Author Topic: Building a milling machine (Read 133765 times)

NormanV · « **Reply #125 on:** June 24, 2014, 03:24:38 PM »

Here's an overall view of the machine as it stands now. The poly V belt arrived this morning and I was relieved to find that it fitted the grooves that I had machined.
The next job it to adjust the head so that it is square to the table.
Once that is done I'll cast the box to contain the switch gear and then I will have no excuses left to avoid starting on the wiring!
I will probably buy a compound table for the XY slides rather than making aluminium castings and having to do lots of scraping.

NormanV · « **Reply #126 on:** June 24, 2014, 03:26:46 PM »

I am also going to make a cast aluminium hand wheel to replace the bodged up handle at the top for adjusting the height of the head.

DavidA · « **Reply #127 on:** June 24, 2014, 04:48:49 PM »

Norman,

I hope you don't mind me making an observation.

The quill seems to be right out over the outer edge of the table. I can't see how you can adjust it closer to the middle as things are.

What am I not seeing here ?

Dave.

NormanV · « **Reply #128 on:** June 24, 2014, 04:54:36 PM »

Yes David you are correct. The compound table that I am planning to get will be centred around that position, unless I can trim the rear end of it down to bring it closer to the main vertical slide.

awemawson · « **Reply #129 on:** June 25, 2014, 01:34:23 AM »

That was also my thought on seeing that last picture. Then I realised that Norman hasn't started the actual table yet. I assume that it's traverse mechanisms in X&Y will sit on the 'bracket'

NormanV · « **Reply #130 on:** June 28, 2014, 03:41:16 PM »

I have just made the worst casting that I have ever done. I knew that the sand was a little damp but when I poured it I immediately knew that all was not well.
Just take a look at this!

awemawson · « **Reply #131 on:** June 28, 2014, 04:11:15 PM »

But the beauty of casting is it can be melted down to hide the evidence and rise phoenix like in a new form

DavidA · « **Reply #132 on:** June 29, 2014, 01:50:43 PM »

Norman,

Looking again at the picture of the machine.

If the whole top section was moved to the right of the left hand frame securing bracket then the quill would be more or less in the centre of the knee table top.

Dave.

NormanV · « **Reply #133 on:** June 29, 2014, 05:10:36 PM »

David, I have more or less decided to buy a compound table rather than make the X & Y axes myself. The position of the quill is centred over where the mid point of the Y axis falls on the table that I intend to buy.

NormanV · « **Reply #134 on:** July 01, 2014, 01:50:30 PM »

I dried the sand in the sun yesterday and recast my dreadful failure. This time it turned out fine, there was a bit of a cavity in it but it machined out fortunately.

PekkaNF · « **Reply #135 on:** July 01, 2014, 03:15:26 PM »

That is the same part? I must say that the first one was artistically whole more interesting. Later one is whole lot more functional though.

Tough call?

You are making a steady progress.

Pekka

NormanV · « **Reply #136 on:** July 05, 2014, 04:08:54 PM »

Earlier this week I cast an aluminium box to house the switchgear and mounted it on the side of the head.
today I more or less completed the wiring, the last task is to replace the temporary plywood switch mounting panel when I can find some sheet aluminium.
I can now raise and lower the knee under power or manually, and I have had the spindle running also. I had problems initially with the pulley alignment causing the belt to run out of line but that was easy to correct.
The last remaining problem is the tachometer, it shows random speeds when the machine is running. I had the sensor within 2mm of the magnet and had no reading but when I moved it further out I got these erratic readings. The magnet is glued in a shallow hole in the cast iron pulley shown in the second photo. Could the iron be causing this?

vtsteam · « **Reply #137 on:** July 05, 2014, 04:23:23 PM »

I don't think the magnet should be recessed like that. It's probably being shielded by the cast iron. Can it be moved flush or slightly proud?

Or maybe moved to another location where it is attached to aluminum?

NormanV · « **Reply #138 on:** July 05, 2014, 04:32:26 PM »

That's what I was wondering, I meant to mount it flush but drilled the hole a bit deep.
The only rotating aluminium is the pulley and there is no space to mount it.

tom osselton · « **Reply #139 on:** July 05, 2014, 05:45:42 PM »

What kind of magnet is it would a rare earth magnet be better?

NormanV · « **Reply #140 on:** July 05, 2014, 06:15:48 PM »

It's a neodymium magnet. I made sure that I had it the right way round. I'll try a bigger one tomorrow.

John Hill · « **Reply #141 on:** July 06, 2014, 02:55:03 AM »

If you have another the same just stick it on top of that one..

NormanV · « **Reply #142 on:** July 06, 2014, 04:12:36 AM »

That's what I was planning to do, if it works then I will glue it to ensure that it doesn't move.

awemawson · « **Reply #143 on:** July 06, 2014, 06:19:08 AM »

Norman,

All the proximity sensors that I've used (and that's quite a few!) don't need a magnet to operate. The sensor senses the iron presumably using it's own magnetic field. So for instance you can bring one up close to the teeth of a gear wheel and sense each tooth.

Try removing your magnet and sensing the hole where it was - I suspect the strong magnet that you are using is stopping the proximity sensor working.

Arbalist · « **Reply #144 on:** July 06, 2014, 07:35:10 AM »

Good info Andrew.

NormanV · « **Reply #145 on:** July 07, 2014, 03:33:11 PM »

Andrew, I have not been able to remove the magnet, it is stuck in with high strength retainer and the hole is close fitting. I tried a larger magnet (20mm) but the centripetal force threw it off.
I have no idea what to do next with the tachometer.
Everything else is working fine but now I have to wait until I can sell some photographic equipment in order to raise the cash to buy a combination table to complete this machine. ( is anyone interested in buying a Mamiya RB67 with a few lenses?)
In the meantime I will go back to the Stirling Traction Engine that I started a few months ago.

tom osselton · « **Reply #146 on:** July 07, 2014, 03:41:06 PM »

Can't you shatter the magnet with a punch? All the magnets I have had break easily.

BaronJ · « **Reply #147 on:** July 07, 2014, 04:11:16 PM »

Or you could leave the magnet as is and go back to your idea of using a hall device...

Will this pdf help ?

awemawson · « **Reply #148 on:** July 07, 2014, 04:23:34 PM »

Norman,

We need to know what the sensor is on your rev counter. If it is a normal proximity switch it doesn't need the magnet. However just possibly it may be a Hall Effect sensor, although it looks like a normal proximity switch.

Can I suggest that you untangle it from your milling machine, power it up, and hold the sensor in your hand near the spinning chuck of your lathe. The chuck key holes should be enough to trigger a proximity switch. If this gives no response we need to investigate further.

NormanV · « **Reply #149 on:** July 07, 2014, 04:57:48 PM »

Here's the spec of the thingamajig that I bought:-
Power requirement:DC 8--12V
Measure range : 5-9999RPM.
Clear zero: Automatic.
Clear zero time:about 10s. the greater the RPM value,the longer the clear zero time.
Refresh frequency: 0.2-0.5S@120-1200RPM;0.25-0.06S@2400-9999RPM.
Measure indication:RPM<5000,±2;RPM>5000,±3.
Display:RED 0.56” LED
Sign:Pusle signal,NPN 3 wires normally open.
Response frequency: 100HZ
Tachometer dimension:72x36x20mm,panel cutout Dimension:68x33mm.
Sensor dimention: M12x10x55mm.
Detection distance: 4mm
Sensor wiring: brown-Power+;blue-Power-;black-signal.
Operating temperature: 0 to 50°C.

Packaging include
Tachometer x 1
NPN proximity sensor x 1

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Author Topic: Building a milling machine (Read 133765 times)