High Speed Turbine Engraving Spindle

[awemawson]

Another project that's been LONG in the gestation !

Back in 2005 I made an air driven high speed engraving spindle for my Bridgeport Interact - it worked well and as well as engraving it also made several PCBs for me. Well I lost the poor old Interact when it fell off a removal lorry  and the machine I replaced it with wasn't so easy to get air to the spindle, as it's a moving gantry (fixed bed / table)

I decided that it was time to knuckle down and run some air pipes through the machine to be able to once more use the engraving spindle.

Here are some pictures that have been posted here before, but I'll put them up for the sake of completeness: it's simple in the extreme, just being an air jet impinging on an aluminium gear wheel that I hobbed. Air exits through the bearings cooling and lubricating them

[awemawson]

Now the problem was purely that of getting 6 mm bore / 8 mm o/d nylon tube from the air input connection to the Beaver Partsmaster through the various guide ways and box sections to a regulator / lubricator and on to a termination point close to the main machine CAT 40 spindle end.

First I made up a little termination block to take push fit input and tap output fittings, and gingerly drilled and tapped to hold it to the spindle housing. I don't like drilling expensive castings by hand with a battery drill - very difficult to get precision - however I got away with it  Still waiting for Allen Cap screw so those M6 hex bolts and washers are only temporary.

Then, by dismantling some of the cable trunking I was able to fit a pair of 6 mm 'Nutserts' in it's wall to take the regulator / filter / lubricator unit and try the Air Spindle for fit via it's umbilical tube. Note that from the tap to the turbine I've stepped down to 4 mm bore / 6 mm o/d for greater flexibility.

[awemawson]

Then it was 'just' a case of threading the 8 mm nylon tube ( 10 mm o/d) through all the flexible and rigid trunks that take wires from the moving head and allow for X, Y, and Z movement.

Bless the Beaver designers, who left lots of room in the trunking - it was actually quite a pleasant surprise. Using the rigid nylon 'snake' that I use for pulling 'singles' through conduit it actually went quite well for a change 

[awemawson]

Now if you look closely at the last picture, you will see the nylon tube emerging vertically from the end of the X axis trunking through a pre-existing hole where all the original air pipes emerge - it's the cleaner one!

Now I've temporarily tapped it into the main air feed for testing - but I have ordered a suitable solenoid valve that will switch it on and off using the command 'M07' . Originally this was intended for the optional 'through spindle coolant' but as my machine has no such provision it's a 'free' output from the Heidenhain TNC355 controller that I've been able to poach.

All I've had to do is mount a suitable relay in the electrical cabinet to power the solenoid, and pick up the already pre-wired drive from the TNC355.

It's obviously my lucky day, as there is even a convenient 'blanking grommet' covering a suitable hole from the cabinet to the area just below where I will mount the solenoid (when it arrives) 

[awemawson]

So does it spin - you bet - I've just clocked it at over 29K RPM 

I need to decide what to use as lubrication - I've fitted an air oiler but want something that is compatible with the soluble oil and slideway oil that the machine uses, yet is thin enough to work at that sort of speed. The lubrication is of course total loss.

While I was running air pipes I at last got round to plumbing up the feed to the air operated brake on the 4th axis, which has it's own regulator.

[Pete W.]

Hi there, Andrew,

That looks like a useful addition to the foundation machine.

While browsing your pictures, I was reminded of the way Sperry drove some of the cockpit gyro instruments of WW2 vintage.  The outer surface of the gyro wheel had a series of curved grooves (can't think of a better description) that looked as though they'd been cut with a dovetail cutter.  If I remember rightly, the jet(s) were offset so they aimed at one side of the groove and the air went round the groove and exited from the other side, giving up its energy with the minimum of turbulence.  (I don't think my techno-jumble museum has any examples in-stock, I'm afraid!)  They were actually driven by vacuum rather than compressed air and they had pendulous lids to various ports on the gimbals that applied 'puff' in the right direction to precess the gyro to the right orientation.

If you're looking for something to try out your engraver, I have a very early Myford ML7 tail-stock barrel that needs an engraved scale - maybe we could agree some quid pro quo? 

[awemawson]

Pete,

Do you have a graphic of what you want to achieve - preferably a .dxf ?  I'm not sure I'd approach a tailstock spindle engraving off the lathe but rather might want to use the feed screw to get the lines at exactly the screw pitch.

[Pete W.]

Andrew,

I'll do some research       and send you a PM when I've got my act together!! 

[awemawson]

The Postman bought a couple of parcels this morning 

Firstly cap screws to replace those hex headed ones on the air 'terminal block' so those went in quickly and it looks so much better.

Secondly a replacement Regulator: Now the gauge on the Lubricator / Filter / Regulator unit didn't return to zero. Sealed unit so no finger poking possible! When I contacted the supplier they amazingly couldn't just replace the gauge, but wanted the whole assembly returned, then they'd send out a replacement 

I explained that that just WASN'T going to happen, as not only was it buried in the bowels of a machine tool, but I'd had to reverse the 'handing' of it so that the lubricator was on the left to aid in the way pipes ran. After about a dozen too's and froe's they eventually saw that I wasn't giving up and offered to send out a complete unit and please keep the old one. I couldn't get through to them that all they had to do was remove the (separately boxed) gauge and send just that !

Oh well, it's not my business 

Anyway - a touch of Loctite 542 - back in and aligned. This 542 is brilliant stuff. Seals threads very effectively, and allows you to put them in the alignment that you want, not just when the thread is tight. In most cases I've ceased using PTFE tape to seal threads and use the 542 for smaller threads and Loctite 577 for the coarser ones.

Still waiting for the air solenoid to arrive, but it's on a slow boat from China, so that could be quite a while yet 

Now I just need to sort out what to use in the lubricator - perhaps just WD40 - or a light oil cut with white spirit perhaps  Any suggestions welcomed 

[Pete W.]

Hi there, Andrew,

I did a search for 'high speed spindles' and this thread was the top of the list that resulted.

I have a couple of questions:

How do you attach the engraving tool to the shaft of the turbine?  How much work does the turbine do when it's working?

I have to make a couple of components from 8 mm Delrin sheet but I don't have a mini (vertical) mill.  My favourite option at present is to contrive a high speed spindle and mount it over the knee & tables of my Flexispeed minimill (horizontal).  A friend has given me some small milling cutters, the sort with 1/4" or 6 mm shanks that have a grub-screw flat and I expect to try using one of those for profiling the part.  I don't think my spindle will be turning as fast as yours but I'm a bit apprehensive that the grub-screw fixing will be out of balance and cause vibration problems.  What do you think?

My spindle will be electrically driven - I don't have compressed air in the shop.  I did wonder whether I could use my Dremel but its business end won't take 1/4" or 6 mm.

This project could galvanise me into doing some renovation on the Flexispeed minimill, in the first instance to fit calibrated hand-wheels to the various feed-screws.

I know those small milling cutters are known as 'throw away' but the ones I've been given seem far from deserving that! 

[awemawson]

Pete I cheated 

I bought a small parallel shank ER11 (I think - it may be ER8) collet shaft that I think is intended to make 'extended access' in difficult machining situations, and I used that as the basis for my high speed spindle, selecting the bearings to suit the shaft.

Obviously the torque produced at mega revs is pretty small, but then so is the load when lightly engraving.