[boydage]

I know NOTHING about 4th axis machining options. I machine smallish apple size parts out of 6061 aluminum. Many of them need to be flipped several times.

China sells a 4th axis assy. US$1500 is an approx price of them. Example https://www.alibaba.com/product-deta...804529077.html

So many times I have thought, "gee if I didn't have to flip this part I would be so much quicker"

I am a little confused and was hoping one of you commercial builders could hop in here? The 4th axis I am looking at the basic model is with no controller. A controller is offered at another $1.5k in the options of Siemens, Fanuc and another I cant remember. I was not expecting that, thinking I might at most need a driver for the servo it came with. Wire that up along with the other sensors into an ESS I am using. And run it in Mach 4 as a 4th axis. Simple as that with the obvious other complications as its never that easy. Or I even considered installing a Nema 34 on it.

The other thing I have learned is there is a difference in these types of 4th axis, this one is an indexing head that locks before machining is done. And the other type can rotate through the machining process. Have I got this wrong as well? I have about $2k to invest. Reaching out to see if anyone else has installed one of these 4th axis's or knows a bit about them. I need one heavy enough to machine 6061 and through experience it needs to be heavy duty like the rest of my machine. I have found a lot of them on the market, its more about what comes in the box I dont know a lot. Manufacturer sales rep only wants to make the sale and thats the crux of it lol

[awerby]

It looks pretty heavy-duty, but how big a machine are you putting this on? At 82 kg, it's a serious load to put on a small mill or router. For an apple-sized part, it might be overkill. The Sherline 4" CNC rotary table would probably be sufficient, since it has a 72-1 planetary gear, which counts for more than sheer mass in keeping its position. https://www.sherline.com/product/370...e/#description

[boydage]

Hi. Yes it does huh? Ha. I built the 300kg gantry on my bench about 3m away from the machine piece by piece. It took me several hours to get it accross the floor, and up onto the bed. Man, now THAT was heavy lol. My machine is the end result of over-engineering so the only item I need to address is clearances under my gantry which is a bonus. And to be honest I actually at times machine some quite large parts. I guess in a nutshell I tend to go for the heaviest duty I can its a New Zealand thing lol

Hey am I correct, that this kind of unit (the Chinese one) needs to be unbraked to move, and braked again prior to machining? Is that normal for a 4th axis? I think about how surprised I was at the amount of forces put into a part during machining.

[joeavaerage]

Hi,
that unit sure looks the part. That it weighs 80kg is no surprise, nor that its costs what it does.

I made one using a 750W Delta B2 servo and an Atlanta Drive 19.5:1 servo reducer. It does not lock but it does either index OR rotate simultaneously. It has 48Nm torque
at rated servo torque and 148NM at overload. The servo reducer has a peak torque limit of 400Nm and a rated torque of 120Nm.

It cost me plenty, about $2000NZD ($1240USD), so a little cheaper than what you have linked to, but not hugely so, but then again your one sure looks professional whereas mine is home-made and looks like it.

Craig

[joeavaerage]

Hi,
just to give a little context, the chuck pictured is 100mm in diameter. It bolts on with three cap screws, and can therefore be removed to reveal
the shaft adapter.

I'm in the process of making a fifth axis, about 90% complete. The chuck will be removed and a trunnion table bolted in its place, and the trunnion table will hold
a rotary axis based on yet another Atlanta Drives servo reducer but 6.75:1 and <1 arc min lash.

I've bought the plasma cut steel for the trunnion table, but I've buggered up my servo spindle and can't machine it until I repair the spindle....another $600NZD, and that hurts
cos it was my own bloody fault!

Craig

[joeavaerage]

Hi,
only one other thing I can think of that you may want to think about.

I have now a few rotary tool paths where the fourth axis rotates continuously in coordination with the X,Y and Z axes....it's mesmerising!. With a high gear reduction the rate of rotation of the fourth
axis at full speed is slow. I can promise you that many of those continuous tool paths are going to take forever to run.

When I first built my fourth axis I ran it using a stepper with a 10:1 planetary reduction. The end result was that the fourth axis at max speed was 10rpm....too bloody slow!.
That's when I bought the servo pictured. Now at max speed it does 150rpm, which is usable but I don't want it to go any slower.

When my fifth axis is done my current fourth axis will be the trunnion drive and its modest speed will be moot, but the fifth axis having a 6.75:1 reduction will have a max speed
(with another servo pictured) of 444rpm....much better....looking forward to that!.

You need to consider what you want your fourth axis to do. Do you just want indexing? If that's the case then what you've linked to is ideal. Even the brake is a good idea
if you are indexing. But if you want continuous rotation, ie simultaneous four axis toolpaths then its max speed will be important to you.

Craig

[joeavaerage]

Hi,
if you are looking on Ebay for these servo reducers you'll want this:

https://www.atlantadrives.com/part.htm

It describes the part numbering system so you can get the right thing. You are looking for a 58 series reducer, their HP series that has <2 arc min lash
or a 98 series, High Torque (HT) series with <1 arc min lash.

I have one of the 58's, and nice it is too, and one 98 and it is superb.

I have one 50mm (between worm and driven gear center) or a '3' size and one 63mm (between worm and driven gear center) or a '4' size. Either I suspect would be adequate for
your purpose, although both are lesser in size and rigidity than the Chinese one you linked to.

This one might suit you:

https://www.ebay.com/itm/20230179089...3ABFBMju6z44pi

Its a 58 series ie <2arc min lash, '4' size, ie about 120Nm continuous 400Nm peak, and a 19.5:1 reduction, New but old stock, ie open box for only $149USD. That's bloody good buying!

I bought the one for my fifth axis about 2.5 months ago and it cost $180USD, new old stock. It cost me $280NZD for the GST to get it into the country and shipping with NZ Post, with their YouShoppe
service. Just a hint under $600NZD all up cost including the original Ebay purchase, GST and shipping to my door. About twelve days it took. Bargain!

Craig

[ardenum2]

I know NOTHING about 4th axis machining options. I machine smallish apple size parts out of 6061 aluminum. Many of them need to be flipped several times.

China sells a 4th axis assy. US$1500 is an approx price of them. Example https://www.alibaba.com/product-deta...804529077.html

So many times I have thought, "gee if I didn't have to flip this part I would be so much quicker"

I am a little confused and was hoping one of you commercial builders could hop in here? The 4th axis I am looking at the basic model is with no controller. A controller is offered at another $1.5k in the options of Siemens, Fanuc and another I cant remember. I was not expecting that, thinking I might at most need a driver for the servo it came with. Wire that up along with the other sensors into an ESS I am using. And run it in Mach 4 as a 4th axis. Simple as that with the obvious other complications as its never that easy. Or I even considered installing a Nema 34 on it.

The other thing I have learned is there is a difference in these types of 4th axis, this one is an indexing head that locks before machining is done. And the other type can rotate through the machining process. Have I got this wrong as well? I have about $2k to invest. Reaching out to see if anyone else has installed one of these 4th axis's or knows a bit about them. I need one heavy enough to machine 6061 and through experience it needs to be heavy duty like the rest of my machine. I have found a lot of them on the market, its more about what comes in the box I dont know a lot. Manufacturer sales rep only wants to make the sale and thats the crux of it lol

these ones look better https://www.alibaba.com/product-deta...227078095.html

they're direct drives so they don't wear out like gears and they use YRT triple row roller bearings, the stiffest bearings you can get. they have 4th axis only too. check the .pdfs for sizes

[joeavaerage]

Hi,
Direct drives don't have the torque. The fourth axis that OP linked to has torque of hundreds of Nm whereas direct drives have torque of tens of Nm and cost more.
They are good in terms of wear and accuracy, but you have to size them to the task, and that's when direct drives come up short. And have you seen what they weigh,
not 82 kg like the one OP linked to but hundreds of kg.

Geared drives wear out, but a hobbyists will get years, decades even, of use before they wear out. Talking about wear on a hobby machine is a bit of a joke. Wear is a consideration on
production machines.

Craig

[ardenum2]

which hundreds of kg are you talking about? eg. BGTK12-200 from what I linked 90Nm cont. 400RPM 55kg. don't forget 90Nm is at a distance of 1m from the center, since the table is 200mm how much newtons do you think you get at the edge of the table at a distance of 100mm?

gears wear out constantly as you go, at some point the backlash will be a major annoyance. Your worm reducers are cheap but the ones boydage linked to are not, it would be a waste of money to pay that much for worm gears. It would be better if he either copies your setup or spend the whole $2 grand on direct drives.

worm gear reducers are a thing of the past and should stay in the past, the only reason to get them now would be if they're cheap.

[joeavaerage]

Hi,
so presumably you've got some of these things? How much did you pay for them?......or do you even have any?
How about linear servos, you seem to think they're really good too, have you got any pictures of those?

When other people are rolling their sleeves up buying parts and materials and actually making things you snipe from the sidelines while apparently building very little.

Craig

[ardenum2]

Hi,
so presumably you've got some of these things? How much did you pay for them?......or do you even have any?
How about linear servos, you seem to think they're really good too, have you got any pictures of those?

When other people are rolling their sleeves up buying parts and materials and actually making things you snipe from the sidelines while apparently building very little.

Craig

I'd rather wait, give it time and achieve some level of quality, let it brew so to speak, instead of buying crap left and right and ending up with something that looks and performs as if I found it at a junkyard.

[joeavaerage]

Hi,
so what are you using for a fourth axis at the moment then?

Craig

[joeavaerage]

Hi boydage,
how about posting a couple of pics of the sort of things you want to make?
Maybe I could try making something similar, see whether my 'junk yard' set up actually works.

Craig

[jaideepshinh]

Ho Boydage

There are quite a few Tsudakoma units available on ebay- you could try buying one of these are these are some of the best you can get. There are some unused pieces as well- make an offer of a few 100 $ and most likely the seller would accept it. These are much better than the alibaba ones you can get.

I bought some large used ones through ebay and they hold tolerances so well even its unbelievable. (I took a risk and bought units made in the 80s! My budget was close to yours, and I had to buy tables for jobs which are 1200-1500mm in diameter)

Best of luck!

Jaideep

[joeavaerage]

Hi,
those Tsudakoma units are very heavy duty,all gear driven. What the Ebay listings don't make clear is whether these units require a servo drive or similar?
Is it normal to buy a Tsudakoma rotary table separately from the drive?

Craig

[jaideepshinh]

Dear Craig,

Yes thats true, but their quality is probably the best you can get in the market. And assuming there is wear out, they have it well documented as to how to adjust the backlash by simply adjusting preload on the shaft axially.

Which machine are you using? Does your machine have a 4th axis wiring in built? If not, which control and what drive configuration do you have? You should not look at an external controller in my opinion. The main CNC control should control your 4th axis as well. I never use external controllers for my applications.

From the photos you have shared of your setup, that gearbox which is being used is a non cnc application gearbox, more commonly used in single direction motion such as conveyors etc. The gear drive for that is not preloaded, and it would have low stiffness even though the torque rating is excellent.

Best of luck!
Jaideep

[joeavaerage]

Hi Jaideep,

Yes thats true, but their quality is probably the best you can get in the market. And assuming there is wear out, they have it well documented as to how to adjust the backlash by simply adjusting preload on the shaft axially.

Please forgive me, I did not mean to suggest that they were in any way compromised by being gear driven, and looking at the Ebay listings I can well understand and agree about their status in the market.
Indeed, I favor gear drives because they result in such high torque for a modest servo, whereas direct drive have much lower torque for their size.

All of the Ebay Tsudakoma listings are well and truly too large for my machine. My fourth axis is based on an Atlanta Drives servo reducer pictured in post #4. It weighs including the drive, the servo
and chuck, 18kg, and has a continuous torque of 48Nm with the servo fitted. It is an appropriate size for my machine and rather cheaper than any of the Tsudakoma's listed.
The pictures in post #5 are the parts for my intended trunnion fifth axis. The entirety of the fifth axis including the drive, the servo, the fifth axis rotary table and the steel work of the trunnion
weigh something like 35kg. When combined with the fourth axis the total weight will be in the region of 55kg-65kg, which is size appropriate for my machine.

The Atlanta Drives are both worm gear types and are adjustable. As they are new old stock they are in the state of adjustment that they left the factory. The ruggedness of them suggests to me
that it will be a long time before I even have to contemplate adjusting them. Whatever the perceived disadvantages that some may see in them, they are size, cost and performance appropriate
to my machine and my budget.

The servos of course have their matching servo drive and they in turn plug directly into the A axis and Baxis ports of my Mach4/ESS motion control.

From the photos you have shared of your setup, that gearbox which is being used is a non cnc application gearbox, more commonly used in single direction motion such as conveyors etc. The gear drive for that is not preloaded, and it would have low stiffness even though the torque rating is excellent.

No, I don't believe that is correct. They are sold as servo reducers, and when they turned up had a pinion that was intended to go in the rack of some very large machine. That is to say they are
designed, sold and marketed as CNC drives. The '58 model, the somewhat lesser spec'ed of my two drives is described here:

https://www.atlantadrives.com/hp-series.htm

In particular note the included applications are:

Typical applications for these reducers include precision rotary axis drives, traveling gantries & columns, material handling axis drives, zero-backlash axis drives and electronic line shafting. Industries served include Material Handling, Automation, Aerospace, Machine Tool and Robotics.

This is of course marketing material and should be weighed as such, but whatever else they maybe, they are not junk. They are of course much smaller than Tsudakoma and therefore less rigid but I would disagree
that they are lesser quality.

Craig

[boydage]

Hi Guys,

Apologies I was locked out of the forum for a few days. Really appreciating the words, good robust conversation. In a nutshell it took a year to chase, rebuild, strengthen - get my machine to acceptable condition to machine aluminum with acceptable results. I think Craig has been there from the start ha. And compare that to my first machine, we are now talking a 2 ton machine with a 6kw spindle. Now its awesome, and has a huge working area. A third of the working area is a 100*900*1100 cast t table weighs enough on its own. Where I am going with this is I am paranoid I will install something that is not strong or rigid enough. Its crazy huh when we think about a little 10mm endmill and the forces it imposes into a part when we hit those really aggressive cutting adaptive programs.

I make a lot of different parts, I manufacture my own tooling for a small joinery business I have here that will go onto conventional woodworking equipment but puts an awesome slant on operations. Lots of additions to my CNC Router. I also am starting to manufacture medical positioning devices. Stuff like clamps and rail holders etc. These would then be tested and certified by the company I work for for regulatory requirements.

Paid out for a flooded workshop from 8 months ago. Ive rebuilt everything off my own money, so this insurance payout is what I have left. I find that I even design parts to avoid too much part flipping, and have often thought how useful an index head would be. A huge time saver that would open up a lot of creativity in my designs. Design is what separates us all I reckon, it also needs to look cool. Yep. And if I can one day have a rotating table at the same time as the other axis's I reckon that oh hell yer that would be fantastic to see. There would be a movie I am positive.

One of my problems, and this is relating to rigidity and my paranoia, is I only have 210mm clearance from my table to my gantry. Only the smallest of the rotary tables I have looked at will fit under and I am worried being too small I will get crappy finishes. So I am considering getting the larger model and keep it in front of my gantry having it in line with the Y axis, unlike all I have seen in the X. I just cant travel over it, but can work on it that way facing the chuck with my gantry I think? Jump in if thats a bad idea In the same consignment out of China I will add in a couple of quite large 3000mm HGR rails. When I get around to installing these new HGR rails I will also block up to give more height to fit the rotary head ive bought thats too high lol. Currently I have full HGR rails except for the Y axis running on the 30mm SBR type.

So thats where I am at currently. I have been fussing and thinking about this height issue and have not had a chance to think about the actual unit itself - but now I have a bit of a plan. The other thing is I have run out of building time I need to get cracking and catch up on workload. Another thing to think about.

[joeavaerage]

Hi,
I have attached the torque ratings of both drives.

The 58 series drive is a slightly larger '4' size and 19.5:1 reduction, 390ft.lb peak and 120ft.lb throughout the speed range.
The 59 series is a somewhat smaller '3' size and a 6.75:1 reduction, 443ft.lb peak and about 75ft.lb throughout the speed range.

Very good capacities, at least for a machine such as mine, approx 800kg total weight.

Craig