Doosan Turning machine ejector engineering flaws

These issues apply to the TT1800SY and Puma series subspindle machines.

We run turning machines 24 hours a day, for years, so this post is not about a problem that happens every day- it's more like a quarterly incident promoter. We have one of these issues about every 1800 run hours, but on specific types of parts they are over-represented, and probably occur every 200 hours.

The Ejector ends on these machines do not spin. We have to use ejector ends, because different parts have different diameters and geometries to eject to keep the processes running. The subspindle housing doesn't tolerate being full of chips. Chips can stop the ejector and leave the part in spindle to stovepipe and damage the ejector, they can also wear out seals in the subspindle and damage the subspindle, so these ends have to block chips period. There is no workaround for every part and often the work arounds eat time, and customers shouldn't perpetually lose time to a flawed ejection system even if every problem could be solved by strange methods of recalling tools and keeping holes just barely blind as long as possible.[/B]It's not terrifically uncommon to turn a part that, on the subspindle side, ends up with some chips passing through a bore. The non spinning ejectors get worn by chips during production runs, and that changes the geometry of the ejector ends.

Sometimes the chips rip the end off the ejector, attempting to spin the pneumatic actuator, bending the forks on the mount, or ruining the actuator.

Sometimes the deformed ejector ends (Deformed in process from wear from rotating chips on the non-rotating ends), become a different shape and stick the part on ejection, drawing it back inside. Then the machine moves to grab a new part and stuffs the non-ejected part into the penumatic actuator. That can damage the ejector or the hydraulic chuck closer the actuator is attached to.

Sometimes a turning tool turns the spindle in the right way for the ejector end to be grabbed by chips and jack screw against the part after thousands of parts are made (indicating this was process stable until it wasn't), and that created tremendous pressure on the actuator mounted pneumatic ejection system and can ruin a hydraulic actuator, blowing the seals, causing all the hydraulic fluid to evacuate in the chip pan.

The ejector end needs to be free spinning, capable of rotating with the part. This solves all of these issues!! Doosan has a team of engineers that apparently don't spend any time on this major issue. I've lost one pneumatic ejector system (the whole thing ruined), straightened forks at least 4 times, spun ends off maybe a dozen times. We've had one machine lose 3-4 hydraulic actuators, all over this issue.

I've got 8 of the subspindle turning machines, one more on the way, and we've reported this issue many times. This issue has never been solved by Doosan engineers.

Our Yama machines weren't great, but they had a simple, vastly superior ejector end that "floated" on the end of the pneumatic rod, and spun with the part- it was like washers and a tube on the end of the ejector rod, spring loaded forward and moving with the pneumatic rod. The shop made ejector ends were screwed into the rotating spring loaded tube rather than the pneumatic ejector end. I didn't take pictures of it and dimension it when I had a Yama because I didn't think the Doosan would have a flawed ejection system. The ejection system on the Yama had never been an issue (it was one of the best systems on the machine) so I had no reason to think these issues even existed.

If I had pictures of the Yama ejector, I would have made my own system by now. This is stupid. Doosan is supposed to care about machines working right. That's my impression of what the brand is supposed to be about.

Maybe Doosan engineers can call Yama Seiki and pay them as consultants to fix their problems. The customers will pay for a solution, but it's not traditionally our job to design it, and it should become std equipment on new machines.

It's easy to get tired of knowing the pneumatic ejector is a hair away from being destroyed all the time. It's easy to get tired of knowing the Hydraulic actuator is in peril all the time, and every time you get into several wasted hours reminding you of this unresolved problem, it's more annoying than the last time.

Sitting at 6 hours of down time, 2 key people working on this one, nothing appears damaged on this one yet so this is a "good one" but we're $2000 in payroll and lost time into this one conservatively, the pneumatic actuator was misaligned and attempts to re-align it haven't worked out yet, so this machine isn't up yet.

There are a lot of things Doosan did really well on these machines. The ejection system isn't one of them, and it's critical on this type of machine.

I under-estimated that. We're at about 12 hours now. The ejector which was replaced 4.5 months ago, has a bent rod. We used a hydraulic press to somewhat straighten it and the bracket it is mounted to. The rod isn't quite centered, we're putting a chamfer on the new ejector end and hoping that will run. It underscores how pathetic this system is. If that were a free spinning, spring loaded end, none of this would have happened because the wear wouldn't have occurred to stick the part we stovepiped on the part transfer.

The bracket the ejector bracket is attached to is bent- the one that doesn't come with the replacement ejection system. We're going to have to true that tomorrow on a bridgeport and hope to solve it with that.

A while back when we first encountered this issue I ordered special 6" stroke ejectors from SMC, and then learned we had to keep the ends near the faces anyway for chip management, so that attempt to improve the issue failed. I would put these thoughts into other replies but the system locks posts after like 15 minutes.

In order to make the ejector invulnerable to damage, it has to have a spring loaded end, and the end has to be able to rotate with the part. Rotating alone would escape most issues, but spring loading it also would allow forgiveness for a rare event like a pushed subspindle part during insert drilling, or a hung part during an A or B axis overload on part transfer.

The Bridgeport trueing of the lower bracket helped and put this in. It was about 4 hours this morning of work, assembly, alignment, and trueing jaws to get the machine up in a total of 17 hours of work. The spare parts would have taken 1-2 weeks. The machine is running but we are pursuing drawings of the doosan and Yama Seiki assemblies and hoping to put our engineering with that of JF Berns to make a solution part for Doosan customers. If I can succeed in co-developing a solution product, I will post that part number here when I've had a little time to test it. I will make nothing on that except being free of this issue. That depends on getting drawings from two companies though and I can't guaranty I'll be able to do that. I'm not a machine engineer so the only great way for me to do it is to get both sets of drawings so I can refresh my memory on the system that I know works and is similarly pneumatic with what I believe is a fixed pneumatic system with a rotating spring loaded end capable of receiving customer pusher ends.

I don't have direct communication with anyone at Doosan that does product development or improvement, but I feel like Doosan failed in 4 years of us reporting this issue to resolve it. The design on the TT1800SYII is from 2013, so it's been 9 years like this. That may be because we couldn't explain it directly to a handler of this type of development/resolution for lack of a product improvement POC with corporate or Korea- so I don't know if they know about it today even. Feedback has to be important or nothing will ever improve through contact with the people who use the machines the most - the customers.

Perhaps design/make your improved ejector end and sell back to Doosan?
As you probably know, they've just been bought out (again) so the new owners might lend an ear.

Our TT1800SY didn't hold sizes on the subspindle from day one. This was with aluminum. Main holds good, but have to keep an eye on subspindle close tolerances (+/-.002 if you can call that tight). Lathe is around 3 years old. My understanding is the whole subspindle had to be replaced during the 7 months I was off on disability last year. It was the second time we've had problems with the subspindle. The ejector assembly has been replaced once. Last week a cross drill holder froze in the lower unit. Running 1/8 inch drill at 5000 RPM in aluminum. However, the holder has been used for side ports in 303SS. When the bearings in the cross holder froze, it damaged parts in the turret. People working on the lathe had to pull out some parts including the shaft. Bearings were bad in another part. Sorry I can't be as technical as the OP, but I'm not maintenance, and don't want to be maintenance. Should be back up and running next week. First part of the week with any luck as it is one of 3 machines running a part that the customer wants over 4200 a week.