Thread: Chain drive

  1. #1
    Hey guys, I've decided to give chain drive a go for my machine, simply because of the size of it. If not chain probably rack and pinion.

    My question is can anyone tell me the pros and cons of either of these?

    Which line should go down etc

    Thanks in advance

  2. #2
    Compared to ballscrews, the main disadvantages are lower accuracy and rigidity. Advantages are it's easier to get a high feed-rate and acceleration, but not necessarily cheaper? I thought you already had the ballscrews since you've posted a picture of the machine with some in an earlier thread, or was that a different length?
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  3. #3
    I wanted to go down the chain or rack/pinion route but the talk of innacuracy scared me off lol however i will follow this thread and see which of the two come out on top


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

  4. #4
    I dont know if the rigidity would be affected but accuracy would be. Also chains tend to stretch over time. If you are going for rack and pinion use helical stuff. I am sure our old small laser at work used to hit 32m/min and this was rack and pinion driven and had great accuracy for a laser cutter. Initial cost might be similar for both systems but I would think that rack and pinion would outlast ballscrews and nuts. The rack is generally a lot harder than the pinion so wont wear very much. The pinions are easy to change being fitted with a key or taper lock or maybe simply a pin through the shaft. Also the pinion wont die if it gets a bit of swarf in it like a ballnut will do. Pinions need to be replaced in pairs when they are changed and you will need a tensioning system to keep them in mesh in the rack correctly.

  5. #5
    Chains and pinions are okay so long as you give them enough teeth. If you go for low tooth count sprockets to get low speeds then cogging becomes an issue. A 6 tooth sprocket is much the same as a hexagonal pulley wheel.

    Pinions tend to have awkward tooth forms in the smaller tooth counts to engage the rack which can lead to minor cogging and you also have the problem of keeeping the pinion engaged. Someone was making racks with a vee back which looked interesting, might have been Hurco.

    Good points with sprocket and chain are:- Low price. If both ends cog in phase you can apply massive spring tension without adding to the rolling resistance or having to worry about stretch. Real easy to connect to the driven item, all you need are a couple of holes.

  6. #6
    Quote Originally Posted by Jonathan View Post
    Compared to ballscrews, the main disadvantages are lower accuracy and rigidity. Advantages are it's easier to get a high feed-rate and acceleration, but not necessarily cheaper? I thought you already had the ballscrews since you've posted a picture of the machine with some in an earlier thread, or was that a different length?
    Ballscrews in the picture are to short, I put them on simply so I could use the table but have a large table and only being able to use quarter of it is frustrating.

  7. #7
    Quote Originally Posted by Robin Hewitt View Post
    Chains and pinions are okay so long as you give them enough teeth. If you go for low tooth count sprockets to get low speeds then cogging becomes an issue. A 6 tooth sprocket is much the same as a hexagonal pulley wheel.

    Pinions tend to have awkward tooth forms in the smaller tooth counts to engage the rack which can lead to minor cogging and you also have the problem of keeeping the pinion engaged. Someone was making racks with a vee back which looked interesting, might have been Hurco.

    Good points with sprocket and chain are:- Low price. If both ends cog in phase you can apply massive spring tension without adding to the rolling resistance or having to worry about stretch. Real easy to connect to the driven item, all you need are a couple of holes.
    So what do you think of the accuracy Issues mentioned with chains by other people and what levels are we talking about??
    Always bear in mind that your own resolution to succeed is more important than any other - Abe Lincoln

  8. #8
    I've mocked up a gantry side for R&P the motor will sit on a plate on the side of the gantry. The plate is bolted through the top right corner whilst on the left is a bolt with a sliding hole in. Bottom left corner I have a tension spring keeping the motor and pinion into te rack and quite snug! Will this still cause inaccuracy problems? I will try get a pic tomorrow...... Although I can't get my mind off this damn thing so might pop down to the unit lol

  9. #9
    Hey guys just a little post to show you the pictures I mentioned earlier. It will be a direct drive nema 34. But still undecided if I'm to use rack of chain


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