computer parallel port help..plz read once

[bryan1]

Hi Sizala,
Ideally for a homemade CNC ball screws are used if the utmost accuracy is needed, just be aware the cost of them isn't for the elcheapo homemade cnc. I much cheaper way is to use all thread and make an anti backlash nut. Acme thread can be used but there's still the problem of the backlash.

What size are the stepper motors you're going to use and how many wires do they have, this will dictate where they are unipolar or bipolar.

Now depending on what is used for carrier slides will dictate the amount of friction the stepper will have to overcome just to move each axis. On my cnc I'm building when time allows I used a pair of 25mm linear bearings on each side and bought the hardened shaft. The Y and Z axis slides are bronze bush's inserted into a cast iron I block I machined in my mill and kept the alignment accuracy very close.


Can you upload some pictures of your cnc design and I can try to help where I can.

Regards Bryan

 

[sizala]

Hi Sizala,
Ideally for a homemade CNC ball screws are used if the utmost accuracy is needed, just be aware the cost of them isn't for the elcheapo homemade cnc. I much cheaper way is to use all thread and make an anti backlash nut. Acme thread can be used but there's still the problem of the backlash.

What size are the stepper motors you're going to use and how many wires do they have, this will dictate where they are unipolar or bipolar.


Now depending on what is used for carrier slides will dictate the amount of friction the stepper will have to overcome just to move each axis. On my cnc I'm building when time allows I used a pair of 25mm linear bearings on each side and bought the hardened shaft. The Y and Z axis slides are bronze bush's inserted into a cast iron I block I machined in my mill and kept the alignment accuracy very close.


Can you upload some pictures of your cnc design and I can try to help where I can.

Regards Bryan

hi bryan1,
i am going to make a cnc like this = How to Make a Three Axis CNC Machine (Cheaply and Easily)
i will go for the acrylic type of cnc ....

and i am using a 6 wire stepper motor..(i think it is a unipolar stepper motor) i currently have a testing stepper motor which is = http://music.columbia.edu/~douglas/classes/motor_mania/stepper.jpg

i know that i have to use a lot more bigger motor then my current motor...so plz tell me that which motor to use and i am thinking to use a road like this = **broken link removed** and i will attach this nut on that road = http://www.chillyintellotech.com/intollo/fastener/jointer_nut2.jpg

i think it will work..but i need the perfect details about the road's thread so my friend can make it for me on his cnc lathe ...

thenkx for reading plz reply ...



-----
and i am going to use this stepper motor controller === http://www.instructables.com/id/Easy-to-build-CNC-Mill-Stepper-Motor-and-Driver-ci/ ....will it work?..or do you know about any other stepper motor controller?

 

[bryan1]

Hi Sizala,
I think you will find that stepper won't have anywhere near enough torque to run an all thread cnc axis. The nut you linked to will still have a heap of backlash but if you are getting a friend to make it for you the go for a spring loaded nut where 2 nuts are separated by a spring. That will give an anti backlash nut but the required torque will increase, go look at this link and try out your stepper's torque Measuring stepper motors

As far as a cnc controller one can buy one off the shelf or make their own, I started by buying and oatley kit which is only a single step controller but trialling out my x-axis on my cnc it did work ok. Micro stepping is the best way to go and I'm on designing a new layout for a bipolar stepper driver. Now off memory with a decent stepper motor with 5 or 6 wires they can still run as bipolar.

For my testing I'm using Kellycam but when I'm finally done I'll be using EMC2 which will allow me easily to use the rotary axis I'm designing.

Regards Bryan

 

[sizala]

Bryan1 ,
can you plz send me a photo of "spring loaded nut" bcoz i dont know about that.. but if you provide me a photo then i will find that nut here in my city.. and i am going to use Kcam4 software for my controller... and you said that you made up a cnc so can you plz tell me that which motor did you used and some details about your threaded road ( or screw ) ....

and my biggest problem is = how to take 0.001 mm accuracy with the use of threaded road or screw? i think i have to design a gear-box for that...

 

[bryan1]

Hi Sizala,
I don't have any pic's of the spring loaded nut but this description should get you on track You place 2 nuts onto the threaded rod with a compression spring in between them, then only one nut is clamped to the axis for travel and the other nut is free to slide but not rotate. The spring under tension will ensure each nut will ride on opposite sides of the thread at all times and thus ensuring a backlash free nut. There will be some friction introduced and by tweaking the spring tension the best medium can be found.

In order to get micron precision you will have to microstep as full steps won't give you the accuracy needed. But with that link you showed of the cnc that you want to make a 0.1mm accuracy will be hard to get on that type of machine. On my X-axis I used M16x2mm pitch high tensile threaded bar and machined up a brass nut with a split and a bolt inserted to get rid of any slop. In Kcam you can set the amount of backlash in steps and the trials I did I was able to have a free running leadscrew with only 4 steps backlash and I'll tweak that down even further when I get the new stepper motor mount made. I do have a mitutoyo digital height gauge I use for calibration and over a 600mm distance and back again repeatedly it was with 0.02mm. For a wood router that is more than enough for accuracy.

Regards Bryan

 

[sizala]

yes brayn1 0.02mm is enough for me. so plz tell me that how to make a thread or a screw for that? i mean tell me the details about the screw...

and i am going to use kcam4 software so i dont know that how take half steps from that software..i mean my motor is 48 step motor so how can i make if 48X2=96 from kcam? is it possible in EMC ? bcoz i cant see and option like that in Kcam...
thankx for all your help...plz reply....

 

[bryan1]

Hi Sizala,
For a 500mm length axis you will get away with M12 threaded rod which you can get from a nut & bolt shop, go for the grade high tensile which will cost abit more and ask the black one otherwise they might supply a galvanized rod which won't be any good. As the X-axis on my cnc is 900mm long I went for M16. Kcam doesn't do micro stepping off memory but the circuit you use to do the microstepping will take of that. All you have to do is multiply the steps by the amount you micro step IE: micro stepping by 4 multiply the steps by 4. Also by micro stepping you can get a much better resolution IE: with going by 4 your stepper will do 192 steps per rev and using a M12x1.75mm threaded rod the resolution will be 0.00911mm per step which for a homemade router is close enough to 0.001mm resoultion. By not micro stepping with 48 steps the resolution will be 0.0365mm per step. With micro stepping the motor runs that much smoother as the waveform is close to a sinewave if the stepper controller is a good one.

One of the many projects on my list is a LMD18245 micro stepper circuit controlled by a 16f88 18 pin pic. The design is off the web and is designed for a 16f628 but I do intend to tweak the code to suit my cnc.

I would suggest first making a simple full step driver circuit and get your cnc up and running then as time goes on and you learn will find the micro stepping is the best way to go.

Regards Bryan

 

[sizala]

ya the same thing i was thinking that = 1st make a working cnc then i will upgrade it . i am thinking to make a 0.05 resolution with the use of 48 steps and 2.4mm threaded screw . what do you think ?will it work?
and if you do know about some good controller that i can made by my self ( which do not require any programmed IC) then plz let me know about it..
so now i am going to make a full step controller than i will go for half stepping ...
thankx for your advise....

 

[sizala]

hey Brayn , one of my friend asked me for help. he have a power press machine . and what he wants to do is = if the operator's hand is touching the power press's plat forum(which is made up from metal) at that time the power press must not work. i think a "capacitive touch switch" will solve his problem... so do you know about any good "capacitive touch switch diagram" ?....

 

[MrAl]

Ok you got me Eric. The OP already is using a DLL with an embedded device driver, but it doesn't work with the USB-2-parallel converter. How does your driver solve the problem?

Luckily for me, I'm a cheap ba***rd, and haven't purchased a new computer in years, so all my machines have a parallel port to use with my projects. Eventually though, I'll have to join the 21st century and start using USB.

Hi there,


Have you tried RS232 or is that too slow for your applications?

 

[BrownOut]

Hi there,


Have you tried RS232 or is that too slow for your applications?

Hello, I think I would have the same problem as the OP, since I'm using a USB2RS232 adaptor. Acutally, I use RS232 to communicate to my system through Hyperterm. I wanted to use the parallel port as a programming conduit. Also, I do JTAG work, and that requires 5 independently controlled signals, so the parallel port is needed ( unless I S2P convert the serial signal ) I would really like to make the switch to USB. Do you know of a kit that allows full USB2.0 speed. Heck, I'd be happy with USB1.1 speed at the endpoint.

 

[MrAl]

Hi again,


I know Microchip has a few solutions but i've never used any of them. I believe they are for use with the 18F series chips (a couple of them anyway). They have full documentation too but i havent read any of it so im not sure how easy it is to get going.

 

[bryan1]

hey Brayn , one of my friend asked me for help. he have a power press machine . and what he wants to do is = if the operator's hand is touching the power press's plat forum(which is made up from metal) at that time the power press must not work. i think a "capacitive touch switch" will solve his problem... so do you know about any good "capacitive touch switch diagram" ?....

Hi Sizala,
The best idea for that power press is a bar that lowers in front of the platen with a guard so NO HANDS can get into the platen and a micro switch to enable the press once the guard is closed. It only has to happen once if your mate slips and his hand goes in you don't want to see the result. Tell him to install a guard with a lockout micro switch and be firm.

Regards Bryan

 

[ericgibbs]

hi sizala,
Ref your PM about the Touch Switch, as I advised do not use it in that application.

As Bryan suggests, use a mechanical gate with micro switches

 

[sizala]

hey guyz. i maded up this board = CNC Driver Board (Multi axis)

but that is not working fine...when i press forward button from Kcam at that time the stepper motor moves one step forward but when i press backwards button the motor moves 2 step back....why is this happening?

AND
if you know about any parallel port stepper motor controller then plz tell me about it (and remember that i dont have any IC programmer...)

thenkx for reading my friends....

 

[BrownOut]

So, you're saying you're going one step forward and two steps back?

 

[sizala]

So, you're saying you're going one step forward and two steps back?

no no...it is not like that.... the problem is when ever i change the direction of motor move it gives me one extra step in that direction.. lets say if i move 3 steps -> and then one step <- at that time it gives me 3 steps -> and 2 step <- ..and if i go 2 steps <- and then press -> button once at that time it gives me 2 steps ->....
do you understand my problem?

 

[sizala]

and can you please guide me to any other good stepper motor controller like this one = CNC 3 Axis Stepper Motor Controller | Lirtex - Technology on the Edge of Time

i searched web for 3 days but i didn't found any information on this controller....
plz plz plz help...i am stuck....

 

[3v0]

Is it possible Kcam is sending the extra step or not configured correctly. That looked like a simple circuit. Not sure it is at fault.

 

[BrownOut]

Is it possible Kcam is sending the extra step or not configured correctly. That looked like a simple circuit. Not sure it is at fault.

Yeah, I'd look for any configuration that proposed to take up backlash.