TTS - Should I Do It?

[spumco]

What else does the TTS buy me?

Told you you'd get a better response than in a PM!

Here's my take on it...

I'm a clutz, and new at this thing - both CNC and machining in general. I want to make stuff, not fiddle with the machine, and I also need to minimize the frequency with which I bugger something up. Every time I changed tools I had to re-set zero, introducing an opportunity to hose it up. I even made a touch-probe arrangement (two plates) that works with an auto-zero macro. Worked OK-ish, but chips would trigger the probe, it wasn't THAT accurate, and it was slow as hell coming all the way down from G53 Z0 to the table surface... every. single. tool change. The macro is superb (UCCNC 2017 screen set), but piles of chips and flood coolant were my nemesis.

Having driven end mills in to both of my vises in the first couple of months after I got this thing going, I quickly decided that the TTS system with a PDB was the ticket. Tightening the drawbar by hand got old about the second time I did it.

1. Tool changes are very, very fast. Step on the foot switch, swap tools, let off, cycle start. I'd be faster than most ATC's if I didn't sit there waiting for a minute so the juice drains off everything.
2. Everything is repeatable to the limits of my ability to measure and the machine's capability.
3. Runout is superb, once I faced the spindle nose dead flat. Used a carbide lathe tool in the vise and took about 0.005" off the face with no collet in it. I think runout is more a function of your bearings, spindle taper, and collet quality than the TTS system in general.
3. Using a surface plate, a homemade collar/riser, and a height gauge I can set up my tools off the machine. I didn't want a tool height dingus - as beautiful as the one you made is - on the table. Frees up setup space and one less 'single-use' item to buy.
4. I bought a set of 10 ER-16 collets and 5 ER-32 collets as I mentioned a while ago. I don't plan on having 100 of the things around - just those loaded with the tools I use most. Jbolt is right - you can't have enough drill chucks, but LMS has a good deal on the TTS/Jacobs + chuck combos.
5. I also made 10 TTS-compatible set-screw holders for a couple bucks each for the small stuff (1/8"-1/4"). Easy to do using ground 41L30 3/4" stock for the shank and some 1-1/2" stock for the flange. If I felt like carving one out of solid stock, I could have up to 1/2" set screw holders - but it bothers me turning 1-1/2" stock down to 3/4".
6. If I break a tool mid-job, I can install a new tool in the same or new holder very quickly off the machine using the height gauge. Back in business, no fiddling with new off-sets mid-program.
7. Part Z0 is set using a blank TTS tool I made with a nice radius tip set to #96 in my table. Once I'm ready to run, having found X/Y, I change to tool 96 and drop it down to the table until a ground pin just squeaks underneath the dummy tool. Set Z to the pin OD and insert the first tool of the job. If I'm feeling anxious (usually), I'll cycle through the tools and double-check the off-sets. Everything has been within 1 or 2 tenths no matter how often I change tools.
8. Once I get a probe, it'll be mounted in a TTS holder with an appropriate off-set and then I can really go to town. One touch X/Y/Z zeroing and all tools set up ready to rock.

Is it perfect? Of course not. There are valid concerns with pull-out, but those can be overcome in a few ways. Since I was building my own air over hydraulic PDB, I just upped the drawbar torque over Tormach's recommended torque and designed the PDB to have more grunt. No pull-out so far, even with chattering end mills and fly cutters. In addition, Tormach's white paper on TTS pull-out is also very useful - but honestly the same thing can happen with a standard R8 collet.

As usual, I've rambled on a bit. If you've got specific questions fire away.

-S

 

[Boswell]

Told you you'd get a better response than in a PM!

Here's my take on it...

I'm a clutz, and new at this thing - both CNC and machining in general. I want to make stuff, not fiddle with the machine, and I also need to minimize the frequency with which I bugger something up. Every time I changed tools I had to re-set zero, introducing an opportunity to hose it up. I even made a touch-probe arrangement (two plates) that works with an auto-zero macro. Worked OK-ish, but chips would trigger the probe, it wasn't THAT accurate, and it was slow as hell coming all the way down from G53 Z0 to the table surface... every. single. tool change. The macro is superb (UCCNC 2017 screen set), but piles of chips and flood coolant were my nemesis.

-S

I don't use a TTS or any type of automatic tool changer. I would like to point out that there are two separate arguments for an Automatic tool Change system (TTS or otherwise).
First is speed gained from not having to re-zero the Z each time you change. I want to point out that this is only a function of the tool holder and not of the automatic release. It seems that you can get this value with little or no fabrication or changes to your mill, just buy the parts.
Second is the speed gained from having an automatic release/change system. This in itself has nothing to do with Z axis repeat-ability and is just a labor saving device. While many have added this to their mills it does seem like a "Project".

Personally, while I have considered both, I still change tools with a wrench on the draw bar and I use a little z-Setter with an LED in it to set the z on each tool change. Tool changes take between 60-120 seconds. If I were making money, I would probably invest in some additional time savings so I could re-coop the 120 seconds per tool change. As for preventing mistakes, I have made a few due to errors during tool changes, but keeping my head in the game is part of the job/hobby and after much "practice" it does not happen very often.

Have fun with what ever you decide to do.

 

[Groundhog]

I have some tools set up with the TTS system and it work good. Even better is a touch plate that measures each tool when a tool change is reached. A lot less expensive and for my hobby needs doesn't add hardly any time.
I use a probe for finding my work zeros and offsets. I have been using MachStdMill screens (a system really) overlay for Mach3 for a long time. It has screens and routines for all sorts of probing and tool length touch plates.

 

[spumco]

I would like to point out that there are two separate arguments for an Automatic tool Change system (TTS or otherwise).

Both points are entirely valid. TTS makes things convenient and faster, but there's no fundamental improvement in the machine's ability to hold to a desired Z-height.

I also like not having to change collets in addition to the tool during a tool change. That - to me - was messy and frustrating since I was using a dab of never-seize on the collet taper. Everyone's tolerance for this is different.

Yes, the PDB was a bit of a project. Not terrible, however, and not expensive - perhaps 3 weekends worth of time to CAD & fabricate. Maybe $200 in parts and materials including the air cylinder and valves. If you go with a 3-stage cylinder typical of standard PDB's, the cost goes up unless you score an Ebay deal. I viewed this project as a learning experience - even if I got it wrong I wasn't out big bucks in materials.

For about $500 (PDB and TTS holders), I reduced the likelihood of a user-induced Z-height crash, and sped up tool changes dramatically. TTS is not necessary - but it's nice.

I used to own junky cars with no power windows or other goo-gaws. Now that I have something with working A/C, heated seats, and a few other nice options I'm never going back.

 

[MontanaAardvark]

Yes, the PDB was a bit of a project. Not terrible, however, and not expensive - perhaps 3 weekends worth of time to CAD & fabricate. Maybe $200 in parts and materials including the air cylinder and valves. If you go with a 3-stage cylinder typical of standard PDB's, the cost goes up unless you score an Ebay deal. I viewed this project as a learning experience - even if I got it wrong I wasn't out big bucks in materials.

The only thing about the stock draw bar that annoys me is the square nut head on my Grizzly. I think it's possible to get a long bolt with a hex head. If not, I could make a replacement bolt. After that, I'd leave the cordless drill there with a nut driver bit on it and a couple of button pushes changes the tool.

There are a few designs that I've seen for a manually activated draw bar, but I think getting the tension balanced just right must be tricky.

 

[jbolt]

Told you you'd get a better response than in a PM!

Here's my take on it...

I'm a clutz, and new at this thing - both CNC and machining in general. I want to make stuff, not fiddle with the machine, and I also need to minimize the frequency with which I bugger something up. Every time I changed tools I had to re-set zero, introducing an opportunity to hose it up. I even made a touch-probe arrangement (two plates) that works with an auto-zero macro. Worked OK-ish, but chips would trigger the probe, it wasn't THAT accurate, and it was slow as hell coming all the way down from G53 Z0 to the table surface... every. single. tool change. The macro is superb (UCCNC 2017 screen set), but piles of chips and flood coolant were my nemesis.

Having driven end mills in to both of my vises in the first couple of months after I got this thing going, I quickly decided that the TTS system with a PDB was the ticket. Tightening the drawbar by hand got old about the second time I did it.

1. Tool changes are very, very fast. Step on the foot switch, swap tools, let off, cycle start. I'd be faster than most ATC's if I didn't sit there waiting for a minute so the juice drains off everything.
2. Everything is repeatable to the limits of my ability to measure and the machine's capability.
3. Runout is superb, once I faced the spindle nose dead flat. Used a carbide lathe tool in the vise and took about 0.005" off the face with no collet in it. I think runout is more a function of your bearings, spindle taper, and collet quality than the TTS system in general.
3. Using a surface plate, a homemade collar/riser, and a height gauge I can set up my tools off the machine. I didn't want a tool height dingus - as beautiful as the one you made is - on the table. Frees up setup space and one less 'single-use' item to buy.
4. I bought a set of 10 ER-16 collets and 5 ER-32 collets as I mentioned a while ago. I don't plan on having 100 of the things around - just those loaded with the tools I use most. Jbolt is right - you can't have enough drill chucks, but LMS has a good deal on the TTS/Jacobs + chuck combos.
5. I also made 10 TTS-compatible set-screw holders for a couple bucks each for the small stuff (1/8"-1/4"). Easy to do using ground 41L30 3/4" stock for the shank and some 1-1/2" stock for the flange. If I felt like carving one out of solid stock, I could have up to 1/2" set screw holders - but it bothers me turning 1-1/2" stock down to 3/4".
6. If I break a tool mid-job, I can install a new tool in the same or new holder very quickly off the machine using the height gauge. Back in business, no fiddling with new off-sets mid-program.
7. Part Z0 is set using a blank TTS tool I made with a nice radius tip set to #96 in my table. Once I'm ready to run, having found X/Y, I change to tool 96 and drop it down to the table until a ground pin just squeaks underneath the dummy tool. Set Z to the pin OD and insert the first tool of the job. If I'm feeling anxious (usually), I'll cycle through the tools and double-check the off-sets. Everything has been within 1 or 2 tenths no matter how often I change tools.
8. Once I get a probe, it'll be mounted in a TTS holder with an appropriate off-set and then I can really go to town. One touch X/Y/Z zeroing and all tools set up ready to rock.

Is it perfect? Of course not. There are valid concerns with pull-out, but those can be overcome in a few ways. Since I was building my own air over hydraulic PDB, I just upped the drawbar torque over Tormach's recommended torque and designed the PDB to have more grunt. No pull-out so far, even with chattering end mills and fly cutters. In addition, Tormach's white paper on TTS pull-out is also very useful - but honestly the same thing can happen with a standard R8 collet.

As usual, I've rambled on a bit. If you've got specific questions fire away.

-S

I'd like to hear more about your air over hydraulic PDB?

 

[spumco]

I think it's possible to get a long bolt with a hex head.

Make a new one. Gr-9 (or 8) 7/16-20 all-thread from Crackmaster Carr, add a heavy hex nut & bearing washer and make a bushing with a couple 'thou clearance to center it in the spindle. Polish the top of the bushing and washer bottom. Pin or weld the nut to the all-thread - done. 7/16-20 Gr-9 is good up to about 40ft-lbs or so, which is double the recommended torque in the TTS white paper.

I'd like to hear more about your air over hydraulic PDB?

Short version - I shamelessly copied the concept from the manual lever drawbar spotted on the Tormach forum (CNCZone).

I was about to go on about the design, but I'll start a new thread so we can stick with the TTS theme here.

-S

 

[MontanaAardvark]

I've got to say I think you guys have convinced me I really don't want to switch over to the TTS, probably without intending to. I think I'm with Boswell.

Personally, while I have considered both, I still change tools with a wrench on the draw bar and I use a little z-Setter with an LED in it to set the z on each tool change. Tool changes take between 60-120 seconds. If I were making money, I would probably invest in some additional time savings so I could re-coop the 120 seconds per tool change. As for preventing mistakes, I have made a few due to errors during tool changes, but keeping my head in the game is part of the job/hobby and after much "practice" it does not happen very often.

I could see getting a few dedicated End Mill holders for my highest use cutters and leaving them ready, but the TTS system seems like it's going to cost me more than I want to spend for the convenience. I ran the numbers on the Little Machine shop site, so I'm sure I could cut those costs some, but LMS tells me an ER-16-9 collet is $9.66 (based on being one of a set of six different sizes), and the TTS ER collet holder is $34.75. That's $44.41 to hold one tool. It looks like with China.com sources, I can get those down to about half that price. I figure I'm looking at easily $250 to $300.

 

[jbolt]

Well that's the thing about CNC. Are you making one part or several of the same part? On a one-off part doing manual tool changes there may not be much different from a time savings aspect when you consider tool setup and entering tools into the tool table. On multiple parts with multiple tools it pays off in time savings. For hobby work its really a personal preference. For me adding the pneumatic draw bar and TTS system has been part of the journey and learning experience.

 

[RJSakowski]

One additional benefit of the TTS system is that it is usually not required to tap the drawbar to release the TTS tool holder. The nature of the beast drawing the tool holder to the spindle face creates enough of a preload to disengage the tool holder when the drawbar tension is released.