New 5 axis

[spoiledbrat]

Hello everyone.
I am building a new machine and need lots of help. I have a decent CAD background, and know my way around a shop.
The machine will have 120" X 60" X 22" capacity, and will be used primarily to cut wood and softer materials. I like the gantry design, and contrary to the posted jpg's, this will have the A and B-axis mounted to the Z-axiscarriage. Every axis will be controlled by ballscrews, except for the A and B-axis. I believe those will be geared for power and precision.
My questions are:
How much servo will it take to drive this monster?
How much can I expect to spend on these servos/controllers/everything except my laptop cpu?
If I decide to use two screws for the x-axis, can two servos be sync'd up worth a darn? (Texas dialect, please ignore)
With all of the above mentioned questions, the budget for this project is $12000 us dollars, 2000 of which is for my machinist' friend.


I have already talked to Chris about the long ballscrew (10 feet) and I am opting for the rotating nut option.
Thank you all who have taken the time to read this.

Rob

[turmite]

Rob,

Mach2 and the newer version 3 can do the sync'd (I'm from Arkansas and understand your language just fine! ) axis' thing for you and still have 5 axis control. As to your decision on the ball screw...just curious if you have considered rack and pinion? Other than the z axis clearance, those dimensions are about the size of my machine which has used rack and pinion for 13 years now. I still get quality parts off of it. N/S/E/W Texas?

Mike

edited www.artofcnc.ca

[turmite]

Hey Rob, rather than edit agian I though I would repost. Your servo needs will be dictated by several things.

1. Linear rail design (friction)
2. Weight
3. Desired feed and rapid speeds

I can tell you that you want that sucker moving when it comes time for a tool change. 120" is a long travel even at 354 ipm which is my machine's max rapid. I will say that I am using steppers rather than servo's and could up that to around 500 imp with good servos.

Are you going to build your a/b axis or purchase? If you purchase, the $12,000 will get you about half way to the price of a new Colombo a/b head.
Spend plenty of time designing before you spend too much money and make sure you have good quotes on the machining. Don't ask me how I know.

Mike

[spoiledbrat]

You gentlemen sure are fast.
My intentions are to machine out the A B head myself, and power it with geared down servos. I will be designing everything, and my friend is a machinist.I left plenty of room in the Z axis to accomodate. I was thinking of using a small rotating table/indexer for part of it.
Correct me if I am wrong guys (and ladies):
I can pretty much build this machine and position servos anywhere, and the software will adjust to the machine. True/False?

As far as speed, is 40 fpm jog speed rediculous? I do not want to put coarser threads on this thing at the expense of accuracy. Say I want +- 0.005 inch accuracy. I am so new at this that I know I sound rediculous. So, without further ado, back to my rediculous demands...
I hope I can do all of this for under 12 grand...

Born Dallas/FT worth
Reside in Tenessee
Sounds like a country song...

[spoiledbrat]

Yet another set ot-so-well-thought-out questions:

My parallel port will operate the controller,
The controller will operate the drivers,
The drivers will operate the servos.

Is this correct? Nothing else to the electro-mechanical side of the house?

[Bloy2004]

Hi Rob,
Looking at your Z-axis movement, I will be having a similar glide. Are you planning to move your z-axis drive motor and screw up and down with the z position while having the nut stationary ? On mine, this would require the motor to project upward increasing the height by the length of the motor, and moreso when the Z-axis is fully retracted....unless you can mount the motor out behind the gantry (y-axis rails) in a downward position.
I've seen other designs that have a stationary motor and screw while the nut moves the axis up and down, but this design won't lend to that type of function.

Bloy

[spoiledbrat]

I want tospin the ballscrew to move the z axis, with the motor mounted on top. Might as well fill up the whole garage with this thing, right?

Still trying to figure out how to interface my laptop to the servos... I guess this is a newbie question

[Bloy2004]

I don't want to be an alarmist, but if you plan on applying large forces to the structure, I would make your z-axis rails a little wider to support the axis when extended. Also, you will probably have to beef up the gantry arms with gussets or some form of support as it will flex there too. the combination of just these two areas will prevent you from achieving good accuracy under loading.

... Just what I see from the drawings...

I'm keeping my X-axis rails high and close to the gantry cross members to eliminate the "arms"...only thing, you lose ability to access the table from the side easily, unless an "open" design is used allowing "reaching in".

[Graham S]

The...

Laptops contected to the driver ...
The drivers connected to the motors ....
The motors connected to the ballscrew
The encoder feedsback to the driver
And here's the word of the lord

So yes you are right. The easiest way to run your machine is from the parallel port, two pins are assigned to each axis, one for direction the other to tell the drive to step. You might think that servos don't step but the encoders are digital and using a driver such as a Geckodrive (www.geckodrive.com) you can make them step. The result is really smooth motion, you don't notice the stepping.

Your A and B axis will have to be geared down heavily using either wormdrive, harmonic drive or a massive great gear or a combination, not easy at all, this you need to sort out before making the rest if you can as it will effect the design. You also need to consider the backlash etc.

Do you know what software you will use? Driving 5-axis is easy, turboCNC (runs in dos free to try and excellent) does upto 6axis and Mach2 (runs in windows also good) I think will run 5. However software for creating tool paths and g-code is less easy.

Check out this site:

http://www.rainnea.com/cnc.htm

He has written a free plugin for creating toolpaths, it is good but a little complicated. The software is for 3Dstudio max but there is a program called gmax which is a free limited version but you can import into that from Rhino and similar 3D programs.

Home this is some help.

Graham

oh yeah, pairing up servos is a bad idea, use one motor and couple the two ballscrews with timing belts, or use timing belts instead of ballscrews and couple two of these. Don't be scared by talk of timing belts or even rack and pinion, they work well and often better than people actually need.

p.s. Geckodrives are on special offer now I think

[ger21]

However software for creating tool paths and g-code is less easy.

Check out this site:

http://www.rainnea.com/cnc.htm

He has written a free plugin for creating toolpaths, it is good but a little complicated. The software is for 3Dstudio max but there is a program called gmax which is a free limited version but you can import into that from Rhino and similar 3D programs.

If you don't use the above mentioned software to create your 5-axis toolpaths, expect to pay well over you're entire budget for the CAM software alone.

[spoiledbrat]

Greetings, and happy turkey day.

I have put away the crack pipe, and decided to use stepper motors. I am going to use 750 oz or better, at least for my rediculous X axis.
Anyone know how I can make 5 drivers connect to my CPU? I have seen packaged controllers of 3 or 4 axis, but not so with the 5 axis.


Rob

[ger21]

TurboCNC can control up to 8 axis with 3 parallel ports. Mach2 can do 6 axis. You may need to make your own breakout boards, but it can be done.