Pneumatic brake for CNC rotary table

[Phil WParticipant @philw78611]

[Phil WParticipant @philw78611]

I thought that this pneumatic brake for a CNC rotary table might be of interest to the forum. It's not difficult to make and just attaches to the original table clamp bosses without any modification. I think the picture says it all. (thats assuming this link works. I don't seem to be able to upload a picture directly to the board…)

The air is supplied by a normal compressor, and a short Macro gets called by Mach3 to operate a solenoid air valve. Each 'A' move is wrapped in a pair of unlock/lock calls and the rotary plane is then held locked for the XYZ moves. I have got very litle backlash on the rotary axis, but it's still much better clamped. Anyway, it's certainly proving to be very effective.

More pics and a short video on my radial build blog:

http://philsradial.blogspot.co.uk/2012/09/air-brake-for-rotary-table.html

Cheers

Phil

[Michael GilliganParticipant @michaelgilligan61133]

Phil,

Sounds very interesting … but your picture link doesn't work.

You need to create an album, then insert images from that.

Meanwhile, I'm off to look at your blog.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Very neat … thanks for sharing that.

Incidentally, it would be wise to use the "insert hyperlink" function instead of directly posting hyperlinks.

This forum has an unfortunate tendency to re-size the messages when long hyperlinks are posted.

[there are several previous threads discussing the problem … but please shout if you need help]

MichaelG.

[Anonymous]

Hi Phil,

Welcome to the forum. The clamps certainly look impressive. Does the air pressure hold the clamp on, ie, failsafe, no air pressure equals no clamp?

On another matter, is that one of the ArcEuroTrade high speed spindles in the pictures? If so, how are you getting on with it?

Regards,

Andrew

[Phil WParticipant @philw78611]

Hi

Thanks for the comments, help, and warm welcome.

Here's the photo that I tried to add, to save going off to find it:

and blog link:

**LINK**

Yes, Andrew, no pressure, no clamp. Also, within the macro that I call to operate it, the A-axis gets disabled when the clamp is on, and re-enabled when it goes off. Not that I would ever try to code an A move with the table clamped But although Mach3 won't do A-moves from Gcode when disabled, the A jog still functions so I can still get it wrong.

Yes, the spindle is from ARC (the ER16 size). I have found it brilliant for engraving and PCBs and using small endmills. I think it will be useful as an internal grinding spindle for the lathe tool post as well. It is a nice size and easy to mount on various fixtures. Unfortunately I destroyed the first one I had by programming the inverter incorrectly (I didn't buy the ARC inverter because I had one already, and have programmed 2 or 3 in the past ok). ARC couldn't tell me what parameters they used in thier inverters so I ended up buying a new spindle and inverter together (I know…). I have now made a list of all the parameters they programmed in their inverter, if anyone wants them to avoid my expensive mistake.

Cheers

Phil

[Anonymous]

Hi Phil,

Thanks for the information. It's good to know that the high speed spindles are sound, as they're not cheap. I have one on the wish list for my CNC mill. I've tried engraving, and even flat out at 5000rpm it wasn't really satisfactory. With 2mm cutters I get a bit bored waiting for the cuts to finish. Anything that'll help speed things up has to be good.

What type of CNC mill do you have?

Regards,

Andrew

[Speedy Builder5Participant @speedybuilder5]

Great bit of kit, now we look forward to a compact unit so you can use the table in both horizontal and vertical axis. By the way, what was the clunk clunk clunk at the end of the video ?

[Phil WParticipant @philw78611]

The cnc mill is my own conversion of a machine identical to a Warco VMC turret mill. You certainly will find engraving fun with a high speed spindle – I can pretty much use max table speeds on easy material.

Yes, a compact version of the clamp for horizontal use would be nice, but I couldn't think of a simple way to do it – some cams under the clamping bolts would probably work. In the end I just wanted to get it made for the job in hand, thinking that normally you don't use the rotary table vertically on a cnc mill because the XY movements can do it all. That is until this week (!) when I came to cutting the internal gear by that clever method suggested by John Pace in last months MEW…

It worked ok without the brake though:

**LINK**

Cheers

Phil

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Phil W on 21/09/2012 14:58:30:

…

That is until this week (!) when I came to cutting the internal gear by that clever method suggested by John Pace in last months MEW…

It worked ok without the brake though:

**LINK**

Cheers

Phil

Nice work Phil … thanks for posting that link.

Regarding Brakes for the Rotary Table … There's one idea that keeps lurking in the back of my mind:

Could we adapt the hydraulic disk brake from a bicycle ?

MichaelG.

[Phil WParticipant @philw78611]

Thanks, Michael.

Yes, using a bicycle brake is a nice idea. I'm sure it would work well. They are very strong with just the lightest of pull at the lever, and quite compact.

mmm… I'm sure he wouln't notice the front brake missing

Cheers

Phil

[joeyParticipant @joey]

Hi Phil , I "copied" your brake, but cant get my own Mach three macro to function. Can you assist please.

Joey,

(Measure and Know)

[Phil WParticipant @philw78611]

Hi Joey,

Glad you thought it worth making. It' has been giving me good service despite it's simplicity.

The problem I found with the macro was knowing which output codes to use. They are listed in the Mach3 documentaion, but which outputs they set depend a bit on your wiring, so I had to do a bit of testing to see which codes operated which physical outputs.

For what its worth, I'll list the two macros I use at the end. The only line that you really need is the 'ActivateSignal/deActivateSignal line. The rest is just paranoid brain fade avoidance – not that I ever have brain fade of course

The macros should be saved to the Mach3 macro style named file. It is picky about this, and the names must not conflict with other macros – I used M90001.m1s and M90002.m1s. Save them in the Mach3 macros folder. Then you can type 'M90001/2' into the MDI in mach3 and it should operate the output. You can also attach M90001/2 to a custom button, or call it from Gcode. Wrap every A axis move with the brakeoff/brakeon macros.

Hope that helps/makes sense. Let me know if not. Good luck

Phil

' call to turn Pneumatic brake on

'—————————————

' NB. ActivateSignal( 16 ) -also sets output #7

Option Explicit

dim OEMButtonAaxisInhibit

dim OEMLEDAaxisInhibit

OEMButtonAaxisInhibit = 253

OEMLEDAaxisInhibit = 89

'wait for any axis movements to stop

While IsMoving()

Sleep 100 '100 milliseconds

Wend

'deactivate the A axis to make sure no moves occur while brake is on

If Not GetOemLed (OEMLEDAaxisInhibit) Then re”>

Call DoOEMButton(OEMButtonAaxisInhibit) 'disable A axis movement

End If

'turn brake on

ActivateSignal( OutPut7 )

'wait to make sure brake has had time to work

Sleep 500 '500 milliseconds

'————————————————————————————–

' call to turn Pneumatic brake off

'—————————————

Option Explicit

dim OEMButtonAaxisInhibit

dim OEMLEDAaxisInhibit

OEMButtonAaxisInhibit = 253

OEMLEDAaxisInhibit = 89

'wait for any axis movements to stop

While IsMoving()

Sleep 100 '100 milliseconds

Wend

'turn brake off

deActivateSignal( OutPut7 )

'wait to make sure brake has released

Sleep 500 '500 milliseconds

're-activate the A axis so it can be moved once the brake is off

If GetOemLed (OEMLEDAaxisInhibit) Then re”>

Call DoOEMButton(OEMButtonAaxisInhibit) 'enable A axis movement

End If

'———————————————————————————————-

[Phil WParticipant @philw78611]

Hi , sorry the code got posted a bit odd – ignore the two re"> bits

Phil

[joeyParticipant @joey]

Hi Phil, Thank you for the quick reaction, Ireally appreciate it. I will try the Mach stuff and will let you know the result.

Joey

(Meusure and know)

[Author]

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