Fixed vs Moving Gantry CNC Router?


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Thread: Fixed vs Moving Gantry CNC Router?

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    Default Fixed vs Moving Gantry CNC Router?

    Hi there. I have been buying parts to build my first cnc router. At the time when ordering parts there was a considerable shortage with COVID, so I bought what I could get being concerned I might not get anything if I didn't just finally order.

    No I am trying to decide the best way is to build a sturdy router that can mill woods, plastics and aluminum. My main design consideration is whether or not I should build my gantry fixed or moving. My inclination is to build a fixed gantry and have the table move. That is the way my manual mills work and they are build that way for rigidness.

    Here are the parts I have so far.

    --HGR20-700mm linear rails and SFU1605 ballscrews for both X and Y axis.

    --HGR20-300mm linear rails and SFU1605 ballscrew for the Z axis.

    --Longs Motors Nema 23 270oz steppers with DM542A drivers. (I bought these over the 425oz steppers because the 425's had an inductance of 3.8mH vs 1.8mH for the 270's. )

    --Makita RT0701C router. (I was worried I would get a bunk chinese spindle or VFD, that seems to be my luck, so went with the Makita as they have a good track record. Plus it is lighter weight, and I can upgrade later and have a nice little trim router for around the shop.)

    So what do you guys and gal think? Fixed vs moving gantry cnc router? Pros and cons of each? What is your preference and why?

    Thanks a lot,
    Greebe

    BTW, I know there are some old threads on this, but all that I saw were between 7 and 15 years old and a lot has changed in tech in that time, which is why I am starting this post.

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    Default Re: Fixed vs Moving Gantry CNC Router?

    Hi Greebe - If you have the space a fixed gantry is always stiffer then a moving one. Plus its table is driven by a single drive so "walking" is not an issue. The Makita is good but you will have to use high feed speeds to compensate for its high speed. I thrashed my Mak for 3 years and wore out its brushes. Put in new brushes and off again. Good but very noisy!! 5mm leads will give you heaps of grunt for the aluminium... but slow rapids....so far so good....Peter



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    Default Re: Fixed vs Moving Gantry CNC Router?

    Quote Originally Posted by peteeng View Post
    Hi Greebe - If you have the space a fixed gantry is always stiffer then a moving one. Plus its table is driven by a single drive so "walking" is not an issue. The Makita is good but you will have to use high feed speeds to compensate for its high speed. I thrashed my Mak for 3 years and wore out its brushes. Put in new brushes and off again. Good but very noisy!! 5mm leads will give you heaps of grunt for the aluminium... but slow rapids....so far so good....Peter
    Thanks for the reply. I just built a new 30x48 shop, so space is not a problem so far. I also have a CNC Gang Lathe, a 9x49 Bridgeport mill, a PM45 mill and 12" swing manual lathe, as well as belt grinders, compressed air, blast cabinet, TIG welder and a host of other tools, including full woodworking tools to help me with my build.

    Yeah I might have been better off with a multiple start ballscrew for faster rapids, but that was all I could find at the time. I am fine with slower rapids if the torque is better with my 270 oz steppers. Really this is just a learning machine for me before building my dream machine.

    I have designed a CAD model of a fixed gantry setup that I was thinking of building. Ultimately my plan is to build a cnc router from granite epoxy, but figured I would build one less complicated out of 1-3/4 thick LVL to learn the ropes first. My experience with LVL is that it is very stable, super strong, and stiff which is why I was planning on using it.

    I had planned to build the gantry uprights with two pieces of LVL glued together to make a solid 3.5" thick supports with a mortise and tenon attachment to the horizontal beam of the gantry. Then there would be two pieces of all thread pulling it all together with pocket screws and glue supporting it all.

    The base would also be build with two layers of LVL perpendicular to each other. On top of that would rest the linear rails and then a 1" thick aluminum table.

    Does that sound like an OK plan so far? Thanks again.

    Last edited by Greebe; 12-20-2020 at 09:37 PM. Reason: Editing


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    Default Re: Fixed vs Moving Gantry CNC Router?

    Hi Greebe - Building a machine from plywood or LVL has many merits. Totally agree with the process. When it comes time to go with EG look up UHPC and CSA concrete much cheaper and stiffer then epoxy. Use your timber machine to build moulds for the concrete machine....

    https://www.rampf-group.com best regards for Xmas Peter



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