What do you think of the New Tormack PCNC-1100

[Willyb]

Hi Guys

I have been looking over the new Tormack CNC mill and it looks like a nice machine. http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7540244496 I am not sure about the stepper motors instead of servos but I guess this is a cheaper way to go? Interested to hear your comments on this new cnc machine.

Regards
Bill

[JFettig]

Theres a lot that can be said about this machine, some positive, some negetive. Overall I think its pretty cool someone finally made a small but big enough machine for a good price. As many people know the dispute apon the drives, thats the negetive. Im sure if that argument gets started again this thread will be shut down.

I am curious to see how the tool changing works, it appears that it has to do with some kind of drawbar grabber and how from there I dont know for sure.

As for the steppers vs servos, servos are a little more complex to set up, and I am sure it has to do with the drive issue too. I am supprised to see it only being able to move 60ipm. I would like to see a machine like that doing 200ipm.

Jon

[Willyb]

Hi Jon

Yes I also thought that the 60 ipm was disappointing. I don't know why this set up would not produce a higher number? I have seen other stepper systems move allot faster.

As for changing tools, this is how I believe it is done. You open the spindle drive cover and on the left hand side of the spindle is a lever called the "spindle locking fork". The end of this fork is like an open end wrench that engages a set of flats on the end of the spindle shaft to prevent the spindle from turning. Using an ordinary wrench, you loosen the draw bar and change your tool holder. After re-tightening the draw bar, you swing the locking fork back out of the way and close the cover. The locking fork has a spring to keep it parked in the open position.
The locking fork could be a problem if you forget to remove it before turning on the spindle motor? The spindle cover has a safety switch to prevent the spindle motor from being accidentally turned on when the cover is open. Maybe the locking lever should also have a safety switch on it?

In regards to the drive dispute, they would have been better to use something different. I think this issue is going to hurt the sales of this product.

I do like the idea of using good ball screws. I would like to see linear rails in a machine like this. That would really allow for faster travels. I guess it all adds to the cost.

It will be interesting to hear from the first few guys that take the plunge to get an idea how they work.

Thanks for your comments.

Regards
Bill

[JFettig]

Willy, I was under the impression that that spindle lock would actualy lock the drawbar and allow some other form of tightening(turning the spindle?) to tighten and loosen. About the speeds, on my (much smaller) mill I can reach 210ipm even though that mill has larger castings, I bet with my motors that mill could move at least 120ipm.

It sure would be nice to see higher speeds in that, its not fun to watch a machine rapid, it should just be there when you blink your eyes

Jon

[Willyb]

Hi Jon

No, the spindle lock lever grabs two flats on the top of the spindle shaft and you use a 13mm wrench to loosen the square end of the draw bar one turn to remove the tool holder. Of coarse they are suggesting that you would be using the "Tormach" Tool System with the Mill which I think is a great way to go on any Mill. They make it really easy to look after tool offsets on a CNC Milling Machine.

Actually you could easily install an air cylinder on this Mill to make tool changing allot easier. Modify the draw bar so that it is longer and would accommodate a stack of spring washers under it to keep your tool holder tight in the spindle. Install an air cylinder over top of the spindle that you could activate with a push button. The air cylinder would push down on the top of the draw bar when you wanted to change the tooling. I think this could be easily added to this machine with out to much trouble. It would do away with the locking arm and wrench and you could change tooling with out opening the spindle drive cover.

Take care.

Bill

[JFettig]

Bill, I have actually started doing exactly that(with the air cylinder and all) but at this point I have been using a large lever. It will take a pretty decent sized air cylinder to get the pressure needed(need around 600lbs of pressure on the drawbar for only decent holding).

I think the way they have it is too much work, it appears that you have to open the casing to change tools and all.

Jon

[Willyb]

Hi Jon

To change tools or the spindle speed on this machine you must first open the spindle drive cover which requires loosening a small knob on the right hand side of the cover and swinging it open. They say 20 seconds for a tool change and 25 for a ratio change. Doesn’t sound all that bad.

You would be better off using your air cylinder to release the tool rather than holding it in the spindle. To use a cylinder to release the tool holder, you would need to lengthen your draw bar and make room for a stack of spring washers under the head of the draw bar and the top of the spindle. These washers are what actually pulls the collect up into the spindle and puts the pressure onto the tool holder, keeping it from slipping in the spindle. The air cylinder is mounted above the spindle with it's shaft approximately 1/8" away from the top of the draw bar. When you want to make a tool change, you put air to the cylinder and it's shaft moves down against the end of the draw bar and compresses the stack of spring washers releasing your tool. Once you have the tool changed you remove air pressure and the cylinder rises allowing the spring washers to return pressure back onto your tool holder. To control your cylinder, you could use a air push button mounted on the side of your spindle cover. Or an electric solenoid controlling the air with an electric push button.

The problem with using an air cylinder to hold your tool in the spindle is that you are putting this extra 700 or 800 lbs of pressure on your spindle bearings. With this other method the pressure is only on the spindle bearings during a tool change when the machine is stopped.

If your spring stack had a pressure of 700 lbs. you could get away with a 3" cylinder at 100 psi to release your tool.

The above method of tool retention with the spring washers is used on 85% of commercial milling machines. They use different tool holders that have a groove around them that small ball go into to grab the holder and pull it up inside the spindle. Neat idea and it works very well.

Take care.

Bill

[JFettig]

I have tried the method you are mentioning on my mill with my tormach tooling, and so far it works. now that I am thinking about it, I am getting a little worried about the stresses on my spindle bearings. I wonder if its an issue?
the only thing I did different is used a lever and my bodyweight to release the tool.

I have started to work on some custom tooling that uses retention nobs, I have a few holes to drill then I am ready to test it out, but that will be a while as I am at college now and probably wont get home till thanksgiving.

Jon

[Willyb]

Jon

Would like to see your new tooling idea when you get it finished. Post some pictures sometime.

Bill

[fc911c]

The PC, Stand and the Rotary Table are Not included. It say's so in the description I don't why it's in the picture. At first look I thought it was, till I read on.

[lerman]

Instead of using an air cylinder, could you just put a block of steel with an adjustable bolt above the drawbar? Set your system up so that the zero on the z axis is offset. Now, when you move the z axis all the way to the top, the bolt will press on the top of the drawbar, compressing the spring and releasing the tool. You would have to give up a small amount of travel in the z direction, but you would get a simple way of releasing a tool.

You might want to have an extra limit switch that stops the motor rotation. It would be bad news if a gcode bug could cause the tool to release.

Ken

[Willyb]

Hi Ken

That would put allot of load on your ballscrew and stepper motor. You would need to push very hard to compress the spring washers to release the tool holder. The air cylinder set up would not put any pressure on the ballscrew or stepper motor. It would only be pushing on the one set of spindle bearings and this is when the spindle is stopped. I don't think it would be hard on the spindle bearings in this application.

Take care.

Bill