Price check and questions on a mid-late 90's QT20

I've decided on a QT20 for my first cnc lathe. What can I expect to reasonably pay for a good condition machine from the late to mid 90's? How much is a tailstock worth? Are there any features that are a must have?

I don't have any work lined up for the machine so I can't say here's the exact parts it will cut, but Mazatrol seems well regarded as user friendly and that makes it seem optimal for a short run or job shop environment.

Are there any pitfalls to avoid in this era of machine?

For example, how does this machine stack up? 1998 Mazak Quick Turn 20 | eBay

Thanks, Cole

You should be able to find a decent mid-90's+ QT for maybe $20k or less.

Yes, Mazatrol is perfect for a job shop --- excellent conversational lathe programming system!

You should know how to use a multi-meter, and learn to interpret and understand the Mazak mechanical and most definitively electrical drawings.

Did I say make sure you get all the manuals!? Or at least a $500 or so credit so you can source a set.

Mazak has excellent documentation and drawings in their manuals. You can trace any electrical fault, as long as you can read the prints.

ToolCat

I can handle all of those things!

Toolcat, I actually tried to PM you with these questions but your box was full.

Supposing the machine comes with a chuck, what can I expect to pay to tool up a machine? This seems less intuitive than just grabbing Cat40 holders like for the mills.

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Cole2534 said:

Supposing the machine comes with a chuck, what can I expect to pay to tool up a machine? This seems less intuitive than just grabbing Cat40 holders like for the mills.

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You will need toolholder holders ("tool blocks"?) for that machine. They were typically not interchangeable between makers, and models. I was lucky to get a bunch of these for my 1980 Mori Seiki when I bought it in 2015 and added a few more later, but if I wanted to buy more today I wouldn't know where to get them.

Regards.

Mike

Finegrain said:

You will need toolholder holders ("tool blocks"?) for that machine. They were typically not interchangeable between makers, and models. I was lucky to get a bunch of these for my 1980 Mori Seiki when I bought it in 2015 and added a few more later, but if I wanted to buy more today I wouldn't know where to get them.

Regards.

Mike

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Kinda sounds like I may be needing to mill my own if it doesn't come with a few.

Probably not a big deal for my intended use.

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sudsy55 said:

Unfortunately they are not always correct (on the earlier ones anyway) I did find a couple marked wrong that cost me a power supply

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Ouch.

New question- are there any major changes in these machines between the mid 80's and late 90's? Ive seen some early machines for sale near 10k and wonder if thats a bargain for me a headache?

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I think the nineties machines used newer generation Mitsubishi electronics which are a better option than the older Freqrol stuff ?

I think the nineties machines used newer generation Mitsubishi electronics which are a better option than the older Freqrol stuff ?

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Yes. The T/M Plus Mazaks (which first came out in '94 I think) are the first to have the newer-generation Mitsubishi "MDS-" series electronics.

Seems like I want to stay in the '95 and on timeframe, in that case.

EDIT-

Here's a '97 SQT-15, looks decent for a 23 year old machine except for the control cabinet. Are they supposed to look like this, or has someone been in there fiddling around?

Here's a '97 SQT-15, looks decent for a 23 year old machine except for the control cabinet. Are they supposed to look like this, or has someone been in there fiddling around?

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They have probably had to replace the MDS-CV main power supply (one of the large white boxes on the lower right). These CV power supplies provide the current for the spindle and servo drives, and are a common failure point after a decade or two --- primarily because of the excessively-fast spindle motor acceleration and deceleration.

I always slow down the spindle accel/decel rates, prolongs the life of the power supply and spindle drives.

The main thing to check in the electrical cabinet is for dust and dirt, if they have operated the machine for a longer period of time with the doors open, everything in there will get filthy --- and this can result in premature failure of a component in the cabinet.

ToolCat Greg

Yes we've had a power supply failure as recently as last week on our QT8N '94 machine. The power supply was updated to a '97 version of same and had been gone though 5 years ago when we first installed this machine. I have read Cnctoolcat's suggestions on slowing spindle accel rates before but never got to it. Unit is coming back from repair this coming week as we swapped a loaner drive in to same effect. Had our third party service tech. scratching his head so he came in for a look last Friday with a couple more power supplies and found our machine to be in great shape. His loaner unit as well as ours proved to be faulty. What's odd is that control and hydraulics run but machine spindle, axis and chuck operation were dead.

He was unable to find fault with it when he bench tested at his shop and not having access to the red LED error code off the window on our live machine. He went through the process of unplugging various power drawing machine connections once here and no change so all motors and what not tested fine. In our case it displays 'L' error code ?

The power supply was unaffected by a possible power surge or brownout I would think. We get Canadian 600V 3 ph. and step down to 230 3 ph. so I'm guessing that affords us a measure of protection. I believe the capacitors play a role in this. He mentioned something about IGBT's ? Forgive my skant electronics knowledge I'm more of a mechanical guy..

When he comes back next week with the repaired power supply we'll start by doing two things
1/ slowing down spindle acceleration rates
2/ reducing hydraulic pressure to the the tool changer / turret by splicing in a pressure reducing valve of some sort. I'll be posting later with outcome.

We did slow down the machine feed rates as much as possible being the beginners we are on it and never run it at 100% feed rates off screen. It's so tiny you don't have time to react.

Machine runs, all the above ( capacitors and IGBT's changed out new )
I bounced reducing accel rate and lowering psi on turret he was skeptical hehe ( I'll be doing it anyways will be pm'ing you soon later over the week Greg )

OK all good here with the QT8N T+ but not with the repair bill we just received ! I don't want to be doing this again any time soon so will be looking into reducing the acceleration rate on the spindle.

PS : cnctoolcat I tried to send you a PM your box is full

For the T/M Plus control, the spindle accel/decel parameter is SP19.

The SP parameters are accessed in “privileged” mode (the 1131 trick...).

On edit: also pretty sure you have to power the control down, then back up, for SP19 to take.

ToolCat

OK thanks Greg will try it out but I'm a little scared playing in there. Have never heard of the 1131 trick..( newbie here ) What was that flow / bleed valve again used on the turret's line ? I'll check out the thread type and see what's out there in small format. I assume that can be put on either end of the hose connection ? I never connected the grounding rod, is this really necessary ? Saw a couple other posts ago to forget about doing it ?

For the turret-rotation speed reduction, I use a standard Parker Hannifin adjustable hydraulic flow-control valve. You can source one via MSC, McMaster Carr, or possibly Ebay.

On edit, here's a link to hyd flow control valves: McMaster-Carr

The flow-control valve body will have female NPT threads on both ends, either 3/8" or 1/2" size. You will need a male nipple or two to adapt the valve body to the machine.

You can attach the flow-control valve wherever is convenient in the turret "pressure" line. I trace back from the "P" on the hydraulic motor to the manifold at the tank, and install the valve body there.

I'm not 100% certain on the Mazak "accessing privileged mode" procedure, without being in front of a machine to try it. But I believe you go to the parameter page, then press the far right soft-key button under the monitor, then 1131, then INPUT. After doing this, you can access more pages of machine parameters, including the spindle drive parameter page where SP19 is.

On edit: I once installed ground rods for each machine, but don't use them anymore. My 7 cnc's have ran fine without individual ground rods for nigh-on 20 years now. (Machine ground wire is properly sized and done all the way of course...)

ToolCat

Thanks for the info Greg I'll order a valve on Saturday and start looking into the parameters as well when things are quiet and I can get into the parameters without distraction.