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Thread: cnc table questions

  1. #1
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    cnc table questions

    I have been looking everywhere and still have a few questions. I am going to build a 4x4 table (60" rails) Parker GDL-25FD for the X axis, vee grove track and wheels for the Y and Z axis. The gantry will be 3X3 3/16 wall aluminum tube. Now some questions and don't be shy on advice, I want to learn from other mistakes/wants.
    (1) Right now I am looking at 11" of travel on the Z axis. Is this too much and should i be shrinking it? The Z travel will be driven by an acme screw.
    (2) What is the down side of driving the Y axis with an acme screw?
    (3) Have not decided on driving the X axis yet. It could be rack and pinion or leaning towards 1" wide timing belt as I am very familiar with using this set up and its adjustment.
    Thanks

  2. #2
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    Re: cnc table questions

    On the z, the amount of travel is more than you need, 3" is enough for regular sheet cutting and avoiding tip ups. More travel might be nice for a rotary axis, etc. What really matters is weight, if the 11" travel means that the carriage is too heavy for quick acceleration, you will have a hard time getting nice cuts on thin material.

    Driving the y with a lead screw you will have a fairly slow maximum speed to avoid screw whip, unless you run a big heavy screw, which will cut into your acceleration.

    Belts vs. rack and pinion. My table (5x10) has 1" belts on x and y and I regret that. The y is fine, but the belts are not strong enough to hold the gantry steady, and on hard acceleration it bounces and vibrates. On a 4x4 belts are probably ok, so long as you keep the gantry lightweight.

    If I were going to get a 4x4 table I would seriously consider a kit from arclight or precision plasma.
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  3. #3
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    Re: cnc table questions

    Acme Z will be fine but you need a zero backlash nut the sell kits on Ebay with both shop around and you can get a good price. I have used #35 chain on the X drive on the tables (4X4 and 4X8 table) I built I use a shelf for the chain to lay on to stop flop it drive both sides with a cross shaft and one stepper motor on one side. I use spar gear and rack for the Y drive
    I also sell plans on ebay check the feed back and parts for you to build your own table.
    Dragon cut for my buddies HD sissy bar. Picture of scrap from cutting parts for other guys to build my table.
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  4. #4
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    Re: cnc table questions

    If you do a surce you will find alot of great built tables. My favorite table build is from Pugs. I had a torchmate 5X10 table and it had about 8 inches of travel on the Z axis and it was more then enough. I like the V groove bearings although again i like the way Pugs built his with the linuar bearings and you can buy the super cheap on Ebay. I would drive it with rack / pinion. I have seen them with acme screws and chains and both work great. I would build a water table as well. I didnt have a water table on my Torchmate and it would smoke the shop up quickly. Again there are so many builds out there and they all work.

  5. #5
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    Re: cnc table questions

    I am trying to do this with parts I already have on hand. I do not have a drive for the X axis, so that will probably be rack and pinion. As far as the water table goes I think that is a must but I am thinking of adjustable height. The reason for the extended Z axis is to be able to add a rotary axis at a later date. Another question is positioning the material in the table. I am familiar with cnc turrets and their positioning but have not seen anything like that on any of the build threads. Am I missing something there? And yes Pugs has a real nice table and build threads.

  6. #6
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    Re: cnc table questions

    To position things to cut just put the metal on the table and move the torch to where you want to start and zero out the X and Y and Z DRO and load the G-code and hit run. You can start anywhere on the table by doing this but some like to tell the table to home to the limits and run from there by having the starting position in the G-code.
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  7. #7
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    Re: cnc table questions

    Thats my plan. Im cutting everything in the middle to the end of my table. So i put the torch where i want it save the location zero all axis and it should be good to go there right? I see when i zero all axis the image is ready to go on mach.
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  8. #8
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    Re: cnc table questions

    If you load the TAP file first and move around to position the torch and zero the DRO's things may be off in the image just click on "regen toolpath" and it makes the image on the screen correct. This also works if you want to restart I go into the diagnostic page and enter the command g0x0yoz1.0 and enter that move the torch back to the start and then hit "regen toopath" to get the image right again.
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  9. #9
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    Re: cnc table questions

    The design keeps on evolving; I think! I just acquired an Electrocraft servomotor Model 4030-Q-HOOAA and amplifier Model BSA-30 Part# 9106-0002 rev J. Does anyone have a manual for these? If this is feasible I am thinking of using this for the main drive and steppers for the Y and Z provided they will all talk to each other and play nice. As always any advise would be helpful.

  10. #10
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    Re: cnc table questions

    Have you tried to google for the manuals, to have them play nice you will need a Break out Board (computer interface) that will have the correct signal outputs for those units.
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  11. #11
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    Re: cnc table questions

    Thanks for the quick reply. Yesterday I had no luck but today I was able to download the manual. I am missing the wire harness the connects the motor and amplifier but it looks doable. This project is going to be a real learning experience.

  12. #12
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    Re: cnc table questions

    the ones I saw on eBay looked like it had cannon connectors I think you could find the parts number on them so you could buy the mates to them.
    If you have the manual it should have a schematic for the wiring between the 2 units.
    DIY CNC Plasma table USB BOB Price THC
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  13. #13
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    Re: cnc table questions

    Still holding out hope that the connectors will show up the same place I got the drive and motor.

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