[b_cybe]

Has started planning to build my first CNC router, I plan to use it for woodworking and (hopefully) milling aluminium.
Since I intend to use it to mill aluminium I decided to build the machine with aluminium since this is both strong and not to hard to work with. After some reading on the forum I also desided I would go for a gantry style cnc. When I started planning I decided to build a machine that was 1000mmX500mmX100mm. But I already have changed the Z-axis to 88mm since I bought a ballscrew with that travel length, I have also bought some linear glides for the Z and Y axis. The Z axis ballscrew is 6mm diameter (the load on the Z ballscrew is going to be vertically so I dont think it matters that that the diameter only is 6mm) and has a lead like 1mm/turn. The reason I chose that slow Z ballscrew was because I thought that this would increase the accuracy for the Z axis, wich for me is more important than speed, and since the Z axis dont travel so long I think it will be fine. Anyways are now looking for Y axis ballscrew that need to be around 470mm (the length of the linear glides) and I am therefore looking for a ballscrew with around 16mm diameter and 5mm/turn. I am planning to use mach3 since I have heard with that program I can compensate for different leads on the ballscrews. I am planning to build a 3 axis L297/L298 bipolar driver for the stepper (probably will build : http://www.hans-w.com/9908-09A.gif). But I am unsure if Mach3 will suport that type of driver? I am further probably going to buy 3 of these stepper motors wich are running on 4.05V and is using 1.5A. Would these motors work alright?
I will probably make some sketch of my design that I will build after once I find and buy the ballscrews and linear slidings I need...

[b_cybe]

Well I think the final size for my CNC machine will be 660,4mmX470mmX88mm (or 66"X18,5"X3,47" aproximately for those you prefer inch...). I am planning to buy a 16mm diameter ballscrew that is 660mm long, but I dont know the movement/turn, I am therefore wondering if I can calculate this by using for example a caliper and measure the length of movement for one turn (or several turn and then divide by the total turns to get the number for one). Will this be accurate enough or will this decrease the accuracy detectable?
Any other start advices also receives with thanks!

(Sorry for my bit bad english...)

Edit: With the size I mean the total movement in the x, y and the Z axis...

[ger21]

I dont know the movement/turn, I am therefore wondering if I can calculate this by using for example a caliper and measure the length of movement for one turn (or several turn and then divide by the total turns to get the number for one). Will this be accurate enough or will this decrease the accuracy detectable?

This will get you close enough to set up the machine, then you can cut some parts, measure them and fine tune it until it's perfect.

[b_cybe]

Ok, dont know how to measure it from the finished part, but I guess that will be solved(either I find it out myself or get some help on teh forum...) after the building is complete. I am a bit unsure of the motors I have choosen to, since they are driven by such low voltage, I see that many others use motors that are driven from higher voltages, should I buy motors with higher voltage too? I dont personally know too much of motors, but I guess the speed atleast will increase with higer voltages, is the holding torque also larger for motors with higer voltages?
How high holding torque should my stepper motors have to be strong enough to mill aluminium? (Well if that is possible with these kind of machines...).

I am also a bit unsure what driver I should use, I have already linked to one in my first post, and I have also seen a bit on this site.
Or are those commercialy available like gecko much better?

[bearwen]

b_cybe,
I am unsure about motor size and what not for milling aluminum. However the higher voltage that you hear about for the motors are motors such as yours rated for 4v however by running them at there rated current but much higher voltage ( dont exceed 20 times the rated voltage good practice) your torque curves change meaning you can spin them faster before the torque drops off.
Pminmo site is great I like the picstep but there not cheap (cheaper than gecko) try the 3977 boards they cost about $30.00 a piece to build. The 3977 chip you will have to search the net for a supplier that will allow you to purchase just a few of them.
Checkout these motors I purchased the nema 23 262oz/in dual shaftshttp://www.homeshopcnc.com/page3.html They also build ballscrews but I used Acme 1/2-10 from http://www.use-enco.com pretty good price.


Good luck

[b_cybe]

Thanks for the reply, I think I try out the motor I originally planned, I get those cheaper than other since I receive "friend-discount" since I know the seller, very practical when buying electronics
Well I think I have a look at that picstep... thinking of implementing it with the 4 axis PC interface, don't think I will get the 4th axis yet, but are interested in implementing it afterwards...

[b_cybe]

Well I found this wich is very like the machine I plan to build, exept that I am going to build the frame from either aluminium angle, or steel angle, and I also are limited to 6mm (0.24") thick aluminium/steel. Mine is also going to be a bit smaller.

[b_cybe]

I am very unsure about those motors... I want the cnc machine to have ok speed (it does not need to be a racer though). Well I did those calculations and ended up with a torque of .2Nm, with 200N force on the nut and a 5mm/turn ballscrew and a 0.05m/sjog speed. This calculation is though pretty simple since i dont see on the weight of the gantry nor the friction. Though I am still cinda confused about the motors...

I am also thinking about the power supply, wich if I understood corectly is going to power the 3 PICstep drivers and the interface to the computer. I have seen on a power supply with around 13V and 10A. Or would it be better to get a 30V power supply? If so I propably build the power supply myself from a 300W transformer (300W/30V = 10A). Is there any reason that I should stay with lower voltage exept from heat?

I am also thinking about how to build up the cnc machine, I guess it would be easiest to first build the Z axis, then the Y, and lastly X?

I am also wondering about compatibility between the PICStep and pmino's 4 axis PC interface.
On pminos pages it stands that is you use the 4 axis interface with the PICStep you have to use jumpers to power the PIC on the PICStep, I don't understand what he rally means with that? Does he mean the jumpers on the top layer or does he means something else?
The second the dont understand is when he says that jumpers for pin 1 (brake or enable) need to be configured. What do I need to configure? Maybe this get clearer when I make the board but as for now I don't understand it...

[b_cybe]

I propably will go for a 425 oz-in (in a bipolar coupling) that cost $49 each. Have ordered some pcbs for the PICStep driver (v 4.0) and the interface, and also bought some components. Still havent found any ballscrew for the X axis though at an acceptable price but I have good time yet so there is no rush...
Once I find a ballscrew I will also buy some sliders for the X axis.


The motor is dual shaft, but I don't think that should be any problem...

[b_cybe]

Well after having a look at the PICStep and the interface design again I think I now understand what he means with the jumpers to power the PIC, he must mean that I have to connect an external 5V power supply to the +5 and to one of the GND pins I guess. About the brake/enable I am still confused... (I see that the PICStep have a Enable pin to connect to the interface, but the interface dont have it. What should I then connect enable to?