- May 9, 2016 at 9:38 am #11941
I heard about the MPCNC a few months ago…sounded interesting but I didn’t feel like tying up my 3D printer long enough to print one right away and didn’t have the money to buy pre-printed parts. So kind of put it on my list of “Things that would be nice to do at some point” and forgot about. For all of maybe a week. Then I found a posting on the Flite Test forms about a needle cutter for cutting dollar tree foam and the guy who had designed it was a huge fan of MPCNC and had built several.
My 3D printer was finally tuned in where I was extremely happy with the print quality I was achieving and I had caught up on most of the prints I wanted to do. So digging in on the MPCNC sounded like fun. I figured I could slowly buy up mechanical parts while I took my time printing the printed parts.
So back in February I started printing parts. My plan was to build a 36″ x 48″ machine so I could also build the foam cutter and cut full 20″ x 30″ sheets of foam board with it. I understimated just how big that would be. But by March I had all my parts printed and had bought up all the hardware and electronics so was able to test assemble things:
The problem was once I had it together I realized just how big it really was! I have no room in my house for this beast. And I live in one of the hottest habitable parts of the country (Yuma, AZ) so feared that if I kept it in my shed or detached office the summer heat would deform the PLA since there’s no A/C out there and we regularly see weeks at a time of 110F+ in the shade temps – so inside the shed and office it gets even hotter. I also had a problem in that the black PLA I had used was utter junk (I ordered hatchbox from Amazon but was sent esun and it was horribly brittle) things printed in it were breaking – even just sitting on my desk with no stresses they’d develop cracks and break in half 🙁
So, I dug in on re-printing everything in PETG instead. I also decided to first assemble it as a smaller “desktop” 24″ x 24″ build that would just barely fit on my dining room table where I could more easily work on it and learn the basics.
On the PETG parts I went with 4 perimeters to help make up for the PETG not being quite as stiff as PLA, which ended up sucking down the filament faster than I anticipated causing me to run out sooner than expected and introducing more delays. But I took advantage of the sale MakerGeeks was running (2 rolls of any filament shipped for $33 – catch was they pick the colors) and was able to keep going. The Dark Blue and Gunmetal grey PETG I used were from Atomic – great stuff but pricey, The turquoise, and black (Bomber Jacket Brown technically) were from MakerGeeks (I also wound up with a roll of glow in the dark PETG from MG but didn’t use it for any MPCNC parts….yet.) With the extra perimeters and my printing settings it took quite some time to reprint everything. By mid April I had the new Z assembly done:
And by the end of April I was ready with the last of the PETG parts and did a full rebuild:
I spent a few evenings doing wiring, I used ethernet jacks to clean it up and make it easy to disconnect the wiring when moving things around (since this is on my dining room table it has to be moved every evening for dinner!)
Finally on May 1st things started to move:
And by that evening I was able to add a sharpie and do my first real test:
Attachments:May 9, 2016 at 9:45 am #11946
I’m still feeling out the forum software here and the best way to include images/videos…so bear with me 😀
With the machine up and running I went ahead and strapped in my trust old dremel and managed to make an engraved wooden coaster with our companies logo. We had a bunch of these done in cardboard recently so I happened to have the vector art handy to work with 😉
Unfortunately my dremel died partway through. I was able to get it going again by giving the brush retainers a squeeze…but the old girl is on her last legs (brushes still look good and beefy…but the springs just won’t make good contact anymore.) It’s going to be a few weeks until I can get a dewalt but I’m looking forward to it!
I’m also hoping to add a laser at some point. And I remixed the needle cutter to use hicwic’s universal mount: http://www.thingiverse.com/thing:1538131 (There was already a version with the other motor bolt pattern, but I wanted to use a motor I had on hand so remixed this version instead.)
I almost have the cutter ready to test, but at the current ~13″ square working area I won’t be able to use it to cut full sheets of foam as I intend.
This weekend my wife and daughter are going on a trip and leaving me home alone…I’m hoping to do a major cleaning on my old detached office and making room for the full 4′ x 4′ base I originally planned to use and rebuilding the whole thing back to it’s original intended size 😀
And now that I’m enjoying using it I’m also tempted to use the PLA parts (though reprinting the ones I had done in black) and build up a second stiffer one on this small base again…just really not sure where I’d keep it. Don’t want to have to keep moving it off the dining room table every night!
So so far I’m absolutely loving this MPCNC and can’t wait to do more with it!
Attachments:May 9, 2016 at 10:28 am #11953
That is awesome, I love the detailed write up.
So….You ready to reprint in the new parts soon? Just messing with you, you have done plenty of printing, but if you break any more parts keep an eye out in the update thread for the new parts that are progressing slower than I would like.
Thanks and I hope it performs better than you hope.May 9, 2016 at 10:43 am #11955
Yeah, I saw those new corner blocks the day after I finished reprinting the old style 😀 So not in a big rush to redo those AGAIN 😉
I am looking forward to trying the new Z, not because I’m unhappy with the current Z but because it looks improved enough to be worth the effort!
So far performance has been far better than I anticipated. It’s far quieter than I expected (based on my experience with my 3D printer) and even with everything loose and untuned I was able to get better precision than I had hoped! (though I did have to tighten things down once I started trying to carve wood.)
Thank you for the wonderful design and sharing it with us all!May 16, 2016 at 10:25 am #12297
As I mentioned I had been hoping to get the machine expanded back out to 36″ x 46″ this weekend. Turns out my office was a bigger mess than I anticipated. I managed to get 3/4 of it cleaned (still have one corner full of electronics to sort through) and made enough room I was able to bring the 4′ x 4′ tabletop in and put the MPCNC on top of it in it’s current configuration.
I also made headway on my needle cutter which is what really got me excited about the MPCNC in the first place when I learned about it here. I made my first cuts in foam with it but am still working on fine tuning the needle length and motor speed.
Most people building these have been using servo testers to control the speed…but that seemed silly to me since the RAMPS can control servos and motor ESC’s take a servo signal. So I first built up a fake servo tester from a spare arduino and a 10k pot to confirm things were working…then dug in on trying to use the RAMPS to control the cutter. Turned out to be easier than I expected!
I’m actually running Marlin RC-6 on my MPCNC, the Marlin team has done a lot of work on the LCD code and it works so much better in RC6 that the older release vicious provides was driving me crazy. So I brought the configs over to RC6 and then dug in on adding a custom MPCNC menu to the LCD for functions I want quick access to when doing CNC work. I’m still working on the menu – right now it just has an option to set the x/y/z positions to 0 (so I don’t have to reset the RAMPS to do that) and options for controlling the needle cutter motor. I plan on adding some other useful functions like “Raise Z 10” and “Move Z to zero” – if anyone has any suggestions on other functions it would be nice to have on a MPCNC custom menu please let me know! The changes I made are on github in my “mpcnc” branch of Marlin here: https://github.com/jhitesma/Marlin-Folger/tree/mpcnc Once it’s more tested and I have all the functions I want in the MPCNC menu I’ll make a .zip for people who are scared of github to try 😉
Anyway, controlling the needle was easy. It’s just a M280 command like “M280 P0 S0” P sets the “port” and I’ve got my ESC plugged into the 1st (Marlin starts counting from 0) servo port – the one closest to the reset button) S sets the “angle” of the servo valid values are 0-180. To use my setup I have to first give a “Needle off” which is “M280 P0 S0” that starts the RAMPS outputting it’s lowest PWM signal for the servo. That wakes up the ESC for the needle motor – but doesn’t power the motor up yet. I can then do a “Needle Low” (or medium or high) from the menu which does a “M280 P0 S90” giving it the equivalent of 50% throttle. Medium does “M280 P0 S135” and high does “M280 P0 S180” currently those are my only three choices but I need to adjust them.
I’m working on trying to add a “Needle speed” option which lets you use the LCD knob to pick a value – but that’s a bit trickier to implement and not ready yet.
Still, I was able to get the needle going and make a few test cuts which has me really excited. Now I just need to expand the machine to it’s originally intended size so I can start cutting full 20″x30″ sheets of foamboard with it!
Attachments:May 16, 2016 at 12:28 pm #12305
I was reading through all the new marlin features since the one most of us are using. I held off hoping the the next big release was coming soon. I will be checking your version out real soon, Thanks!
I’m sure dj4linux will be excited to try your version out.May 16, 2016 at 1:52 pm #12307
Yeah, dj4linux sounded pretty excited when I posted about it over on FT this weekend 🙂 Was waiting to get things a bit further along before I shared here but once I got everything moved to a submenu I figured it was good enough. I’m not good at keeping secrets anyway.
The next major release of Marlin is imminent, they sat on RC3 for a long time then went through 4-5 and 6 really quick. But it’s been on 6 for a few weeks and it looks like the changes are slowing down. Still looks like they’ve done enough I’m guessing there will be a RC7 before they do an actual release. But I’d expect the next major release sometime this summer the way things appear to be going.
Most of the changes don’t really affect the MPCNC much, lots of stuff geared towards delta printers, CoreXY and other unusual designs, plus some more improvements to autolevel. But there have also been smaller things like fine tuning the settings so the LCD is easier to use and the knob is more predictable. At this point big changes are done, they’re just still nailing little bugs as they crop up.August 29, 2016 at 11:14 am #16815
Well, three months later I’m finally getting to expanding my machine to meet my original goals 😀
I spent the last three months struggling with my needle cutter before finally breaking down and buying a servo tester and a tachometer. Turns out I had forgotten that RC ESC’s are totally non-linear so my guesstimate at throttle values to get the RPM I was after were WAY off. I had it at about 80% throttle but it turns out I only need about 20%. No wonder my machine sounded so angry! $13 tach was well worth the money. Purring along at just over 6krpm the needle cutter is MUCH happier and I I’m getting much nicer results.
I also redrew djk4linux’s needle cutter in openSCAD and shared it on Thingiverse as a customizer: http://www.thingiverse.com/thing:1723915 The defaults will give a working cutter with hicwic’s QC mount. I’m still working on adding the new default mount but haven’t printed the parts to upgrade my own machine yet so it’s been a slow process. I put the scad file up on github so it would be easy for others to collaborate if anyone is more motivated than me about adding the new default mounts: https://github.com/jhitesma/parametric_needle_cutter
Additionally I found that a new lipo charger I was given to review has a “motor driver” mode that’s designed for driving brushed motors – but can power a brushless ESC just fine which gave me a good way to dial in my cutter without having to worry about varying voltage from batteries.
I’ve also been thinking about the cutter RPM more and think I’m going to experiment with the closed loop governor options in BLheli (the firmware I’m running on my ESC) to see if I can get it to give me a precisely set RPM and hold it reliably.
I also finally got a DW660 which blows away my old dremel…and really has me wanting to print those new Z parts 😀
So with everything working so well I decided it’s finally time to expand it so I can cut full sheets of foam board. Spent most of yesterday prepping then an hour and a half or so to rebuild:
I also have footage from the next 2 hours I spent squaring it up…forgot how much I hate that step 😛
One thing that did help somewhat was the corner check tool I designed based on a post someone made to the vicious1 FB group:
On the smaller setup it worked great, on the big one…well…I ended up calling my wife in to help hold the tape. It still made it easier to get consistent measurements but the magnet I used to hold my tape to the corner tool wasn’t strong enough so it kept falling off and frustrating me.
But the machine is back together on the big rails again – at least mechanically. I still have to lengthen two sets of stepper wires (and shorten the other two) then re-wire and install my new belts before it will be moving again. Can’t wait to start cutting full sheets of foam!
Attachments:August 29, 2016 at 4:25 pm #16838
ohhhhh I want a tachometer, amazon?August 29, 2016 at 5:26 pm #16841
I actually got mine from banggood (On sale for <$9 with free shipping right now too) because I couldn’t find one on Amazon with Prime shipping:
But then sure enough soon as I mentioned to him djk4linux shared a link to one on Amazon:
It’s a bit more…but you can have it in a day or two instead of a week or two 😀
My DW660 actually clocks in at about 28,000 straight to the wall and I was surprised how far I had to turn down my speed controller to get it to 20k. Though my readings on there may not be super accurate as I just put a bit of the reflective tape that comes with the tach on one face of the collet nut and didn’t bother to put black tape on the other faces, so if it’s catching a reflection off them it would read artificially high. But since it read low right to the wall I figure it’s probably pretty close.
On my needle cutter the bell of the motor is chrome so I put black tape over most of it and just a little bit of reflective tape there.
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