2x2 feet working area? Or total area?
I interpret that as 610x610 mm usable working area.
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Working area. I think the work area/foot print is prerry close for both machines, just different shapes.
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If space is an issue then go for a LR3 - when itās not in use you can unclip the belts, store it and youāve got your workbench back.
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I have the space for a fullsize LR3 in another location.
So Iāll build a small MPCNC at home and learn and then move on towards the LR3.
My primo is 2āx2ā working area. It has served me well.
Iām considering a 4āx4ā larger machine. Either a lr3 or my own design.
With a 610x610 working area, the table size will be 880x889 mm.
What about thickness of the table top? 12mm mdf is sufficient?
Can I cut the table top in 3 parts, mounting the Y rails on the two outer parts and have the middle as my spoilboard?
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Yes, a lot of us have done that. I did it with my Primo as well as my LowRider, because you can then easily swap the spoilboard or even take it out to mill larger stock. 
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I am printing parts and cutting tubes but I canāt decide on the usability of a square build? Compared to a non square build?
I am thinking of a X-axis of 610mm and a Y-axis of 305mm?
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I think I did a square build because it made all the tubes the same length. It is also easier to rip sheet stock down to squares. Only have to set up one dimension on the table sawā¦ Rip, turn, rip, repeat.
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Hi David,
thank you for your reply. The easeness of cutting is a good advice!
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I think I heard Jeff say his lowrider is set up for cutting 2X4 sheets of plywood because that fits in his car, and they sell that size already at lowes and home depot. If you built a 5 foot by 3 foot table, you could easily do that with the lowrider.
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It is a great size for me. I think it is about 28"x48". I prefer the baltic birch sheets, which come in 60"x60". I have them cut it down the middle to fit in my car. 30"x60" fits fine in the table, even though I canāt quite cut the whole thing at once.
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This is the size Iām considering. I was going to do a 4āx4ā, but Iām wanting more floor space.
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Canāt decide on a 610x610 mm MPCNC or a small Lowrider 3? I was going full sheet but I still donāt have the space. The lowrider 3 would be 610x610mm working area?
What to do?
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Personally, I have a MPCNC that I originally started building long before the LowRider existed. I built it at 600x600 and havenāt found that much use for outside a few specific scenarios like cutting holes in things like ABS or fibreglass electrical enclosures and certainly nothing remotely close to its maximum footprint. It was rigid enough to cut aluminium if I stayed near the corners but gets noticeably less rigid towards the center. To be fair, this is more an issue with my personal build as itās built with thick-walled aluminium tube (all that was available in 25mm here at the time) and I also had a cheap and terrible spindle on it which completely soured me on using the whole machine because I was always aware of how hamstrung it was by the crappy spindle.
Iām in the process of building it into a Primo with 300x300 working area and adding a Makita RT0702C as the spindle. Hopefully that should alleviate some of the mistakes I made with the original build.
Iām also printing/cutting some parts for an LR3 for a build that my Dad is going to do.
For me, the extra height was convenient for what I wanted it for, but not much else. It needing a space to stay set up was fine but not ideal. I never figured out a storage solution that would allow it to be put away and eventually it got buried as I needed to store stuff around it. I also ended up with other ways of doing the same things I was originally planning to do with the MPCNC.
Looking at it now, an LR3 with a similar size would still do everything I have needed the MPCNC to do, while also being much easier to share space with, either by removing the LR3 and putting it away, or just having it moved to one end of its travel.
I think ultimately the answer comes down to what youād be doing with it. If youāre mostly planning to cut/carve sheet goods then Iād probably build an LR3 and spend the effort on making it usable on a general purpose workbench. Especially if youāre planning to build a larger LR3 at some point. In theory it should be pretty easy to swap out the gantry tubes for longer ones to expand the LR3 which would give you a large-format version of a machine youāre already familiar with and hopefully have dialed in somewhat.
I donāt have any experience running an LR3 and wouldnāt say Iāve ever run my MPCNC anywhere close to its capabilities, so take all of this with a decent pinch of salt. This may also just be āthe grass is greenerā talking here, so hopefully some others with more experience will set me straight if Iām off in the weeds.
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This. 
I questioned the Primo before, because the LowRider is, in my eyes, the more versatile machine. What I did like with the Primo was that it canāt lift off the rails. Also, if you want to cut higher stock the Primo might be for you, but itās really hard to find endmills that can cut deeper than 4cm. 3cm was the deepest I ever went. You could also add a drop table to achieve this. I also donāt like that the LowRider canāt touch the spoilboard with the collet, I had to rethink carvings in thin materials and the short V endmill. If you never had a Primo this might not be a problem though.
Iād love a LowRider with trucks like the Primo. 
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I still havenāt had time to finish this build.
I am looking at the docs and the size page, when it says outer dimensions, is that of the workspace or total machine footprint?
EDIT: I (finally) have a use case for the MPCNC and I want to mill aluminium at 15mm height and about 110x110mm.
With this size in mind, what size would you make the MPCNC?
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The Primo is more rigid when the Z is up and the LR3 is more rigid when the Z is down. I just am building a new, smaller LR3 for this kind of work.
Mike
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One of the nice things about the MPCNC is that you can always use longer rods for the frame than you need, which makes it trivial to re-size the whole thing.
In your case there, Iād probably try to make it somewhere in the 120x120 to 150x150 range to give you as much rigidity as possible and keep the Z height as low as possible, especially considering that youāre trying to mill to quite a significant depth in aluminium.
I made mine 600x600 originally and shrunk it to 300x300 by just sliding everything inwards on the rods. It looks a bit weird but āfeelsā a lot more rigid, at least. Tough to tell for sure because I also replaced the spindle but itās a noticeably different machine after that.
Edit: So you could cut the rods for 300x300 and do the initial build for 150x150, for instance. If youāre making things that are 110x110 then make sure youāve got at least an extra cutter width so you can profile the entire outside of the part. That and making sure youāve got enough Z height to clear whatever cutter, as well. Later if you find that you need something larger or have plenty enough performance for your needs, you can just loosen all the clamps, slide the thing out and youāve got a larger machine.
Hi Jono, thank you for the good advice.
I am thinking about going smaller but also non square, perhaps 150x250mm.
Is there any difference in rigidity on the X- and Y-axis?
Also, do you have a picture on everything slided inwards? Not sure if I follow on how you mean.