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Author Topic: MB concave build  (Read 3866 times)

MakkyBrown

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Re: MB concave build
« Reply #45 on: October 26, 2019, 09:41:53 AM »
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I'll enter aswell Giel. Just build it is the best approach, as you'll probably find unexpected issues you will need to change.

Yeah I know that I will probably run into unexpected issues, I already am while building it: I need to find a metal worker in the area for some parts, need to find a nerd to help me with the dc motor and driver, because stepper online will not answer my emails.
slowly but surely I am getting there.
I might be able to help with the motor.

Giel

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Re: MB concave build
« Reply #46 on: October 26, 2019, 07:04:31 PM »
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I might be able to help with the motor.

I finally have an email from stepper online and I just ordered the cables to hook it up to the computer.
I think I will manage in the end, if I dont I will let you know. thanx for the offer!

First my idea was to use a brushless dc and threaded rod for both motions (swivel and positioning). But I cannot make it myself as I dont know much about electronics and programming.
Brushless dc mode 1: for swivel action, needs a speed control and  a circuit for polarity change every second or two. The time of
                                polarity change needs to be adjustable also.
                   mode 2: for positioning, needs a very slow and precise rotation so I can position the mandrel and lock it down.
So that would mean two motors, and circuits, one for each slide table. This way I could also use a V-wheel.
I really like the idea of a V-wheel for cutting large stones that are relatively flat, with a few V-grooves on the pavilion you can still have a great lively stone. (great when you have big but flat rough)

If I cannot find someone in town who can help me with the above, I think I am going the easy way on the machine.
I have a "12V DC 100 RPM High Torque Gear Box Electric Motor for Speed Control" that I will use for the swivel action.
I will use a threaded rod for the other slide table to adjust the position of the mandrel by hand. But that means I can only use cylindrical mandrels for now. So it will only swivel in one direction instead of two, and positioning will also be in one direction instead of two.

Hope this makes sense.




MakkyBrown

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Re: MB concave build
« Reply #47 on: October 26, 2019, 07:55:04 PM »
Hi Giel,
You are welcome to my code and wiring diagram for my controller. I am using the key pad to stop/start/directions/ and speed for the dc motor(with collet holder)
The oscillation motor where I was planning to use the stepper. I'm changing to a worm drive using a dc motor with an encoder on it. This will be controlled from the same control box as the main dc motor. Key pad will be able to stop/start oscialtion, and control oscillation speed, start position and stroke length.If you have not used arduino before it is great and lots of sample code out there to steal etc.
But didn't you purchase a driver box for the bldc motor?? You should be able to just wire a pot to it for speed control if it is like some of the others I've seen.
CheersMB


Giel

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Re: MB concave build
« Reply #48 on: October 26, 2019, 09:55:17 PM »
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But didn't you purchase a driver box for the bldc motor?? You should be able to just wire a pot to it for speed control if it is like some of the others I've seen.

Yes I did, and I will be using a pot for speed control as you describe.
I think I did the wiring correctly, but apparently I have to set the whole thing up connected to a computer using brushless dc software to get it going. And to modify it with the softare so it can be used with a pot.
I have all the parts but I did not order the cables needed, as it was not mentioned on the website, I ordered those this morning so I have to wait for those to arrive.
I think I will be able to get the motor for the collet holder going.


FlashGP

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Re: MB concave build
« Reply #49 on: October 28, 2019, 12:29:17 AM »
Hi Giel,

I just used a small 30rpm 12v motor from Banggood.  It is tiny and looks like a motor from a model, but it is geared with a worm drive and  works better than a 2w turntable motor from a microwave oven, safer too.

I made an arm that fits on the worm drive  out of some 10mm square rod drilled and tapped with my bench drill.  The taps are 5mm threaded holes and I cut and filed that part of the  arm o 5mm thick using a hacksaw and file.  The holes are offset and spaced at 15, 20 and 25mm from the centre giving me adjustments for the length of travel.

I then bought a male and female tie rod ends from Banggoood and connected them, one end to the arm on the motor, the other to a post on my base plate of my concave cutter.  Polarity isn't important for the oscillator,  the rotary motion of the arm pushes and pulls the cutter head equally well in CW or CCW rotation.  It looks a bit like a steam engine crank.

I just use a 12 to 36v 775 motor from banggood.  It does 3500rpm at 12v, 10,000 rpm at 36v.  With small diameter cutters, 3500 rmp is about OK.  I wouldnt use a slower motor, it takes too long to cut.

Switch mode power supply is the way to go.  They are cheap and have 110/220v terminals and 12v and ground terminals on the 12v side, plus an earth terminal.  They are about 1/4 the cost of a traditional supply and pack more punch.  I bought a 25amp supply for about $35 Australian.  It would have cost me about $300 for the 2 transformers needed for the same current  for a traditional supply.  I went big as the price difference between a 10A and 25A supplĂ˝ was only $10.  I figured if I needed bigger motors, I would already have the power supply.

The basic circuit is, mains in to the switch mode supply, with the Active Brown wire, rumming via a switch.  Two 12v wires 10A to from the power supply, one each to a pulse width modulator (dc speed controller). One set of wires from each pulse width modulator to a 4 pin plug, both motors are fed via this plug so I cant mix them up.

The small motor is controlled with a 10A PWM, one direction only, that cost about $4.  The big PWM can handle up to 40A at up to 50v.  It cost about $12  from Banggood.

next supply I make, I'lllhouse in an old computer case or CD case from the recycling shop, the plastic electrical box I bought cost me abput $50 and everything was a tight fit.

lastly, put a 47ohm 5w resistor across one of the 12v outputs.  Thiskeeps the switch mode supply under load when the motors arenot turning.  It is supposed to make the switch mode supply run better.

Regards,
Flash
« Last Edit: October 28, 2019, 12:39:03 AM by FlashGP »
Yours Sincerely
Flash (Gordon)

Giel

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Re: MB concave build
« Reply #50 on: October 28, 2019, 02:41:29 AM »
We think alike Flash, I have made something similar as you describe for the swivel action.
I have a 12 V 100 rpm motor with a speed control, with a "swivel block"
Made the black block on the 3d printer, It has a threaded rod running through, a square aluminium plate runs through the block connected to the arm. When I turn the two nuts the aluminium plate slides up and down, that way I can adjust the swivel length. (just need to print the turning knob and fit it over the two nuts.)



I also have DC motor for the mandrels, 3500 rpm, already have the speed control and power supply.
I have almost all the parts now, looking for a metal worker in the area to make the aluminium plates as I cannot do that myself.

FlashGP

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Re: MB concave build
« Reply #51 on: October 28, 2019, 08:33:54 AM »
Hi Giel,

Necessity is the mother of invention.  Yours looks a bit nicer than mine,  maybe I should buy a 3d printer.  Rej (Gem Cut Studio) Poirier madr his faceting machine using one.

The neatest oscillator I have seen is on the VJ, it is two disks with a ball bearing race and offset locators that screw to the machine's platten and the base of the cutter housing.  But this is way beyond my capability using silversmithing tools and a bench drill.
Yours Sincerely
Flash (Gordon)

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