[Teyber]

hey!

yeah im sure you all get really tired of this question... but a couple quick-ish searches didn't answer my questions here.
want 4 axis, im thinking the xylotex looks really nice. want to make own mounts and completely lost on ballscews...
i have an x3 mill, and around x-mas id like to cnc it. my budget is around 1000 not including software, obviously under is nice. here is a page i just made myself:

http://www.xylotex.com/4AxSysKit.htm- 380$
4 axis driver, 4 269oz nema 23’s, PSU, fan, cable. Can it use a larger
Stepper on the Z axis? Will 269oz be good enough for rotary table, x and
Y axis? For x3 mill what should be used for Z axis?

http://www.cnc4pc.com/Store/osc/prod...products_id=47 57$
Breakout board- thoughts? Better alternatives?

http://www.harborfreight.com/cpi/cta...emnumber=44859 525$
for grinding ballscrews- is it up to the job?

http://www.machsupport.com/purchase.php 160$
mach 3- any advice?

http://www.solidworks.com/ 140$/Free
solidworks- what versions?



Cam software- what do you recommend for 4 axis?

Ballscrews- what do you recommend? Id like to grind and turn them myself as an excuse to buy a lathe.

Motor mounts- id like to do this myself. What plans are popular? How is the Z axis mostly done?

What other nuts, bearings, et cetera are needed? Im pretty lost here.

Any good guides for learning g-code? Is cam necessary? Does writing your own g-code take the place of using CAM software? (forgive the noob questions...)

Cnc question- how does your mill know where to start cutting on the Z axis? I mean how does it know where your work piece is, im lost on how to start milling, or where to set it so you start the toolpeice where its supposed to?


ANY advice or tips relevant or not relevant to the thread are welcomed...

regards

[Mike Stevenson]

I don't know about any cheap 4 axis software.

[Crevice Reamer]

One thing at a time. Let's start with this:

CNC Software:

There are three programs involved:

CAD: (Computer Aided Design) A program to draw plans and maybe 3D objects with.
CAM (Computer Aided Manufacturing) This program sets up the tool paths for the mill or lathe. It may translate the CAD output to G code.
Control: This software actually runs the mill or lathe or router from the G code.

MACH3 is the hobbiest defacto best computer software for machine control. It can control either Steppers or Servos. Mach operates by sending out pulses to to the drivers that control the motors. The NUMBER of pulses is limited by the speed of the computer and by an upper limit. 35 to 50 thousand pulses is an average amount.

BREAK OUT BOARDS: Mach3 uses the many wires in a parallel port (printer) cable to send control from the computer to the drives. Rather than fastening each tiny wire in the cable to its destination, the breakout board accepts the cable plug and then puts each wire on an accessable screw terminal.

BACKLASH: When reversing direction, any handle movement that does not also move the axis (or table or head/quill) is backlash. It is measurable directly by the dial on the handwheel. For CNC, backlash must be checked and adjusted often. Backlash will turn a circle into a vague blob.

RAPIDS: Non-cutter axis moves to get quickly from one point to another. These are cumulative, so if they are slow it slows down the whole job.

ACME SCREWS are the standard for most manual mills. They are just a relatively close tolerance screw thread and give fairly high precision and backlash while the adjustment lasts.

Acme screws and nuts wear quickly. Usually the screw wears most in the middle and less on the ends. After a while, you can't use the ends because it's too tight.

Even relatively cheap ballscrews, which HAVE some backlash, are better because the backlash does not vary so often. Mach3 can compensate for backlash that doesn't keep getting worse

BALLSCREWS have large threads that allow a ball bearing to roll IN them. The ballscrew nut contains many small steel balls that recirculate inside to reduce friction. The ball nuts can be extremely tight to eliminate backlash--yet still have little friction.

Once ballscrews are installed, manual control may not be possible. Because ballscrews turn so easily, the table or head might not hold a position, but be free to move on its own. So while you COULD install hand cranks on double shaft motors, you might have to constantly lock the gibs on the other axes and it just may not be practical.

Ballscrews come in two types: Rolled and ground. Ground ballscrews are best, but can cost thousands of dollars for just one screw. We small-time automators usually can't afford them.

Rolled ballscrews come in several grades. The better they are for accuracy and low backlash per length, the more they cost. We usually use a medium grade.

If you buy say a six foot length of ballscrew, it needs to first be cut to axis lengths. It is hardened material, so this is usually best done with an abrasive cutting disk.

After they are cut, each end is turned down on a lathe. Because they are hardened, this is difficult to do. One end is usually turned to one diameter to fit a bearing. The other end may be turned to several decreasing diameters to accomodate thrust bearings, threaded for clamp nuts, and turned at the end to fit stepper coupling or pulley.

Once you have determined the LENGTH of the screws you need, there are companies who will make your ballscrews to order.

PULLEYS are used to increase torque by gearing down the motor RPM. However, stepper motors get weaker as speed increases, (To a limit of 800-1500 RPM depending on PS voltage--up to 20-25 times motor rated voltage if the drivers can handle it.) so most of the gain in torque results in lost speed. That's why most stepper motors are connected direct drive.

IPM: Inch Per Minute is the speed rating for the X, Y & Z axis motion. Cutting in a mill usually happens below 30 IPM. But rapids may need to be as fast as possible.

STEPPER MOTORS are designed to move just a tiny bit each time they receive an electrical pulse.

MICROSTEPPING: Some drivers are designed to artificially reduce the distance the motor will turn by electronics. A full step is hardwired at 1.8 degrees and with 200 computer pulses it will complete one revolution. With microstepping set at 10 (Or one tenth) The motor will theoretically take 2000 steps (And computer pulses) to complete a revolution. I say theoretically because microsteps get just a little more vague in size as their number increases. Micro stepping operates at the expense of speed, and promises extremely high accuracy by increasing steps per revolution, but practically 8 or 10 microsteps are the limit. The computer and software can only put out just so many pulses, and the higher the step count, the slower the motor will run.

CONTROL DRIVES:

Stepper drives are the electronics that translate the pulses from the computer into useable current for the motors. They are fairly expensive and many are easily damaged. Wiring the drive wrong or disconnecting it during use will destroy most drives. Generally, the more expensive drives (Like the Gecko G203 Vampires) offer the best features like overheat protection, micro stepping and speed morphing. Steppers tend to get hottest standing still. Overheat protection will 1. Cut the current down, and 2. Put the motor in "sleep" mode after a short wait. Both will drastically reduce heat buildup. Morphing changes the speed to micro step at low speed accuracy, but jump to full steps for high speed rapids.

PID: A Proportional–Integral–derivative controller (PID controller) is a generic control loop feedback mechanism widely used in servo control systems.

Servo Drives that WE can afford, use basically the same pulse system as stepper drives. Actual expensive commercial servo drives use a different, more expensive system.

GECKO DRIVES are generally acknowledged as the best. Gecko "Vampire" drives are virtually unkillable.

The new low-cost Gecko G540 board (Accepts up to 50 volt power supply) will combine four axes of tiny cheap drives with a "Vampire" morphing breakout board so that all you need to connect is the parallel cable, power wires, and motor cables. In a short while, CNC conversion is going to be a LOT easier and less expensive.

SERVO MOTORS, which are more expensive, do not have the starting torque that steppers have, but they maintain what torque they have into high rpms. They are usually geared down 2 or 3 to 1 to gain starting torque. Even geared down, they can still attain thousands of RPM, so speed is not a problem with pulleys. Servo motors are also equipped to tell the computer (through encoder feedback) exactly where the motor is at any given time so there are no missed steps. Stepper motors can stall and miss steps unbenownst to the operator until the finished part is measured. Servo motors will destroy themselves if stalled or if encoder fails.

CPR: Count Per Revolution.

PPS: Pulse Per Second.

Encoders: These send position and speed feedback to the controller and are rated in CPR. They are quadrature devices that require 4 times the PPS per revolution. For example: An encoder rated at 250 CPR, will require 1000 drive Pulses Per Second.

Each system has its pros and cons. Steppers used with proper power supplies are reliable, consistent and cost effective--That's why most hobby applications use steppers.

POWER SUPPLY: Both types of motors run on DC Voltage. The power supply simply converts ordinary alternating current into this direct current. Stepper motors need around 20 times their rated voltage to perform at their best. For example, a motor rated at 2 volts will perform best, without stalling or losing steps, with a 40 volt power supply.

NEMA= National Electrical Manufacturers Association. They set the USA electrical standards.

NEMA SIZES: Both steppers and servos may come in different Nema flange sizes.
Nema 23= 2.3 inch flange. Nema 34= 3.4 inch flange etc. We usually use either the smaller Nema 23 or the somewhat larger Nema 34. The torque may overlap between the sizes, but generally the larger motor has an easier time.

For example, a 500 oz Nema 23 stepper motor will be working hard (and getting hotter) to attain the torque at which a 500 oz Nema 34 will be easily cruising. Generally, power is added by extending the length (stack) of the motor.

RESOLUTION: The measured (In mm. or inch) amount of accuracy possible in an axis move. This is a combination of number of steps per motor revolution and number of turns per inch of the lead screw. For example: A direct-drive Stepper motor with driver set for full step will take 200 steps for one full revolution. If that revolution turns a ballscrew with 5 turns per inch, then there will be 1000 steps per inch or a resolution of one thousanth of an inch. (.001) If that same motor was turning a 20 turn per inch Acme screw, the resolution would be 4000 steps per inch, or 4 thousanths of an inch. (.0004) Pulley or gear ratios add to the resolution.

CR.

[Crevice Reamer]

The Zylotex will not give you the best performance in the X3 because it won't survive a high enough voltage to run most steppers at max speed. The new Gecko 540 will be your best bet--especially since you won't need it 'til Christmas.

Minimum recommended motors for X3 are usually 400-500 Oz N23s for X & Y and 600-700 oz N34 for Z.

Keling is one of the best places to get Geckos and stepper motors:

http://kelinginc.net/

Right now, none of his motors are optimum for the new 540. In a few months, I expect that to change. I'm sure he will have a good selection and prices.

CR.

[Crevice Reamer]

The trick to turning ball screws is to get through the surface hardening. Once the hard layer is gone--Even a mini lathe can do them. So a mini lathe, tool post grinder and 4 jaw chuck could do it. The 7 X 10 (actually 7 X 8) mini lathe is a little short for many tasks though.

CR.

[Crevice Reamer]

Theoretically, you could write the G code in Mach3 and bypass the CAM step--If you were experienced enough. Mach has some nice CAM add ons though. True 4 Axis software is NOT cheap. But you may not NEED it. As long as you are not contouring, you may be able to write the code by trial and error to duplicate your hand motions on the rotary table.

CR.

[Crevice Reamer]

Cnc question- how does your mill know where to start cutting on the Z axis? I mean how does it know where your work piece is, im lost on how to start milling, or where to set it so you start the toolpeice where its supposed to?

The program needs to know where it is starting from and where it will move to and start cutting. You will establish these coordinates for each job that you program.

You can set up switches for reference points to start the mill from. You will have measured every tool length and width. (Tormach tool holders allow the same length each time.)

It is best to attach your vise or tooling to a permantly indexed position on a tooling fixture plate. That way the same job will always start at the same place.

CR.

[Crevice Reamer]

Here are some sites to start your programming education:

http://en.wikipedia.org/wiki/G-code

http://www.linuxcnc.org/handbook/gcode/g-code.html

http://xdobs.com/cnc/gcode-introduction.html

This is for a router, but gives insight into the process:

http://ddf.mit.edu/devices/CNC_Tutorial.pdf

Free software tutorial videos:

http://www.cncinformation.com/cad-videos/

CR.

[Crevice Reamer]

The Ball screws you will use on the X3 will probably be 5/8 inch diameter. Whatever lathe you get will need to accept this both through the spindle and through the chuck. Most of the small Asian lathes come standard with a chuck that won't accept this--so a new chuck with larger through bore will be a must--preferably 4 jaw self centering for gentler grip of the screw.

CR.

[Teyber]

wow!

was NOT expecting all of that! thank you SOO much!
i have spent about 10 minutes reading this thread
http://www.cnczone.com/forums/showth...=51083&page=73
and still have 73 or so pages to go... It definately seems like the 540 is exactly what i want.

3 amps though limits me to nema 23's it seems, and i can't find a nema 23 over the 425oz ones. Will it really struggle on the z, even with ballscrews? or perhaps a counterweight will help.

you described everything in such amazing detail, thank you so very much!

a couple questions on what you said-

so http://kelinginc.net/SMotorstock.html look at number 8. that runs at 4.17, so i would need a 83.4 psu?

if 4th axis software is so difficult to come by at a low price, should i definitely ditch the 4th axis then? i wasn't really getting what you said about guess and check with the G-code for the 4th axis? i can always add it later...

what do you mean by contouring?

any recommendations on CAM software?

also...

when you say direct drive, i am not sure if you are saying pulleys are direct drive or actually driving the table?

What would i spin onto the ballscrews, and what would go on the other end? you said a bearing but is it an ordinary one or a rare expensive one?

Ill read around on the proper length... or is it somethign i will have to do myself? will it be the same size as the ACME ones in my mill?

thank you SO much for your time and help.

regards

edit-
http://www.harborfreight.com/cpi/cta...emnumber=44859
the hf 8x12 has a 3/4" hole... i have seen some 7x10 lathes spinning the ballscrews with the 3/4" hole

[cjdavis618]

Teyber, I can give you some advice based on experiance with what you are thinking about.

I have the Sx3 version from grizzly and due to some "vendor confusion" ended up ordering the Xylotex 3 axis and 4 axis kit from them. I had planned on CNC'ing a home built Plasma table and also a X2 mini mill.

Due to that Vendor Confusion, I ended up with a X2 mill and a Sx3 (The SX3 that I canceled the order for since it wasn't supposed to ship for months.) Anyway, Grizzly found one and a week after I ordered the mill, Ups called to arrange delivery. I was somewhat dumbfounded. I then had 2 mills and had to decide which to CNC. I decided to give the SX3 a shot, and ended up selling the x2 to my dad. I already had another X2 that was part of a Lathe/mill combo and didn't want to separate the machine and be only CNC.

I had already ordered the CNC components with both kits having 425 oz Nema 23 motors. These motors work great for the X,Y and A axis, but the Z..... Not so well.

Without a counterweight, I could get about 15ipm. With a 100lb counter weight at a 1:1 ratio (No pulleys to reduce weight), I could get about 40 ipm. This worked very well for a while until one afternoon when I was doing some peck drilling, the Z axis shaft broke. There was no damage to the mill, but I did loose a 1/4 Drill bit that snapped and held the weight.

I used the CNC fusion kit on my mill and it is supplied with 1/2" ballscrews. They seem to work great, but I believe what CR said about 5/8" screws would be a good choice for the Z and X axis. The y is fine at 1/2"

What he means by direct drive is a coupler between the motor and the shaft of the screw. Not using any kind of belt or similar system.

You can go to this site and see what Ball Screws and Ball nuts look like and how they work.
http://www.nookindustries.com/ball/BallHome.cfm

[Crevice Reamer]

wow!

was NOT expecting all of that! thank you SOO much!
i have spent about 10 minutes reading this thread
http://www.cnczone.com/forums/showth...=51083&page=73
and still have 73 or so pages to go... It definately seems like the 540 is exactly what i want.

3 amps though limits me to nema 23's it seems, and i can't find a nema 23 over the 425oz ones. Will it really struggle on the z, even with ballscrews? or perhaps a counterweight will help.

3.5 A is the max for G540. As I stated, I'm sure that Keling will find suitable motors in a month or two.

you described everything in such amazing detail, thank you so very much!

a couple questions on what you said-

so http://kelinginc.net/SMotorstock.html look at number 8. that runs at 4.17, so i would need a 83.4 psu?

Yes! But 72 Volts is the highest PSU voltage that Keling has--and it's more expensive. The motor will run at much lower voltage--but with much lower performance.

if 4th axis software is so difficult to come by at a low price, should i definitely ditch the 4th axis then? i wasn't really getting what you said about guess and check with the G-code for the 4th axis? i can always add it later...

No. I think that once you are familier with G code programming, you will find a way to do what you want.

what do you mean by contouring?

Contouring is if you were going to stand your 4th axis on end, (vertically) and try to CNC machine a 3D topography. (following a curve vertically with the Z) The software to make this easily possible is expensive.

any recommendations on CAM software?

Nope! Try the Mach3 addons first.

also... when you say direct drive, i am not sure if you are saying pulleys are direct drive or actually driving the table?

Direct drive does not involve pulleys. The motor shaft connects directly to the lead screw end--which is turned down to accept a coupling.

What would i spin onto the ballscrews, and what would go on the other end? you said a bearing but is it an ordinary one or a rare expensive one?

A coupling attatches with set screws. Keling has some interestingly cheap helical ones. Simple skate bearings come with the mill--and are cheap. Angular thrust bearings are better--but more expensive.

Ill read around on the proper length... or is it somethign i will have to do myself? will it be the same size as the ACME ones in my mill?

Yes, unless you modify the length to get more axis travel.

thank you SO much for your time and help.

You're welcome!

regards

edit-
http://www.harborfreight.com/cpi/cta...emnumber=44859
the hf 8x12 has a 3/4" hole... i have seen some 7x10 lathes spinning the ballscrews with the 3/4" hole

Actually, the spindle hole is a tad larger than 3/4", but the stock CHUCK won't even pass 5/8" through it.

CR.

[Crevice Reamer]

....I used the CNC fusion kit on my mill and it is supplied with 1/2" ballscrews....

My CNC Fusion (deluxe) kit came with 5/8" ball screws and N34 mount for the Z.

CR.

[cyclestart]

I'm not sure how the term "true 4 axis" is being used here. Mach can certainly control a rotary axis along with the xyz. Maybe I skipped over something in this thread?

Another control solution is emc2. One of the developers runs a 5 axis. There's another guy running a horizontal machining center which could be considered "true" 4 axis. Reportedly emc2 is controlling an 8 axis machine out there somewhere. If anyone has pictures of this beast I'd love to see it.

Emc2 is free. Of course mach is only $159, a very good price for this type of software.

[Crevice Reamer]

Thanks CS, for pointing out my confusing statement. I will try to clear it up:

Mach can control up to six axes. The problem lies in finding inexpensive 3D CAD and CAM software. The IDEAL solution would be cheap 3D CAD software that would design the product, transfer the design to 3D CAM software that would write the G code and transfer that to the control software and make the part--All seamlessly.

I don't know of any inexpensive software to do this.

What Teyber wants to do, though SHOULD be cheaply possible, albeit with a little effort.

I'd also like to see that beast!

CR.

[Crevice Reamer]

Incidentally, Teyber: Many software companies offer student discounts. You might want to investigate this.

CR.

[Teyber]

awsooooommweee!

looks like ill have to play the waiting game.

- I have a 5" 3 jaw chuck for my rotary table, i will most likely buy a 5" 4 jaw chuck for the lathe. ill measure the through hole on my current chuck.

- yeah ill just wait and see for the motors...

- is there a point in getting gecko's if i will just end up sacrificing performance in getting a smaller PSU? what do the majority of other people use then?

- What stops the ballscrews from pulling out when running?(i mean if you go to far)? is there a sort of limit switch?

davis- thanks! so what do you recomend for z?

im hoping to "obtain" a copy of solidworks sometime this summer, we will see. they had a 140$ student version and i was going to buy it about 2 weeks ago but now they are asking 300$...
I currently use... sigh... sketchup and kerkythea for rendering. i can actually get visually pleasing drawings but its very limited.

I will Definately be getting mach 3, and which of the addons?

regards

EDIT:

cycle- whats emc2?

[Crevice Reamer]

Another possibility, which we have not spoken of, is that with CNC you probably won't even NEED the 4th axis as you are using it now. The CNC control is capable of making circular cuts without a rotary table.

CR.

[Teyber]

tbh, i also agree with you. but there are a couple times where id like to have it (for a spiral) . it may not be worth it, but if the steppers are 50$ and a drive is 30$, maybe just have quick disconnects so i can disconnect it when im using it?


regards

[Crevice Reamer]

There are more expensive Geckos that can handle 80 volts and 7 amps. The G540 totally outclasses any other cheap alternative. 50 volts and 3.5 A is WAY better than 24 volts and 2.5 A.

On the X3, only the Y axis can pull out. I end drilled, tapped and screwed a washer to the inside Y ballscrew to prevent this.

CR.