[CoolHand]

I don't think that removing and changing pulleys would be a good idea especially if this occurred several times on a job

You realize that the thing uses a VFD to drive the spindle motor, right?

The only reason you'd change pulleys at all is if you needed more low end torque than you could squeeze out of a motor being chopped by the VFD.

It's not like shifting the belts around on a drill press every time you want a different speed, it's more like engaging the back gears on a lathe to give you a low speed high torque range.

Nobody is going to be rigid tapping with this machine, let's be realistic about what people are going to be doing with it before you start trying to talk the guy into building a much more complex drive system.

Most guys running aluminum and steel will probably never switch the pulleys from high to low for the entire time they own the machine.

Hell, my actual VMC's gearbox in the head only has two speeds, and the only time it ever runs in low gear is when I'm tapping. Not much gets done below 1,000 rpm anymore, especially when you're talking about the small diameter tools that this kind of machine will be using most of the time.

Two speeds with a little hassle at the changeover is fine.

To speed things up a bit, you could have the hub center on a boss on the shaft, be driven by an dog pin (or two), and be held onto the shaft and dogs via a simple threaded handwheel, the same way that the wheels are held on road racing cars. The hub has a register and drive dogs, and a central threaded pin that a bigass wheel nut threads onto to hold the wheel in solid contact with the hub. Replace "wheel" with "pulley", and you're there.

Don't over think things.

[Skyfire]

Hi guys. I uploaded the panel engraving video to Youtube today. I tried several times but seems my video is too wide to show full screen. You can right click the video and copy its Youtube address to watch the full screen version.

[Skyfire]

Hi guys. Seems the spindle issue is a big item here
I reviewed all of your points and I think the best solution maybe take wizard’s suggestion to make the 2:1 ratio gear and belts to be optional parts. I agree that nobody use the machine same way. So just make various options for customers. I think as handlewalker said, two speed range up to 7000RPM is quite enough for most applications. So I will make the extra 2:1 ratoas the standard option.
As CoolHand said, many users may just need high speed slight cutting app. I’ve considered this and can just provide special electric spindle version also—or electric spindle exchangeable electric spindle option parts as I said in former posts. I will get the last detailed datasheet to list all features and options very soon.. So. Just choose what you really need. I can support whatever fitful to customer.

[wizard]

You realize that the thing uses a VFD to drive the spindle motor, right?

The only reason you'd change pulleys at all is if you needed more low end torque than you could squeeze out of a motor being chopped by the VFD.

This is what I would suspect, that is the primary use would be low end torque. Of course I'm not sure how the frame of the mill would handle additional torque, this is always an issue on really small machines. The other issue is cooler operation of your spindle motor due to keeping RPMs up.

It's not like shifting the belts around on a drill press every time you want a different speed, it's more like engaging the back gears on a lathe to give you a low speed high torque range.

Nobody is going to be rigid tapping with this machine, let's be realistic about what people are going to be doing with it before you start trying to talk the guy into building a much more complex drive system.

People will often try to do more than what a machine is capable of. Sometimes deleting options means there are fewer ways to screw up a machine.

Most guys running aluminum and steel will probably never switch the pulleys from high to low for the entire time they own the machine.

This is where things vary a lot between individual users, some may never need the option. Others could be switch ratios several times a day.

Hell, my actual VMC's gearbox in the head only has two speeds, and the only time it ever runs in low gear is when I'm tapping. Not much gets done below 1,000 rpm anymore, especially when you're talking about the small diameter tools that this kind of machine will be using most of the time.

This is a rational point of view. There is a real limit to what one can do with an ER spindle.

Two speeds with a little hassle at the changeover is fine.

To speed things up a bit, you could have the hub center on a boss on the shaft, be driven by an dog pin (or two), and be held onto the shaft and dogs via a simple threaded handwheel, the same way that the wheels are held on road racing cars. The hub has a register and drive dogs, and a central threaded pin that a bigass wheel nut threads onto to hold the wheel in solid contact with the hub. Replace "wheel" with "pulley", and you're there.

Don't over think things.

There are actually a number of options when it comes to changing ratios. I'm just not sure it is worthwhile to offer a quick change option.

[handlewanker]

I'd be happy with just the 3,500 rpm spindle drive if it could handle milling efficiently when it goes to the lower range.....that is, not for hacking off steel in great lumps but milling within the spindle's and the machine build's capacity.....taking small bites but many of them, in which case probably the one set of pulleys would never need to be changed.

Going down in RPM for CNC work might not be a requirement, whereas going up in RPM has a lot of advantages, so extra pulleys if required.

BTW, what is the problem with rigid tapping if the tap driver has a clutch and is spring loaded?

I speak about small tapping jobs, probably up to 1/2" UNF or 9mm max.

I used to tap regularly with a reversible tapping head in my 1/2" drill press with a 1/4 HP motor at approx. 150 rpm for taps around the 1/2" size.

The tapping head I used drives the tap in when you put pressure on it and reverses out when the pressure is released.

Rigid tapping, as far as I know, is a rigidly fixed tap in a solid holder that drives the tap into the job under program control at the same rate as the pitch of the thread.

A machine may be made capable of ploughing metal off at prodigious rates, but for "Normal" work, getting there under CNC control to do the intricate cutting by a program is what it's all about.

I expect if the demand is there, a larger machine will soon be on the slipways, ready to be launched for those that want large machining capability for minimal cost, not so much fun when it starts to get professional.

I was quite awed when I re-read the earlier posts and looked at the collection of castings painted in green and loosely stacked together to represent the mill.....this is not a tin pot milling machine by any means.....the table casting alone is massive.
Ian.

[Skyfire]

Hi wizard. I agree with your points. Different people with different applications definately have different demands with the spindle torque and speed. I can only cover the most common range and others may just special cases. The spindle unit can handle the 7000RPM for long time working no problem because I have made a bigger R8 spindle unit with similiar structure but bigger bearings that can handle 6000RPM long time without high temperature arising. So normally this spindle should be able to handle higher speed than that one because of smaller bearings. But the point is that the spindle unit must be dynamic balanced when come with 7000RPM option.

I think users always want to gain bigger "Value" from a machine but must be in a reasonable range. Or, just what you said, they may screw up a machine

[Skyfire]

I'd be happy with just the 3,500 rpm spindle drive if it could handle milling efficiently when it goes to the lower range.....that is, not for hacking off steel in great lumps but milling within the spindle's and the machine build's capacity.....taking small bites but many of them, in which case probably the one set of pulleys would never need to be changed.

Going down in RPM for CNC work might not be a requirement, whereas going up in RPM has a lot of advantages, so extra pulleys if required.

BTW, what is the problem with rigid tapping if the tap driver has a clutch and is spring loaded?

I speak about small tapping jobs, probably up to 1/2" UNF or 9mm max.

I used to tap regularly with a reversible tapping head in my 1/2" drill press with a 1/4 HP motor at approx. 150 rpm for taps around the 1/2" size.

The tapping head I used drives the tap in when you put pressure on it and reverses out when the pressure is released.

Rigid tapping, as far as I know, is a rigidly fixed tap in a solid holder that drives the tap into the job under program control at the same rate as the pitch of the thread.

A machine may be made capable of ploughing metal off at prodigious rates, but for "Normal" work, getting there under CNC control to do the intricate cutting by a program is what it's all about.

I expect if the demand is there, a larger machine will soon be on the slipways, ready to be launched for those that want large machining capability for minimal cost, not so much fun when it starts to get professional.

I was quite awed when I re-read the earlier posts and looked at the collection of castings painted in green and loosely stacked together to represent the mill.....this is not a tin pot milling machine by any means.....the table casting alone is massive.
Ian.

Hi, I've done some cutting capactiy tests today and think the milling efficiency should be satisfied within 3500RPM. I will post the aluminium cutting test results soon. I will test the steel cutting tomorrow.

I agree that for most "normal" works, user don't need to change the pullye at all. But for some users always use higher speed slight cut, may just always use 2:1 ratio pulley to gain MAX7000RPM.

From your rigid tapping experience with " reversible tapping head in my 1/2" drill press with a 1/4 HP motor at approx. 150 rpm for taps around the 1/2" size", I think my mill will be able to handle this work with 075HP BLDC motor. Especially big torque is a key feature to BLDC motors. And I think even can use a lower ratio pulley like 1:2 to gain double tapping torque.

And you are right that the rigid tapping with a solid holder will need the spindle rotation synchro with Z feed rate. It will need the servo spindle motor with encoder.

I think "making fun" and "getting professional" is quite different sometimes. Everything when you "dig" deep, there will be much less "fun",but more "headache" to be professional.

My machine is always industrial level thinking from the initial design of rigidity.. So, it's really developed to do some thing real

[Skyfire]

I finished two things today: The accuracy approving tests and aluminium cutting capacity tests.

Firstly I confirmed the machine traveling accuracy again as it's totally finished now. The result completely as what I announced <0.02mm.

And I tested the repeat accuracy with dialgage and confirmed to be <0.01mm for all three axies. So I think I can get the machine datasheet very soon now That will be standard to all formal producted machines.



And I did some cutting capacity tests then on a aluminium workpiece. I used a 10mm 3blade end milling tool and cut under:

spindle speed: 3500RPM
MAX feed rate: 13inch/min
MAX radial depth of cut: 0.3 inch
MAX axial depth of cut: 0.3 inch
material removal rate:1.17 in3/min

I think it's near to the top cutting capacity for this spindle motor power now. I didn't push the machine too hard to avoid tool damage. What you guys think about the cutting capacity?

Here is the cutting pictures. Today I just tested under jog mode for safety. I will do some real works under CNC mode then. I will upload the video tomorrow because I can't upload to Youtube directly from Mainland of China. I have to ask my friend oversea help me.:bs:

[CoolHand]

BTW, what is the problem with rigid tapping if the tap driver has a clutch and is spring loaded?

If the tap holder is spring loaded and has a clutch, it's not "rigid" or synchronous taping.

Plus, if you're gonna use a clutch type tension/compression tap holder, you could do that in any common drill press, no need for CNC there.

[CoolHand]

Did you program this gradual Z depth spiral, or was that tool pulling out of the collet?

Not picking nits, just suggesting that if it did pull out that you degrease the tool shank and torque the hell out of the collet nut before you shoot your YouTube video.

Won't be good advertising if the resulting finish is uneven or otherwise crummy, ya know?

It's a dandy little machine that you've built here.

Mayhaps we could speak about doing a design and casting set for a medium sized slant bed CNC lathe.

CNC Lathes are pretty simple, iron wise, and hardly anyone sells anything more useful than a 7x10 or maybe a 9x13.

I'm thinking something that can honestly swing 10" diameter with 30"-36" between centers.

PM me if you'd like to discuss further. I'd be willing to assist if it would help bring this project to fruition.

[handlewanker]

If the tap holder is spring loaded and has a clutch, it's not "rigid" or synchronous taping.

Plus, if you're gonna use a clutch type tension/compression tap holder, you could do that in any common drill press, no need for CNC there.

Why ever would you need to go to rigid tapping?......don't complicate a simple process....I said you CAN, as in COULD IF YOU WANTED TO, do tapping with a spring loaded tapper, and although it is not CNC per se, you can do milling, drilling and tapping in one set-up without the need to go onto another machine, or didn't you understand that.

The Z axis just goes up and down at each co-ordinate as a last operation.....perhaps I did not make it clear enough......that is, unless the production rate would be so high that the tapping needed to be done while the mill was doing the CNC work, but perhaps if the rate was in the hundreds or maybe just a few dozen items, then off mill tapping could save some time by doing it in a drill, but you'd be working at labour rates for the manual tapping operation, whereas you could be sitting down reading a book and drinking coffee while the machine did it for you...... sigh.

BTW, there's nothing very complicated about a spring loaded clutch driven tapping head......they sell them on EBAY all the time.
Ian.

[wizard]

Did you program this gradual Z depth spiral, or was that tool pulling out of the collet?

Not picking nits, just suggesting that if it did pull out that you degrease the tool shank and torque the hell out of the collet nut before you shoot your YouTube video.

I had to take a second look, makes me wonder if it is pullout.

Won't be good advertising if the resulting finish is uneven or otherwise crummy, ya know?

It's a dandy little machine that you've built here.

I'm impressed with it. Size wise it looks like it could really give many of the small machines on the market a run for their money. I'd like to see him produce a companion machine that is maybe twice maybe 3 times as large.

Mayhaps we could speak about doing a design and casting set for a medium sized slant bed CNC lathe.

Since there are no good, purpose designed small CNC slant bed lathes on the market, I'd like to see him do on of comparable size to this mill.

CNC Lathes are pretty simple, iron wise, and hardly anyone sells anything more useful than a 7x10 or maybe a 9x13.

Conversion lathes leave a lot to be desired. A seven or eight inch lathe with 16 to 20 inches between centers would be most interesting. Actually now that I'm thinking about it I'm not even sure that much distance between centers makes sense. There are many applications where huge center distances would not mean much on a CNC lathe. Note though that I'm talking about a purpose built small CNC lathe.

I'm thinking something that can honestly swing 10" diameter with 30"-36" between centers.

That is a rather large lathe that frankly already has offerings that one can choose from. I'd rather see a unique product enter the market.

PM me if you'd like to discuss further. I'd be willing to assist if it would help bring this project to fruition.

I'm certain others would like to provide input as there are few solidly designed small CNC lathes on the market. CNC lathes just don't seem to have the appeal of a mill. I would caution against going too big for the first machine, I'd rather see it as a counter part to this mill.

[handlewanker]

Aww gee Skyfire, you've made the machine all dirty and covered in chips.....does this mean this machine will be sold as a demo model, shop soiled etc, priced accordingly....pant, pant....?

BTW, I would not imagine there was enough torque developed to pull the cutter down out of the ER collet, but as the cutter has a very fast spiral it could happen.

Under those conditions, where a cutter was pulled out of the collet under a load, would an opposite handed spiral, IE, anticlockwise instead of clockwise looking end on, (spindle running in reverse), force the cutter back into the collet.......it would mean that you could not drill into the metal or ramp in as it is an end mill designed for milling on the side, and the end face would have a negative rake anyway, but the advantage of not digging deeper into the job than planned would outweigh this lack of drilling ability.

I have a set of Metric ER 32 collets and also a number of Imperial endmills and slot drills, and when the shank size is 3/4", it means you have to go to a 20mm collet and squeeze it down to 19.05mm, which it is designed to do, but as it's rather extreme, I invested in a set of imperial collets to offset the problem.
Ian.

[Skyfire]

Did you program this gradual Z depth spiral, or was that tool pulling out of the collet?

Not picking nits, just suggesting that if it did pull out that you degrease the tool shank and torque the hell out of the collet nut before you shoot your YouTube video.

Won't be good advertising if the resulting finish is uneven or otherwise crummy, ya know?

It's a dandy little machine that you've built here.

Mayhaps we could speak about doing a design and casting set for a medium sized slant bed CNC lathe.

CNC Lathes are pretty simple, iron wise, and hardly anyone sells anything more useful than a 7x10 or maybe a 9x13.

I'm thinking something that can honestly swing 10" diameter with 30"-36" between centers.

PM me if you'd like to discuss further. I'd be willing to assist if it would help bring this project to fruition.

Hi, The reason is tooling pull out of collet indeed. When I did this test last night, I found I can't find my 28mm spanner to fasten the collet! I have to hold the pulley by hand and obviously I'm not Popeye So the tool has been pulled out under the heavy cutting test. It will not be a trouble today. I just got the fitful spanner.

Yes, as you suggested, I will take the video again today. should be much better now.

I do have thought about the CNC lathe to bring series of CNC machines to market if I can have initial win for the current CNC mill. Sure, I will contact you for discuss when I be able to start the lathe project! Thank you very much my friend.:cheers:

[CoolHand]

I have a set of Metric ER 32 collets and also a number of Imperial endmills and slot drills, and when the shank size is 3/4", it means you have to go to a 20mm collet and squeeze it down to 19.05mm, which it is designed to do, but as it's rather extreme, I invested in a set of imperial collets to offset the problem.
Ian.

If it's pull out, this is probably the cause of it.

You'd be surprised how much thrust a high helix endmill will exert. I've had bigger endmills pull out of R8 and TG100 collets before too.

Wizard, if he wants to build a smaller machine than the one I suggested, I say go for it. I'd probably have a use for it too, but I could really use a machine of the size I noted before.

Got any links to what's available already? I've been looking for a while now, and coming up pretty much empty. Nothing but quasi-CNC flat bed conversions from China and India.

I could use a slant bed big enough to get rifle barrels inside, but I don't have $60k to drop on a used machine that's 20 yrs old.

[Skyfire]

Hi, wizard. I have the same thinking that the CNC lathe should be a counter part to the mill series. The scale should be fitful to the mill size. And yes the larger ones are provided on market now. I also plan to build 2X,3X one by one to market if can get initial success from this one. So I think if the current mill business can go smooth I will do that. The slant bed CNC lathe structure is the best choice. I will let you guys know too for some ideas and discussions. :cheers:

[Skyfire]

Aww gee Skyfire, you've made the machine all dirty and covered in chips.....does this mean this machine will be sold as a demo model, shop soiled etc, priced accordingly....pant, pant....?

BTW, I would not imagine there was enough torque developed to pull the cutter down out of the ER collet, but as the cutter has a very fast spiral it could happen.

Under those conditions, where a cutter was pulled out of the collet under a load, would an opposite handed spiral, IE, anticlockwise instead of clockwise looking end on, (spindle running in reverse), force the cutter back into the collet.......it would mean that you could not drill into the metal or ramp in as it is an end mill designed for milling on the side, and the end face would have a negative rake anyway, but the advantage of not digging deeper into the job than planned would outweigh this lack of drilling ability.

I have a set of Metric ER 32 collets and also a number of Imperial endmills and slot drills, and when the shank size is 3/4", it means you have to go to a 20mm collet and squeeze it down to 19.05mm, which it is designed to do, but as it's rather extreme, I invested in a set of imperial collets to offset the problem.
Ian.

Hi my friend, I think I have to sacrifice some of this prototype appearance to prove it's a real deal.. I think maybe it will be sold as the demo one with some discount... But if I could I prefer more to keep it as a record,,haha..

The tool out of collet issue is just the spanner issue.. So I couldn't fasten the collet tight enough especially for heavy cutting test. I will do it again today and it will not be a problem

I agree that really need many size collets to hold tools properly. Or it could happen the situation like this. I think MAX 1mm adaptale for a collet is some extream range.

[diyengineer]

I'd keep it, use it as your customers would, and use it hard. See what breaks, or can be improved, and incorporate those changes into the second machine.

[handlewanker]

Whew, glad the loose tool issue was just the lack of a spanner.

I hope the 4th axis design gets off the drawing board before the lathe is thought about.

I couldn't think of any current design upgrade, apart from coolant, one shot lube and/or built in ratio change....maybe a QCT or power drawbar, that would make the machine more versatile....if you increase the X, Y or Z range you just start getting out of proportion....... this is something like pumping a midget full of steroids in the hope that he'll exceed the 4 minute mile record....LOL.

If the machine build went to ICNC-2 or 3, and the parameters were scaled up, all you'd achieve is another big mill and a higher cost pro rata, eventually you'd have to decide if you really want to have another knee mill as big as a Bridgeport.....LOL.

On the topic of a CNC lathe, it would be cool to have a midi lathe that really barked......something that would hold a 30mm bar of steel through the headstock and have a gang tool slide for simplicity......short bed and no tailstock.......I'm not all that wowed by a slant bed design.

In my opinion, the moment you have an enclosure and coolant gushing at a rate of knots, it becomes something like a commercial scene where you just become an operator that pushes the green button when the red light flashes.....or feed bars as the hungry beast gnaws away to itself, but if the need is for a commercial machine, then the list is already long and as varied as the price range.

One of the most sort after aspects of lathe design, be it manual or CNC, is the ability to cut any thread pitch electronically.

If the design also incorporated a milling head on the tool slide, then that makes it pretty versatile.
Ian.

[handlewanker]

I'd keep it, use it as your customers would, and use it hard. See what breaks, or can be improved, and incorporate those changes into the second machine.

Hi, spoil sport......I was just thinking we'd be offered a good deal on the demo model after the testing.

Possibly the first item to become a problem would be the ball screws if they had single nuts, and any form of backlash here would cause grief.....I would have preferred to have a slightly longer table and saddle casting to allow double ballnuts, but as the current design has travel of 200 X 125 X 200, any extra on the nuts would reduce this spec unacceptably.

It could be done for the Mark 2 model, with the same design characteristics but double nuts.

I don't think Skyfire is going to saw the patterns in half to add a few more millimetres of length to the castings, although it would not take much to do that.....hmmmmm......maybe the steppers could be moved back a bit, I don't know if that is possible, but if it could be, that would be my preference.

The photos in post #90 show that there is still some room at the end of the screw mounting blocks under the table to allow this to happen.

Double ball nuts, although costing more, would be an option most would want to have to ensure tight resolution figures were maintained......this would also apply to a better class of ballscrew, once you experience the quality of the machine you want it to last forever.

What would be the sense of saving $100 on a ball screw if the better one was available in the beginning.
Ian.