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rackbox
11-27-2004, 06:55 PM
Now, I registered in order to place a series of questions. I have been looking around in here as a guest trying to find just that info I need. So here goes:

I am just in the process of deciding how to get started CNC'ing. I have been looking at http://www.machinecnc.com/router__2.html and I thing I have chosen my path.

Now - is there any demands as to how far the bed should move at one revolution of the rod under the table? (I don't know the proper english word for this rod being like a long screw) Or is this just something i adjust in the software?

Where do I find plans for a stepper motor controller and which pins on the parallel interface should I use to control it?

How strong should the stepper motors be (I have no idea of what I am talking about, so just some specs I can show the electronics store)

How do I go about not exceeding the cutting area, so the stepper motor won't try to pull the beds off the slider/whatever?

Is there any free software for WinXP that either lets me convert CorelDraw / Maya3d / other drawings into something usable or that lets me design something that I visually can see before milling/routing?

How small a milling bit is required to make cut out letters and logos in foamex or even plywood?

Sorry if I have asked questions, that have been previously answered, but I didn't seem to be able to find this information anywhere.

cncadmin
11-29-2004, 01:15 PM
Where do I find plans for a stepper motor controller and which pins on the parallel interface should I use to control it?
You can find that on the site in the "open source" forums http://www.cnczone.com/forums/forumdisplay.php?f=175

buscht
11-29-2004, 02:13 PM
=rackbox
Now - is there any demands as to how far the bed should move at one revolution of the rod under the table? (I don't know the proper english word for this rod being like a long screw) Or is this just something i adjust in the software?

The screw works with the software, anywhere from 2 to 10 turns per centimeter will work. You have to decide upon the mechanics and set the software up accordingly

How strong should the stepper motors be (I have no idea of what I am talking about, so just some specs I can show the electronics store)

At least 100 oz-in. I like about 250 oz-in.
How do I go about not exceeding the cutting area, so the stepper motor won't try to pull the beds off the slider/whatever?

You can have mechanical stops, or set up limit switches. Either way, you don't want to rely on these methods. Proper programming techniques will insure that this doesn't happen.
Is there any free software for WinXP that either lets me convert CorelDraw / Maya3d / other drawings into something usable or that lets me design something that I visually can see before milling/routing?

I don't know.

How small a milling bit is required to make cut out letters and logos in foamex or even plywood?

This depends upon the size of the letters and what end result you want.
2mm, 3mm, 6mm, 12mm will all work. It just depends upon the part, not the machine.

rackbox
11-29-2004, 03:37 PM
Is there any rules or advice as to how many steps pr revolution and should it be uni- og bipolar? Anything else I have forgotten about the motors?

buscht
11-29-2004, 03:54 PM
Yes, 200 steps per revolution seems to be a good standard. that is 1.8 degrees per step.

I use bipolar steppers, but it doesn't matter as long as the stepper motor matches the drive. For example, a unipolar drive will not work with a bipolar stepper, but a unipolar motor can be rewired to work with a bipolar drive.

There are more things that you need to know about the motors; physical size, mounting, shaft size, plus the rated voltage and amps. The voltage and amps are important when matching with the drive that you pick.

I use a Xylotex drive and they recommend a bipolar motor rated for 3 amps 4 volts DC. around 100 to 250 oz-in of torque. This means you can run a 30 volt DC power supply with 6 to 8 amps to run 3 motors. I might be off on my numbers a little and some other people can improve my specs, but you should be OK

High Seas
11-29-2004, 05:59 PM
rackbox -
Seems like buscht got about 90%+ on the questions you were looking for! I'll add: you can use Coreldraw to do some 2 1/2 D work and still need to get it into G-Code however. I did a short rerview -- you might take a look at the "magazine" section on the 'zone here - "the quest for 2 1/2 or 3D" (or something like that!) or do a search on CorelTrace here and Google. Torchmate has a nice review of using Corel and thats what turned me on to the method.
Best of luck - The answers you've gotten already put you miles ahead of where I was a year or so ago! Cheers - Jim

rackbox
11-30-2004, 08:03 AM
thanks a lot! Just keep posting, as I am loving all this information!

rackbox
11-30-2004, 10:25 AM
I just called the local RS Component warehouse and presented them for the 250 oz/in stepper motor spec. They asked me if I were going to build an industry precision crane for lifting buildings. Might have misunderstood something. They work in metric, hence the 250 oz/in converts into somthing like 3,7 kg/cm which seems a lot. Am I totally off? Anyone know the correct number in Newtonmeters? The best they could do was something along the lines of a 2 Ampere 40 millinewtonmeters steppermotor at approx. $150,- a piece.

Here are the specs for the one I've been looking at:

Rated voltage (V): 5
Rated Current (I): 0,5
Resistance (Ohm): 10
Inductance (mH): 6
Detnet torque (mHm): 5
Holding torque (mHm): 70
Step angle accuracy (%): 5
Step angle: 1,8 degrees
Insulation class: B

With these types of specs - what should the correct numbers be if I want to bull the routing head using 3 leadscrews (is it called that?) with 10 rounds pr cm and having a max cutting depth of 5 mm in both wood and plastics? (I can do eith 2 mm in aluminum/other types of metal)

rackbox
11-30-2004, 10:33 AM
Oh, and I have made the pdf with specs available on www.rackbox.dk/data.pdf - anyone would like to help me choose?

ger21
11-30-2004, 10:39 AM
They work in metric, hence the 250 oz/in converts into somthing like 3,7 kg/cm which seems a lot. Am I totally off? Anyone know the correct number in Newtonmeters?

About 1.76

rackbox
11-30-2004, 10:46 AM
That would be 1.76 NewtonMeter in holding torque? How about detent? mHm?

ger21
11-30-2004, 11:09 AM
I don't know what mHm is? 1.76NewtonMeter is 250 oz-in. Are you sure it's not mNm?

rackbox
11-30-2004, 12:24 PM
I don't know. It's taken directly out of the spec sheets on www.rackbox.dk/data.pdf

ger21
11-30-2004, 01:20 PM
I think it might be a misprint, as the holding torque is in mNm. (milliNewtonMeters)
Don't worry about the detent torque.

Your 40mNm motor above is 5.6 oz-in of torque - not nearly enough.

You probably want something like these:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=78196&item=3855528779&rd=1

ViperTX
12-01-2004, 01:12 PM
Conversion routine:
http://www.onlineconversion.com/torque.htm

ger21
12-01-2004, 03:34 PM
This on'es a must have.

http://www.joshmadison.com/software/convert/

trubleshtr
12-01-2004, 05:56 PM
thanks ger21 that software is very handy to have, I am going to D/L it on my work computer too. :)