Narrow LR3 Build

Was thinking about building a small LR3 build for MRRF. I had built the LR2 in 2020 but then Covid hit and never got it out.
My table is 22 5/8 wide which calculates to a 10" print area. When I go to the calculator, it will not generate a 434 strut.


Take a bigger one and cut it down? Stick with the temporary struts?

Am i going down an impossible path?

Hello Ronald!

The Calc has Strut SVGs auto generated for sizes 480mm to 1700mm

Some context on how they came to be in this topic… LowRider 3 CNC, LR3 Release notes - #357 by azab2c

Some info on how to make your own Custom Struts in…

That said... If the table is 22 5/8" wide, what's the table length? If length > width then could maybe orientate the LR3 such that rail is on the right, and belt is on the left. Doing that would make it easier to modify and extend Y-axis with more belt later on if/when you have a larger table available. Pic that may help...

One nice benefit to this is that there’s no belt/rail in the way when you’re at the bench/table.


Mine is like that as well, 1220 in X, 880 in Y.


What about bringjng a board that sits on top of the table and adds some width?


It has to sit on a standard banquet table and I am afraid people will bump it if it is too wide
As it stands, it may be a bit too wide since they put 2 people side by side at a table. If @vicious1 sponsors, then he would get a dedicated table.

I may need to build this in two sizes.

i like the idea, thanks! it only gives 8" y then. Oi! that is SHORT!

I’ve been thinking of building an LR3 those same dimensions, and wider than deeper. It’s an appealing size for my workspace. But when I walked myself through the instructions, there isn’t room to cut the struts.

According to the LR3 calculator, a 1220mm wide cutting area requires struts 1400mm long. So how do I get around that if I want to keep the depth closer to 600mm?

(My first post here. I’m really excited about building my first CNC–either the Primo or LR3–but I’m still trying to figure out advantages and disadvantages of each and reading through various posts. What an amazing community).

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Welcome @scampbell! Have seen people cut struts from stock diagonally clamped. If y is long enough (temporarily even), the diagonal between xmin, Y-min to xmax, ymax will be long enough to cut the permanent struts.

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Hey, you can find info on how to do it here: Canadian lr3 build - #31 by Tokoloshe

We went through it yesterday. :smiley:

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Great Idea!

i think i am going to design my LR3 for the table i used for my MPCNC which is 3’x4’. I will then move it to the 4’x2’ for the show if i choose to take it. I will be keeping the 3’ X dimension so i will have some extra on the X dimension if don’t cut it down to 3’ or replace the table. I work for Haworth, an office furniture company and we get VERY nice work surfaces for a buck a foot. Perhaps i will buy a pretty one for the show.

buck a foot, nice company perk!

Some other ideas… From Printables

Haven’t even bothered to screw down the two 3/4" plywood strips my LR3 rides on. My cheapo grips and friction between the ply strip and benchtop are enough to not be weakest rigidity link. Doing this lets me quickly move the entire setup to other spots for experimenting.

Good luck!

I have back problems and bought a Haworth Fern, best chair I’ve ever had. :slight_smile:

Interesting. I hope I make it to MRRF!

I am just about to try and start a LR3 build for RMRRF Similar sized tables I assume. Let me see what I come up with. I want to try and run it length wise, clamp down the belt clamps and use some of the removable 3M stickers for the Y rail. Sounding like it might be too narrow, although as long as I can get at least a 8.5x11" paper in there I would be happy. I would really like larger though so maybe turn it sideways.

I highly recommend building the X axis the short axis for daily use. You can reach over it and the belt comes off for table access. The X axis is the weak point the shorter it is the faster and more accurate your machine will be, by a lot. Ron’s idea is for a show machine so it makes sense, but not as a daily driver.

This might be true, but look at my earrings or my cutting 6mm deep in beech plywood at 6000mm/s. It might theoretically be smarter to make it smaller, but I didn’t notice any problems. :smiley: Also, if you do the full width X you can always make a bigger table. Otherwise you have to do X again. :slight_smile:

For a 4’ gantry, would main cause for X axis weak point be due to overall Gantry flex, or the amount of X belt? If belt play is the main weakness, could maybe compensate with a mid gantry belt clamp to tighten things up when doing earrings and similar small projects?

The earring as an extremely light load. The harder you push it the more you will notice.

I have no problems with users building it that way, I just like to warn new users why it was designed the way it is.

Torsion. From what I can tell.

Thanks for the explanation Ryan, and the ideas from everyone. I really appreciate it.

Can I ask what would amount to an extremely high load? Do you mean trying to do aluminum, or just going too fast?

My thinking was that a wide X and short Y LR3 would fit my indoor shop for most stuff, but if I really dreamed up something big, like an arcade cabinet, I could put a longer, full size table temporarily in the unheated garage and move the gantry. But a perfect tool that does everything is probably a fantasy.

I tend to spend months, if not years, planning these sorts of things, when I should probably just go for it and figure it out as I go. It took most of a year to even decide that I really did want to build one after a terrible experience with a cheap 3018 from Amazon. But then I built a small plotter and egg-drawing bot to learn gcode and the software tool chain, and I’m looking to do bigger things with more robust tools.

You should really just dive in there, otherwise you will end up like @bitingmidge, finishing a whole camper first and then contemplating the colour for 2 months. :stuck_out_tongue: (Love you Midge! <3)