Legs conduit too short - should I get new ones?

Hey guys, just signed up. Building my first MPCNC and I absolutely love the project!

I stumbled into a problem, basically what the title says. I went for the minimum height, and I apparently miscalculated and ordered all 4 legs 1mm shorter than they should be. Now, when pushed all the way in with leg locks, all 4 of them miss that 1mm, as in the image

I know the tutorial says that it should go the other way around, but I wanted to consult with you guys whether it’s alright to have some “free space” inside leg locks when they are mounted, or not? If I’m ordering new ones, minimum conduit order is 6 metres, so I’d have enough conduit to build a second MPCNC lol

I’m going to use the machine for wood and aluminum mostly, but I’d like to try working with steel at some point, if that changes anything.

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What part is in the photo, one of the feet?
The feet should have the conduit well outside of the top of the foot so that the “corner bottom” part can slip over the conduit that sticks out.

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I’m not sure how to explain in words what I mean.

Here in the image, x should be the minimum length of the leg conduit… and mine ended up x - 1mm. Should I order a new one if it’s going to be a problem, or should this be fine?

If it’s fine, should I make sure end touches bottom (table), or top (leg lock conduit slot roof)?

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I can’t imaging having 1 mm of “breathing room” on the leg conduit is going to be an issue. I would have them completely to the top of the leg lock, and let the bottom of the conduit “float” inside the leg. That way you are relying on the height of the plastic parts to determine the rail height and to carry the weight of the rest of the machine. If the conduit sticks out the bottom of one leg a little bit, then you’ve given yourself a harder to diagnose cause for rails being uneven.

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I know that one person had the legs a little too short, and supplemented them with a spacer that went at the bottom of the feet. That seemed to work. I don’t see any reason why you can’t print a 1mm spacer disc 23.5mm diameter that will fit under the feet. (I am assuming that this is a photo of the bottom of the feet)

However, if the leg lock is firmly planted on top of the foot, then the spacer is probably not necessary.

If this were my machine, I might print 2mm disc spacers to enforce a 1mm gap between the leg lock and the foot, or I would use the parts as-is, for that minimum height.

I think someone even 3D printed replacements for the leg tubes on a Primo, and didn’t have any trouble.

Basically, I don’t think that it’ll cause you much trouble. It’s a problem if it causes the height of the legs to be different, or you don’t get enough engagement between the part and the steel.

For your intended use:

Conduit isn’t going to be as strong or rigid as stainless steel or DOM tube. It should be plenty strong enough for a smaller sized machine, but for aluminum, your CAM (Gcode generation) had better be good, and for steel, it had better be almost perfect. The larger your machining area, the more perfect it will have to be.

Mine is largish, I have a 25" by 37" working area. I’ve managed some aluminum, but I’m not going to do much with it at that size. I’m building a LowRider, and when I do, I’ll cut down the Primo to a size that is more capable.

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Rather than printing spacers, why not put a washer or 2 in the bottom of the leg? Agreed it’s probably belt & braces given the leg locks.

Sure, if you happen to have a set of washers that are the appropriate diameter already.

It’s not worth it if you have to buy them though. Compare a $4 package of washers to the cost of plastic filament to print some 2mm plastic rings. Even factoring in power it can’t be more than a couple cents.

I can’t imagine that it would make any difference at all, I wouldn’t worry about it.

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Fair point. I have things like that around anyway.

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I’ve been super busy lately so I haven’t gotten to it until this week. Found 4 washers for less than a $ total, so ended up going “full metal” for legs. Now that it’s finished, I don’t think it made much of a difference, but at the time I wanted to be super careful.

Thanks for the help, I made my first cuts tonight!

Now if only CNC was as easy to use as a 3D printer :smiley:

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