Thank you Dan, I am looking to purchase and the 0.065" is almost half the price of the 0.120" stuff so I will probably go with the DOM 0.065" tube if there is minimal difference between SS and DOM.
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Thank you guys and thank you @OutlawECHO for starting things off, I appreciate your help and insights.
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I don’t think it matters, but I made my X longer. Partly this is due to how I author files. I like my Y to go up and X across, and monitors are almost always landscape. I also access my machine from the front, so having X longer means I lean less over the bed trying to mount my stock or aligning my cut.
is there any advantage in using 0.120" thickness tube for the outer perimeter rails to increase rigidity and then 0.065"
Personally, I don’t think the benefit is worth the money. The benefit is going to be very minor given your working area, and you could get better results by just adding mid-span supports. And you definitely don’t want to increase the wall thickness for your moving tubes. Thicker tubes mean more mass to accelerate, leading to the necessity of slowing your feedrate for cutting and rapids.
Would there be any advantage in running a 24volt power supply vs a 12volt power supply?
Higher voltage allows you to move your machine faster before you begin to lose steps. If you are just routing wood, then you will get little benefit from running at a higher voltage, since it is unlikely you will approach a feedrate where the higher voltage would make a difference. It starts to have an impact if you are attempting to speed up your laser engraving, or if you are trying to rapidly cut foam, or if you routinely do jobs with a lot of non-cutting movements that you want to be as fast as possible.
Is there a specific infill type that is recommended vs just the values stated?
I’ve wondered the same both when I build my original MPCNC and when I upgraded. I took my direction from watching CNC Kitchen’s videos on infill like this one. But this data is really soft. First, he is testing for strength. Stiffness is what matters for an MPCNC. Second, he acknowledges that for a given infill pattern, different patterns use different amounts of plastic, and that also likely varies by slicer. Bottom line, I’ve never seen someone on the forum say, “I really wish I used a different infill pattern.” Oh and for my parts, I believe I selected Cubic infill as a balance between strength and printing time.
What is your YouTube channel?
Oh, I’m not fancy enough to call it a channel. Here is the last video i made, though.
I share the fail because i know we all do it, but it sticks to think we’re the only ones. Eventually I’ll start posting my wins, too. Right now I’m looking for the limits of my new primo build, and for me it’s more fun to push until it fails, then back off vs creeping up on the envelope until I THINK I have it.
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I used 0.0120 in my teeny tiny build. The work area was 8x10, and i stood on the rails while assembling it. That thing was STOUT. On the other hand, i got the tubes from the remnant bin, so they were cheap. MAYBE 20 bucks all in.
You’re going to get flexing from the plastic parts first. I’m confident in that. But in experimenting with cutting steel on my newer, larger primo that has 0.065 gantry tubes), I’m pretty sure that my longer gantry tube also flexed and combined with the plastic flex, i got a couple of pretty nasty jumps.
I started out with acceleration at 750, pulled it back to 500, pulled it back to 250 last night. It was hitting corners like a giant printer. Handled fine, but was unsettling to watch. I think the motors can handle the tube weight fine at the accelerations we use. The motors don’t get enough credit just because they’re small, but we have TWO of them on x and y, and pretty small pulleys.
Did you mean “acceleration”?
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That is intense machining steel! Have you considered lubrication on the bit?
Doesn’t end well. Slightest bit of moisture and the chips stick to everything, then recutting. So far, best results with coated endmills, second best with big fat endmills. When I get around to trying again, it will be with a big fat coated endmill.
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Thank you @turbomacncheese for sharing your insights that helps alot. At most I plan to work with hardwoods and maybe (big maybe) some soft aluminum I think I will go with the 0.065" tube. If I need to work with harder materials in the future I will probably look to build a smaller more rigid unit as needed.
I have no doubt these steppers can push around a lot of mass. I’ve seen MPCNC builds using 2.2 KW water cooled spindles on this forum. The question is what price is paid for this added mass. The user may have to decrease the acceleration settings and/or reduce feedrate settings to compensate. This means longer cutting times. For the size of machine Sparkyyyc specified, using 0.12 walled tubing instead of the 0.065 walls would add about 3.7 pounds for the steppers to move. That’s more weight than a Makita router. If cutting steel is the goal like you are doing, then maybe the tradeoff is worth it, but for most MPCNC user who only do softer materials, I just cannot see the benefit.
Did you mean “acceleration”?
As someone who focused on STEM and ignored English classes, I frequently mangle my writing, but in this specific instance, I think the verb form “accelerate” is right over the noun form acceleration.
I meant vs slowing the feedrate. I’m not one to pick on grammer, as i frequently fail to proofread for even spelling.
I’ve seen plenty of mentions to slow acceleration, but that’s the first time I’ve heard of needing to slow a feedrate for tube mass.
I don’t think one has to be a clown(my words, i own it, lol) like me trying to cut steel (with more failure than success, yet) to consider gantry stiffness. My x is only 4 inches longer than what he’s planning, and i wish I had bought stiffer tube than what I had in my scrap pile just for cutting wood. Maybe I’m a lot more aggressive than average, but after seeing the speed tests, i don’t think I’m alone. I cut some cherry yesterday and settled on 0.25" DOC because of flexing, then maxed out the feedrate with my 6mm mill. Going deeper would really be useful (for me).
I’m not disagreeing with you, just saying that after building and pushing 4 mpcncs (3 of them to their limits) that I favor rigidity over weight (at least this far) because the rigidity is useful sometimes and the weight penalty (in the tubes) is nowhere near as severe as I used to think.
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Thank you @turbomacncheese so what I have been quoted is
Steel Round Tube A500/A513 (Welded) 1.000 X 0.065 at $106.80
or
Stainless Round Tube 304 Welded Ornamental 180 Grit 1.000 X 0.065 at $144.58
or
Cold Rolled Round Tube 1026 DOM 1.000 X 0.120 at $203.63
Given the cost difference and this being my first machine I was thinking of the A500 tube to keep the cost down but would be happy to have a 2nd or 3rd opinion.
Jesse
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I wouldn’t have paid for that either.
Fair chance you’ll want to rebuild the size before the difference is important to you anyway.
Last time I bought tube specifically for a build it came up to something like 30 bucks (again, remnants) i told the counter guy what we were getting quoted from various shops and online sources, how much the difference was, and he was shocked.
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Ahhh. No, I meant feedrate, though I’m not an expert. For a given acceleration setting, more mass takes more torque from the motors to move at a given feedrate. The faster the motors are spinning, the less torque they produce. So, slowing the feedrate gives the motors more torque and allows the operation without missed steps. The right solution for missed steps might be to adjust the acceleration, but I think most MPCNC users will slow the feedrate to solve their problem (myself included).
Maybe I’m a lot more aggressive than average, but after seeing the speed tests, i don’t think I’m alone. I cut some cherry yesterday and settled on 0.25" DOC because of flexing, then maxed out the feedrate with my 6mm mill. Going deeper would really be useful (for me).
On the bright side, all it takes is $$…slide the 0.065 tubes out and slide the 0.120 tubes in.
weight penalty (in the tubes) is nowhere near as severe as I used to think.
Your practical experience trumps theory. The problem we have is there is little formal data, and lots of builds with different parameters.
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Hey guys, Thank you all for your answers and guidance.
I have all my parts printed and have my steel rough cut and almost ready to start the build.
Question what is the best way to prep and finish the DOM Steel?
I have heard scotch bright or green scrub pad and paste wax but just want to confirm?
Clean is nice.
Paste wax makes for a reasonable sealer. I have a small jar of tool wax from Lee Valley Tools that I got for the tablesaw and intended to use on the Primo, but haven’t yet. I gave the steel a quick wipe with a rag that had a bit of light mineral oil on it. That was in August 2020, and haven’t really done anything other than wipe chips and sawdust off since.
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Thanks Dan thats great I was actually looking at LeeValley last night and found they had a few options one was a spray for saw tops and stuff and was pretty expensive and one was a LeeValley brand that looks good and is much cheaper, Might give it a try.
One more question I have the Dewalt 660 I got cheap off Facebook and plan to start with that as my router but would there be any issues running this spindle weight wise? Other thoughts on Spindle vs the 660?
The DeWalt 660 spec sheet says that hte weight is a little less than the Makita RT0701C that I’m using. I’ve bought tools from many different brands, but I’ve never been disappointed when I buy Makita. Anyway, that’s what I use, and the mass isn’t a problem. I can’t see why the DeWalt would be.
Sorry Dan my question was not very clear I see now. What I meant to ask was would there be any issue with the 800w Air cooled Spindle and its weight.
It looks like I might have found the answer to my own question as I stumbled onto this thread in the forum about this topic.
Yeah, sort of realized that after…
I think that the machine is capable of lifting a fair amount more than it does. Even more if you’re willing to go to a 1 start threaded rod.
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