First Build 5 x 12 Steel Frame CNC router

First I would like to say the information here is amazing and has greatly helped my design and learning for this CNC router build.

Objectives,

5 foot by at least 10 ft of machining area
Z height high enough for paddleboard foam blanks ~ need roughly 12 inches under the tool
ability to machine wood, aluminum, foam
good accuracy/precision (still trying to figure out where I want/need to be)
Vacuum hold down


Parts I already have
Linear rails - INA 25mm 4 row linear rails - I have enough to do all axis's and enough bearings
Y axis ballscrew - 10mm/rev rolled ballscrew
1850 oz/in stepper motors - 2 for X (long axis) and 1 for Y
2 4hp regenerative vacuum blowers
Colombo 10hp spindle with ISO30 ATC

I will start out where I am now and then go into some questions I have.

The gantry legs mock-up 4 x6 x 1/4wall box tubing, 1/2 inch plate for the feet.
Attachment 17792

Attachment 17793

Attachment 17794

Gantry partially welded up, Gantry is built from 4in x 6in x 1/4in wall box tubing and will get blocking in between the 2 tubing with some vertical bracing on the back. I machined the ends of the gantry before welding them up so I can put an e-stop on each end. The ballscrew is laying ontop of the gantry and will live between the 2 box tubing when complete.

Attachment 17795

Here is the plan for the Z axis, made from 3in x 6in x 1/4wall box as a starting point. I plan to make an A axis and have mounted the motor up and off to the side. Although this could still get in the way. Should I put the motor for the A axis above the spindle motor? This will make the HTD belt 20 inches center to center. If I did that would I be looking for trouble as far as belt stretch is concerned?

Attachment 17796
Attachment 17797

Heres what I was thinking for A axis
https://youtu.be/Lq3Ei8oALXY

A few questions,
Gantry and Z axis is going to be ~550lbs (~250kg), am I shooting myself in the foot using steppers for this weight? I would like to get decent speed out of the thing without the risk of missing steps. When I purchased the steppers I was trying to balance cost but now im worried I will have trouble with it when im done.

What pitch should I shoot for on the Z axis screw? I was planning on using the stepper motor with a ~4:1 reduction. Total travel as it stands right now will be 16 inches. Weight of Z with Spindle will be around 100lbs should I add spring assist to this? or air springs etc?

Next steps for me,

I am working on mounting the rails on the Y Axis and getting prepped for pouring epoxy as soon as the temp rises a bit. Here is the plan for the pour and looking for any insight.

Lay gantry on its back
Level with starrett precision level as close as I can in both planes
pour epoxy for Y axis linear slides
at the same time pour the mount pads for the Y Axis ballscrew, in my mind this gets the ballscrew on the same plane (albeit at a different height) as the linear rails
Paint Gantry
Mount the lower linear rail for the Y Axis
Flip gantry upside down
Use precision level on the linear rail and set rail level and also use a precision square and the level to level in the other plane
Pour expoxy on gantry feet (my thinking here is that I can then get the gantry feet 90 deg to the Y axis linear rails and also on the same plane as the linear rails) I would assume there may be some slight shimming still but the epoxy will be close.


Thanks
Scott

Some updates on the gantry

All of the bracing clamped in place ready for spot welding. The ballscrew is in place to set the distance between mounts.
Attachment 17802

Attachment 17803

Here is one of ballscrew mounts
Attachment 17804
Attachment 17805
Attachment 17806

this is the end of the gantry showing the space for the estop
Attachment 17807

This is one of the longer braces that connect to the ballscrew mount block

Attachment 17809
Attachment 17808

Here is the backside with all the bracing welded up
Attachment 17810

And the front side, notice I drilled some 1/2 in holes on the wrong side. My linear rails are threaded from the backside so I have to through drill from the back. The good news is I am welding on 3/8 plate (I drilled the holes to the correct spacing on the mill first and used the 3/8 plates as templates) on the front side where the linear rails are going to mount.
Attachment 17811

Very impressed, with a lot of things. Very excited about your A-axis, sometimes one should just go to ahead and build it instead of pondering if it will work or not :D I have not attempted to build it yet, as I dont even have an idea of how I would use it. I really have no clue how one would incorporate 4 axis programming.

I would probably fit the widest possible belt there, if I were to use belt, you want the spindle to be rigid enough. What kind of bearings, if that is how you are pivoting the A-axis? Got any detailed view of it?

Nice work so far.

Quote:

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Originally Posted by sinnsvak

What kind of bearings, if that is how you are pivoting the A-axis? Got any detailed view of it?

Nice work so far.

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Thanks for the comments

Heres a view of the bottom of the Z axis and a section cut into it.

Attachment 17814

Attachment 17815
**sorry the drawings are upside down**

Attachment 17816
Here is the box tubing removed

The bearings are roller bearings that I can get from McMaster Carr easily. 1 1/4 diameter shaft. Bearings are designed to be held into aluminum housings bolted into the 3 x6 steel tubing. The shaft is a 6 inch threaded on both ends. Again something I can just order from McMaster. The bolts into the shaft allow me to put preload into the bearings. I was thinking of bolting the pulley hub (pulley is not pictured) to the spindle mount.

Open to thoughts on this design. I think it will work....

A couple more updates sorry for the bad pictures
Drilled backside holes out to 1/2 inch to allow bolt and ratchet to be put through from the back. Im thinking I will just order a bunch of plastic plugs to put into these holes once I am done.
Attachment 17818
Attachment 17819

I threw a couple bolts into one of the linear rails just to see how things were coming together.
Attachment 17820
Attachment 17821

So far I am pretty happy with how the build is coming together. Time will tell if I have some precision/accuracy when im done...

Here is a ~bad video of me test running the used colombo 10hp ATC spindle that I got. Running it at ~18,000rpm after running at ~8,000rpm for 10 mins to get the grease moving in the bearings.
https://youtu.be/yyiDn-8hFaE

Very ambitious for a first build.

Some thoughts:

-the gantry legs dont seem adequate for the rest of the parts you will use on your machine

-the A may work for foam but i dont see it serious for anything more than wood

-the stepper motors , ok- the huge stepper motors, what drives will power them? 230VAC?

-that bracing may be was totally unnecessary. I dont see how that will strengthen anything. It could even make things worse, strengthening one point too much and not allowing the forces to spread uniformly and creating pressure points. So later all rings.


What will you be using this machine for? Remember- the weakest point is the criteria for how strong your machine would be. Again-the gantry legs.


PS:
That gantry legs will greatly benefit from bolting or welding on them 10mm steel plates in both directions, 2 per leg in total

Hi Scott,

This is how I see couple of not so little things.

Steppers:
Really Cannot comment if they will be good enough because you haven't said anything about what your using for linear motion on the X axis. I assume Rack n pinion but what ratio etc.? . . . But let me put it this way 550lbs or put anohter way 1/4 Ton is lot of Mass to Accel and stop so better get this correct or you'll seriously regret using steppers.


A Axis: You need to think again on this I'm afraid NO WAY will Stepper with such small ratio hold that Big spindle at angle without moving or vibrating.
Remember the Z axis is the MOST important area on machine so weaken this and all that OTT work you have done on the frame is pointless.

Quote:

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Originally Posted by Boyan Silyavski

Very ambitious for a first build.

Some thoughts:

-the gantry legs dont seem adequate for the rest of the parts you will use on your machine

-the A may work for foam but i dont see it serious for anything more than wood

-the stepper motors , ok- the huge stepper motors, what drives will power them? 230VAC?

-that bracing may be was totally unnecessary. I dont see how that will strengthen anything. It could even make things worse, strengthening one point too much and not allowing the forces to spread uniformly and creating pressure points. So later all rings.


What will you be using this machine for? Remember- the weakest point is the criteria for how strong your machine would be. Again-the gantry legs.


PS:
That gantry legs will greatly benefit from bolting or welding on them 10mm steel plates in both directions, 2 per leg in total

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Quote:

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Hi Scott,

This is how I see couple of not so little things.

Steppers:
Really Cannot comment if they will be good enough because you haven't said anything about what your using for linear motion on the X axis. I assume Rack n pinion but what ratio etc.? . . . But let me put it this way 550lbs or put anohter way 1/4 Ton is lot of Mass to Accel and stop so better get this correct or you'll seriously regret using steppers.


A Axis: You need to think again on this I'm afraid NO WAY will Stepper with such small ratio hold that Big spindle at angle without moving or vibrating.
Remember the Z axis is the MOST important area on machine so weaken this and all that OTT work you have done on the frame is pointless.

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I think you are talking something along these lines for the sides of the gantry legs? I was wanting to do FEA on these legs but never got around to it, I did however do calculations (free body diagram) to try to calculate total deflection based on 1000lb force at the bit and keeping the total deflection ~3 thou at full load.

I could go higher with the bracing as well this is just a quick drawing.
Attachment 17835

The thinking behind the bracing was to connect the upper and lower gantry beams. I used box tubing between the beams. Now the rear bracing, the thought there was to reduce the twist in the gantry. Hopefully it doesnt cause issues...

So the A axis, this is exactly what I am worried about, holding it in place when at angle and also moving it. The A axis would really only be used when machining foam blanks for paddle boards. However since I want to be able to machine wood, and aluminum as well then I really need to make sure this thing is right.

Couple things I am thinking thoughts are greatly appreciated.
- Eliminate A Axis...
- greatly increase the belt ratio
- keep A Axis but have an air operated taper pin that holds it at 0 when machining wood/alum
- look into a harmonic drive rather than belt drive

X drive
I was planning on using rack and pinion with a pinion of 1 inch I was going for 4:1 ratio to the pinion.
so 3.14 inches per revolution of the pinion, 0.785 inches per motor revolution, works out to 0.0039 inches per step. I was thinking of micro stepping them x10 = 0.000395inch per micro step.

I am brand new to this and trying to learn what feed and rapid movements I need to shoot for to cut wood/aluminum properly. I know it depends on the number of flutes on the bit etc. Am I crazy to think I should shoot for 1000ipm?

The motors I have are chinese 1841 oz/in with MA860H drivers along with 60V drives. Based on the questions it sounds like these are not adequate?

Servos
So if scrap the steppers for X axis then im looking at servos. Something I am even more NEW to than steppers. I need to do more learning on how to size them please correct where I have errors!

Things to keep in mind when sizing?
Gear ratio - want to keep the servo motor spinning at higher speed to stay in its power range - unlike steppers which have the most power at 0 speed
Load to motor inertia, this one I have seen 10:1 ratio but I dont really understand how to use that

One thing I dont understand, when X is not moving what is holding if from moving? I had assumed that the steppers hold the load from moving at 0 speed (is this the case with steppers?). If that is the case what is doing the holding when using servos?

Can my router have both steppers and servo motors? I think the stepper would still be adequate for the Y Axis and could use one for the Z axis (as Im sure I can not send them back)... I plan to use ethernet smooth stepper with mach4.

Got the X axis steel drilled these needed to be through drilled as well since the linear rails are bolted from the back. 244 holes!!!!
Attachment 17836
Attachment 17837

Any help with servos for this size of gantry is greatly appreciated.

Hi Scott
I don't have any experience of the 4/5 axis machines but i would imagine that the "A" axis you are trying to emulate would be a wheel & pinion mechanism.
Regards
Mike

Ok, lets start from the beginning. I will try to resume some things, you just need to further research the topics:

1. You should absolutely know what weight your gantry is with all things mounted. Knowing the mass of the gantry will be decisive on what motors, what size ball screw, rotating nut, Rack and pinion, etc..

2. Be realistic about the feeds and speeds. And what you really need the machine for. All in one would be usually a disaster in some area.

3. Motor sizing. People drive 3nm nema 23 motors at 70VDC. And we are talking low inductance motors. Expected reliable performance from such motors coupled with xx10 ball screws is 10000mm/min. The motors you have are high inductance motors. I am not a specialist here but there are a lot of knowledgeable people here that will tell you at what voltage, but i am sure that it must be more than 110VDC. Do your research and find at what voltage these motors perform well. And if these drives will be ok.

4.Without knowing the total weight of the gantry... but i see you start ambitious, so yes, you will need servos to drive the gantry reliably fast if you aim at 25000mm/min. And you will need rotating ball nut or rack and pinion

5. There is a very well made calculator at the forum here, search for it, and i am sure that the gantry legs deflection will not be as you say...but may be i am wrong




I dont want to discourage you, but i am having the feeling that if you continue without thinking it too much, there will be disappointments on the way. WHY JUST DONT YOU SLOW A BIT AND READ MORE BUILD LOGS. All the info is there.

And by the way it seems the american thing is to desire rapids of 1000ipm. And make rack and pinion machines. We here in EU prefer precise ball screw machines and rotating ball nuts for big machines and heavy gantries.

Hi Scott,

Just to scale point #3 from Boyan - 3Nm Nema 23 at 70VDC could be used up to gantry weight of 50-70kg tops. As yours is 5 times this weight the stepper / driver combo needs careful thought.

I can sort of see the machine you are trying to make by piecing all the photo together - and it looks like a commercial wood router with raised gantry.

If you want to cut aluminium as well I would suggest you chop the legs off the gantry, and go for a raised X axis instead. Lift the X axis members up on supports away from the bed until they meet the bottom of the gantry. This makes a much stiffer machine for little effort. Your span is quite wide so you will need all the help you can get for aluminium.

Can you post up a picture of the overall machine design?

Quote:

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Originally Posted by Boyan Silyavski

Ok, lets start from the beginning. I will try to resume some things, you just need to further research the topics:

1. You should absolutely know what weight your gantry is with all things mounted. Knowing the mass of the gantry will be decisive on what motors, what size ball screw, rotating nut, Rack and pinion, etc..

2. Be realistic about the feeds and speeds. And what you really need the machine for. All in one would be usually a disaster in some area.

3. Motor sizing. People drive 3nm nema 23 motors at 70VDC. And we are talking low inductance motors. Expected reliable performance from such motors coupled with xx10 ball screws is 10000mm/min. The motors you have are high inductance motors. I am not a specialist here but there are a lot of knowledgeable people here that will tell you at what voltage, but i am sure that it must be more than 110VDC. Do your research and find at what voltage these motors perform well. And if these drives will be ok.

4.Without knowing the total weight of the gantry... but i see you start ambitious, so yes, you will need servos to drive the gantry reliably fast if you aim at 25000mm/min. And you will need rotating ball nut or rack and pinion

5. There is a very well made calculator at the forum here, search for it, and i am sure that the gantry legs deflection will not be as you say...but may be i am wrong




I dont want to discourage you, but i am having the feeling that if you continue without thinking it too much, there will be disappointments on the way. WHY JUST DONT YOU SLOW A BIT AND READ MORE BUILD LOGS. All the info is there.

And by the way it seems the american thing is to desire rapids of 1000ipm. And make rack and pinion machines. We here in EU prefer precise ball screw machines and rotating ball nuts for big machines and heavy gantries.

---

The gantry will weight around 550lbs, this number comes from the 3d drawing which worked out to 494 (this included the Z axis and the spindle) and I added 50 lbs for cables and cable routing. This was my bassis for sizing the motors. Sorry I thought I had been clear on it earlier in my thread about the weight.

Feeds I am happy to be realistic and dont care much about super fast rapids but I want to be able to drive the machine at proper cutting speeds.

Im sorry I came across as I jumped into this without any research when the opposite is true, I have done lots and lots of research both on forums and by inspecting commercial machines. I would not have been able to get to the point I am without lots of learning from all sources. I find there a very different views on most subjects associated with the gantry style cnc router so its hard to nail down whats the best design. And thats where some of my questions came from. The stepper route was more of a cost thing and I should have done more research on servos before going down that road.

I will find the calculator you speak of and give it a try. I just started out by doing the math, the hard part was actually finding out how much force would be applied at the tool so I could back calculate the flex at the gantry.

**I want to say machining Aluminum is a bonus for this machine as it will mainly be used for wood**

Quote:

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Hi Scott,

Just to scale point #3 from Boyan - 3Nm Nema 23 at 70VDC could be used up to gantry weight of 50-70kg tops. As yours is 5 times this weight the stepper / driver combo needs careful thought.

I can sort of see the machine you are trying to make by piecing all the photo together - and it looks like a commercial wood router with raised gantry.

If you want to cut aluminium as well I would suggest you chop the legs off the gantry, and go for a raised X axis instead. Lift the X axis members up on supports away from the bed until they meet the bottom of the gantry. This makes a much stiffer machine for little effort. Your span is quite wide so you will need all the help you can get for aluminium.

Can you post up a picture of the overall machine design?

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I looked carefully at doing a bridge style machine with high sides, the problem that kept running into this design was not easily being able to side load the machine. I do alot of work with large wood slabs which this machine will be used to flatten and I need to be able to side loads these as I dont have an overhead crane. (they weigh in excess of 1200 lbs)

Here is the Frame starting, I have blocked up the frame to level and used the gantry to set the exact distance.
Attachment 17845

Initially checking square with a precision square, final squaring will need to be done once its all welded up and before pour epoxy.
Attachment 17846
Attachment 17847

Alright so I ran the numbers through the excel spreadsheet.

Heres what I got
Attachment 17848

0.010mm deflection
0.00028 deg delfection
deflection at tool 0.002mm
Attachment 17849

0.00094mm deflection

Maybe I am entering the numbers wrong I will run through the numbers again but these look better than what I got when I just did the free body diagram. Thoughts on these?

These seem acceptable but im not sure what I should be shoot for as far as max deflection?

Thanks for any help. Want to make sure this is right before I get too far that I cant make changes.

Hi Scott,

I wrote that spreadsheet some time ago to compare simple shapes. For the numbers you have entered it looks like it is giving the correct answers.

Things to note:
It assumes everything else (e.g. spindle, tool, bearings, bedplate, joints . . . .) is infinitely stiff - so it is best case
Have you entered just one of the two gantry beams? If so the real stiffness will be higher as you have 2
Or have you given the overall gantry dimensions as a single beam? If so the real stiffness will be lower
It makes no prediction for deflection due to cutting vibration and machine resonance

It terms of max deflection it is personal choice but I would say wood <0.05mm and alum <0.01mm as a starting point. Others opinions welcome!

I get the point about raised gantry vs raised X axis (in the US this can be Y axis) for material loading, so as long as you've thought about the options and made a choice that's fine. Didn't know what you knew.

In summary you have a very stiff machine that is stiff enough for wood, but that gantry is heavy (hence our concern over stepper/driver/voltage - if you know these are OK then that's good), and resonance is unknown (the sheet can't show this).

Is this what you have?
http://www.ebay.com/itm/3-Axis-CNC-K...-/231424600113

If so, you're better off re-selling them and taking a loss.

A quality 300oz motor driver kit will typically cost more than that one does. What does that tell you? Do you really think that you're getting 6x the performance for the same price?

As Boyan mentioned, those are high inductance motors. Ideally, you want an inductance of around 2mH. Those motors really need about 100-120V to get the best performance from them. But even then, they won't spin nearly as fast as a much smaller motor.
You generally won't find large motors with low inductance, because they would require very high currents, and very expensive drives.

A few other things to consider. As steppers get larger, their maximum rpm's tend to decrease. I wouldn't be surprised if you can't get much more than 300rpm from those before they run out of torque. Which probably equals around 250ipm with your setup?

Also be aware that you often can't count on the microstep accuracy. Especially with large motors, where the microstep torque may not always be able to overcome the high detent torque those large motors have. When calculating resolution with steppers, 1/2 step is the best that you should hope to achieve.

Personally, I think a machine like that would really need something like 1Kw AC servos. Expect to spend at least $2000-$2500 for three.

As for cutting speeds. I run a Morbidelli at work, and we cut at 1000+ipm every day. Rapids much faster. But this is cutting sheet goods, plywood, MDF, particle board.
Hardwoods are not cut as fast. I typically will cut hardwoods at 300-500ipm with 1/4" and 3/8" bits.

If you're not cutting at these speeds, then you're not taking advantage of your machine and spindle.
One thing that most people don't consider, is that it can be very difficult to hold materials in place at high cutting speeds. My hardwood speeds are limited by my vacuum holding power. If the hardwoods are not held tightly enough, cut quality will suffer, and you'll need to cut slower to get acceptable quality. Slower = shorter tool life.

Ok the bottom line is that large steppers need Mains voltage Drives to get any speed from them. Like Ger says 110v will only get you limited speed.

If using R&P then you 100% will need Servos because they are so much less efficient than ballscrews so with heavy gantry like this you will need really high torque motors and Large steppers just won't give the speed you'll need.

Servos from China are now so low that it's No brainer to me that you need to look east.! Approx $400 per set drive/mootr/cables.

However be aware that you'll also need match the rest of the electronics to match so you'll need an external motion control card with high pulse frequency to get the full speed/smoothness of the servos.

Gerry, those are the ones, I have come to that conclusion as well. I think I will re-list those and find some servos.

Now do I keep a stepper for the Z (a smaller stepper not these big honking ones)? I would lean toward 2 servos on the X and 1 on the Y. Then I am thinking a smooth stepper in between it looks like that is fast enough to run the servos...

I know that my table is still going to be vacuum limited even with 8hp of regenerative vacuum. I plan to have 4 zones and also thinking about ways to include T-slot for hold down of hardwood parts.

Jazz, Im coming up empty on sets that are $400 im finding ~$600 for 1kw AC servo with driver. If you have any links to what you are talking about that would be greatly appreciated.

Im really leaning toward running a powered ballnut/ballscrew setup for the X, like Boyan said most builds here in the states use R&P but the 0 backlash and less wear aspect of the ballscrew is really appealing. Learning as much as I can from this forum and how other people implemented it. Im sure I will have questions...

A few updates, I dont love the look of the legs they look out of proportion to the rest of the machine but its steel that I already had on hand from other projects and its plenty strong with bracing. It gets a 3rd leg just havent gotten that far yet. Lots of bracing. I am trying to keep the one end open so I can use some of the space under the machine for rough sawn lumber storage...
Attachment 17870
Attachment 17871
Attachment 17872

Thanks for all the help so far! opened my eyes to some issues.

Just for fun I took a quick vid of me manually moving the gantry, its amazing with the linear guides allow...~move 500lbs with just fingers.
https://youtu.be/OTUE6K_w3Zk

I'm building a 4x8 machine and using AC servos, and I'm using steppers and Leadshine AM882 drives for the Z axis (two, it's a dual Z machine) to save money.

I would think that a 5mm pitch ballscrew and a 600oz stepper would be OK for your machine? That's just a guess, though.

As for $400 servos. I've seen 400W servos on AliExpress for around $400, but not larger ones. And at that price, you may not know exactly what you're getting. I'm paying around $575 for 400w Leadshine motors and drives for my machine. 750W and 1Kw are closer to $800 a set. The price difference between 750W and 1Kw is very small, so I'd definitely go with larger ones for a little more money. http://americanmotiontech.com/motor-...tage-ac-input/

As for vacuum, you can never have enough. We have two 10HP Becker's on our Morbidelli with a 5x12 table, and could always use a bit more.

Our friend Fred from BST Automation has 1kw servo motor + drive for 332euro +shipping which will cost you in total~400$ for the combo when you buy 4.


I am not sure you need exactly 1kw if you go with rotating ball nut. But as prices are similar. I think you will need 0.75kw geared like mine 20t:30t and that will give you speed of 20000mm/min on the long axis/ball screw with rotating nut/.

Quote:

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Originally Posted by Ger21

I'm building a 4x8 machine and using AC servos, and I'm using steppers and Leadshine AM882 drives for the Z axis (two, it's a dual Z machine) to save money.

I would think that a 5mm pitch ballscrew and a 600oz stepper would be OK for your machine? That's just a guess, though.

As for $400 servos. I've seen 400W servos on AliExpress for around $400, but not larger ones. And at that price, you may not know exactly what you're getting. I'm paying around $575 for 400w Leadshine motors and drives for my machine. 750W and 1Kw are closer to $800 a set. The price difference between 750W and 1Kw is very small, so I'd definitely go with larger ones for a little more money. http://americanmotiontech.com/motor-...tage-ac-input/

As for vacuum, you can never have enough. We have two 10HP Becker's on our Morbidelli with a 5x12 table, and could always use a bit more.

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Gerry do you have a forum for your build? I tried to do a search and didnt come up with anything.

The vacuum does worry me, I may have to add more or sell these I have an get a single larger unit... But we will see I think for now I will be able to work around the vacuum pumps that I have and see how things are.

Quote:

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Our friend Fred from BST Automation has 1kw servo motor + drive for 332euro +shipping which will cost you in total~400$ for the combo when you buy 4.


I am not sure you need exactly 1kw if you go with rotating ball nut. But as prices are similar. I think you will need 0.75kw geared like mine 20t:30t and that will give you speed of 20000mm/min on the long axis/ball screw with rotating nut/.

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Ok I had came those on ali but like Gerry said I had no idea what I was looking at or what I would be getting. So having someone point them out is very helpful. For the cables, do you just make up longer cables or order specific lengths? 3m wont make it for the far side X motor. How have you found the shipping to be? I see it says 23 days... I wonder if thats pretty accurate or if they come faster than that.

The other motors/drives I came across was dynamic motor motion technology.

I need to dig deeper into your build Boyan and see how to built those ballnut drives. I found a few options online and on the forum here for how to build them.

Have your guys seen these
http://www.stober.com/motion_control/EZM_series/

I havent priced them and I know they cant be geared so that has to be taken into account but seems like a great way to run the ballnut.

I hope to have a plan here in the next couple days then I can run it by you all for advice before ordering everything up...

BST automation is the usual choice for Chinese stuff and linear rails, so its a well known and recommended seller. Price wise, packing, support and warranty.

Do you have a cable chain? If not i highly recommend the Russian ARKO 22x80 R60 which is cheaper and better than the similar Chinese

Leadshine has 10m cables available for their motors.
I would email BST and ask if he has them for his motors. Or, you can always make your own.

At those prices, I'll have to seriously consider going that route, if it saves $225/motor.

I have a "build log" at CNC Zone, that's about 7 years long, with almost no actual building, and another 2 year old thread when I started the design.
I've got a few thousand dollars in components, but life doesn't leave me any time to get to it.
I also spent the last 3 years of my spare time working on this: www.jointcam.com
(Actually 2 years, and a year of doing nothing)

BST will provide cables upto 7mtr long. This is Video I made showing there 1.8Kw set.

https://www.youtube.com/watch?v=tW8knRAOr7s

Hi guys sorry to but in but could someone post a link for BST Automation.
Please
Regards
Mike

BST Automation = http://www.aliexpress.com/store/314742

Quote:

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Originally Posted by mekanik

Hi guys sorry to but in but could someone post a link for BST Automation.
Please
Regards
Mike

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here you go http://www.aliexpress.com/store/314742 but you can email him direct bstlinear [[@ ]] gmail.com

Quote:

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Originally Posted by Boyan Silyavski

BST automation is the usual choice for Chinese stuff and linear rails, so its a well known and recommended seller. Price wise, packing, support and warranty.

Do you have a cable chain? If not i highly recommend the Russian ARKO 22x80 R60 which is cheaper and better than the similar Chinese

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Awesome, those are good prices, I need to see how much shipping is going to be but that was good timing cause I have not purchased chain yet.

Jazz, thanks for the video exactly what I was looking for in a review. Time to order some motors and drives... I emailed to see if I could get a price for motor/drive and 7m cable set.

So the resolver feedback into Mach is awesome, shows how new I am to this I didnt even know that was possible. Anyone know if the smooth stepper from warp9 can do this? It shows resolver connections on the board but does it send back to mach? Also looking at the CS lab boards as well since Jazz has a good review on them. Im thinking I might go for a servo for Z as well since that can give me position feedback into Mach rather cool feature.

Gerry, I had started a build log over at CNC Zone but after finding the great information here I decided to put my build log here instead. Also for me the cnc zone website is painfully slow!

Currently using the rotating ballscrew design to design one that I can build with the machines I have. Might be a little crude, also sending out designs to some local cnc metal shops for quotes on parts. One question, (of many im sure) do you guys find you need to grease the ballnut more since it is sometimes spinning rather fast?

Thanks for all the help, I will post some design ideas shortly for the rotating ballnut.

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Originally Posted by Scott Damman

Anyone know if the smooth stepper from warp9 can do this? It shows resolver connections on the board but does it send back to mach? Also looking at the CS lab boards as well since Jazz has a good review on them. Im thinking I might go for a servo for Z as well since that can give me position feedback into Mach rather cool feature.

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Yes and No. The ESS can send the encoder signals back to Mach but only for display purposes and to different set of Encoder DRO's on separate screen. (or can add to Custom screen if you like) Mach will not know anything about positional error and the Main Work DRO's will not update if position moves.

To work like you see in my Video the Controller deals with the Encoders and informs Mach of position directly. The Closed loop between motor and drive is then extended to the controller which keeps track of position and updates Mach's Main DRO's. The ESS cannot do this.

Very Few Step and Dir Controllers do this. Even the CSlabs IP-S which uses STEP & DIR cannot do this. Only the Analog IP-A Version does this.

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One question, (of many im sure) do you guys find you need to grease the ballnut more since it is sometimes spinning rather fast?

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On our Morbidelli, it's recommended to grease the spinning nut every 40 hours of run time. linear bearings and non spinning nuts get greased every 3 hours of run time with an auto lube system.

But a lot more grease goes into the spinning nut, as it's much larger.

So Im looking into and learning more about long ballscrews and how to run them. Obviously spinning the ball nut is a way to go but each unit gets to be pretty costly by the time you are said and done.

Another thing I found was supports along the ballscrew which effectively push the critical speed to a higher rpm. Has anyone ever looked into this type of design?
http://www.linearmotiontips.com/achi...d-ball-screws/

Thermwood does this on the long axis of some of their CNC machines. It looks like the support flips as the ballnut passes and then supports the ballscrew again on the other side of the ballnut.
Attachment 17899

I assume these are just nylon but cant find any further details on this type of support. I wonder if it could be considerably less expensive to incorporate this, provided the same performance is achieved in the end. Thoughts?

So still learning about the CSLabs IP-A and trying to decide if the extra money is worth it. With all ballscrews, I dont know that there will ever be a time that the system could move while the drives are disabled? I.e. I would have to manually turn the ballscrew or the motor to put it out of position. However, if Mach knows absolute position does that mean that the system needs to be "homed" less often? Between cuts etc. Are there other benefits to having Mach know the absolute position from the resolver? I hope to make a decision here soon on a motion control card... If anyone has any further thoughts I greatly appreciate it.

Thanks to Fred over at BST for working with me, I have ordered motors, 2 for X, 1 for Y, and 1 for Z. I decided to go with servo on Z as it seemed silly for the price difference to have that axis be a stepper.

Next up is HTD timing gears/belts just need to figure out speeds and gear ratio. Thanks Boyan for posting the 20t:30t Starting point and after putting it on paper sure makes sense to me.

So some math just to make sure I have things right
Lets say 20000mm/min travel
Ballnut is 5mm per revolution

(20000mm/min ) / (5mm/rev) = Ballscrew rpm => 4000rpm

Gear ratio 20t:30t = 0.666

4000rpm * gear ratio => Motor Speed => 2666rpm.

The motors I purchased from Fred are 3000rpm so this looks reasonable to me.

Figure out what you want your max velocity to be, and gear it so it reaches that at 80% of the servos rated speed.

ball nut is 10mm per revolution. Only z is 5mm

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Originally Posted by Boyan Silyavski

ball nut is 10mm per revolution. Only z is 5mm

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Figure out what you want your max velocity to be, and gear it so it reaches that at 80% of the servos rated speed.

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Gerry thats just the problem, dont know what I want or need my max velocity to be...

Boyan, so you are taking the gear ratio the other way then? i.e. screw speed (or ballnut speed) * 1.5 to give motor speed. If I take the same equation from before your 20,000 mm/min with a 10mm/rev screw gives a motor speed of 3000rpm?

What would be the disadvantage to doing a 5mm screw? I know the torque issue with gearing the motors the other way. However I ended up ordering 1.8kw 6Nm 3000rpm motors since they ended up being cheaper than the 1kw motors so I think I can sacrifice some torque to a gear ratio. Are there other issues with 5mm? I havent ordered the long screws so I can go either way just asking the question.

I am thinking about implementing brake resistors, I do this on my VFD's (to run 3 phase woodworking equipment) for quick motor braking. Im just trying to decide if the inertia of the gantry being so high warrants braking resistors or not. Has anyone needed to add them to their setup?

My motor order was as follows (in case anyone is interested)
Qty: 3 - 6Nm 1.8kW 3000 rpm servo motors - these will be for 2 for X axis and 1 for Y axis
http://www.aliexpress.com/store/prod...761095604.html

Qty:1 - 2.4Nm 0.75kW 3000 rpm servo motor - this one is for the Z axis
http://www.aliexpress.com/store/prod...760999511.html

i was trying to say / but as i was busy at workshop/ people typically use for woodworking machines xx10 screws on all axis and xx05 on Z, as this more or less gives compromise between speed, precision and step count/pulse train needed to generate movement


So say you have a servo motor that will spin to 3000rpm. From look of the servo it says 2500PPR/ pulses per revolution/ if i am not wrong. And ball screw moves 10mm per revolution.
Then ball screw needs 1/10 rev to move 1mm. If no geared then 3000/max rpm/x10=30 000mm/min max speed , like Gerry says thats your max velocity in Mach3. So from above it seems then you will need 250pulses per mm , so 1mm/250pulses=0.004mm resolution.

There is something important that Gerry told you but you missed his point. The servos should not be greatly OTT as you may think, they must be closed mutch to what effort they will do, otherwise youwill run in other problems. read literature about servo sizing. Its not a good thing to be much bigger than job they are meant to do.

Then read carefully page 14 from my build thread where Johnatan explained me very well how to calculate details and especially about snappiness.

And by the way i was suggesting 20t at the motor and 30t at the rotating ball nut, not vice versa. So you finish with slightly geared up machine, 0.7-1kw servos, and very fast acceleration. But just do your self the calc. My gantry is moved by 2x 400w servos, not 2x1.5kw ha ha

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Scott Damman

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Did you remember you needed longer cables !! that listing say 3mtrs

Most industrial servo driven routers use 25-32mm pitch screws, which virtually eliminates whipping. With steppers, you don't want to go that high because you lose resolution, but with 10,000 steps/rev with servos, resolution isn't an issue.

Imo, on a machine that large, you want at least 1000ipm, preferable closer to 1500ipm. With a 10HP spindle, you should have no trouble cutting sheet goods at 1000ipm if you want.

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Originally Posted by Boyan Silyavski

i was trying to say / but as i was busy at workshop/ people typically use for woodworking machines xx10 screws on all axis and xx05 on Z, as this more or less gives compromise between speed, precision and step count/pulse train needed to generate movement


So say you have a servo motor that will spin to 3000rpm. From look of the servo it says 2500PPR/ pulses per revolution/ if i am not wrong. And ball screw moves 10mm per revolution.
Then ball screw needs 1/10 rev to move 1mm. If no geared then 3000/max rpm/x10=30 000mm/min max speed , like Gerry says thats your max velocity in Mach3. So from above it seems then you will need 250pulses per mm , so 1mm/250pulses=0.004mm resolution.

There is something important that Gerry told you but you missed his point. The servos should not be greatly OTT as you may think, they must be closed mutch to what effort they will do, otherwise youwill run in other problems. read literature about servo sizing. Its not a good thing to be much bigger than job they are meant to do.

Then read carefully page 14 from my build thread where Johnatan explained me very well how to calculate details and especially about snappiness.

And by the way i was suggesting 20t at the motor and 30t at the rotating ball nut, not vice versa. So you finish with slightly geared up machine, 0.7-1kw servos, and very fast acceleration. But just do your self the calc. My gantry is moved by 2x 400w servos, not 2x1.5kw ha ha

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Yeah I think I did miss understand what Ger meant by OTT. Anyway Fred is holding the order for me so I can make some changes if I want.

Alright doing the math for the inertias of the system I did it based on a rotating ballscrew at the moment.

Some assumptions:
with 2 motors each motor on the X will handle 1/2 of the gantry inertia
Steel pulleys
2/3 ratio on the pulleys

Ballscrew inertia = 7.4E-4 kgm2
Gantry equivalent inertia (1/2 of total) = 3.44E-4
Pulley inertia Driven = 9.86E-5
Pulley inertia Drive = 1.48E-4
Total Inertia = 1.33E-3

Motor inertia for 1.8kw from BST page = 7.6E-4kgm2

So Inertia ratio with the 1.8kw motor = 1.75

I also ran Jonathans Matlab Script and got
Feedrate in m/min: [x y z]=[20.0 10.0 7.50]
Inertia in g-m^2: [x y z]=[1.56 0.96 0.80]
Torque in Nm: [x y z]=[4.29 2.63 2.27]
Inertia ratios: [x y z]=[2.06 1.27 1.06]

It looks like my X axis needs 4.29 Nm, how much above this number generally do I go?
These numbers show a slightly different inertia ratio for X but pretty close.

I know the general rule of thumb here is the keep the ratio under 10 but is there a lower limit as well? Ive searched to see if there is any information about that particular motor for inertia ratio but I havent found anything. Boyan I see your motors show an allowable of 12 but I dont see that for the motors BST sells (searched the model number online as well) so not sure how high I can go with them.

I guess based on these numbers the motors are probably oversized however by how much? These motors show 6Nm continuous, how much is that number trusted for the chinese motors? If I need 4.29Nm per the torque calculation?
Should I be closer to an intertia ratio of 5,6,7,etc?

Dont know if I know more now than I did or less...

Thanks for the heads up

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Originally Posted by Clive S

Did you remember you needed longer cables !! that listing say 3mtrs

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Email to Fred before I ordered and he confimed he can make the longer cables for me.

OK, maybe I am missing something here, but the more I read about proper servo motor design the more I see that the load inertia to motor inertia should be as close to 1:1 as possible. So although the rule of thumb is to be under 10 what I am seeing is for the ratio to be closer to 1. From what I am reading (and it is very possible I am mis-understanding this) the system should be better tuned and more responsive the closer to 1:1 ratio that can be achieved. This can be achieved with gearing or with sizing the motor to the load. I have included a 2:3 ratio in my calculations.

http://www.motion-designs.com/images...s_Dec_2008.pdf

http://www.diequa.com/download/articles/inertia.pdf

Am I mis understanding this? To me this would tell me that my inertia ratio of 1.75 --> 2.06 that was calculated for the system would be pretty good.

So as long as the inertia ratio doesnt go the other way...i.e. the motor inertia is larger than the equivalent load inertia... it is better to have the load to motor inertia as close to 1:1 as possible.

Of course from there one has to consider continuous torque and peak torque for the motor etc etc...

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Originally Posted by Boyan Silyavski

Then ball screw needs 1/10 rev to move 1mm. If no geared then 3000/max rpm/x10=30 000mm/min max speed , like Gerry says thats your max velocity in Mach3. So from above it seems then you will need 250pulses per mm , so 1mm/250pulses=0.004mm resolution.

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Boyan Your forgetting the Encoders are Quadrature so that's 2500 x 4 =10,000ppr.!


Scott welcome to the reality's of BIG heavy Machines. Need to Slow down with the Ordering and rushing in. The fact you even considered 5mm pitch screws and Steppers on such large machine shows you need to do much more research.

You enter another world which becomes expensive very quickly if you go rushing in without doing home work.!!