Controler for new router table

[DESERT RAT]

Hi. I am new to this site as well as CNC. I have really enjoyed this site and the information on it. I don't get much sleep though.

I am having a dificult time deciding on which controler board to get. I have very limited funds, so many like Gecko are ruled out. If I understand right, I would need a board for each axis. My machine will start with 4 axis and I may add more later. I will need to push a considerable amount of weight (guessing around 50 lbs). I would like to push it around 900 rpms, so I am thinking of motors with 1.8 degree steps. I am also planning on using ball screws to make it easier.

I am considering 3 boards.

First and the one I am leaning towards is the FET-4. It seems to have plenty of power with the upgrade. I dont know If 2 can be used together, or if it has microsteps or if it is bipolar, how many volts it has, or if it is a chopper board.

Second is the Pico systems board from John Elson. It is closed loop and 4 axis. Two boards can be used together. It seems a little weak though. I also don't know if it microsteps, is bipolar, or a chopper.

Last is Xylotex. It microsteps and is bipolar. However, it seems a little weak and I dont know if I can get more than 4 axis out of it. I also dont know if it is a chopper board.

I will get answers to many of these questions from the manufacturer but I would like to get input and sugestions from people who know more about this than me.

[ger21]

If you need more than 4 axis, as long as your software supports more axis and 2 parallel ports, you can use more than one board. TurboCNC will let you have 8 axis I believe. Stepper motor torque drops off rapidly as speed increases. To still maintain high torque at 900 rpm, you'll need to use a very high voltage. Probably at least 48V or more, depending on the motors you choose.

The Pico board, I believe, is not a driver board. It feeds the signals to driver boards such as Geckos.

The FET-4 is a unipolar board, not sure of the voltage it can handle.

The xylotex board can onlyreally use around 27v with high powered motors. I've got one with some 253 oz-in motors wired in series. My machine is not finished yet, so I can't give you any real performance info, but I don't think I'll be able to use much more than around 400-500 rpm, if even that. I intend to use 4 tpi acme screws to make up for the speed.

Gerry

[balsaman]

What he said. Also, you don't need a board for each axis. Most of the boards you mention are 3 axis boards.

I think you are asking too much of any of those boards if you want a high torque motor to run at 900 rpm. You will need to save your money and go with gecko or rulex boards. I would drive servo's, so you get constant torque over the speed envelope.

If you can live with 400- 500 rpm, driving 100 -150 oz steppers, go with the xylotex board and a 24 or 36 volt powersupply.

Eric

[DESERT RAT]

Thank you Gerry and Eric.

I am going to look into turboCNC.

I hope I am not asking to much of these boards. I don't know how much the torque drops off at higher rpms. I checked the stats on the ball screws and with the numbers from the company, I only need 1.75 in/lbs to drive 50 lbs. I am not sure how to convert in/lbs to oz/in. If it is as simple as multiplying by 16, I am looking at 28oz/in. This seems hard to believe and I don't want to use the motors at there peak level.

Was I wrong about Gecko boards needing 1 per axis. If I was wrong I might be able to fit servos into my budget.

Why do you prefer Xylotex over FET-4?

Can you run bipolar motors from a unipolar board?


Rich.

[balsaman]

Gecko's you need one per axis.

Xylotex is a chopper board, so you will get more speed and don't need dropping resistors. The FET4, while a good board, is a unipolar board. I use the FET3

You can run unipolar motors on a bipolar board, but not bipolar motors on a unipolar board.

Eric

[ger21]

If you buy the xylotex board, you can get 116oz=in motors with the board for about $50 for 3. You can get the same motors on Ebay for about $30. They are listed usually at least once a week. Like I said before, I have 250 oz-in motors to run with my xylotex. I got them on Ebay for about $60-$70 each. From the charts I've seen, NEMA 23 size steppers lose about half of their torque by around 500 rpm, when running at 24V. I'm not positive, but I don't think 28 oz-in will even be able to turn your ballscrews. And yes, multiply by 16 to get lbs.

Gerry

[WOODKNACK]

Another good sorce for stepper motors is Herbach & Rademan . I want to thank HomeCNC for that link. I just bought there 187oz steppers the other day. I think they are going to be just right for my Taig mill I ordered!

[DESERT RAT]

I am going to check with the manufacture and make sure the data on the ball screws was not a typo. I find it hard to believe also.

My only concerns with the Xylotex were if I could get more than a 4th axis and it seemed weak. I bought a small bipolar motor to play with. When it arrived I was surprised to see how small it was. I can't test it untill I have a controler but it looks like it couldn't power much. It is rated at 2.8 amps bipolar series and 35 volts. Xylotex is rated at 2.5 amps and 35 volts. That made me nervous. I did not think Xylotex could drive a 250 oz/in motor. I guess I can't judge this motor by its looks. It is also rated at 1500 rpm. This motor by the way is a Pacific Scientific Powermax II M21NRXA-LSN-M1-02.

As far as more axis is concerned, I just need anouther parallel port and anouther board and appropriate software. I think I may get the Xylotex.


Rich

[DESERT RAT]

WOODKNACK

Do your motors say on them what rpm they are rated at.

[WOODKNACK]

That motor probably wont do you much good with a Xylotex board. What you want is something with less volts. Somewhere around 5 or less. I have some 187oz motors and they are rated 2.5 volt 2 amps. Usually with a
bipolar chopper type drive you want to run the motor somewhere between 10-25
times nameplate rating.The higher voltage (24V +) allows current to
build up in the coils faster, thus you can have a faster step rate.

In your case with the motor your have, you are already over the rate volts that the board can take.

I think the board is srong enough to do what you might want it to do. You just need to find some differnt motors..

[WOODKNACK]

What is it that your are trying to do? What are you going to put motors on? And how many IPM (Inches Per Minute) are you looking for?

[ger21]

I believe his motors are these:

http://www.orientalmotor.co.jp/cgi-b...frameSize=56.4

Notice how fast the torque falls off. This is typical for just about all motors this size unless very high voltages are used.

Gerry