put back together with the new parts. The X-Y is much stiffer and therefore stays square better. Here is my new simple cutter mount.

View attachment 90624

I will try to load it to Thingiverse tomorrow, but FFE17 preps take priority.
After seeing your setup in person at Flite Fest East 2017 on Saturday, I am so very impressed with the upgraded parts that I now know that I must update my MPCNC soon. Downloading the print files is underway. Thank you for answering my questions and sharing your talent with the Flite Test community.
 
I'm baack!

All,

I apologize for my late response to all these latest posts... I've been out of pocket for the past week or so. My fishing/golfing buddy and I had opportunity to spend five days at the lake for fishing and golf and, to top it all, I got a pretty good sun-burn and have been taking it easy the past couple of days... "recuperating".

Anyway, thanks Jason for the videos. I found the FT file preparation one especially interesting... I'd never really fully processed a FT plan, with all the new line types/styles, so was interested to see how you handled it. I'd bogged down a bit, when I gave it a cursory try, trying to delete all the line hatching and extraneous lines and it never occurred to me to simply leave them and only assign cut-lines to the ones that are needed. I've also not really used Estlcam for much... I haven't fired up my Windows machine in several months. I really wish there was a way to run Estlcam through Wine so I could stay on the Linux side of things... I guess I should probably check in to see what progress has been made, if any, on that front.

I must admit I was a bit concerned over your rather ragged-sounding cutter on the second video. I, too, was guessing it was due to bad bearings and was apprehensive as to whether it was going to hold up for the duration of the cut. But the motor needs to be securely held as well so glad that you found the source of the ragged-ness. I usually remove the grub-screws on that style mount and replace them with short 3mm machine screws... those tiny Allen sockets/wrenches strip out far too easily and don't allow me to tighten the motor shaft properly. I haven't had any problems at all when using "real" machine screws to secure the motor with that style mount.

Also, I really think moving to a flywheel version of the cutter would be a good move for you. With all the "straight-line" needle-motion work we did a few months ago it appears most of us (Jaochim, GreminRC, moebeast, me, etc.) are now using the flywheel and bearing. The bent crank-pin version really won't hold up for too many sheets and, as you've seen, though balancing is not absolutely essential for occasional use... that version could probably stand balancing as well. Finding a suitable bearing for the flywheel shouldn't be a problem for you since you're bound to have a few junker motors lying around. And those little electronic scales -- though nice, not terribly expensive, and very helpful for balancing the flywheel -- are not absolutely necessary either; i.e. you can get by without it. Use a prop-balancing setup of some kind (parallel "knife"-edges, the sides of a plastic parts tray, etc), add a shaft and all the shaft mounting hardware, then the bearing and its mounting hardware, and, finally, add counter-weight to bring it into balance... just iike a see-saw.

Again, thanks for the videos. I know I'm not the only one how finds them very helpful and informative.

-- David
 
After seeing your setup in person at Flite Fest East 2017 on Saturday, I am so very impressed with the upgraded parts that I now know that I must update my MPCNC soon. Downloading the print files is underway. Thank you for answering my questions and sharing your talent with the Flite Test community.
That's right!!!! Moebeast... you took your MPCNC foam cutter system to FliteFest again??? And offered cutting services to a plethora of interested RC folks??? Goodness, it's been a year already??? I/we would love to hear of your experiences and get a report on how things went.

Without doubt, you've got to be one of the bravest and most prolific needle cutter users out there... and I see you're still using the needle cutter in its most basic configuration! How did it hold up? Were you as busy as last year?

Nice remix on the cutter BTW... thanks for doing it. -- David
 

jhitesma

Some guy in the desert
Mentor
Glad to hear you like the vids David. I did the same thing at first trying to remove all the extra stuff. Then it hit me that I simply didn't have to use all of them to setup cuts - was a major ahha moment. Sponz actually sent me the "raw" dxf files for the pietenpol since they have all the different types of cuts on separate layers and I figured that would make it quicker and easier. It was kind of nice, but really didn't make it that much easier for me. I actually found it somewhat harder to work with since the different types of cuts were harder to tell apart unless I viewed it only one layer at a time (or took the time to color layers differently or something.)

And yeah, I was really worried when making that video because my needle has NEVER sounded THAT bad before. I actually don't have a problem tightening the grub screws as I can tighten them to the point that they squish the motor shaft and start to bind the motor. I've just never had good luck with that style of mount even on planes. They seem to go from too loose and will come apart to too tight and will bind the motor with no "just right" zone for me.

I've actually been changing my workflow the past few days to try and improve things a bit more. When I built my test cub I noticed that things weren't quite 100% square. So I printed a set of these: https://www.thingiverse.com/thing:1755510 to help square the machine before each cut.

Those ALMOST work...on my pre-525 parts they don't quite work on the X axis because the center part hits the left Y roller before the X rollers hit the alignment tools. Would probably work to align to the right...but that would mean doing a lot of moving the machine with the steppers engaged and that's kind of annoying since I run untethered and have to use the LCD to do those moves which I don't really enjoy. I'm kind of tempted to grab an arduino and some buttons and make up a controller I can plug into the RAMPS to send my most commonly used commands without messing with the LCD - will probably do it at some point but lower priority for now.

Anyway - alignment. It turns out my X axis is pretty good. I just added a spacer to the alignment tools to move them out a bit further and my X axis is almost always square. But my Y...not so great. It's always about 1/4"-1/2" off. So that explains a few issues I've had.

But I'm starting to think this WP foam or the cub have it out for me. My DTFB version went just fine - other than one bad cut due to me forgetting to zero the machine between sheets. My own mistake no doubt. But with the WP foam...every other sheet I cut is failing :(

That first failure was totally my fault with the short Z wires. Fixed that. Cut another sheet...no problem. Then went to cut the next sheet...that went ok. Then tried to cut the 3rd sheet...and...ugh:

20170716_102300.jpg


I'm not 100% sure what happened here but I have a theory. I think it's a bug in Marlin where the command to reset the machine position doesn't always work properly. I've heard reports of this and been told it's why people like to reset the RAMPS instead of giving a command to set zero. But with the alignment stuff I need to keep the steppers powered. The way I do the alignment is:

1) Pull the machine against the "stops"
2) Use the Prepare-Move Axis to power up an axis and position the machine at my workpiece origin
3) Print before the steppers timeout so the machine stays square

So doing a reset on the RAPS in #2 would cause the steppers to power down and loose lock/square so isn't a viable option.

But it seems doing that zero command more than once without powering down can often result in Marlin's coordinate system getting confused. (at least in the old RC6 version I'm still running on this machine.. I should update it this week but want to get this cub cut before I go messing with it that much.)

So what happened there? Well. I first started the cut but had forgot to reset Marlin's coordinates to 0 on XYZ before doing #3...so it immediately started moving off the workpiece and I stopped it before it even touched the foam. I then did the square/home setup procedure again making sure to zero the axes this time. And the cutting started ok.

First two cuts were the score cuts in the lower left piece. Just fine. Then it went to cut the piece above that...and seemed to do fine...but...cut it way too short. I figured it must have been a mistake I made in the gcode and let it keep cutting. But then it went to cut the bevel in the horizontal stab to the right of that...and again they came out way short? Now I was curious what was going on and let it keep cutting...and for a bit it did just fine. Seemed like as long as it stayed below a certain Y coordinate all was fine.

Until it go over on the long horizontal cuts on the wing...when it did the same thing in X. If it went past a certain point it just suddenly decided it was done. But I still let it keep going out of curiosity. Then it got to stuff above the Y coordinates it didn't like...and it just went crazy doing those triangles. I let it keep going thinking it may get back on track after the cut it was doing (should have been the outside of the wing) but it just kept doing goofier and goofier triangles. Finally I decided it really was a lost cause and stopped it.

All I can figure is that it was the resetting of the zero point that got the machine confused. I called it a night at that point. Well...almost. I saw Ryan's video of etching aluminum and had to swap to my laser and give that a try. Grabbed and SVG of the rotor riot logo and setup a 50mm/min burn on the back of my wattmeter. Nothing :( Must be some TOUGH anodizing on there! Put my trusty accucell6 charger under there instead, figured it's black anodizing may be easier to etch. And...got results but not nearly as nice as what Ryan got...I really need to swap to a 3 element lens, I think the larger spot of the G2 is really hurting me on this kind of stuff:

20170716_110532.jpg

(BTW hard to tell scale but the whole logo is less than 1" across)


So...today...gave sheet 3 of the cub another go. Didn't have the odd problems from last night...but something else went horribly wrong:

20170716_102137.jpg

20170716_102132.jpg

The cut started in the lower left and went clockwise around the part. I know exactly what happened...but before I reveal it I'm curious if anyone can guess. Big hint - it had nothing to do with the gcode, or MPCNC.
 

jhitesma

Some guy in the desert
Mentor
So just fixed the problem that caused the last issue...and now...

20170716_113006.jpg

I think someone is trying to tell me I should do something else this weekend :p
 
Took a little break and figured I should make that video I said I would like a month ago about how I work with STL's in onshape:

Wow! You made that look easy, Jason. I recognize the needle cutter body is a fairly simple part but that went far faster than I thought possible. I had learned enough to "use" points in the mesh for reference but not gotten the hang of extruding "in place" and up to the next vertex, as you show. I definitely need to get serious about using Onshape more... and this video is a great encouragement. Thanks! -- David
 

jhitesma

Some guy in the desert
Mentor
Glad to hear you liked the video. Once you get the hang of it it really does go quick. I've used microsofts 3Dbuilder that comes free with W10 to edit stl's directly - and it's actually pretty good and easy to use. I've also played with tinkercad and fusion360's mesh editing. But for most simple parts I can re-create and modify in onshape quicker. And once re-created in onshape it's a lot easier to do major modifications and add in things like fillets and chamfers. Plus a lot of published STL's are remarkably poor quality, even my own needle cutter body that I used for that demo you can see I didn't render the holes with many points so they show up as clunky polygons instead of circles. But once re-drawn in onshape and then re-exported I get a much cleaner (though somewhat larger) mesh with nicer circles.

Also, forgot to mention it yesterday...but...I also wish I could get estlcam to run in wine. I've seen reports in a few forums of people who say they managed to get it to work...but I've yet to have any luck. Wine is just such deep black magic to me I get frustrated with it quick when it doesn't "just work". Would love to ditch windows on the machine in my shop but I'm totally hooked on estlcam. I also started using version 10 finally over the weekend and have been pretty happy with it. Though it turns out that the two "new" features I found in it were actually there in 9 and I just never noticed them :black_eyed: One being that you can define your work area so you don't have to count grid squares to tell if something will fit or not - and the other being that in preview mode you can click on an operation to see just it in the preview. Defining a work area makes it so much easier to set things up and position the cuts, and being able to view individual operations in preview makes it much easier to follow along with how the cut will go.

Started working on my new cutter but haven't got very far yet:
Screen Shot 2017-07-17 at 9.11.19 AM.png

Still trying to get the hang of working with derived parts in onshape and positioning them - which I need to do so I can get the motor and flywheel accurately positioned in the model to reference where the needle will go. But basically I made it a bit taller again, but also shorter since this motor I'm using has a very short shaft. I may also modify the flywheel so it bolts to the motor with the holes the motor has for attaching a prop shaft since the shaft is so short I'm not sure the "butterfly" will have a sufficient grip on it.

Also plan on adding some supports to mount more bearings to guide the needle (since as David suspected I have plenty of dead motors with good bearings I can extract.) I don't think I'll go as crazy as Verris did with his bearing guides...but I like the idea of bearings more than sideboards.

The benefits of going taller seem fairly well established at this point, but making the "tongue" shorter I'm hoping will help increase accuracy as well since it will make for a shorter lever arm. I notice on my current setup that when it does vibrate that long body really makes it noticeable.

Also, finally snapped a shot of my improved cable management:
20170716_165104.jpg

The shower hangers really work well. I spaced them so that when I push them together the wires between them are about 1/2" above the worksurface. Zip tying the wires to the hangers was key to making this work. So nice not having to worry about my wires anymore, and the hangers were <$1 with enough to do 3-4 machines :D
 

jhitesma

Some guy in the desert
Mentor
You know what's way better than thumbs up on a video or even positive comments - seeing someone actually put the info in a video into practice :D

Love it David!

I put a bit more work into my new version over lunch:

Screen Shot 2017-07-17 at 2.15.16 PM.png

Already decided I can make it shorter still, more space than I want between the needle hole and the front edge now that I know where the hole needs to go. Also probably not going to do the side braces like that - need to add in bearing/sideboard supports first and see what I come up with...may try to use the support as the braces.

But things will probably have to change some more since right now there's no way I'd be able to put a nut on the pivot bearing screw as it would interfere with the motor. So trying to rethink the flywheel design a bit more - kind of tricky to keep it printable with what I want to do since I need recesses for the mounting screws on front (so they won't interfere wtih the needle/bearing) and one on the rear so it will fit over the lump on front of the motor and mate up properly. But...got some ideas just need to play around a bit more. Will probably shift the flywheel out another 5-8mm though so will have to move the guide mount as well.

Idea is coming together though.....