[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]

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