Thanks Ryan, thats helpful! Especially the last big about upgrade leading to upgrade. I’m far from an expert in any of this as I have limited CNC Milling exposure. The bulk of my toying is in 3D printing, with bits of exposure to CNC milling here and there… but enough to get the bug !
Maybe a single Nema 17 would work fine, I just had my concerns about it pulling the milling ‘sled’ up a steep angle like that while cutting. Perhaps compensating with feeds/speeds could make or break this.
In any case i’m excited to learn more about the whole build, especially the electrical component side of things as I know very little at this point, so very helpful in pointing out the power supply/driver/software issues associated with trying to upgrade to a larger stepper (I just figured I could run it through a bigger driver assuming the power supply was sufficient … shows what I know ha!)
My best advice is just try it as is. From there you will easily be able to look into other options. My way probably isn’t the best but I honestly feel it is the easiest to learn from and easiest on the wallet as well. Every part can be reused easily.
I’d lean more toward a design that tilts up to the 60° level for storage, then pulls back down to level for work. You’d open a huge can of worms changing the gravity load on everything.
I managed to get 8’ 1" solid steel round from the scrap yard for about $5.
From the thread, it sounds like it will be too heavy / too much inertia for the gantry. Is this usable or will it be too heavy for the outer frame?
edit: Also: parts of it are rusty, ideas on how to clean it up will help. I’m thinking some sort of drill “lathe” + sand paper… but I’m still trying to figure out how to hold the opposite end.
Never thought of putting concreat into the tubes, however inserting a secondary tube into my EMT, I’m still considering. No doubt additional support is the way to go for the frame, but what is with the movable XYZ axis, no good way to reinforce them. Of course only suitable if you can source something suitable.
I thought with 3 sets of dimensions it would be an easy task to source qualifying tubes, but then something, maybe the good weather, reminded me that I live in Thailand is easy to come by easy besides beer and h…s.
However we get EMT, even just around the corner, it’s paper thin, so the first build will get a pretty small one. It seems we have a good supply of power tools like the 660 available, I might even start only with a Dremel or a Laser.
However, Project officcialy started today, as I brought two lengths of conduit home.
An idea that comes to mind is to put inside the empty pipes of the outside structure a second pipe, heavier than the outside frame, attached with 3d printed spiralized springs that caps the pipe of the outside structure, these might absorb more vibration than the filled pipes you proposed…
I have no math to prove this, but generally speaking this kind of chained weights works.
My theory was to fill the conduit with 50/50 epoxy and micro balloons. The added strength was not enough to compensate for the extra weight and the deflection actually got worse.
recent mistake here (I did read the thread before and it didn’t stop me :P): I filled the static tubes with epoxy concrete for crush resistance (the only easily available 25mm tube around here is the kind you hang curtains on, chromed 0.5mm wall thickness steel tube; it is flexible enough to be deformed by the bearings, and tends to become a bit sloppy eventually); the filling did achieve the “crush resistant” goal, dampens vibration really well, but I got the concrete composition wrong (gravel too large, not enough fine sand, maybe not enough epoxy), so after a few trips of the gantry the exterior steel took the shape of the underlying pebbles / small voids and looks like the surface of the Moon
I located some 25mm / 2mm wall steel tube on the website of a hardware store nearby[1], but I need to go there and see if it’s straight, and if they’re willing to cut the thing into 2m pieces (because using public transit with a 6m pipe is… awkward, and it wouldn’t fit the elevator anyway)
[1] it’s the first time I see such a thing actually, usually they carry inch sizes for water / gas / etc., and those use some funny math - 3/4 in is 26.7mm, no big box store sells stainless, and stainless suppliers won’t even talk to you unless you buy like half a ton (no, really, I added some bar to the cart at one of the rare ones who had an online shop, and the cart refused to let me pay saying “you have 2 kg in your cart, please add 498 kg more”); the joys of living in Eastern Europe, I guess.
If you ask for “pipe” you’ll usually get it based on the inside diameter. So 3/4" on the inside. The 3/4" conduit from the big box stores around here is 23.5mm outside diameter, which is why that’s the original size of the MPCNC.
If you as for “tubing” you’ll usually get it based on the outside diametere. I think a lot of places will either carry 25mm or 25.4mm (1in). It’s not common at the big box stores here, but there are lots of metal supply places around.
maybe in English, in Romanian it’s the equivalent of “pipe” for everything
basically plastic and copper pipe is sold by the outside diameter and measured in metric, steel pipe is generally some sort of large inches (I just measured a piece of 3/4 steel pipe, it’s 26.7 mm outside, 21mm inside); electricals use plastic tubing here, there’s no such thing as EMT, and the (steel) pipe that is metric-sized and measured by OD is probably meant for fabrication
going to pay the store a visit tomorrow morning and see if the thing is in stock and is straight enough
That’s why Ryan made the 25mm size. Steel emt doesn’t really exist in Europe. You guys treat electricity differently over there. You should be able to find 25mm structural tube though.
A very late entry to this discussion - I have only just found MPCNC and am seriously thinking of giving it a go. My contribution is; why not redesign the unit with a different size “Frame Tube”. Some time ago I designed a skateboard-bearing carrier to run on 2" (50.8mm) stainless steel balustrade tubing. It ran beautifully although the design was too light for any serious work. I am not convinced I had the best design, but the 2" SS balustrade was rock solid. I was able to buy 3.9m (12’10.4") for $99 AUD.
I have attached snapshot that attempts to show the bearing layout of my 2" prototype.
Being new to PMCNC, I also have a raft of questions:
What is the effective work size to rail length of this design ie, a side rail of 600mm would give a Y travel of ??mm.
What sort of tool travel speed can one expect this this.
Can anyone who has printed this in PLA tell me what wall thickness and fill density % they used.
Ron, take a look at the links from the top of the page. There is a ton of info, including these answers (I hate telling people to look on their own, but my guess is you just haven’t seen these pages). If you still have questions, start a fresh topic that will pic up some more eyes.
Why not 2" tube? Why not 10"? Because 1" is good enough. You really don’t need anything bigger and you don’t need to fill it with anything.
Thanks for your response - it may not surprise you I am new to this (blogging).
I have been searching for the link at the top of the page, but can’t find it, could you give me a clue please.
re the 2" tube, I only mentioned this as an alternative to concrete filing as I had already tried this size in my prototype before discovering the PMCNC. The 2" tube would perhaps suit larger builds and I found it for the same price as the 1".
I concur, 1 in / 25mm should be enough even for large-ish sizes if the wall is thick enough; just don’t use the really thin curtain / wardrobe stuff, or if you do, use extra fine sand to make your concrete filling)
220 / 240V means the standard 16A household supply can deliver at least 3.5 kW without much heat (assuming the outlets aren’t cabled by drunken monkeys - don’t get me started…), and then the walls tend to be made of concrete and / or brick, not kindling (if the wires get hot enough for the insulation to melt and short out, the breakers will usually trip long before anything can catch fire; most fires around here are cooking-related, and cooking is mostly natural gas)
looks like I have some yak shaving to do: waiting for a cordless angle grinder ATM so I can then order a 6m length of structural 25mm pipe and cut it quickly in the parking lot (they don’t want to cut it, and the brick-and-mortar store didn’t have it in stock, and I can fit at most 2.2m in the elevator - I did extensive measurements after I had to carry a 2.4m beech counter top up the stairs for 10 floors, alone)
!
(if the wires get hot enough for the insulation to melt and short out, the breakers will usually trip long before anything can catch fire; most fires around here are cooking-related, and cooking is mostly natural gas)