[David Da Costa]

I have started buying components for a Power Drawbar for my NM-135 as I don't have 3 hands and the NM-135 with TTS requires 3 (two to loosen the drawbar as there is no spindle lock) and one to catch the tool holder.

I want to keep the power drawbar as compact as possible and with as few moving parts so I want a direct acting air cylinder rather than using levers.

I ordered this Fabco cylinder from ebay http://cgi.ebay.com/ws/eBayISAPI.dll...#ht_700wt_1167 which has a 4" bore and 1' stroke which I think should be more than enough force. It has a non-rotating piston which should help avoid the drawbar un-screwing over time.

I also ordered a 4 Way 2 Position Hand Lever Pneumatic Valve 1/4NPT Momentary for manual control and will change to solenoid at a later date when/if I add an ATC.

Additionally I ordered a One Touch Push In to Connect Speed Control 1/4" OD Tube and a filter/ muffler plus some 1/4 npt - 1/4 od quick connect fittings.

Having never played with pneumatics before, can someone give me a simple "circuit" diagram of how to plumb the cylinder to the valve to the compressor.

Now I need to design the power drawbar , but as the top plate on the mill head is approx. 1/4" steel plate which is easily removed I will be mounting the cylinder to that using stand offs.

David

[slatronic]

David,

On the valve, I'm guessing it's a five port. There should be 3 ports on one side and 2 on the other. The middle one on the 3 port side should be in from compressor. The 2 other ports are exhaust. The 2 ports on the other side are the outlets to the cylinder. I think that cylinder is double acting. So you will need to pipe the bottom hole of valve to the bottom of cylinder. By bottom of valve I mean side down from lever. By bottom of cylinder I mean end opposite of rod. Then pipe the top hole to top of cylinder. Put your muffler's in exhaust ports. Lever should be mounted up. When you pull lever down air should push down cylinder and rod. When you pull up on lever, air should push up cylinder and air should exhaust. If it works opposite of this just flip output hoses and your good. I think it's easier to remember if you pull down handle and cylinder moves same way. If you need drawing still I can whip one up.

[David Da Costa]

Thanks for the info.

I actually think it is 3 ports (see http://www.fabco-air.com/products/hi-power/hipower.html)

David

[slatronic]

I was meaning the lever valve is 5 port 4way/2postion and the pneumatic cylinder is double acting cylinder. So the cylinder needs air to push and to pull. When the lever is pulled down it will allow air to push down on diaphram in cylinder. Then when you pull up on lever air is exhausted from top and air is pushing on bottom of diaphram returning it to normal position. I am not seasoned on this stuff but have messed around a bit and been doing tons of research lately. I also think you really cant hurt anything if you pipe this wrong. You can always just have air turned down and hook it up to valve to see where air comes out of before you attach to cylinder.

[David Da Costa]

Got it thanks

[Frogblender]

How's it going with the drawbar?

I've grown weary of wrenches.


Also, where are you getting your TTS holders? What I'd like is several ER20 collet holders (like which came with Novakon's quickchange set) with the 3/4" shaft.

[David Da Costa]

I almost have all the parts and the design is done so I should start building next week once the enclosure is finished.

I have the TTS holders from Novakon and Tormach.

David

[Crevice Reamer]

Hi David. Nice find on the cylinder!

...where are you getting your TTS holders? What I'd like is several ER20 collet holders (like which came with Novakon's quickchange set) with the 3/4" shaft.

You can get them at little machine shop:

http://littlemachineshop.com/product...itFast=tormach

or from Tormach:

http://www.tormach.com/Product_TTS.html

CR.

[David Da Costa]

My power drawbar for my NM-135 is pretty much completer apart from a couple of finishing touches.

I am running my compressor at 65 PSI and with the 4" bore on the piston and 6 belleville washers it is working fine.

I followed the instructions for the power drawbar that LMS sells and set the the drawbar to finger tight with a tool in place and then tightened it one full turn.

Attached is a photo and a video of it in operation.

David

[ame="http://www.youtube.com/watch?v=pVzmLmMelH0"]YouTube- NM-135 Power Drawbar.wmv[/ame]

[sseaner]

Ok, I am new here so I have figured out you need to change the tools manually. I watched the video of your power draw bar. Does it just need to depress or is it also turning? how would I normally change the tools? Are you using a quick tool change kit? I apologize for all the questions but I am trying to learn as much as I can.

Thanks,

Scott

[David Da Costa]

Hi Scott, yes I am using the quick tooling available from www.tormach.com (TTS) and Novakon.

The piston is depressing the drawbar which relaxes the pressure on the collet which is part of the TTS system. When the piston is retracted the 6 belleville washers (springs) maintain the pressure on the drawbar which grips the the tool holder.

This animation on the Tormach site gives you an idea of how the quck change tooling works http://www.tormach.com/Flash/TTS_small.html.

David

[Frogblender]

That looks dang handy.

Where did you get the drawbar? I assume the stock drawbar was a little too short?

FYI One of Hoss' videos shows him measuring, using a dialmeter, how much the spindle deflects in the -Z direction when the piston is actively subjecting the bearings to the ~800lb axial load. IIRC, his moved .002" - "but at least they move back" when the load is removed.

[sseaner]

Would you suggest the TTS kit for $745.00 or the Novakon for $199.00? Or do you think it is better to piece meal it?

Also, do you have a part # for your valve?

Thanks,

Scott

[David Da Costa]

No, it is the standard drawbar, there was plenty of thread on it to allow the addition of the 6 belleville washers.

I will test the deflection tomorrow, I expect it to be similar to Hoss and I think the impact of the piston on the drawbar and bearings is probably less than if you were hitting it with a mallet. I have a muffler/ speed control coming that I will put on the exhaust of the cylinder extension to slow it down, but with the big bore and 65psi it is not to rapid an extension anyway.

I adjusted the cylinder and psi so it was the minimum needed to release the tool.

David

[David Da Costa]

Would you suggest the TTS kit for $745.00 or the Novakon for $199.00? Or do you think it is better to piece meal it?

Also, do you have a part # for your valve?

Thanks,

Scott

Scott I actually have a mixture of the Novakon set and specific holders from Tormach. I use the Tormach collet as the tool fit better where as the Novakon one is a little tighter.

I got the valve from Ebay, http://cgi.ebay.com/ws/eBayISAPI.dll...#ht_2224wt_812


David

[slatronic]

David,

Nice job, really simple. I like it. Almost to simple, not enough machining Just kidding.

Need to do some testing on tool retention as well. That's been my concern with this. I know hoss hasn't had any issues but guys with tormachs and bigger have. I have a good feeling everything will work perfect though. Any plans far ATC?

[David Da Costa]

Once I get my enclosure built (which I hope to do this week) I will test out the retention.

Eventually, I do want to add ATC, but that will be a little further down the road.

[Teyber12]

sheesh how much would you charge to make me something like that... would it mount right onto a cnc x3... that is a great bit of kit there david!

[David Da Costa]

The problem is the way I have built it which is by having a cylinder acting directly on the drawbar there are advantages and disadvantages.

The advantage is evident in that it is very simple, no levers etc.

The disadvantage is that you have to use a much bigger cylinder which is much more expensive (unless you are lucky to find one on ebay like I did).

A 4" bore cylinder is in the range of $160 - $200.

Having said all that, and even though I have not specifically looked at an X3, I am sure it is all transferable.

PM me if you want more information.

David

[kvom]

Can you post a pic of the washer setup? I assume that they are acting between a collar on the drawbar and the top of the casting.

How did you spec the spring constant on the washers?

Can I also assume that the lengths of the supports was necessitated by the throw of the piston?