Build Thread- Bridgeport TC3 Tool Changer Repair

[ThePrecisionist]

I would like to start a Thread about the problems with the Circa Year 2001 Bridgeport TC Series Tool Changer. If anyone owns one of these machines, you will soon find out how prone to breakage the Tool Change Motor and Gear reduction box are.

I purchased my TC3 in 2007. It had one owner that took care of the machine.
Three months into running a light production job (8 hrs day, 5 tool program)
The Tool Changer started to bang hard and studder when moving and running rough overall.
I called a Local (New England) repairman. He was an Ex. BP Tech.
MIND YOU, The machine was still operating at the time. When the Tech. arrived he went to work. In less than a half hour, he crashed the flash drive in the machine, losing all the memory and tried to blame it on me for "Having a black cloud over my head." I knew then I had chose the wrong man to come repair my machine. Over the course of FIVE attemps in FIVE DAYS to fix and debugg the machine he got it to run OK. When we investigated the Tool Changer problem, we found a broken gear in the reduction gearbox. The original was a Panasonic Motor and Gearbox. He told me that unit is not available anymore. So we used a setup from Oriental Motor. The unit was installed and the Gearbox was a 50% Reduction. I believe the Panasonic was a 30% reduction.
One thing he told me was. "This sould last much longer due to the 20% reduction from the factory unit.

Fast forward to 2011. The EXACT same failure has happened. This time however I am not using thie last repairman. I am taking matters into my own hands. I am going to install a 75% reduction gearbox on my TC3. It should, by my calculations, reduce the motor speed to 375 RPM and add one second of travel time of the Carousel. I hope this will end the banging of the Tool Changer. The banging is the reason this system breaks. The PLC in the BPT control can not see the Proximity sensors in time to stop the Tool Change Motor fast enough. That is why you have banging. It's an over travel. Check out this YOU TUBE Video.

Bridgeport TC3 with Centroid control: tool change - YouTube

Do you see how smooth the Carousel travels in the Video? No banging. This is due to a PLC that can react to the Proximity Sensors in 1-2 milliseconds. Shuting down the power to the Tool Change Motor before banging at the end of travel.

Now, a BP service and parts provider (who will not be named by myself) has offered a kit to reduce this banging.
It consists of rubber bumpers and a radiused sheet metal part to increase the arc profile of the Swing Arm. The idea is to give the Proximity Switches an increased chance to see the Tool Swing Arm. I installed this part and the bumpers on my TC3

Let me tell you. It does not work. Nice idea, but no. I know from first hand experience. Does it help? Not really. I am waiting on the 75% Reduction Gear Box to come from Japan. When it does I will post on the outcome of the install.

Your experiences and advice will be most welcome on this topic.

Jake

[machintek]

Also there is a shock absorber (yes, a oil filled hydraulic unit in miniature) that helps in this banging at the end of stoke that is standard issue on all these machines. I have seen some with the ends broken off and some with no oil. They do take a beating no pun intended. Check it out.
BTW, these controls are relatively reliable. Not as good as FANUC. Power spikes and lack of maintenance cause a lot of issues. Fortunately most viruses are no longer DOS based or boot sector. Fought that battle a while.

George

[ThePrecisionist]

Thanks George,

I find that Damper you are talking about is quite useless. My finger could dampen that swing arm more! And yes I have a "new" damper in there. It's a lousy design. Currently, I have a Bungee cord dampening the OUT travel of the Carousel. Makes a big difference. Over the years, I have had every part replaced on this ATC mechanism to the total tune of $4,000.00 in parts and labor. No amount of Rubber bumpers, Afterthought parts, undersized dampers and the like will improve a faulty design such as this.

However, I am optimistic about slowing down the speed. When the 75% reduction gearbox arrives we will see what happens. It's gotta be smoother than 50%. I am sure that it will break someday too. But maybe it will break every 6 years instead of every 4 years.

P.S. More on that damper to come.....

Jake

[vmax549]

Why not just add a second prox switch and have it SLOW the drive motor down before it sees the stop switch. That would give you the best of each world Fast changes and NO banging.

Just a thought, (;-) TP

[ThePrecisionist]

Not a boad idea Vmax, but the motor is not speed variable. Really, what should be on there is a servo motor with it's own drive. Then you could just dial in the out and in positions.

On that damper note:

With a correct damper this system would have less to zero banging. But I feel it needs to be a pneumatic damper. If you have ever seen the pneumatic bump stop in a Hardinge CHNC series of lathes, you will know what I am talking about.

When you use an air motor or an electric motor to index or actuate an in/out movement you need something to "catch" the mass at the end of the stroke. Otherwise it will bang.
On the CHNC, there is a Bump Stop that is filled with incoming shop air. The air is on top of the piston. When the turret indexes via the air motor this Bump Stop is engaged and the air pressure "catches" the inertia of the mass via the "air cushion" that is inbetween the vent and the piston forcing the air out. The air is forced out through the small vent then recharged after the turret seats.

This design leaks air. But the TC3 is already an air-hog so what's the difference?

I am going to try to make one of these Bump Stops for the TC3. I know this will soften the blow.

Anyone who played Ice Hockey knows this principle. If you try to collect a hard pass with your stick rigid on the ice, the puck just bounces off. But if you "collect" the pass by giving way or cushioning the pass before it hits your blade, you will receive the pass everytime.

Jake

[ThePrecisionist]

The 75% reduction gearbox is installed. Works perfect. The Capacitor had to to brought down to a 5 MF from the 20 MF that was installed. Other than that modification, the install went nicely.

The control's tool changr time out did not have to be modified. The changer is much smoother with no banging. This setup should last much longer than the previous 50% gearbox. I believe it will be the last time I will have to touch this toolchange motor/gearbox.

If anyone wants to change their TC3 etc. over to this setup. Let me know.

Jake

[ThePrecisionist]

Here is a YouTube video of the end result.

Bridgeport TC3 Tool Change - YouTube

Enjoy! I know I am! No more repairs!

Jake