The best conversion kit for X3

[OilMan]

How much axial force is a 400oz/in nema23 motor is capable of generating when used with a 5TPI ballscrew? I ran the drive torque calculator formula thats on rockfordballscrew.com, and it looks like not more than 500lbs. (bearing in mind my math skills may be a little off, but I think thats pretty close)

The closest bearings I can find to the ones that come with the X3, on McMaster.com, part #6681K12 and are rated at 2110lbs. Lets say the sieg bearings are inferior, which they probably are, they should at least handle a 1000lb load?

I also looked up the angular contact bearings, the cheap ones, part #6680K12 $23, are rated at 1711lbs dynamic. Thrust load was not listed. The expensive ones, HOLY COW $133!! each! part# 2385K31 are rated at 1231lbs.

Now heres my question, am I likely to generate the kind of forces that require these expensive bearings? I know they are the "proper" way to install a ballscrew, but i'm not retrofitting a Haas or a Mazak super mill. This is just a small hobby thing for me, and I need it to be as in-expensive as possible. Besides, if the stock bearings give me trouble, couldn't i buy my own angle bearings with the $250 plus i will save?

PS: who has the best deal on gecko drives? homeshopcnc?

[Greolt]

Oilman

I think my comment was not put well.

There must be a combination of bearing and retaining method to get the best out of it.

The kit in question uses a lock collar of some sort to preload and carry the force in that direction. No thread and nut.

See this thread http://www.cnczone.com/forums/showth...1&page=1&pp=15
It's a long thread and the relevant bit is well down.

Apart from being difficult to set a proper preload (no backlash) it then must withstand the forces on rapid change of direction.

[Ed from NY]

This is not going to help much, but...

When you factor all the parts and hassles the 3 kits seem to be competitively priced given what they offer... Because things are so complicated and because I could easily butcher one or more expensive parts I decided to add 15-20% more, 1-2 months waiting, dealing with customs and the docks and just get a turn-key (minus the software) machine.

If I already had another mill and if I was looking at the conversion "as a project" as opposed to just "wanting the end result" perhaps I would have gone for a kit.

One of the main questions is probably whether you have access to another mill since with the Syil kit you will need to machine the base to make room for the Z-axis motor. OTOH I kind of like that all screws, even the Z axis, are direct driven. I guess the other question then becomes if you prefer direct drive or belt driven screws.

Hmmm... I'm not sure if the Ausie motors are microstep like the Syil's. Are they? I read someplace that microstep diminishes vibration. I think it was here: http://www.arceurotrade.co.uk/projec...CNC/index.html <= very nice article on an X3 conversion.

Being a noob I was also kind of surprised on how much work (and money) goes into converting a machine

.

[syil]

WE also notice that AUS conversion suppliers.them have good price,hehe,but i think our ballscrew was better.so price a little higher.also,i think we use different Z-axis brackets between them.different motor.too...

we will post some details of our ballscrew,step motor,and other accessories,and our new factroy,new products in future coming soon.

any good advise please info us too.

[OilMan]

Ok i think understand now, (MAN that other post was long, whew!)

So with a nut threaded on the end of the ballscrew, the stock bearings would perform fine, because preloading them would be simple. But the shaft collar on the Fusion kit makes it tough to get a preload on the thrust bearings.

I'm gonna send them an email saying i am interested in their kit, but i have concerns about the shaft collars. Mabye link them to that long post too. We'll see just how "open" to suggestions they are to improve their product.

Hey Ed, i wouldn't worry much about belt driven steppers/ballscrews, if you look at the design of most industrial $$$ cnc machines, many use timing belts between the servo and ballscrew. My guess is if the pros use timing belts, they will work great for us hobby guys.


PSS: geckos, geckos..... lowest price??

[Greolt]

Originally Posted by Ed from NY Hmmm... I'm not sure if the Ausie motors are microstep like the Syil's. Are they?

It does not say on the website. At least not that I could see.

However in answer to my query, CNCkits told me that microstepping is configurable.

Best thing would be ask Marc. He posted earlier in this thread.

[mhuett]

The PROMiCA kit does implement microstepping which is user configurable ...

Currently the kit requires a couple of tapped holes in the existing lower Z mount however I am currently desiging an all new replacement lower Z mount which means that there would be no modifications necessary (ie you can take the X3 from manual to CNC control without any additional holes, mods or column removal).


Marc

EDIT:
I should point out that by lower Z mount I mean the lower Z mounting bracket that is inside the column - it needs to be removed in order to fit the new Z leadscrew so while it's out you simply drill & tap two 6mm or (1/4") holes in the bottom of it and optionally a further 2 X 4mm in the side to hold a brace .... none need to be overly accurate and so can be done with a hand drill.

[Moondog]

Hello..

Just a couple of questions regarding the Promica kits.

I noticed the Ballscrews are not Double Nut or pre-loaded like the Syil Kits. Obviously there will be less resolution without the Double nut... How much does pre-loaded Ballscrews add to the Kit price. Then we could compare the Syil Kit to oyurs.

Also what Drivers are you using.. Geckos???...

Noticed you are using Belt drives.... No matter how good the belts are they will be some backlash... IMHO direct Drive is better. Steppers are better at lower RPM anyway...

cheers

Frans

[mhuett]

Hello Moondog,

We do not use or supply preloaded at this point in time. We only use Thomson quality running gear and the additional cost involved would be in the order or AU$900.00 - we are looking into options though for using twin nuts to preload...this will be available as a retro-fit to our existing kit. No matter how much is spent though you will not get a $1500 Asian mill to perform like a $100K commercial system and that needs to be kept in perspective ...get the best possible from it but don't try to turn a Hyundia into a Rolls.... the Thomson signle nuts seem to average around the 0.005 backlash which is extremely good for a single nut system. Any good software will also have backlash compensation will all but eleviates the problem too.

The preloading makes no difference at all to resollution - this is governed by drivers, motors, pitch etc ...

Our drives and controller are purpose built for the job design and built by us ...far more than a breakout box with a couple of Geckos (not that there's anything wrong with Geckos!!) ... check the Details page of our website for more info.

Belts and backlash .... gets back to the Hyundia/Rolls thing again but using our Mitutoyo gages there is no decernable backlash from the belts. These belts are designed specifically for precision control and their internal radial ply prevents stretch on the belt ... even our 4 year old workhorse has it's original belts still and they are as good as the day they were put on. Direct drive can also put stress on the stepper bearings that they aren't designed to have ... we're more interested in making a product that will last and that is designed correctly ... again please check our website for all the information and please feel free to email us any questions you have.

Thanks

Marc

[SyilAmerica]

We will have several kits (with English documentation) in the states shortly. Just a little late to the game.

Our ballscrews are of a high grade of Italian stainless steel. Made in Italy. Double nut.

I think some valuable points are being made here:

True, you can not expect a 400lb mill to compete with 15,000lb monsters. However, you can make a darn good effort trying, and get great results.

Conversions have a place. They can be a wonderful experience. Knowing your machines intimate details, inside and out. However, don’t be mislead in thinking it will save you a tremendous about of money over a “converted” machine. I would make a guess and say that it takes dozens of hours to begin with. When the math is complete, you will find yourself in a quandary. A great experience though for those of us who just love the tear things apart.

Direct drive or belt. Each has it’s positive and negative. My personal preference is direct drive. Simply for the fact of adjustments. When the belt is worked hard, I have noticed they do tend to lengthen and slack slightly. You can make them extremely tight, but I wonder about the loading to the stepper. Direct drive has it’s problems too. Main disadvantage is that torque is limited to the motors output. With a belt drive you can take away some speed and gain some torque, simply by gearing it differently. This gives you the choice of several smaller stepper combinations. Belt also allows for various placement choices of your stepper, where the direct drive limits you to just a few. It's like comparing a Braeburn apple to a Gala. Still apples. Some like one, some like the other.

[Moondog]

Originally Posted by mhuett Hello Moondog, We do not use or supply preloaded at this point in time. We only use Thomson quality running gear and the additional cost involved would be in the order or AU$900.00 - we are looking into options though for using twin nuts to preload...this will be available as a retro-fit to our existing kit. No matter how much is spent though you will not get a $1500 Asian mill to perform like a $100K commercial system and that needs to be kept in perspective ...get the best possible from it but don't try to turn a Hyundia into a Rolls.... the Thomson signle nuts seem to average around the 0.005 backlash which is extremely good for a single nut system. Any good software will also have backlash compensation will all but eleviates the problem too. The preloading makes no difference at all to resollution - this is governed by drivers, motors, pitch etc ... Our drives and controller are purpose built for the job design and built by us ...far more than a breakout box with a couple of Geckos (not that there's anything wrong with Geckos!!) ... check the Details page of our website for more info. Belts and backlash .... gets back to the Hyundia/Rolls thing again but using our Mitutoyo gages there is no decernable backlash from the belts. These belts are designed specifically for precision control and their internal radial ply prevents stretch on the belt ... even our 4 year old workhorse has it's original belts still and they are as good as the day they were put on. Direct drive can also put stress on the stepper bearings that they aren't designed to have ... we're more interested in making a product that will last and that is designed correctly ... again please check our website for all the information and please feel free to email us any questions you have. Thanks Marc

marc.. Correct.. resolution is drivers etc... I was meaning accuracy...

as with any mechanical system when you incorporate additional components ie,. Belt, cogs etc you ALWAYS induce some play/movement/backlash.

True you can compensate for Backlash in your program such as Mach3. However, as stated in Mach3, ART does not recommend using Backlash compensation for what he states as' Poor machine Design'.. not saying your design is poor. .005" is a lot of lost accuracy and I know we are not looking for a 'Rolls royce' but rather a good Ford.

Direct coupling is the closest you can get to Nil Backlash/flex of components. A well aligned direct coupling puts virtually NO loads on the bearings of the stepper.. A mis-aligned one does.

Belts on the other hand induce loads on the bearings and flex the rotor shaft. As soon as you put any load on a belt you induce flex in the rotor shaft, and this puts wear on the bearings.

All belts have some stretch, no matter how good they are.

No one is expecting their $1,500 mill to be a $100K unit. But if you want accuracy, and I mean less that .001" then the Ballscrews need to be either pre-loaded or double nut.

Moondog

[mhuett]

Thanks Moondog ...

As SyilAmerica pointed out above there are pro's & con's with each system ...we've utilised belts to enable us to keep the system low profile among other reasons.

Regarding the bearing/shaft points you raised you need to remember that all stepper motors have standard bearings (well any we've seen in this price category!!) which ARE DESIGNED for radial load but will take some axial load ....in a normal bearing this is roughly 75/25 split - according to SKF's data even their deep groove bearing should not exceed those figures ...and steppers don't have deep grove bearings. Again please refer to our website which details the various bearing we use and WHY they are used.

Shaft flex ... even the smaller motors have a 6mm shaft ... mount a pulley over that and we add on another 6mm of aluminium over the last 15mm of it. That leaves about 1.5mm of exposed shaft which a 10mm wide belt isn't going to have much effect on. In reality users will have more trouble from tool flex than anything from either coupling system...

As mentioned above in another post by a member there are NC systems costing $$$K and many of them use belt running gear... it really isn't an issue ..it's just another method of achieving the same end

Having choices and options is a good thing ... otherwise we'd all drive Fords (and I'm a Holden man!!) ...

(PS - certaintly agree with you re pre-loaded/dual ball nuts ...which is why we will be offering it as an option soon ... for those who need it and want to pay for it... again it's about options and choice