I need to Build a 8’ x 30’ cnc plasma table

[Al_The_Man]

The rack I used was from Boston gear http://www.bostongear.com/literature/index.asp
L2012-6 6ft rack and YD28 spur gear.
It sounds like you just need a table for the one project? It might be worth while looking at getting the local steel supplier to cut them for you, the time and effort to build the table will probabally equal the cutting time by hand.
Al

[Al_The_Man]

Can any Drive software or g-code conversion software be told to make
enough steps to go the entire length of the table without having to sacrifice detail.

.

I have retro-fitted a table as long as 80ft and if you keep the rack and pinion meshed with a slight pressure, and calibrate the system accurately, there should be no problem with accuracy.
Al

[kanankeban]

I have retro-fitted a table as long as 80ft and if you keep the rack and pinion meshed with a slight pressure, and calibrate the system accurately, there should be no problem with accuracy.
Al

Hi Al,
I'm planning a 6ftx20ft table, I need some advice, Im planning to build a heavy steel table, and a light wieght gantry, to drive a plasma torch. My idea is to drvie the x,y with rack and prinion (boston gear), I don't know what to use if Vee Bearings ridding over steel channel or Cam Folloers over a rectified steel flat on both sides od the x of course. Next to choose the vee bearings or cam followers, and next what kind of motors (and torque needed) and drive bards...I don't know to go for servos and geckos or rutex or to go for steppers...Could you help me figure out this doubts? And what do you mean with slight pressure in the rack and pinion, do you mean like a spring mechanism appling pressure to the rack from the pinion? as in the shopbot design?
Thanks....
Hector

[Al_The_Man]

The motor size etc depends on the projected weight of your gantry and the acceleration and feed speed you can/want to achieve.
For meshing, I used a motor tensioning product by Rosta It can be seen in the photo's as the pivot point for the motor assy. It will be most probable that you are going to need some kind of reduction on the drive, I used NOS Bayside planetary gearboxes off eBay.
Pic's 1 & 2 show two different machine X axis.
Al

[Al_The_Man]

The air cyclinders seen in the photo's are because the user wanted to retain an original feature, because of the long travel, when the cyclinder is operated it disengages the rack drive and the gantry can be pushed alon the rail by by the operator.
This is the Y axis.
Al

[kanankeban]

The motor size etc depends on the projected weight of your gantry and the acceleration and feed speed you can/want to achieve.
For meshing, I used a motor tensioning product by Rosta It can be seen in the photo's as the pivot point for the motor assy. It will be most probable that you are going to need some kind of reduction on the drive, I used NOS Bayside planetary gearboxes off eBay.
Pic's 1 & 2 show two different machine X axis.
Al

Well, the maximum speed that the plasma can cut is 380 IPM thats the maximum speed that the table can go in cutting, I dont have a clue what will be a good positioning speed, could you give me feedback on this? that way I can pick my reduction ratio for the servos, I want to use timing belts on that matter. that Rosta product, by any chance do you have the part number, I got to Rosta web site, but I can not see which component you are talking about...
About calculating the motors torque do, you have a formula to calculate the dynamic force applied upon the gantry?
Regards...
Hector
Regards...
Hector

[Al_The_Man]

Well, the maximum speed that the plasma can cut is 380 IPM thats the maximum speed that the table can go in cutting, I dont have a clue what will be a good positioning speed, could you give me feedback on this? that way I can pick my reduction ratio for the servos, I want to use timing belts on that matter. that Rosta product, by any chance do you have the part number, I got to Rosta web site, but I can not see which component you are talking about...
About calculating the motors torque do, you have a formula to calculate the dynamic force applied upon the gantry?

The Rosta parts are DR-A27X100 BR27 & WS18-27
If your cutting at 380 ipm then I would aim for a max of at least 500 or 600ipm.
Commercial plasma machines run around 1000ipm max.
There is an industry standard that it is considered normal to keep the inertia ratio of the motor to final load to under 10:1 the deciding factors are motor, all gear/speed reduction components, the weight of the final load and the acceleration required.
It is a good idea to obtain one of the free motor sizing software's available from many of the motion/servo motor manufacturers and play around with it, plugging in various numbers. One of those is Kolmorgen http://www.electromate.com/technical...morgansoftware
There are others, this allows you to get a feel for what you are looking at for final sizing.
Increasing your reduction ratio greatly improves your inertia factor, but if you go too high, you will need a very high motor rpm to get the max feedrate you want. To grasp the effect of inertia, Imagine cutting a square at 380ipm with a 200lb gantry, the Y axis has completed it cut, now the 200lb gantry has to immediatly travel at 380ipm in the X with, ideally, hardly any visible sign of acceleration.
Al

[kanankeban]

The Rosta parts are DR-A27X100 BR27 & WS18-27
If your cutting at 380 ipm then I would aim for a max of at least 500 or 600ipm.
Commercial plasma machines run around 1000ipm max.
There is an industry standard that it is considered normal to keep the inertia ratio of the motor to final load to under 10:1 the deciding factors are motor, all gear/speed reduction components, the weight of the final load and the acceleration required.
It is a good idea to obtain one of the free motor sizing software's available from many of the motion/servo motor manufacturers and play around with it, plugging in various numbers. One of those is Kolmorgen http://www.electromate.com/technical...morgansoftware
There are others, this allows you to get a feel for what you are looking at for final sizing.
Increasing your reduction ratio greatly improves your inertia factor, but if you go too high, you will need a very high motor rpm to get the max feedrate you want. To grasp the effect of inertia, Imagine cutting a square at 380ipm with a 200lb gantry, the Y axis has completed it cut, now the 200lb gantry has to immediatly travel at 380ipm in the X with, ideally, hardly any visible sign of acceleration.
Al

I see you know what you are talking about Is nice to have guys like you around helping guys like me
Thanks so much for your help...
Hector