[yulolaf]

Clearly someone has never heard of the floating drawbar concept, many fine examples have been posted on these forums but when you spent most of your time here argueing about the "climate" you miss things that most of us know.

[louieatienza]

Yes it can be a lot better than just an air cylinder, you can generate a lot more force, & have a very small unit, smoother movement than with just an air cylinder, air cylinder stages can be less also, just think of it like the brakes on you car, you have a small master cylinder piston, pushing the fluid to a large diameter piston, depending on the ratio of the ( 2 ) piston will determine the force you get, it can easily be thousands of lbs output from a 100 PSI air supply & still be a very small unit, there is a lot that you can find on the internet on this subject

A small machine like this though, with a need of only 800lbs, a multi stage air cylinder is all that is needed this can be very small around 3" tall or less

Thanks... I suppose another benefit of air over oilis less "springiness" so to speak than pure air since the oil does not compress for all intents and purposes.

It would be pretty simple to modify Defeng's SVM-2 setup with a "floating" draw bar, I've seen some really good examples in the Benchtop forum and such...

[mactec54]

And what about the life time comparison between this two different systems air vs oil ? Maintenance etc...

Air & oil, is used in this same system,that's why it's called air over oil, there is almost zero maintenance in the oil part of the system just ( 1 ) shaft seal, the air part just normal oring's to replace & ( 1 ) shaft seal as well,usually after many years of use you would need to service the unit being used

There are more parts to a air over oil system, but it does not even have to be mounted on top above the spindle, could be mounted anywhere on the machine, & a hydraulic line to feed a very small floating cylinder above the spindle to activate the drawbar

When you want more PSI/Force air over oil is best, for low PSI/force just a multi stack air cylinder would be fine to use

[G59]

This whole thread is turning away from SVM0 to theory and operations of a cnc. No wonder their are over 1700 posts.
I'm partially to blame I guess, but all these mechanisms are discussed on other threads specifically towards these topics.
Ian, I don't know what to think anymore. I'm disappointed by your constant criticism of people in the know. Why your ideas are better? Or trying to get technical on something you know nothing about.
Too bad a moderator can't eliminate 90% of the posts that discuss theory.
it is shameful that someone wanting to see and learn from Defeng's experience, has to go through 1700 posts mostly, garbage.
How tiring.

[handlewanker]

Hi, it's not my prime intention to be argumentative, despite the comments some output in that direction......the power draw bar is an important feature in my book........getting it right first time is the most important part, and that does not mean just following the crowd because they're going in that direction........I like to think outside of the box .....frequently.

No matter what has been said.....the current power draw bars all put force on the bearings.......when they are stationary.....that is not all that good, but probably within the capacity of the bearing.....if the bearing type is known, and that is not available.

Having seen what ball denting can do to a bearing raceway from bad fitting practices, I endeavour to apply only the force that is needed and as designed for.

The worst design for a PDB is the air type.....direct pressure using the machine frame or spindle housing as the fulcrum.

If the PDB comes down at speed as Louie has suggested is good......seconds count apparently.....the inertia of the mechanism will come to an abrupt and sudden stop when it hits the top of the draw bar........tantamount to a hammer blow.........if that's not a ball denting situation on a stationary bearing race I don't know what is.

The design I previously mentioned applies force by a toggle action and it's a "between a rock and a hard place" type of action.

There are no Bellville washers applying the clamping pressure, but the tool is held with more force than any Bellville washer can ever apply and is released without the force of a hammer blow.

If anyone understands how a toggle clamp works you can put two and two together and there you have it.

The toggle clamp principle does not apply force to the object it clamps by having a compressed spring in a relaxing mode as the Bellville washer does.

The mechanism I've designed works by simply locking and unlocking the clamping mechanism, and so retains the tool with an extremely inflexible force......no load on the bearings etc.

No doubt Defeng will surprise us with his PDB design, or should I say with his version of the PDB.....LOL.....it'll be innovative that's for sure.
Ian.

[handlewanker]

This whole thread is turning away from SVM0 to theory and operations of a cnc. No wonder their are over 1700 posts.
I'm partially to blame I guess, but all these mechanisms are discussed on other threads specifically towards these topics.
Ian, I don't know what to think anymore. I'm disappointed by your constant criticism of people in the know. Why your ideas are better? Or trying to get technical on something you know nothing about.
Too bad a moderator can't eliminate 90% of the posts that discuss theory.
it is shameful that someone wanting to see and learn from Defeng's experience, has to go through 1700 posts mostly, garbage.
How tiring.

Sorry it takes so much word time to get a point across......perhaps we should desist with theory and stay purely on SVM-0 -1 -2 topics for the sake of peace.....amen.
Ian.

[jips]

The worst design for a PDB is the air type.....direct pressure using the machine frame or spindle housing as the fulcrum.

seriously!? Please...

[ihavenofish]

No matter what has been said.....the current power draw bars all put force on the bearings.......

NO THEY DONT. period. end of discussion. you are wrong and keep basing a massive argument on a single incorrect assertion.

The worst design for a PDB is the air type.....direct pressure using the machine frame or spindle housing as the fulcrum.

the BEST and virtually only type used in the industry is the cylinder type, weather air or oil they all act the same. this is literally 99.5% of all machines in service in the world. the only time something else is used is in a special case where there is no room. even the fanuc robodrill mechanical drawbar is configured in an identical manner. the drawbar has a stack of (usually)belleville springs, and is pressed by something.

If the PDB comes down at speed as Louie has suggested is good......seconds count apparently.....the inertia of the mechanism will come to an abrupt and sudden stop when it hits the top of the draw bar........tantamount to a hammer blow.........if that's not a ball denting situation on a stationary bearing race I don't know what is.

you dont know what is. if the drawbar spring stack compresses with 800lbs of force, and that is ALL the force it will ever see unless you overextend it beyond the 4 or 5mm it needs to release. this is the nature of springs, and why we use them to soften blows. if you were to take a sledge hammer and whack the top of the drawbar with just the right amount of force, the only thing that would happen is the tool release.

The design I previously mentioned applies force by a toggle action and it's a "between a rock and a hard place" type of action.

you mean like almost every air or hydraulic drawbar in use since their invention?

There are no Bellville washers applying the clamping pressure, but the tool is held with more force than any Bellville washer can ever apply and is released without the force of a hammer blow.

If anyone understands how a toggle clamp works you can put two and two together and there you have it.

The toggle clamp principle does not apply force to the object it clamps by having a compressed spring in a relaxing mode as the Bellville washer does.

The mechanism I've designed works by simply locking and unlocking the clamping mechanism, and so retains the tool with an extremely inflexible force......no load on the bearings etc.

toggle clamp. on a spindle spinning at 8000+rpm? would be interesting to see.... theres been many mechanical style drawbars. tubes, cams(which is how a toggle works) etc. all have been abandoned due to poor functionality or reliability vs an air cylinder, except the screw of course, which is only used because of its cost and simplicity on manual equipement. the only time they get used is when a compromise is required. usually when trying to integrate with ancient equipment.

[louieatienza]

This whole thread is turning away from SVM0 to theory and operations of a cnc. No wonder their are over 1700 posts.
I'm partially to blame I guess, but all these mechanisms are discussed on other threads specifically towards these topics.
Ian, I don't know what to think anymore. I'm disappointed by your constant criticism of people in the know. Why your ideas are better? Or trying to get technical on something you know nothing about.
Too bad a moderator can't eliminate 90% of the posts that discuss theory.
it is shameful that someone wanting to see and learn from Defeng's experience, has to go through 1700 posts mostly, garbage.
How tiring.

I believe you should be able to filter posters.

[jalessi]

Mr. Handlewanker,

Have you viewed the attached video, it may be enlightening.

https://www.youtube.com/watch?v=6vhhSoWHE9w

Jeff...

[G59]

Teach me.
Can't find filter button or tab.

[ger21]

Click on his username and select the "ignore" option.

[handlewanker]

Mr. Handlewanker,

Have you viewed the attached video, it may be enlightening.

https://www.youtube.com/watch?v=6vhhSoWHE9w

Jeff...

Hi, quite neat....good video.
Ian.

[G59]

Click on his username and select the "ignore" option.

Cool

[handlewanker]

For anyone who's still listening and other original thinkers.......I have a ride on mower starter motor, just bought on EBAY, and if you doubt the power of a 12 volt motor in a package you can hold in your hand, this one will dispel any doubts.......powerful, wow.

In the design I originally planned for the SVM-0 over a year ago when the need for a power draw was realised and the ISO 20 spindle was offered sans PDB, I planned on using a stepper motor driving a cam and 3:1 lever.

As the starter motor is hugely powerful, the design got altered to only having a small worm wheel and pinion driving a cam directly on top of the draw bar.........the speed of the motor is tamed by the worm/wormwheel ratio so a complete 360 deg turn of the cam effects the push down and return to base need in seconds without having to install tricky timing switches to ensure 100% position on return....... a micro switch cut out will do, and a bit of overrun from inertia is not a problem.

The starter motor design can be made for under $100........ motor, worm and worm wheel plus a couple of needle bearings etc.

The low cost was not a prime factor, just a solution at the time.

Now that Defeng has a solution in the pipeline, I'll wait to see what he can come up with.
Ian.

[LeeWay]

Personally I think Sigmund Freud might have more to say about what is going on in this thread than Thomas Edison. Some people are not happy unless they are pulling chains. I am not talking about sailors or riggers either. I have designed and built quite a few machines for various tasks over the years. Sometimes for a bit of economy, but mostly for knowledge and experience. Not all of them worked as intended initially. Many received an upgrade or two to finally do the intended task. Some where turned back into the spare parts bin.
One thing is for sure, there are often many different ways of achieving the same or at least acceptable results.

[asuratman]

It is better to try first then make conclusion to make the next step. Electric motor driven PDB could be simpler than pneumatic/hydraulic. We do not need other type power source, all we need is electric power source.

[handlewanker]

Well one thing is for sure, if Defeng only has the electric PDB as the main force for tool removal, better start liking it or design your own, make it and be prepared to drill holes and fit it on the machine when you get it.

I don't think Defeng will want to do lots of re-engineering on an existing electric actuator if the majority of the buyers want air actuators, so in that case I'll offer to buy the prototype and go for broke.

The fact that he's working on a re-design of an existing electric one is an indication that it might be either, better, more cost effective or just simpler to implement......we'll just have to see.

If the pneumatic one is an off the shelf bolt on item, it will be interesting to see how the cost compares.......whichever way, I will still go all electric.
Ian.

[mountaindew]

Hi, quite neat....good video.
Ian.

When is someone going to post a video of a skyfire ? I have followed this thread for years and would like to see one running.

[handlewanker]

A Skyfire???............if you mean an SVM-0 go to UTUBE, the prototype was demoed back in 2014.
Ian.