CNC Router Engineering// Fixed VS. Moving Gantry
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- Опубликовано: 1 апр 2020
- In this video, I will guide you through whether or not you should choose a fixed gantry type router for your CNC build. I will walk you through the differences between the two design types and talk about the pros and cons of each design.
Actually one version of moving gantry gives you the best option for cutting fluid drain: you need to mount linear rails on the bottom side of the table. One of the biggest problems with fixed gantry is the problem with covering linear rails and driving screw - the best option is metal plates, popular "harmonic" from plastic would be destroyed very quickly.
I have watched all your videos as they are spot on for relevance for me right now. I think you'll find Piotr Fox Wysocki's channel interesting. Maybe not for the theoretical engineering stuff, but lots of practical engineering as he has built and rebuilt his granite CNC machine over several years. He also has interesting spindle information etc. Good luck on your build.
As I mentioned in the comment on one of your other videos, I plan for a raised moving gantry based on granite. Well, the jury is still out regarding moving vs fixed since my gantry will be rather massive. But for now, all my designs are on a moving gantry.
Thank you for sharing, I already follow Piotr Fox Wysocki, and I'm most certainly a fan of his work. It's an excellent machine he has built! I also like the simplicity.
Granite is very damp, as it's a composite material. Vibrations will not travel far, and it's therefore well suited to achieve great surface quality and to produce precision parts if the machine is rigid enough. You can make a mockup of both designs, raised gantry and fixed gantry, to figure out which is the lightest. If the gantry is lighter than the moving table, then that is what I would recommend. But please note that a moving gantry configuration can have other advantages. It is for example possible to have large workpieces that extend out of the machines working envelope.
It can also depend on what your requirements are, maximum stiffness, high speed, or perhaps whatever is cheapest? You can put each feature/property into a category and assign a weight of how important each area is, and then calculate a score for each design. The design with the highest score will be the best. Fx: stiffness = 5/5, high speed = 2/5 and so on. Then you will compare the properties of each design and multiply it with its category coefficient. So if design 1 has a stiffness of ID of 4 and a speed ID of 1 then its final score will be 5 * 5/5 + 1 * 2/5 = 27/5 = 5.4 (final score for design 1).
Great video! Btw an idea if you sacrifice some side area of the build plate on the moving gantry you can make chip and drain holes on the into the bed. Good example is how the DMG Mori moving gantry mills work.
These videos are awesome man :)
Thanks for your great contribution
Thank you, these are the types of comments that make me want to create more videos! Have a great weekend :-)
I have a fixed gantry and im building a raised gantry now
I mostly mill aluminum so it will be good enough
Great vid thank you
I like the fixed gantry, because I don't need to budget space or materials and the work pieces I will be machining will be lighter than the gantry, so with fixed gantry I will be moving less mass.
I really like Fox's use of granite plates, but also, I think the use of stiff high sides on a moving gantry design should help stiffen up the gantry itself (as it will be less tall)? Furthermore, I am hoping the high sides would help keep in chips and it also keeps the rails further away from chips and coolant. I even thought of adding acylic end plates to a high side frame (with gaskets) so that I could cut carbon fiber in a water bath. My machine would be desktop size, too so I am hoping the high sides would even allow me not to use an enclosure at all. I would likely cut mostly delrin and alu with a mist coolant.
[Edit] Sorry, commented before I got to the part of your video with high sides;)
I think the high rail design would do a better job of keeping the chips away. Look into "Leather bellows for linear rails". You can buy linear rails protectors commercially, then you don't have much to worry about.
I get the feeling that you would like to avoid building an enclosure. Have you worked with aluminum profiles before? It is very easy to build a frame of 3030 aluminum profiles. Then it's just a matter of mounting some acrylic plates or whatever you would like to use.
Excellent design explanation. Thanks. I’m using 100% granite.
you can easily make moving gantry heavy and rigid. don't underestimate power of motors available today. couple of nema34 closed loop steppers can move a ton (half a ton).
Ok, you are right, but how much momentum and inertia half a ton has ??
Thanks for your knowledge I've been looking for an answer to this for a long time. Which one is useful and how is it suitable for what kind of use? Please make a video like this again. I press follow for
Yes stick around, I started on university and I'm now studying mechanical engineering. I'll begin researching some different combinations for fillable composite materials soon. These will then be used to cast the frame.
Please Wade,more videos 😋😋😋😋
Question i cant find on google:
Should i install my linear rails on moving bed, or machine base?(fixed gantry setup)
If you made the gantry wider (lets call that X axis) you could shorten the length of travel (Y axis) of the moving table
I think you missed the biggest drawback of fixed-gantry machines: you cannot work on specific zones of a big/long part exceeding the working area of the machine.
It has happened to me to be asked to make such kind of jobs. I simply slided the specific area under the gantry, positioned, clamped and machined. Simply as that.
I got jobs that others cannot do with their fixed gantry machines. 😎
Literally every fixed gantry I’ve seen destroys the regular ones, look at datron, look at any of the fixed gantry mills built on a shoestring budget.
I’ve 50 years in machine tools working on all types including Gantry’s and to put it in simple terms you have little knowledge of what you’re talking about? Your arguments contradict each other 🤷♂️? I understand your not talking in your first language but🤷♂️