Tweakie CNC Machine

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Tweakie CNC Machine

Postby bdring » Tue Apr 27, 2010 5:05 pm

I have been following this machine for a while and it recently became functional enough to engrave some parts. He gave me permission to post some of his pictures and a link to the web site. It is a nice high quality, well detailed build.

http://www.cooperman.talktalk.net/files/27.htm
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Bart
"If you didn't build it, you will never own it."
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Re: Tweakie CNC Machine

Postby Tweakie » Sat May 01, 2010 4:44 pm

By way of an update; The (imported from China) digital current display, shown in the picture above, did not work well at low current settings and although it looked good it just had to go.
It’s replacement is this ‘retro’ 1960’s panel meter with a new, (yes you guessed it) laser engraved, scale.

Tweakie.

Image
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Re: Tweakie CNC Machine

Postby Tweakie » Sat Jun 19, 2010 10:54 am

My new air pump (made in China, of course :D ).
This is an oil less, piston pump intended for aquariums which is rated for 45 litres/minute (in free air) but probably half this with the restriction of my tubing and air nozzle.

Image

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Re: Tweakie CNC Machine

Postby Ben » Sun Jun 20, 2010 7:23 pm

That custom case for the laser power supply looks great! Did you make it yourself? If not, where did you get it?

That air assist pump looks pretty slick. How loud is it?

If you arrange your liquid cooling circuit to flow: Header/Expansion Tank -> Pump -> Radiator -> CO2 Tube -> Flow sensor -> Filter ->
You will gain the following benefits:
    Lower Coolant Temperatures in the CO2 Tube (with the radiator right before the CO2 Tube, the tube gets the coldest coolant. With your current setup your dumping the heat from the pump into the laser tube, depending on the heat dump from your pump this could be negligible)
    Increased pump life (pumps tend to last longer when their intake is unimpeded, depending on how restrictive your filter is this could be negligible)
    Faster error response time (if the tube was to clog or break, the sensor would know immediately. with your current setup, most of the coolant in the circuit would have to empty before the flow sensor values would go out of range)

You mentioned that because the PC liquid cooling radiator is made from brass that it will cause conductive contamination; are you referring to galvanic corrosion? What metals are you mixing in your loop? For reference, I ran a liquid cooled workstation 24/7 for an entire year at approx 35C which contained brass, copper, nickel, silver, delrin, acrylic, and premixed liquid coolant with no adverse affects.

In any case, it’s common practice to drain, flush, and refill liquid cooling loops once a year; which is how often I drain my loops. It’s not ideal to simply top off the loop when using coolant containing additives; the reason being, when evaporation occurs, some of the additives will be left behind and when you top off the coolant it becomes unbalanced and those additives can build up and restrict flow. This is an issue for CPU coolers which often contain small pin matrixes but shouldn’t be a major concern in our application.
-Ben

My Lasers:
40w CO2 Laser (Chinese Glass Tube), Directed Energy Inc. 30w RF CO2 Laser (Needs Repair), Laakmann Electro-Optics 20w RF CO2 Laser (Needs Repair), 7-10w RF CO2 Laser
Coherent 12w 808nm FAP LASER DIODE
MELLES GRIOT He-Ne Laser
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Re: Tweakie CNC Machine

Postby Tweakie » Mon Jun 21, 2010 6:19 am

Thanks for all the info Ben it is much appreciated.

Yes I made the psu case myself but got a professional to do the TIG ( my ally TIG work looks like pigeon droppings most of the time, I need more practice :D ).

The air pump runs whisper quiet. (I have mounted it on it's side and so replaced the existing AV feet with slightly more substantial items).

Tweakie.
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Re: Tweakie CNC Machine

Postby bdring » Mon Jun 21, 2010 6:19 pm

I think I have the same pump. It is a lot quieter than most alternatives, but I don't think I would call it "wisper quiet".

Pros
...Relatively quiet compared to a compressor.
...Has good airflow even into a lot of backpressure from a thin hose or small nozzle.

Cons.
...No reservior, so it sends strong pulses down the line that can cause vibration at the nozzle.
...Vibration in the device itself. I mounted it away from the cabinet to fix that. It will dance off the table if you turn it on and don't bolt it down.
... Occasionally it spits out little black flakes of something. It sort of looks like flashing from the rubber diaphragm. Consider a filter on the output if the air gets close to you lens.
Bart
"If you didn't build it, you will never own it."
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Re: Tweakie CNC Machine

Postby willyinaus » Mon Jun 21, 2010 9:47 pm

yes I have one of the little pumps myself 87lt a min or something not sure if I believe the specs was thinking of a one way valve and a little plastic reservior to get rid of the pulses do you guys think it could work?
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Re: Tweakie CNC Machine

Postby bdring » Mon Jun 21, 2010 10:12 pm

I don't think the valve is needed. I was thinking of the mechanical equivalent of a RC filter.

C...Capacitor = Reservoir
R...Resistor = Flow impedance (the hose and nozzle would probably be enough).

I think if you put the reservoir right after the pump and have some amount of impedance after it, it should work. I have about 8 feet of 1/4" ID hose coming off the pump to a ball valve. Then about 5 feet of thinner hose to the nozzle. If I restrict the flow at the valve by about half (adding R) it smooths the flow a lot.

Another idea might be to add some sort of baffles at the output end of the reservoir.
Bart
"If you didn't build it, you will never own it."
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Re: Tweakie CNC Machine

Postby Tweakie » Tue Jun 22, 2010 7:44 am

I think I have the same pump. It is a lot quieter than most alternatives, but I don't think I would call it "wisper quiet".


Hey Bart,
I suppose it depends on your definitions but my pump cannot be heard above the sound of the air escaping my nozzle and that to me is 'whisper quiet'. (perhaps you need to replace your AV mountings :D )

Tweakie.
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