[tigox]

Hello, i've been following this forum for a while now because of my eagerness to build a cnc myself, after much searching and "studying" i've concluded to build a rectangular moving gauntry design 1150mm (y axis) by 1000mm (x axis) and 400mm of z axis, i will be using 40x40mm aluminium profile for the cnc Y structure, 80x20mm aluminium profile for the x axis, the 80x20mm extrusion will be between the two plates of the gauntry, i still need to figure out the design of the z axis though.
Anyways, i would like some opinion, if possible on some subjects regarding this build.

-First of all, do the aluminium extrusion sizes seem adequate?

-Second, for the gauntry plates do i use aluminium solid plates or can i make them out of aluminium profiles too?

-And third and most important, these are the rails/screws i was thinking of using for my build:
-2xSBR20 rails 1150mm long with 4pcs respective bearings; (Y axis)
-2xSBR16 rails 1000mm long with 4pcs respective bearings; (X axis)
-2xSBR16 rails 400mm long with 4pcs respective bearings; (Z axis)
-2xRM2510 ballscrews 1150mm long end machined with 2SETS respective support bearings BK/BF15 and nuts; (Y axis)
-1xRM1610 ballscrew 1000mm long end machined with 1 SET respective support bearings BK/BF12and nuts; (X axis)
-1xRM1605 ballscrew 400mm long end machined with 1SET respective support bearings BK/BF12and nuts; (Z axis)

i shall purchase these items from "our friend" linearmotionbearings2008" as it seems to be the best for my budget.

So, does this build seem ok? are the rails/screws too small for the X and Z axis, as they are smaller than the Y which needs to be the most rigid axis?

Thank you very much in advance, any help is crucial

[louieatienza]

Hello, i've been following this forum for a while now because of my eagerness to build a cnc myself, after much searching and "studying" i've concluded to build a rectangular moving gauntry design 1150mm (y axis) by 1000mm (x axis) and 400mm of z axis, i will be using 40x40mm aluminium profile for the cnc Y structure, 80x20mm aluminium profile for the x axis, the 80x20mm extrusion will be between the two plates of the gauntry, i still need to figure out the design of the z axis though.
Anyways, i would like some opinion, if possible on some subjects regarding this build.

-First of all, do the aluminium extrusion sizes seem adequate?

-Second, for the gauntry plates do i use aluminium solid plates or can i make them out of aluminium profiles too?

-And third and most important, these are the rails/screws i was thinking of using for my build:
-2xSBR20 rails 1150mm long with 4pcs respective bearings; (Y axis)
-2xSBR16 rails 1000mm long with 4pcs respective bearings; (X axis)
-2xSBR16 rails 400mm long with 4pcs respective bearings; (Z axis)
-2xRM2510 ballscrews 1150mm long end machined with 2SETS respective support bearings BK/BF15 and nuts; (Y axis)
-1xRM1610 ballscrew 1000mm long end machined with 1 SET respective support bearings BK/BF12and nuts; (X axis)
-1xRM1605 ballscrew 400mm long end machined with 1SET respective support bearings BK/BF12and nuts; (Z axis)

i shall purchase these items from "our friend" linearmotionbearings2008" as it seems to be the best for my budget.

So, does this build seem ok? are the rails/screws too small for the X and Z axis, as they are smaller than the Y which needs to be the most rigid axis?

Thank you very much in advance, any help is crucial

You should draw this all out before starting. You can't just bolt the SBR rail to the extrusion. Also if the listed dimensions are your desired travels you'll need more length from the rails and ballscrews to accommodate the length of the ballnut and support blocks and bearing and drive journals, as well as extra room for limit switches.

[tigox]

You should draw this all out before starting. You can't just bolt the SBR rail to the extrusion. Also if the listed dimensions are your desired travels you'll need more length from the rails and ballscrews to accommodate the length of the ballnut and support blocks and bearing and drive journals, as well as extra room for limit switches.

Hum, if I cannot bolt directly to the extrusions how do I do it may I ask?
And about the travel, I am designing the CNC around the bakkscrews and rails, so whatever travel I have left is good, will certainly be above 1m on the y axis for example and that, being low, is still good enough for me.

[louieatienza]

Hum, if I cannot bolt directly to the extrusions how do I do it may I ask?
And about the travel, I am designing the CNC around the bakkscrews and rails, so whatever travel I have left is good, will certainly be above 1m on the y axis for example and that, being low, is still good enough for me.

Well, look at the t slot configuration of the extrusion and compare it to the bolt hole pattern of the SBR mount, and it should be painfully obvious!

I've seen plates bolted to the extrusion, and I've seen the extrusion drilled out. But if you need to do either you may as well use aluminum tube which is cheaper.

[tigox]

Well, look at the t slot configuration of the extrusion and compare it to the bolt hole pattern of the SBR mount, and it should be painfully obvious!

I've seen plates bolted to the extrusion, and I've seen the extrusion drilled out. But if you need to do either you may as well use aluminum tube which is cheaper.

So what do you advise in your experience?

[pippin88]

Don't design around rails etc. They are available custom lengths (usually cheaper to message linearmotionbearings and ask for what you want anyway)

10mm lead ballscrews would be preferable.

Seriously consider a kit such as CNC router parts.

You need to spend some months reading and reviewing other people's builds.

[RicknBeachcrest]

Believe it or not, all the answers are here in this forum. I know, I built a very nice machine from all the knowledge contained here. Don't get over anxious and start buying stuff without a well laid out plan. This linear motion stuff is not cheap and it's re-sale value is not much compared to what you payed. Take your time and find a build that is close to what you have in mind. There are many successful routers here and I would say a number of unsuccessful one also.

Good luck.
Rick

[tigox]

Don't design around rails etc. They are available custom lengths (usually cheaper to message linearmotionbearings and ask for what you want anyway)

10mm lead ballscrews would be preferable.

Seriously consider a kit such as CNC router parts.

You need to spend some months reading and reviewing other people's builds.

Actually... I picked the size I wanted that was 1200mm by 900mm by 400mm, but the only options were 1150mm by 1000mm by 400mm, so after that only then I started constructing around the sizes chai said were available, and these were about the travel I had in mind for my machine so it's OK with me


And yes, regarding the pitch of the screws, I changed the x axis to a 2510 also but kept 1605 on the z because I need the adicional precision and not so much of speed.

What seems to be the main flaws people do on new builds?
I know of some like unsupported rails and weak gauntries, but I know not, at least that I remember, many other flaws.

Thank you all so much for your help, hope one day soon I'll make a post with a 3d sketch up of the machine I had visioned

[louieatienza]

So what do you advise in your experience?

I just checked, the bolt hole distance side to side is about 30mm, so if you use 60mm extrusion, base 30, you should be able to bolt directly to the t-slots. My experience? I'd rather use profile rail. But if I did use SBR I'd space the trucks out a lot further than most builds I've seen especially if you are center driving the gantry, or even consider dual screws.

One of the biggest pitfall I've seen is oversizing steppers which in fact can hinder machine performance. Second,usung the dreaded TB6560 drives on eBay. Third, insufficient gusseting. A lot is depending on your final use for the machine.

[tigox]

I just checked, the bolt hole distance side to side is about 30mm, so if you use 60mm extrusion, base 30, you should be able to bolt directly to the t-slots. My experience? I'd rather use profile rail. But if I did use SBR I'd space the trucks out a lot further than most builds I've seen especially if you are center driving the gantry, or even consider dual screws.

One of the biggest pitfall I've seen is oversizing steppers which in fact can hinder machine performance. Second,usung the dreaded TB6560 drives on eBay. Third, insufficient gusseting. A lot is depending on your final use for the machine.

Realized that about the 30x60 last night, forgot to post it haha

By spacing the trucks do you mean the distance between both rails on the y axis? (Horizontally speaking)? And yes I'll be using dual screws.

Would like to have profile rails yes but they are too damn ezpensive .. Oh well

I'll have to convert rotary to linear motion to choose the steppers.

What is gusseting might I ask? Never heard the term

The main use for the machine will be cutting and milling wood at a fairly high speed, and maybe cutting and milling some aluminum slowly.

[louieatienza]

Realized that about the 30x60 last night, forgot to post it haha

By spacing the trucks do you mean the distance between both rails on the y axis? (Horizontally speaking)? And yes I'll be using dual screws.

Would like to have profile rails yes but they are too damn ezpensive .. Oh well

I'll have to convert rotary to linear motion to choose the steppers.

What is gusseting might I ask? Never heard the term

The main use for the machine will be cutting and milling wood at a fairly high speed, and maybe cutting and milling some aluminum slowly.

Gusseting would be angle plates that span an inside corner which strengthens that corner. If you use t-slot, they make pre-made gusseting and plates; or you can make them yourself out of aluminum plate.

By spacing the trucks, I mean along each rail. For the gantry legs you'd want the trucks spaced such that the center of gravity of the gantry falls somewhere between the two trucks, or else one will wear faster than the other. This is more important at higher speed. Also you'll need a pretty beefy spindle to cut wood at speed.

You won't be able to cut aluminum slowly; the higher speeds of woodworking spindles dictate higher speeds (and maybe lower depth of cut) for aluminum. I cut aluminum frequently on my machine. the key is using the right tooling and choosing the right toolpaths (almost always climb milling) to get the chips to flow away from the toolpath.

There's a lot to be said about using steel tubing and plates for higher-speed wood cutting, and indeed there's merit to that. I cut at a relatively brisk rate for my machine and spindle (about 125-150ipm and 3/8"
doc with a 1/2" single-flute endmill) though my machine is not the stiffest. I simply allow for "spring away" with my roughing passes by climb-milling, and do my finish passes conventional milling at a slower federate.

Here's some vids of my machines cutting:

https://www.youtube.com/user/AtienzaLouie

[tigox]

Gusseting would be angle plates that span an inside corner which strengthens that corner. If you use t-slot, they make pre-made gusseting and plates; or you can make them yourself out of aluminum plate.

By spacing the trucks, I mean along each rail. For the gantry legs you'd want the trucks spaced such that the center of gravity of the gantry falls somewhere between the two trucks, or else one will wear faster than the other. This is more important at higher speed. Also you'll need a pretty beefy spindle to cut wood at speed.

You won't be able to cut aluminum slowly; the higher speeds of woodworking spindles dictate higher speeds (and maybe lower depth of cut) for aluminum. I cut aluminum frequently on my machine. the key is using the right tooling and choosing the right toolpaths (almost always climb milling) to get the chips to flow away from the toolpath.

There's a lot to be said about using steel tubing and plates for higher-speed wood cutting, and indeed there's merit to that. I cut at a relatively brisk rate for my machine and spindle (about 125-150ipm and 3/8"
doc with a 1/2" single-flute endmill) though my machine is not the stiffest. I simply allow for "spring away" with my roughing passes by climb-milling, and do my finish passes conventional milling at a slower federate.

Here's some vids of my machines cutting:

https://www.youtube.com/user/AtienzaLouie

i'm currently trying to design the machine i have in mind in solidworks, hope to have something soon, i could try to explain however if you'd like to put you mind to imagination mode :P
invision a rectangular frame made of aluminium extrusion (1400mm by 1000mm) and then for the Y axis i would put the rails with the screw holes above the 1400mm aluminium extrusions this meaning i woul only have two rails on the Y and the gauntry would roll above the rails instead of sideways rails commonly seen, finally for the gauntry arms they would be solid aluminium plates (or aluminium extrusions too if i'd find a way to make them as solid as the aluminium plates) leaning to one side to "off-center" the spindle so the spindle center of gravity is directly above the SBR20 bearings.
Really sorry to make you invision it, but i will surely and honestly understand if you don't even try, as it seems a bit unprofessional... anyways, thank you so much for all the help, and will come back soon with the design or at least a visual representation.

[wizard]

Well, look at the t slot configuration of the extrusion and compare it to the bolt hole pattern of the SBR mount, and it should be painfully obvious!

I've seen plates bolted to the extrusion, and I've seen the extrusion drilled out. But if you need to do either you may as well use aluminum tube which is cheaper.

Or a steel tube that is cheaper again.

I have to agree with a sketch or physical mock up to get an idea about form and function. Even simple cardboard mock ups can enlighten especially if one has not worked with the materials before.

[wizard]

Hello, i've been following this forum for a while now because of my eagerness to build a cnc myself, after much searching and "studying" i've concluded to build a rectangular moving gauntry design 1150mm (y axis) by 1000mm (x axis) and 400mm of z axis, i will be using 40x40mm aluminium profile for the cnc Y structure, 80x20mm aluminium profile for the x axis, the 80x20mm extrusion will be between the two plates of the gauntry, i still need to figure out the design of the z axis though.
Anyways, i would like some opinion, if possible on some subjects regarding this build.

The first thing I noticed is that the Z axis is relatively high, that could be a problem.

-First of all, do the aluminium extrusion sizes seem adequate?

Honestly no. Then again I may be confused by what you are calling the X and Y. In any even the axis that supports the Z needs a fairly good size beam to support that long Z well. Probably 250 to 300 mm. I'm assuming you are implying 400 mm of vertical clearance under the gantry.

-Second, for the gauntry plates do i use aluminium solid plates or can i make them out of aluminium profiles too?

If you mean the supports for the gantry I'd go for a box section. Plate can be used but almost no one buys a thick enough plate due to the expense and further they never reinforce it. In the end a box section is cheaper and easier to deal with.

-And third and most important, these are the rails/screws i was thinking of using for my build:
-2xSBR20 rails 1150mm long with 4pcs respective bearings; (Y axis)
-2xSBR16 rails 1000mm long with 4pcs respective bearings; (X axis)
-2xSBR16 rails 400mm long with 4pcs respective bearings; (Z axis)
-2xRM2510 ballscrews 1150mm long end machined with 2SETS respective support bearings BK/BF15 and nuts; (Y axis)
-1xRM1610 ballscrew 1000mm long end machined with 1 SET respective support bearings BK/BF12and nuts; (X axis)
-1xRM1605 ballscrew 400mm long end machined with 1SET respective support bearings BK/BF12and nuts; (Z axis)

For that long Z axis I'd go with Profile rails. 400 mm is a big distance to span. The rest of the machine should be designed for upgrading to profile rails in the future.

i shall purchase these items from "our friend" linearmotionbearings2008" as it seems to be the best for my budget.

So, does this build seem ok? are the rails/screws too small for the X and Z axis, as they are smaller than the Y which needs to be the most rigid axis?

Well yes they are too small. You can space the bearings out a bit and add additional bearings which will help but this impacts you ability to cover a large cutting area. A good part of your problem is the 400 mm of clearance.

Thank you very much in advance, any help is crucial

No problem.

I don't know about your local area but do consider steel in your design as it is often dramatically cheaper. The machine doesn't need to be all steel either but it would likely to be a good investment in the gantry. There is a very good sticky thread about the importance of this beam. Of course what your usage intentions are make an impact here.

It is helpful on a low end machine to minimize Z axis capability. Here of course you need to know what the intended usage is but a high Z puts a lot of torque on the gantry components. If you are going to process sheet goods I'd cut down the Z clearance. If you need that tall Z then you may have to accept a more expensive machine.

[louieatienza]

Or a steel tube that is cheaper again.

I have to agree with a sketch or physical mock up to get an idea about form and function. Even simple cardboard mock ups can enlighten especially if one has not worked with the materials before.

While steel tube is initially cheaper (maybe) you'll have to weld, stress relieve, then machine mounting surfaces or epoxy level. I don't know how much of this is absolutely necessary for a wood router. Misumi sells extrusion with milled flat faces and the price is relatively affordable. I can't imagine it cheaper sending a welded frame to a machine shop to true mounting surfaces.

What's nice is that most all suppliers provide CAD models of their parts, making modeling a machine so much easier...

[tigox]

so, after many, many hours (solidworks is hard for a beginner) i've come up with the beginning of the full design, i still haven't finished it, not by a log shot but in its current state, will help me explain to you and also will allow you to see what i had in mind.
So after integrating your considerations on my design, i've decided to use profile to form the gauntry's "legs" and thus lowered enormously the center of gravity (and also cost of the machine :P) the picture you are about to see includes only the ballscrew couplings (in black), the linear rails, bearings, and the gauntry basic assembly, hope it help you to see what i have in mind after considering your tips.





Attachment 266582
Attachment 266584
Attachment 266586

[tigox]

The first thing I noticed is that the Z axis is relatively high, that could be a problem.

Honestly no. Then again I may be confused by what you are calling the X and Y. In any even the axis that supports the Z needs a fairly good size beam to support that long Z well. Probably 250 to 300 mm. I'm assuming you are implying 400 mm of vertical clearance under the gantry.

If you mean the supports for the gantry I'd go for a box section. Plate can be used but almost no one buys a thick enough plate due to the expense and further they never reinforce it. In the end a box section is cheaper and easier to deal with.

For that long Z axis I'd go with Profile rails. 400 mm is a big distance to span. The rest of the machine should be designed for upgrading to profile rails in the future.

Well yes they are too small. You can space the bearings out a bit and add additional bearings which will help but this impacts you ability to cover a large cutting area. A good part of your problem is the 400 mm of clearance.


No problem.

I don't know about your local area but do consider steel in your design as it is often dramatically cheaper. The machine doesn't need to be all steel either but it would likely to be a good investment in the gantry. There is a very good sticky thread about the importance of this beam. Of course what your usage intentions are make an impact here.

It is helpful on a low end machine to minimize Z axis capability. Here of course you need to know what the intended usage is but a high Z puts a lot of torque on the gantry components. If you are going to process sheet goods I'd cut down the Z clearance. If you need that tall Z then you may have to accept a more expensive machine.

Updated images.

Attachment 266698
Attachment 266700

[wizard]

While steel tube is initially cheaper (maybe) you'll have to weld, stress relieve, then machine mounting surfaces or epoxy level. I don't know how much of this is absolutely necessary for a wood router.

For a wood router where high precision isn't expected you can do away with a lot of that extra work. If you go round rails you may be able to avoid grinding or epoxy leveling. Round rails can deal with the convexity or concavity across the face of the beam, a carefully selected beam may be straight enough for wood working also. It is certainly a question of expectations.

For a low cost approach I see it as the cheapest way to a CNC router that gives the owner a relatively stiff gantry. There is no need to weld to the beam. I don't see this as a machine that competes with a finely built router capable of machining aluminum precisely. Rather I see it as an alternative to wood, or aluminum beams fabricated in a home shop.

Misumi sells extrusion with milled flat faces and the price is relatively affordable. I can't imagine it cheaper sending a welded frame to a machine shop to true mounting surfaces.

This wouldn't be a welded frame either, just a beam that frankly could be supported in the same way the Misumi extrusion would be.

What's nice is that most all suppliers provide CAD models of their parts, making modeling a machine so much easier...

That is one way to go about it. Sometimes though manipulating real physical objects helps one get a feel for how a design will work out. It also takes a long time to get a CAD based model correct.

[louieatienza]

For a wood router where high precision isn't expected you can do away with a lot of that extra work. If you go round rails you may be able to avoid grinding or epoxy leveling. Round rails can deal with the convexity or concavity across the face of the beam, a carefully selected beam may be straight enough for wood working also. It is certainly a question of expectations.

Well what God giveth in one regard he taketh away in another. If you have concavity or convexity in whatever rail you choose that telegraphs to your parts. Even if the round rail and mounts will take up any irregularity in the tube, the bearing blocks will be unevenly loaded, causing premature wear to the tracks and.or blocks. Also while steel tube may start out relatively cheaper, holes still need to be drilled and tapped; this requires thicker wall tubing be used. This also adds to the weight, which means larger motors to drive the axis. And to truly get the benefit of stiffness, ribs and /or diagonals need to be used; further adding weight; extrusions have enough webbing to aid with twist for its weight. Then there is time; all extrusion suppliers will precision cut, and everything is bolted on. Even stepper plates can be drilled out of flat stock and bolted to the end of extrusions; you'd have to weld a plate at the end of a tube to do that. Precision drilling many holes may not be within one's grasp, and there really is not a lot of room for error; that is all time consuming, you can enlargen the holes to the rail mounts to allow clearance but then again that's more time involved. Not to mention the time and expense of welding.

This is long-winded, but the point is, if an imperfect steel tube is good enough, then a (straighter and flatter) extrusion of proper size is good enough too.

That is one way to go about it. Sometimes though manipulating real physical objects helps one get a feel for how a design will work out. It also takes a long time to get a CAD based model correct.

I believe Misumi and Bosch Rexroth both have downloadable CAD libraries, making this very easy. This includes models for extrusion, linear rails, etc. As a woodworker and cabinetmaker by trade, I grew up on using story poles to lay out work. A full scale layout with top, side, and front views on plywood would be beneficial. Or just buying components and connectors from FLA or CNCRP, and supplying the recommended size extrusions, would be a lot easier.

[tigox]

anyone got some tips on the sketches i posted? haha