MPCNCM Idea and MPCNC Pro Edition

Mostly Printed CNC - MPCNC Advice
1

I had a really dumb idea…what I am about to type MAY get deleted. I was thinking if I could make a mostly printed cnc mill, not router style. Now I know that mills aren’t as craved by the hobbyist community. A router is more the DIY type due to it’s huge work plane and less complexity in it’s gantry, but their geometry also holds them back in rigidity. What if you could make a machine out of pipe and plastic that can mill mild steels? Hard aluminum alloys?

Most mills are huge blocks of cast iron that are far more rigid than conduit or plastic parts could ever be. But with a certain geometry that I may draw out soon, it could be possible with our emt conduit, 608 bearing rails, and ramps board. The bed would move x and y like any normal mill, with the z that is fixed at the top. Ditch the belts and go with t8 leadscrews for both all 3 axis.

Smaller work area, but more vice friendly and more rigid…? Yeah I am kind of just rambling here.

Wonder if an MPCNC pro edition would really be worth perusing. I am talking SS tubes, proper spindle, stainless metric hardware(eye candy), future end stop system, and possibly thicker belts. Don’t get me wrong I like my machine now, but it does have its limits. I get a little jealous watching other machines that are well…a lot more expensive.
Wish I had something to compare it to, I have no baseline!

2

A moving xy bed requires 4x’s the foot print or more depending on what size material you want to handle on top of that your support system for the spindle will be even larger than that.

Leadscrews are not better to drive a horizontal axis, they actually are not better for any axis. We use them on the Z because it is gravity assisted, and the bras nut is very inexpensive, but slop will occur where it generally will not on a belt for a very long time, belts have less friction, extremely small amount of slop, almost Zero and the same for backlash. Belts can have a much higher efficiency and longer life. Ball screws require maintenance and adjustments and are 20x’s the cost, plus whip, and debris can foul them up. The T8 are not proper for that application.

Thicker belts are cool, but very expensive belt, pullers and idlers, much cheaper and more accurate to use two gt2’s.

You understand milling times now, why not just make your machine smaller and mill faster (even though you have the fastest aluminum cutting MPCNC ever…? You are making very small parts but have a large machine? If you look at those really expensive mills there usable area is tiny. So many people keep making the mpcnc huge and saying they only want to do a little aluminum work. A machine for metal is tiny in its work area, wood machines are gigantic. You can’t crossover different materials that easily. It has to be built for one and used within reason for the other.

Proper spindles are very expensive and heavy. Import motors are of questionable quality and not proper spindles (usually).

The secret is 3D printing has made certain items stupidly inexpensive. I am always looking to make the best machine possible with the right materials. As soon as you stray from standard printer parts things go up in price 10 fold at least. Economics of scale. Our drv8825 drivers are under $3, gecko drivers $131 each. Conduit $4/10’ extruded rails start at $3/foot for small ones.

What I am getting at is a very small “upgrade” will have a very large financial impact but honestly a very small performance gain. A gain that could be handled much easier with two machines. Purpose built. A small mpcnc for aluminum with stainless rails, conduit larger one for wood or a lowrider. Two of my machine will cost less than 1 of what I consider the next best thing and 2 machines will easily outperform 1 in every scenario.

If you want steel you are beyond hobby grade and the tormach 440 ($7K+shipping and 220 power for the basic) seems to be at its limits with steel. It looks like they make about 1.5" depth fast aluminum cuts and about 1/8" slow steel cuts, it’s that much harder.

 

3

Gotta hand it to yah, you knew how to make it cheap. I mean seriously…emt conduit is dirt compared to the nice hiwin style rails. All the hardware is easily sourced. It’s mostly plastic, and uses one of the most common bearing sizes! After reading what you said, I am swaying to building a second one. Just wait, you will see a farm of 3 mpcncs cutting aluminum together. In your face milling times! Issue with building more machines is I would run out of amperage. My compressor uses 10, the dw660 uses up to 5a depending on load.

My friend just realized after months of me telling him about my MPCNC and him not caring, that he wants to get a CNC. If he agrees, I might trade my mpcnc setup for a “fresh start” with stainless steel. Also for the robotics club, they just got a hitorque bench mill 5500 from littlemachineshop.com and apparently were getting a laser cutter and a cnc machine(no info on what type).

I overheard you about how you tried making the design more rigid, but it mostly comes down to conduit flex. I need to quote the guys that I bought my aluminum bar from to see how much the ss will cost me. If they want like $200 hell no, I can just clone the thing. It is hard to tell where my flex(I don’t have that much) is coming from. Everything can tilt a little bit when I get 160lbs California grizzly bear on the gantry.

My main bottleneck right now is actually alignment, not power or rigidity at all. Getting the z perpendicular has been a non stop challenge and it’s showing. Can’t narrow it down, I rebuilt the thing at least 3 times, fiddled with tension bolts, etc. I had a really nasty fail the other day, I should of recorded it.

Fun fact of the day, the longboard motor mount took in total just over an hour for both parts.

All this alone time with just one cnc machine is making me crazy lol. I need to get my hands on another cnc router just to see what it’s like. With all this work I put into tuning the thing you would think I get tension bolt nightmares.

Just ordered some loc line 1/4" hose. The one I bought from china land kinda sucks, it leaks a ton of air especially since I have a steep angle on mine. Also wanna try a different end mill. I think I have spent about $50 on kyocera single flutes alone, lets see how some fancy $25 Onsrud endmills do!

4

Did you print your own parts? Are they square? The z axis should not be an issue.

Your problems always sound very dramatic but when you complained about speed, turns out you were milling 4x’s faster than me. How far off is you z axis, and is that really the problem? This goes along with the previous point, the more straight/perpendicular you can measure and try to achieve the harder it is. If you were measuring things with a tape measure it would be perfect, but bring out the calipers and all the sudden it looks like a mess. Diminishing returns happens in measurements as well. At some point you just have to deal with the tools you have and make them work or make a more forgiving design. If you need a deep pocket and the perpendicularity is giving you issues make it two pieces or use tapered walls. A more expensive machine isn’t usually the best answer.

Cnc mills were out of everyone’s reach 4 years ago. Now I get complaints that my machine can’t do 0.002" tolerances on the first try there is nothing my machine can do that can’t be done by hand, sometimes my machine is just faster.

This year is so different than a year an a half ago.

 

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I do have a notepad full of pro version ideas but there are some other things that need attention first. Currently the firmware edits, then wrap up the ZenXY. Get through the holidays then see where we are at.

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All the parts were printed by you. Out of all the endmills I have broken, I would say 20% of them are from biting off more than it could chew. The rest are funky chatter points at very specific angles. You can’t tell from the videos cause the audio is a total mess with all the air flying around but it chatters in repeated locations over and over. The rest sounds fantastic, it has that low cutting sound.

When putting a square to the tool mount with one piece of the square making contact, it is about 1/16" off at the very end of the angle. X axis is good, the Y needs work. If I somehow got both axis perfect, oh man I would have full faith. You can see the angle in the cuts. The vertical sides have an angle to them as if not cut totally straight.

When cutting 3/8" aluminum, any angle at all causes a huge problem. If I were cutting signs or making coasters, this would be totally invisible. My cuts are like a debug, they bring out any flaw at all in an audible chatter that makes you uncomfortable.

My measurements are all whacko. I have done so many test cuts now with my tolerances varying from .5mm to .1mm. I have yet to get that one gcode that I have full faith in running while I am at school. Once I find it, I couldn’t care less how slow the cut is, I can run it day and night knowing when I come back, I will have my parts finished. Sure my brushes on my dewalt will be crying for mercy, but there is the warranty.

The SD card helped, no more repetier freezes. :slight_smile:

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You really shouldn’t consider to let the CNC run without anyone looking, it could be really dangerous. You never know what can happen, the Z axis could plunge and get stuck, leading to overheating the motor and fire, don’t take that kind of risk.

If you absolutely plan on not listening to this advice, at least do yourself a favor and use some software like Octopi, to be able to monitor and see what’s going on no matter where you are.

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Yea, I wouldn’t give it very much alone time. That’s how fires start…

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Nope you can never leave it alone, if you get some story published about how my machine burned down a house I will be pissed.

Maybe a few pictures of your angle issue and I could help a bit. 1/16 over a foot is less that a 1/3 of 1 degree (0.298°). CAM might be the solution not the hardware, or a different bit (a roughing bit or shorter or longer flutes), but you can also try making the Z axis as perfect as you can measure and then just pulling the X and Y axis into square before every cut. If that makes it easier for you.

10

Lol well now you got me thinking. I don’t want your rep to die for me being a dumbass, oh god if I was at school and I heard there was a fire caused by a “random machine” that would be a nightmare. “The firefighters and crime investigation are looking for the corporate.”

 

Seriously though, I would love to try the octoprint but I can’t get internet through my little side garage where it’s at. I can only run an Ethernet cable through the kitchen, at least 40ft. Not gonna happen. I would love to be able to leave it alone though. If I have to monitor it 24/7 then it feels less like the automation that I seeked through cnc. I get how dangerous this can be but up til now, all my crashes have been user error. I don’t want to take the chance though, now I am really on the fence :confused:

I would really like to have it cutting slow and reliable. Even if it takes over an hour per part, that is fine by me as long as I know that it will get the job done. As for the angle issue, there is not much CAM I can do to resolve it. It gets bad when it does the finishing pass. Pictures coming soon

 

11

You really can’t leave it alone. I have run my lowrider parts job on the lowrider many many many times but I still stand there the entire time. I ran to the restroom one time and I was not comfortable even leaving it alone for 2 minutes. Matter of fact the second to last job I ran on it I had the 611 fall out of it’s mount, I have no idea how or why, I had not touched anything it dropped straight into the wood and of course the machine just kept pushing it through, but if I was not standing right there it could have gotten bad really fast.

Barry is speaking from experience above. Three people in this thread started fires but were able to stop it.

https://www.v1engineering.com/forum/topic/warning/

12

If another voice helps…

I agree with the rest, you can’t leave it alone. If you’re thinking about safety, you should really think about the backup. If something goes wrong, how many things have to go wrong before catastrophe. If you’re not there, one simple mistake can cause loss of significant property or even lives. It’s not sufficient to estimate the rate of those kinds of errors, because there’s a high enough chance that you’ll calculate the risk wrong.

I was adding a fire alarm to my garage when a mistake I made in estlcam started smoking. I was literally holding the alarm, and it did not go off. I climbed off the ladder, and unplugged it. So I don’t even trust a smoke alarm to warn me in time. Interestingly, that particular mistake was when I tried the start height in EstlCAM the first time, and it tried to cut to 36mm instead of 18mm.

If you had everything outside, on a driveway or something, then maybe you could leave it because it would only destroy itself, but short of that, you need to pay attention to it. Hopefully, you won’t ever have to jump into action.

I wouldn’t even trust octoprint, because who is going to sit there and watch it with their full attention, and there’s no sound. When I made my smoke, I smelled it first, then realized it didn’t sound right, then I looked and noticed what was wrong. Without my sense of smell, it might have been another minute or so before I noticed (It wasn’t cutting too much or anything, it was just going way too deep, and that caused the collet to rub).

If you’re going to the bathroom, I think the best monitor is a baby monitor, that would at least give you sound.

13

Well you guys have convinced me, but I still need a plan though. I don’t have the time to be watching it as much as I need it running. Either I need to decrease cycle times(how about no) or a safety plan. I was thinking of putting an acrylic case I will make out of sheets. Stops some sound and the chips won’t fly everywhere. Won’t do jack for a fire though. I can’t watch it for hours on end through, I have my limit. Being in the same room with it is hell. Its like 90 degrees, ear protection is a must. I may have to suck it up, at least it will be making money!

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Mine is in my garage, and I like to find other projects to work on at the same time. Hanging tools on the wall, sorting screws, watching netflix, planing boards…

Maybe your margins need to be higher to accommodate the PITA it is.

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Costs me $8, sells for $45. The labor is annoying though. My lack of tools and patience doesn’t make it any better. For a teenage job though, I could be doing a whole lot worse.

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[attachment file=42796]
A day in the life. I sand and clean the parts, do CAD, answer question, bitch online, but never leave the machine. I usually sit at the end of the lowrider table dressed just like this for hours on end.

The best thing is to find a system to keep you working while it is running, can you do any of it by hand while it is cutting critical dimensions? Make a fixture and slam them out faster? Package them, work on your site, packaging, shipping, design, CAD. I am literally doing the same thing for less money and I already have my degree and this is by far the best job I ever had.

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I have enough to do I don’t have time to sweep…or I’m lazy can’t be sure.

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It’s just going to get dirty again.

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Exactly!!! Why make the bed?!@?!?? Those are the things that perplex me.

20

I definitely need to come up with a system. Now with school back in session…junior year, the hard classes kicking in, I don’t have that much time. The plan was for this to be a summer thing but I thought it was way too easy going in. I felt all confident when all I milled were 1.5mm plates stacked together. This thick bar is a whole different challenge. I can clean edges and tap holes while it is doing it’s job, wish it was quieter though. Having the garage open is so nice but the noise is gonna get me hostile neighbors quick.

If I make anything at all my friend who is more talented in software can help with the web design, don’t think I’ll need it.

I know I complain a lot on here, that’s just the way I roll I guess. Still so new to this stuff. I put a lot of money and risk into this, I am not giving up this easily :slight_smile: I could think of worse things of wasting money on than end mills bags of screws. (cough, supreme…cough)

 

If I could sell at least 1-2 mounts per day, I would be happy. It is either this or I work at Target or something. This is almost tax free and more educational. :smiley:

 

Still waiting for that v1 engineering tour Ryan, I want to see where my kit came from