The New Machine

Yippee my wait is over..:dance: the new machine has been delivered:naughty:
Attachment 4488

Just waiting for the ali stock now to start the conversion, Ive got some rolled ballscrews and nuts that will fit the bill for the time being, but i need these for another job so i will be purchasing some ground Ballscrews in the near future. All the design work for the conversion will be completed on V-Carve and machined with Mach3 i will upload files as and when they have been proven, with the odd video here and there.

My Initial opinion is the build quality is not as bad as i thought it would be in fact its very good, the supplier was very helpfull and it was delivered on time. :tongue: I will get some picks of the strip down as i do it.....:twisted:

Look forward to following this one!

Just a thought, will you be offering a conversion kit once proven or?

.me

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Originally Posted by Lee Roberts

Look forward to following this one!

Just a thought, will you be offering a conversion kit once proven or?

.me

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:naughty:I suspect you will.:whistling:

OK the first question... i will be gearing the steppers at 2.5:1 and I will be using T5 10mm pulleys to give me 0.01mm resolution per step i wonder what size is the smallest pulley available i know i can get a 10 tooth but do they go smaller?

I would be very surprised if you can get a pulley with less than 10 teeth. 10 teeth is the least I have ever seen anyway.

Ian

I would advise against getting a small pulley as I heard the belt wear is greater. Also you may struggle to get enough teeth meshed on a very small pulley.

Only disadvantage I can think of with a bigger pulley is the moment of inertia is greater, but that's probably negligible on a mill.

I would avoid belt drive, extra complexity is extra problems. They will also limit the maximum speed of the machine if you look at my convertion or the hoss machine you would be better to follow that template. The g540 is the way to go i have used some of the drives from the uk and they are not a patch on this setup. Keling was where i go my drive and motors from.

http://www.cnczone.com/forums/bencht...g_machine.html

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Originally Posted by Web Goblin

I would be very surprised if you can get a pulley with less than 10 teeth. 10 teeth is the least I have ever seen anyway.

Ian

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Cheers Ian:smile:, Me too, In fact many of the sites I checked started at 12 teeth.

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Originally Posted by Jonathan

I would advise against getting a small pulley as I heard the belt wear is greater. Also you may struggle to get enough teeth meshed on a very small pulley.

Only disadvantage I can think of with a bigger pulley is the moment of inertia is greater, but that's probably negligible on a mill.

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Thanks Jonathan:smile:, I did Intend to use a 10 and 25 tooth pulley to give me the ratio I needed, and going for anything smaller as you say may put too much load on the reduced number of meshed teeth. So 10 and 25 then.

So the pulleys will be as above.

For those people that are not aware of why I would like to use pulleys then let me explain.

:confused:Using 1605 ballscrews will give me a pitch of 5mm, that is to say 360 degrees in 1 rotation of spindle will advance the axis 5mm.

If i use a direct coupling stepper to screw,

The stepper will give full steps of 1.8 degrees.

360/1.8 will give me 200 steps per revolution.

5mm / 200 will give a resolution of 0.025mm per full step.

This is an odd measurement to use in my head, i have done it though..

Using a ratio of 2.5 to 1 ( 10 and 25 tooth pulleys) will give me a step resolution of 0.001mm per step.

and if i were to use half steps as the stepper is capable of doing, it would be 0.0005mm per step...

thats a fair bit of resolution/accuracy, there are however disadavantages to using pulleys.

its upto the individual who is designing/building and using the machine.

(a special thank you to i2i who educated me on this subject in the first place)

There you go clear as mud!!!!:confused:

Rick

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Originally Posted by Ricardoco

Cheers Ian:smile:, Me too, In fact many of the sites I checked started at 12 teeth.



Thanks Jonathan:smile:, I did Intend to use a 10 and 25 tooth pulley to give me the ratio I needed, and going for anything smaller as you say may put too much load on the reduced number of meshed teeth. So 10 and 25 then.

So the pulleys will be as above.

For those people that are not aware of why I would like to use pulleys then let me explain.

:confused:Using 1605 ballscrews will give me a pitch of 5mm, that is to say 360 degrees in 1 rotation of spindle will advance the axis 5mm.

If i use a direct coupling stepper to screw,

The stepper will give full steps of 1.8 degrees.

360/1.8 will give me 200 steps per revolution.

5mm / 200 will give a resolution of 0.025mm per full step.

This is an odd measurement to use in my head, i have done it though..

Using a ratio of 2.5 to 1 ( 10 and 25 tooth pulleys) will give me a step resolution of 0.001mm per step.

and if i were to use half steps as the stepper is capable of doing, it would be 0.0005mm per step...

thats a fair bit of resolution/accuracy, there are however disadavantages to using pulleys.

its upto the individual who is designing/building and using the machine.

(a special thank you to i2i who educated me on this subject in the first place)

There you go clear as mud!!!!:confused:

Rick

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And hurry up moderator.

But you should be using 8 / 10 mirco stepping for best performance of the motors and why are you worried about the interger as it is a cnc'd machine that will be controlling it.

As before i have done it with this machine, 0.001 res is pie in the sky, £200,000 machine tool struggle to get that with direct drive and servo's. 0.025 per step is what i run and gives me 1500mm/min rapid you would be lucky to get 700mm/min as you would be over spinning the motor and have not torque.

resolution and power work againest each other.

here a like to my Thread on cnc zone.

http://www.cnczone.com/forums/bencht...g_machine.html

Sorry for the delay and welcome fragger!

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Originally Posted by fragger6662000

And hurry up moderator.

But you should be using 8 / 10 mirco stepping for best performance of the motors and why are you worried about the interger as it is a cnc'd machine that will be controlling it.

As before i have done it with this machine, 0.001 res is pie in the sky, £200,000 machine tool struggle to get that with direct drive and servo's. 0.025 per step is what i run and gives me 1500mm/min rapid you would be lucky to get 700mm/min as you would be over spinning the motor and have not torque.

resolution and power work againest each other.

here a like to my Thread on cnc zone.

http://www.cnczone.com/forums/bencht...g_machine.html

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Ok Hi There fragger, the steppers two x 23 & 1 x 34 from motionking, the 'integer' is for me, not the software, I design what would end up on the machine in the first place as i said "This is an odd measurement to use in my head" Now as for accuracy, wouldnt you say, that aiming for the highest accuracy you can in the begining is the correct thing to do.

I would never suggest I would get that resolution at the end of the project but if i allow the push for accuracy to become secondary to simplicity of build i would not be true to myself, and speed/feedrate well this is a hobby for me, im not in a hurry, im still one of those sad individuals that likes to sit there and watch, and i know im not the only one :wink: AM I???

Would i not get more torque with a 2.5:1 setup then?

I have read with interest the posts about this machine type on cnczone.

Pulleys are the way i would like to go as i dont like the positioning of the steppers in the other projects I have seen, they may be fine for you and make the conversion simple and speedy but that is not what im after, I have learned a lot from the conversions on cnczone but they just dont fit my requirements.

Stevie Nicks and her famous song told me all i needed to know lol

I do like the way you have mounted your x axis ballnut, that is simple effective and a touch inspired and look much more stable than the other ways i have seen.

I will follow your thread with interest and i may even use some of your ideas (giving credit of course), "if thats ok of course"

Rick
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No worries

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Originally Posted by Lee Roberts

Sorry for the delay and welcome fragger!

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No you don't get more torque, stepper motor produce most torque when stalled, as you increase the rpm the torque drops.

I know well know manufactures of encoder scale that produce an 8um pitch and you have all the american stuff.

When i built my first cnc'd x1 i was using a imperial z screw, you never need to know the interger apart from the time you enter it into the control software.

By using pulleys you get
-another source of backlash
-drive flex(belt stretch)
-reduced top speed
-side load on the screw
+ratio change
+allignment flexabilty

i tried belts on a lathe, big disapointment. now directly driven.

if we are quoting "you can lead a horse to water but cannot make it drink" I personally think your logic is flawed, if you want an additonal challenge that is far enough.

As for i am old school i like to watch it, the x1 had a rapid of 400mm/min and it got very old very quickly and that was a smaller machine.

I don't see the point of wanting a round number. As soon as you've entered it into mach3/EMC you won't need to know about it at all. I've forgotten what the value is per step on mine...

As fragger said, you will almost certainly be using 1/4 or 1/8 micro-stepping anyway which effectively changes the value but doesn't really gain accuracy.

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Originally Posted by fragger6662000

By using pulleys you get
-another source of backlash
-drive flex(belt stretch)
-reduced top speed
-side load on the screw

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1) no, unless your pulleys are awful. Mine have not added backlash.
2) negligible from my experience.
3) What! That's impossible to judge without calculating it properly. You need to get the motor running in the optimal region of the torque/rpm curve and to do that you need to get the ratio right which, unless you're very lucky, requires pulleys.
4) Surely the bearings in the mill are going to cope with that...if not add more? I'd be more worried about the bearing on the stepper motor.

On my router I've found that generally increasing the size of the pulley on the stepper motor has increased the top speed, but of course sacrificed resolution. It's less clear cut on a milling machine as it's heavier and the coefficient of friction is greater.

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Originally Posted by fragger6662000

No you don't get more torque, stepper motor produce most torque when stalled, as you increase the rpm the torque drops.

I know well know manufactures of encoder scale that produce an 8um pitch and you have all the american stuff.

When i built my first cnc'd x1 i was using a imperial z screw, you never need to know the interger apart from the time you enter it into the control software.

By using pulleys you get
-another source of backlash
-drive flex(belt stretch)
-reduced top speed
-side load on the screw
+ratio change
+allignment flexabilty

i tried belts on a lathe, big disapointment. now directly driven.

if we are quoting "you can lead a horse to water but cannot make it drink" I personally think your logic is flawed, if you want an additonal challenge that is far enough.

As for i am old school i like to watch it, the x1 had a rapid of 400mm/min and it got very old very quickly and that was a smaller machine.

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:redface: I actually felt like you were telling me off then....

Well i will consider myself told shall I....:cry:

Usually people dont have to be so blunt to get the point across, Im not so stuck in my ways that im not open to suggestion, On a recent project I took a lot of advice from the members of this forum and put it into practice, that is why i participate in forums.

I dont really want to just copy you or hoss, but neither do i want to re-invent the wheel.

thats why i dont just guess at this, I've looked at several sources of information and am still looking, here is just one source.

http://www.arrickrobotics.com/pr23.html

I dont disagree with all you say, and there are sacrifices to be made using pulleys however my 260 is not direct drive, it is very accurate, as much as i need anyhow, and i really dont want the steppers hanging of the end of the axis (not sure what you would call a group of axis lol), so do you have any other suggestions?

Thanks in advance for your input.

I forgot to mention the other big advantage of belts which is that they greatly reduce resonance problems.

The site you linked to has mentioned what I did:

'Even though the output speed is reduced by the reduction ratio, some systems will actually have their overall speed performance increased due to better use of the motor's torque curve.'

I wouldn't hesitate to use belts again - I will when I convert my lathe, though admittedly that's partly because it'll have a rotating ballnut.

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Originally Posted by Jonathan

I don't see the point of wanting a round number. As soon as you've entered it into mach3/EMC you won't need to know about it at all. I've forgotten what the value is per step on mine....

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I had decided that for the way i wanted to position the steppers that belts and pulleys was the way to go and at a 2.5:1 ratio i would get that round '1' it was not a requirement i could have even gone 1:1 and still can ill just swap out the pulleys and belts if need be and i will probably forget about it as you have.

The little ratio and ballscrew tutorial I wrote down in the middle of the post was perhaps to make things easier for some people to understand as it was a source of many questions from me when i did the other conversion. Using round numbers just made it easier in my mind to see what was going on thats all..

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Originally Posted by Jonathan

As fragger said, you will almost certainly be using 1/4 or 1/8 micro-stepping anyway which effectively changes the value but doesn't really gain accuracy..

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Shouted! :lol:

on another note what do you think of the idea of a counter balance on the Z... please dont shout your reply its only a question...:heehee:

Rick

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Originally Posted by Ricardoco

on another note what do you think of the idea of a counter balance on the Z... please dont shout your reply its only a question...:heehee:

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[whisper]I think someone on this forum is considering it / has done it...
As I'm sure you know it should improve your Z-axis feedrate, but when do you actually need a high feed there? Possibly small drills (definitely with PCBs) and maybe with 4th axis in some situations but that's about it?
You can use an 'oversize' (i.e. greater than the mass of the head) counterweight to eliminate backlash in the Z-axis.
[/whisper]

Are you using a rotating ballnut on Z, just out of interest?

If you are thinking of under slinging the motors on x you will loose lots of travel.

Hope you have fun doing the machine as it is certainly a rewarding thing to do. especially when it works!

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Originally Posted by Jonathan

Are you using a rotating ballnut on Z, just out of interest?

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Hmmm tell me more...

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Originally Posted by fragger6662000

If you are thinking of under slinging the motors on x you will loose lots of travel.!

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it will be in front i suspect, just a tad lower than the bed. although it would have been nice if i could have put it underneath without the loss of travel.

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Originally Posted by fragger6662000

Hope you have fun doing the machine as it is certainly a rewarding thing to do.!

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Likewise :tup:

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Originally Posted by fragger6662000

especially when it works!

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Well here's hoping. Needless to say i will only post what works...:rofl:

Well here is an idea, im sure there will be people with experience of this sort of thing.

Attachment 4490

just a basic concept and yes There are covers missing for clarity...

This type of thing is what i was looking into and it all misses the y axis as well so no loss of x or y. excuse the drawing its my first google sketchup

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Originally Posted by Ricardoco

Using a ratio of 2.5 to 1 ( 10 and 25 tooth pulleys) will give me a step resolution of 0.001mm per step.

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Hi Rick

AH! Confidence truly is that feeling you get just before you understand the problem :heehee:

.001mm is one micron. Standard ball nuts give you 50 microns, shimmed gives you 20, the only way to get 1 is to use double nuts and spring them. Helps if you can hold the screws in tension with more springs. The Belleville washer is your friend. You can compensate for backlash, but you will forever expect the tool to dig in.

Ball nuts bed in, they may feel firm but you are probably pushing against the dust seals and kidding yourself. The seals can't hold it when the tool loading kicks in.

If you bolt the column to a brick wall I would suggest a 5 micron step, 200 steps/mm is optimal for accuracy and speed. Half step is good, quarter step is vaguely credible, beyond that everything gets too springy.

Getting high accuracy is more a problem of rigidity than anything else. You can't mill to 5 microns because the tool will bend, you can't skim 10 microns, it will simply ignore you. To get 5 microns your tooling needs to cut a mirror finish. IMHO 5 microns or better has to be ground.

Good luck :naughty:

Robin

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Originally Posted by Robin Hewitt

Hi Rick

AH! Confidence truly is that feeling you get just before you understand the problem :heehee:

.001mm is one micron. Standard ball nuts give you 50 microns, shimmed gives you 20, the only way to get 1 is to use double nuts and spring them. Helps if you can hold the screws in tension with more springs. The Belleville washer is your friend. You can compensate for backlash, but you will forever expect the tool to dig in.

Ball nuts bed in, they may feel firm but you are probably pushing against the dust seals and kidding yourself. The seals can't hold it when the tool loading kicks in.

If you bolt the column to a brick wall I would suggest a 5 micron step, 200 steps/mm is optimal for accuracy and speed. Half step is good, quarter step is vaguely credible, beyond that everything gets too springy.

Getting high accuracy is more a problem of rigidity than anything else. You can't mill to 5 microns because the tool will bend, you can't skim 10 microns, it will simply ignore you. To get 5 microns your tooling needs to cut a mirror finish. IMHO 5 microns or better has to be ground.

Good luck :naughty:

Robin

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Well as I said if I aim high and do the best i can with what i have its an education and im not sure it will hurt will it. I do wish in my original post i had used the work theoretical...

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Originally Posted by Robin Hewitt

.001mm is one micron. Standard ball nuts give you 50 microns, shimmed gives you 20, the only way to get 1 is to use double nuts and spring them. Helps if you can hold the screws in tension with more springs. The Belleville washer is your friend.

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By double nuts do you mean the "double ballnut" that somewhere like Zapp sells, or do you mean using two seperate nuts and combining them with the spring?

I've seen the latter in different places around the internet, but I didn't know if the former was simply a commercial version of the latter.

I'm pretty sure Robin will mean two nuts sprung, hence the Belleville washers. I think the commercial versions are just shimmed. To eliminate backlash you need them to be pushed apart using a spring applying a force greater than any cutting force plus acceleration, F=ma, you anticipate.

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Originally Posted by Jonathan

[whisper]I think someone on this forum is considering it / has done it...[/whisper]

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I'm playing with the idea, primarily because I think it looks good, effectiveness be damned! :twisted:

On a related note, I also asked similar questions about the under-table mounting, the consensus seemed to be that it wasn't a problem. The following thread might have useful things for you: http://www.mycncuk.com/forums/showth...or-under-table

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Originally Posted by Rogue

By double nuts do you mean the "double ballnut" that somewhere like Zapp sells, or do you mean using two seperate nuts and combining them with the spring?

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Either, if you use a double take the shim out

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Originally Posted by Ricardoco

on another note what do you think of the idea of a counter balance on the Z...
Rick

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Denford used to do this on the early triacs, they stopped it quite quickly.

Quote:

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Originally Posted by Rogue

I'm playing with the idea, primarily because I think it looks good, effectiveness be damned! :twisted:

On a related note, I also asked similar questions about the under-table mounting, the consensus seemed to be that it wasn't a problem. The following thread might have useful things for you: http://www.mycncuk.com/forums/showth...or-under-table

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I will be using the Double ballnut if needed when i fit the ground Ballscrew but for now with the rolled i will use just the 1 with the ability to encorperate a double in the design..

LOL well here is the Vcarve output for the endplate for the Z with a side mounted stepper, or if prefered it can be hung on the end infact ive desinged it so you could hang it on the left rignt or even underneath,Ive not included the tensioning system yet as im still working on it. I still think it looks bodged on the end but that is just my opinion lol

Attachment 4496
Attachment 4497

I will make the prototypes out of a non metalic material i suspect...:smile:

Oh and ive made it incorperate the ballscrew Double A/C bearing housing as well.

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Originally Posted by i2i

Denford used to do this on the early triacs, they stopped it quite quickly.

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Hmmmm Your not the first to tell me that, i wonder if the bell is tolling for the counter balance idea!!!!

I expect the cutter needs the weight of the head to give it "balls"

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Originally Posted by i2i

I expect the cutter needs the weight of the head to give it "balls"

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All of it!!!:surprised: thats just greedy.:heehee:

you don't need to counter weight this machine if the correct steppers are used.

A setup with light stepper and poor z slide ways will cause crabbing and stalling. You counter weight to reduce the crabbing of the head. counter weighting does nothing to the cutting force as the slide ways and the screw resist this not the weight of the head. It does affect the acceleration as there is a greater amount of inertia.

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Originally Posted by fragger6662000

you don't need to counter weight this machine if the correct steppers are used.

A setup with light stepper and poor z slide ways will cause crabbing and stalling. You counter weight to reduce the crabbing of the head. counter weighting does nothing to the cutting force as the slide ways and the screw resist this not the weight of the head. It does affect the acceleration as there is a greater amount of inertia.

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Cheers Fragger, I had seen a thread on another forum about the counterweight and threw the question out to see what everybody thought as the concept was one that i was not famillier to me , you are with the majority in thinking it is not required or even desired, In an Ideal world what stepper would you suggest ive got a 34.

Rick..

i used the keling kit with 900ozin on Z and 381 on the XY.

The X is rated at 900oz but the drive is only delivering 3.5 amps so i think it is 500oz.

Have you go the motors and and drives because i would recomend the kelinginc kit as the motor are low impedance and give the best performance. UK motors seams to have a lot higher impedence and poorer performance.

http://www.kelinginc.net/CNCNEMA23G540Package.html

sorry the z was 34 and xy 23

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Originally Posted by fragger6662000

i would recomend the kelinginc kit as the motor are low impedance and give the best performance. UK motors seams to have a lot higher impedence and poorer performance.

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Surprising that you imply all UK motors have a high inductance. It clearly depends which you get and where. Can you link to a datasheet for the ones you have so we can compare?

Edit, actually ignore that - found it:

http://www.kelinginc.net/KL34H295-43-8B.pdf

To be fair that's quite a low inductance for that size motor. Still with a Nema 34 motor you really should be running it on a LOT more than 50 volts.

http://www.kelinginc.net/CNCNEMA23G540Package.html

sorry the z was 34 and xy 23

http://www.motioncontrolproducts.com...tors.php?cat=1
http://www.arceurotrade.co.uk/Catalo...Stepper-Motors

http://www.kelinginc.net/KL23H2100-35-4B.pdf

i have not looked recently but this was what i found jan this year