1. #1
    Hi all, I'm just starting out building a BUDGET small 4x4 plasma table. I had planned to actually make a start this evening rather than plan, but I've read a few posts on the internet that has caused me to question my plans.

    I'm going to be using a "cut 40" plasma cutter and be predominantly cutting 3mm mild steel.
    My understanding is that a plasma cutter CNC needs "less torque and more speed" as the head will (should) not come into contact with the work piece.
    My plan was to use m8 threaded rod to move the x, y & z, BUT m8 has a standard thread of 1.25mm point to point.
    this means the stepper would need to spin these rods pretty quick to get the head speed required.

    So, my questions are
    • Does anyone have experience of using m8 (or other threaded rod) with a plasma cutter CNC table? and
    • What sort of approx head speed should I be aiming for to cut 3mm mild steel?


    Any other advice you think may be useful to a newbie will be greatly received.

    Regards

    Danny

  2. #2
    New to all this myself but from what I have seen & read so far 8mm would be way to small especially if you are looking for speed during cutting. Threaded bar is probably not a very good option as even if you increase the diameter you are still going to struggle to get much more than a 2mm pitch which is still going to be slow.
    Although I understand you are looking to build a budget machine if you want to use it for business use then there will be a limit on how cheaply you can achieve what you need because the machine is likely to get more use that a DIY machine plus it will need a certain degree of reliability so your not constantly fixing it (takes time) & your not letting customers down. It's really an investment in your business so although you may need to watch costs don't try & do it to cheaply as it will end up costing you more in the long run.

  3. #3
    Quote Originally Posted by gr8fun View Post
    Hi all, I'm just starting out building a BUDGET small 4x4 plasma table. I had planned to actually make a start this evening rather than plan, but I've read a few posts on the internet that has caused me to question my plans.

    I'm going to be using a "cut 40" plasma cutter and be predominantly cutting 3mm mild steel.
    My understanding is that a plasma cutter CNC needs "less torque and more speed" as the head will (should) not come into contact with the work piece.
    My plan was to use m8 threaded rod to move the x, y & z, BUT m8 has a standard thread of 1.25mm point to point.
    this means the stepper would need to spin these rods pretty quick to get the head speed required.

    So, my questions are
    • Does anyone have experience of using m8 (or other threaded rod) with a plasma cutter CNC table? and
    • What sort of approx head speed should I be aiming for to cut 3mm mild steel?


    Any other advice you think may be useful to a newbie will be greatly received.

    Regards

    Danny
    Ok I dont Usually post with as much confidence as some of the others on this site but on this occation I can, if you are only going to use the setup for plasma then use belts and pulleys, get yourself a THC like this one, Proffessional Compact CNC Plasma THC Controller ( Torch Height Control ) | eBay and fit it Just like it shows you in the ad.. end of story, Ive done 2 now and they work very well, Ive also seen them made with sprockets and chains, but had no experience of them..

    Rick
    Always bear in mind that your own resolution to succeed is more important than any other - Abe Lincoln

  4. #4
    Sorry for got to post this link: its the one ive based my two on..

    CNC PLASMA PROGRESS #1 - YouTube

    Rick
    Always bear in mind that your own resolution to succeed is more important than any other - Abe Lincoln

  5. #5
    Thanks for your replies chaps.
    Your comments Martin54 reinforce my concerns. I think it safe to say the idea of using a threaded bar has been scrapped. Now to find a supplier of pulleys and belts..... I found Zapp Automation (http://www.zappautomation.co.uk) are they good? Are there any better ones available?

    WRT "business use" It would only be used to prototype, I get my parts laser cut commercially, but need to do so in quantities of 100+. When first creating a new product it would be good to do a short plasma run and try things out before committing to a lasered batch. Getting it wrong with the laser is a very gutting experience, one I would rather not do again..
    But my business is one where I sell products when they are completed, I rarely have customers waiting and do not take commissions, which is nice as there is no additional pressure...

    Ricardoco, that is a cool bit of kit. I didn't know they were available, but can see the benefit and for a reasonable amount of money too. cheers for the link!

    Danny

  6. #6
    Quote Originally Posted by gr8fun View Post
    Now to find a supplier of pulleys and belts..... I found Zapp Automation (http://www.zappautomation.co.uk) are they good? Are there any better ones available?
    I have no idea how different suppliers or components compare, but I recently got my belts and pulleys from 5mm HTDŽ Timing Belts [4575] : Beltingonline.com, Supplier of power transmission and conveying products based on a pointer from somewhere on this forum, and was more than happy with their service.

  7. The Following User Says Thank You to WandrinAndy For This Useful Post:


  8. #7
    Quote Originally Posted by WandrinAndy View Post
    I have no idea how different suppliers or components compare, but I recently got my belts and pulleys from 5mm HTDŽ Timing Belts [4575] : Beltingonline.com, Supplier of power transmission and conveying products based on a pointer from somewhere on this forum, and was more than happy with their service.
    As was I andy, and i got my pulleys from here:=
    Pulleys - Timing Pulleys

    Im sure there are many alternatives but i asked sometime ago on this forum,and they were the most popular suggestions.
    Incidently they do chain and sprockets on Belting online as well..

    Rick
    Always bear in mind that your own resolution to succeed is more important than any other - Abe Lincoln

  9. The Following User Says Thank You to Ricardoco For This Useful Post:


  10. #8
    Quote Originally Posted by WandrinAndy View Post
    I have no idea how different suppliers or components compare, but I recently got my belts and pulleys from 5mm HTDŽ Timing Belts [4575] : Beltingonline.com, Supplier of power transmission and conveying products based on a pointer from somewhere on this forum, and was more than happy with their service.
    Ohh and they are about 5 miles away, just down the M27.... and half the price of zapp automation for the belts and pulleys. Thank you!!

    Quote Originally Posted by Ricardoco
    As was I andy, and i got my pulleys from here:=
    Pulleys - Timing Pulleys
    These guys do some great prices on bearings too (their belts and pulleys are competitive as well) - VERY handy.
    Much appreciated

    Danny

  11. #9
    Quote Originally Posted by gr8fun View Post
    These guys do some great prices on bearings too (their belts and pulleys are competitive as well) - VERY handy.
    Much appreciated
    Bearing station's prices on the timing pulleys work out better than beltingonline by the time you include VAT and delivery, although if you've not got a lathe to bore them it may be worth paying the extra and using beltingonline.

    You're not going to get anywhere with 8mm threaded rod. Even if you use pulleys to have a high ratio between the motor and screw, to compensate for the low pitch, you're still not going to get a very good speed because the efficiency of the drive system is so low. Driving the X and Y axes with a belt directly may be the way to go since the forces on the head are low, so the lack of rigidity with this system isn't such a big deal so long as the gantry is quite light.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

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