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machining thread
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Nick
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I would also go with telescoping gauges and the best outside mic you can afford; its got the best combination of versatility & accuracy. I bought a lower end digital inside mic and its absolute rubbish! You don't get anything worth using until you pay top dollar and for some reason, inside mics are much more expensive than the same quality outside mics Confused

If you want to save time, consider going digital, that makes measurements much faster for me.

The other thing I found with the inside mic when boring holes on the mill is that the mic takes up WAY more room then a telescoping gauge so I have to extend & the quill a lot further to take a measurement, never good for accuracy.

I recently bought two small Mitutoyo telescoping gauges on Amazon and I can't feel any difference between them and my older Starrett gauges; that might be worth thinking about.
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Post Wed Jan 21, 2015 11:20 pm 
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marto
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So guys I am looking to setup my mill with some servos as I sort of have the shits with my stepper setup. I am gong to roll my own controller. I have some encoders and I will probably set it up with some form of hacked ESC/arduino controller.

What I really need is some advice what size motors I should be using, the best way to physically attach them and how to interface to the PC.

Any help would be appreciated. First step will be to mount a motor and just see if I can do an arduino controller to move to positions.

Steve
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Post Sat Feb 28, 2015 8:39 pm 
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Nick
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What size mill do you have? Jake & Russell use a scooter motor (500W version, I think) on their CNC mill and while they are a bit bulky, they definitely get the job done. The other downside of scooter motors is that they are not particularly coolant-proof, which means more work designing and fitting them to your mill.

For driving them you should look at the Gecko controllers, this is the local reseller: http://tinyurl.com/mbo2x3o . He has some other useful CNC gear including real servo motors for not much more than scooter motors.
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Post Sat Feb 28, 2015 9:08 pm 
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marto
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Yeh I have looked at the gecko controllers and stuff previously but I thought I would give rolling my own a go simple for the sake of it.

I know it won't work out cheaper or probably better but its a project.

Steve
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Post Sat Feb 28, 2015 9:13 pm 
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Nick
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Better to buy a known excellent product IMHO; you already have a lot on your plate! Razz. BTW: Hare & Forbes have another 3 day sale at the end of March for anyone wanting a better deal on machinery
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Post Sat Feb 28, 2015 9:22 pm 
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miles&Jules
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Is your cnc setup not working?
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Post Sat Feb 28, 2015 11:31 pm 
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Nick
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Welding question:

Does anyone know anything about plug welding? I want to get some of the tabs on Jolt's frame welded to increase their strength:



At the moment, most of the tabs on the sides stick out 2mm in case I could buy thicker sheet. The question is: is it better to leave them a bit long, grind them flush or to have them a bit recessed for plug welding?
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Post Sat Feb 28, 2015 11:53 pm 
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Glen
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From a welders viewpoint having them flush would be the easiest to weld as you wouldn't need to reposition each time as you would for fillet welds.

Plug would be ideal for smaller holes or tabs, but they look large. I imagine trying to fill them up with filler would be rather wasteful and would put a bunch of heat into the metal.

I'd go with having them flush then welding them butt weld style. Unless the tabs are much smaller then they appear, then go with plug.
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Post Sun Mar 01, 2015 12:04 am 
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Nick
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Flush tabs it is! The tabs on the wedge are 14 x 10mm and I am worried that if a spinner hits them a chunk of the side panel will be ripped off. Welding up the ends of the tabs should make that a little bit harder. Would there be any point in adding a small chamfer to the ends of the tabs to allow more weld penetration?
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Post Sun Mar 01, 2015 12:15 am 
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Glen
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Definitely putting a hefty fillet on the tab (or a smaller fillet on the slot and tab, id probably just do the former for simplicity) would help. The weld would stay flush as well then.
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Post Sun Mar 01, 2015 12:21 am 
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Nick
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Thanks, I will do the chamfer as well Smile.
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Post Sun Mar 01, 2015 12:30 am 
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maddox



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Flush, and a 3mm chamfer to get better penetration.

Or, in other words, you already knew.


And the opposition, if they do some research, they will have this kind of feeling.


https://www.youtube.com/watch?v=hQvMWD-_Nfo

Post Sun Mar 01, 2015 2:45 am 
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Valen
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We use the mesa toolchain with our mill.
http://www.mesanet.com/

I suggest getting their FPGA card, if you use linuxcnc its plug and play.
They have some pretty cheap ones (5i25 I think).

Then if you want to build your own motor drivers you are going to be getting direction and PWM input, you just need to add your own deadtime and fets and an interface for your encoders.

We use 500w scooter motors 1:1 direct mounted to the ballscrews, I had to defeat the current limiting on the mesa motor drivers, (7i40) so we are pulling more than 10A (I'm guessing 20A peaks perhaps a bit more)
But our setup is very intolerant of backlash because we are using glass scales for the position feedback, no encoders on the motors.

The biggest problem we had with the motors was they have tiny tiny shafts on them so the couplers don't have a lot to grab on to.
Go a smaller motor (250w would be fine), belt drives and encoders on the motors and it'd probably run nicer. You can combine motor encoders as well as linear scales in linuxcnc ,it uses the motor encoders for velocity feedback and the scales for position feedback. You wind up with great accuracy and nice smooth control.

We cant fit motor encoders on ours because the shaft is too darn small. As a result we have some control loop issues due to the spring in everything (20mm ballscrew, preloaded everything)
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Post Mon Mar 02, 2015 10:07 am 
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Glen
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Hey hey,

Australian waterjet cutting flat out made a mess of cutting decimators weapons.

The bolt circle is off and the quality of the cut is shocking. Thusly the holes don't quite line up and i need to drill them out possibly between 8.2 or 8.5mm. Seemingly I'll need a carbide drill to do this.

Anyone know where i can get them? Preferably in sydney would be best so i can go pick it up for the weekend. Cheers!
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Post Thu Mar 05, 2015 8:59 pm 
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Nick
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A carbide drill might not work; if you are drilling out the hole on-centre it would be fine, but if you need to shift the holes, the side forces on the drill bit will likely snap them. I never bought metal cutting bits in Sydney, however Blackwoods Engineering would be the first place I would call. They have the straight flute carbide drills that will chew thru anything, but no on-line prices.

For off-centre hole making, a mini boring bar would be less likely to break.

Option 3: I can lend you a top quality cobalt drill and my drill sharpener.
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Post Thu Mar 05, 2015 9:08 pm 
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