Видео

thanks a lot for the assembly

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. 😎

Every Machinist is somehow a THIS OLD TONY fan 🤷

why confine ourselves to just 2 X rails? The major problem I had with pcb making with my 3018 are the vibrations induced by the spindle motor. Anything with a fulcrum in the design greatly amplified those vibrations, increasing the the deflections at the tip of the router bit - breaking it, even with just pcb making.

Wow that was a lot of work to put together, thank you for that !

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🤷‍♂️

I think it's important to have mentioned the taper interface. Standard Steep taper holders like BT30/CAT40, etc are only taper contact and low in radial stiffness. Dual contact interfaces like HSK, Capto, and Big Plus are Face + Taper contact to the spindle and thus inherently have greater radial stiffness.

I kinda disagree with the 0.02mm threshold for chatter to occur. You can get chatter with even less deflection, or take monster cuts that deflect way more than that with no chatter (despite being prone to)

Will separating the xaxis linear rails make it more stable.

I hope you continue this series!

My only criticism of this is while the final gantry may be as stiff as the original, all of the extra geometry on it might make the original simple version cheaper to make, so unless there is a performance gain, going with the simplest design is often times best.

Is 1400 newton's a lot of force for a cnc or a normal amount?

Would be great if you made a full course on this for precision CNC machine builds using granite or epoxy granite.

Excellent design explanation. Thanks. I’m using 100% granite.

This guy is wrong about flute to RPM levels. The number of flutes effects maximuim/minimuim feed rates and HP requirement. It does not change optimal RPM. Optimal RPM is a function of the SFM rating and circumference of the tool. Has nothing to do with how many flutes you have. You can have like 20 flutes and still be able to run at the same RPM as a 2 flute endmill.

Many thanks, dear. very interesting and excellent explanation

I’m silly late to comment on this video, but I have two questions. First off, is it correct to apply the force to the entire X rails rather than the center of them? The rails have just as much if not more deflection, so I would think applying force in the middle would produce a different optimized shape. Also, something I’ve wondered about many CNC gantry designs is whether they should be stiffer in the x direction, or parallel to the gantry. Often time the sides of the gantry are just aluminum/steel plates instead of boxed members or otherwise reinforced. I’d be curious to see the optimization if you changed the force to be 90° perpendicular to the simulation you ran. I guess I should download fusion and try it out myself, huh?

@Williams Garage Engineer, As this video is about 1 year old, i was hoping if there a way to communicate with you over a paid consultation ? an email even or something

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.

WHERE U AT

Any updates on these amazingly informative videos?

Question i cant find on google: Should i install my linear rails on moving bed, or machine base?(fixed gantry setup)

Hello. Good work! I'm designing my own machine now and really appreciate the work you put in to this very specific area of study. Any updates on the progress of this project?

Hej, hvordan går projektet? 😊

Again, thanks, really interesting. It did ocur to me when you cut away lots of material from the 'legs', this only made sense for the very specific force perpendicular to the axis of the gantry. Ahhh, got to 20:25 and you're just talking about that now. But do you underplay it a bit? I guess the dynamic way forces would shift and change direction when cutting a circle, for example, make just analyzing it the way you did the most practical. All very interesting thanks :)

Hey Williams, I really enjoyed this, thanks for sharing. Impressed by your scientific approach! We made a gantry beam recently (well we started ages ago - it's kinda been a side project) and used the extrusion from an old stairlift. It has strategic EG infill too. It seems to be working great, but the complexity of the build was off the charts (though I found it fun :) If your are interested in seeing out practical experiments with it ruclips.net/video/obR-l7qVhQY/видео.html Peace, Bongo.

this is pure gold, thank you so much!

Thanks! You rock!

What a totally unfair comparison! The design on the left makes no sense, the carriages should be mounted lower and the spindle upper. The design on the right has limited travel possibilities that's why the design on the left is used. You started with a good project: compare the 2 designs. But then you should compare both at best this is not the case, then try to compare both with a 300mm travel

Was this really approved by TOT? 🤷‍♀️

Thank you very much. How to decide distance between two lm rails.

I think the point of "type 1" design is that the z-carriages will be placed much lower down, like right in front of where the horizontal rails are, to have a more direct force transfer to the gantry itself. You certainly wouldn't want those carriages way up high like you've shown. The deflection of "type 1" may change with z-position, but it will always be the strongest possible, which seems like a good thing to me. The main downside is that the bottom of the z-plate will end up closer to the toolbit, so it's not as good for making deep cuts. Another downside is that the moving weight of the z-assembly is heavier because the rails have to move as well.

Hi Williams Garage Engineering ! Great Work & Excellent Video ! Very Impressive, with a great amount of details being provided ! However ! Where can I download the Files from this Video, as the current download link doesn't work ? With kindest regards GCG CNC Group.

excellent - thank you!

Great modelling!

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.

Your Chanel is absolutely awsome thank you for that ! Would ask you two questions though. - wherebdonyoy study cnc machines university /country ? - can you advice me a book or books so as to get good at cnc CNC Theory and calculations please ? i am starving for that.

The damping coefficient should be between 0-1, as a ratio of how much force is damps as a ratio i think?

Please Wade,more videos 😋😋😋😋

someone who understands, confining the deflection and suported rails

people need to be realistic, a $200 cnc engraver is not a milling machine and not even a good cnc router, $200 cnc are designed for NO ! spindle side pressure, even for wood decient cnc routers start at $2000 plus and maybe can mill aluminum without to much chatter and wearing out the end mills , I am building a cnc router on a 1/2 aluminum plate with rect ball bearing linear rails with closed loop steppers with mist coolent around $1400

chatter is caused by excess axis play the end mill bites and moves away from the cut back and forth, I do cnc service and when the ball screws and thrust bearings go you get chatter and sloppy parts, there is not much hope for a $200 engraving cnc router

As Mihai Dumitrescu reminded us, be aware of the fact that almost every CNC-machine has a different stiffness, depending on where the machine spindle has moved to. Routers will for example have the most deflection when the spindle is lowered fully, and located in the middle of the gantry. Another thing is that the machine's deflection also depends on which direction you're machining in.

Hi William; nice videos and also nice and good intentions to document the build. I would like to chip in with some thoughts, hoping they may be of some help. First of all, big manufacturers do FEA, then make mock-ups, many iterations, until theory and practice coincide. That calls for resources. We, hobbyists do not have the luxury to do that, therefore we make guesstimates and it is perfectly acceptable. In a gantry design, tool displacement depends on where on the X axis (transversal axis) the carriage is horizontally, and also where on the Z axis the carriage is vertically, at any moment in time. The influence on tool displacement of the horizontal milling force acting on the gantry (parallel to the ground) is rather small. The biggest influence is, as you may know, the rotation angle of the gantry beam caused by the mass of the Z axis acting at a distance X from the center of the mass of the beam. The cutting force has its share, but not that much unless the beam is very short and the motor is very strong. If you lower the carriage on the Z axis by, say 100 mm , you will have a certain tip of the tool displacement, but if you lower it 200 mm the displacement will be bigger. Also, 100 mm lowering the carriage in the middle of the beam will produce a bigger displacement than 100 mm lowering the carriage at the end of the beam. So, the beam should be designed to a specific Z travel, for instance: how should I design the beam so that to have a maximum displacement of no more than 25 N/micron at 300 mm Z axis travel (and obviously at the middle of the beam where it is got the weakest point). Let me give you an worked out example. Suppose a beam of rectangular carbon steel of 400 mm height , 200 mm width, 6 mm thickness; 800 mm unsupported length of the beam; horizontal distance between center beam and Z axis carriage center = 300 mm (out of which 100 mm is half the width of the beam); mass of the Z axis = 1500 N; cutting force = 200 N. Now, the parameter that we will vary is the vertical distance between center of the beam to the tip of the tool. If this distance is 300 mm (which means 100 mm effective Z travel under the beam, as 200 mm is half the height of the beam), the tool deflection will be 10 microns. If we lower the carriage down by 100 mm, (which means 200 mm effective Z axis travel) the tool deflection will be 14 microns. If we lower it further by 100 mm (300 mm effective Z axis travel), the tool deflection will be 18 microns. Lastly, lowering it down even further by 100 mm, the tool displacement will be 22 microns. So, the angle of twist is the ''hot'' parameter. Tool displacement is basically the amount of distance the tool deviates from perpendicularity, which is consistent with the angle of twist around the longitudinal axis of the beam. Chatter is partly caused by this displacement and I have noticed that in practice, when face milling for instance, the milling marks on the floor of the work piece are sometimes wrongly attributed to either the material the mill is made out of (steel, cast iron, etc), or to the lack of tramming the head of the Z axis carriage. These have their share too, but there is an amount of , let's just called them ''chatter marks'', that will be there forever by design, IF the angle of twist was not well conceived from the outset. In practical terms, a hobbyist should raise the work as much as possible to the Z carriage, as the accuracy is better the higher up the work is set to.

I am building a CNC router for machining steel etc - I have already purchased the spindle & steppers etc. The spindle is quite a high quality one with lower speed for steel cutting/with water cooling - 100mm in dia. weighing about 14 kg - I guess the fixed gantry design will be the best solution for that weight of spindle??

The music adds nothing. It is distracting and it make it harder to hear what you are saying.

If you made the gantry wider (lets call that X axis) you could shorten the length of travel (Y axis) of the moving table

You didn not show the results of the "L" profile. Thanks anyways.

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;)

Hej William, fantastisk indhold! Thanks a ton:). I am in the research phase of making a stiff router, too so finding your channel is great. I will either cast mine in Epoxy Granite or make it out of granite surface plate a la Fox - just cuz I like how he managed to make a very precise frame with basic tools.