Building a chain driven Plasma table.
22 Apr 2021 05:13 - 22 Apr 2021 05:18 #206762
by beefy
Replied by beefy on topic Building a chain driven Plasma table.
With todays engineering capability even cheap sprockets should be pretty close to having their bores concentric with the teeth. 1mm is hugely out of tolerance.
I made my table with chain (on the cheap) but wouldn't do it again. Next time I'll be going with heavy duty non-stretch synchronous belt. My chains are horizontally suspended and with a table size of 2500 x 1500, even with tight chains, you get lots of chain bouncing and that transfers to the cut. It would be better if the chains can be laid along a flat surface and they wrap around a drive sprocket on the gantry. That would eliminate chain bounce.
One other issue though may be chain wear (stretch as many call it). If you cut more in one section of the table than others the chain wear will be more in that area and you won't get linear travel any more. It's a bit like a toothed rack "stretching" in length at a certain section. I'm a mechanical fitter and it's quite surprising how much length change you get when a chain starts wearing. Not a massive issue for transmission purposes but may be for accuracy on a long CNC table.
Another issue is keeping the chains lubricated. You oil chains and oil helps plasma dust stick to it. Belts are dry and if you install a belt with the teeth facing down, resting on a flat surface, and wrapping around a sprocket on the gantry, I think you've got the best of all worlds. The main thing will be to get a belt/pulley type that has zero or very little backlash, as the drive pulley reverses direction.
Keith
I made my table with chain (on the cheap) but wouldn't do it again. Next time I'll be going with heavy duty non-stretch synchronous belt. My chains are horizontally suspended and with a table size of 2500 x 1500, even with tight chains, you get lots of chain bouncing and that transfers to the cut. It would be better if the chains can be laid along a flat surface and they wrap around a drive sprocket on the gantry. That would eliminate chain bounce.
One other issue though may be chain wear (stretch as many call it). If you cut more in one section of the table than others the chain wear will be more in that area and you won't get linear travel any more. It's a bit like a toothed rack "stretching" in length at a certain section. I'm a mechanical fitter and it's quite surprising how much length change you get when a chain starts wearing. Not a massive issue for transmission purposes but may be for accuracy on a long CNC table.
Another issue is keeping the chains lubricated. You oil chains and oil helps plasma dust stick to it. Belts are dry and if you install a belt with the teeth facing down, resting on a flat surface, and wrapping around a sprocket on the gantry, I think you've got the best of all worlds. The main thing will be to get a belt/pulley type that has zero or very little backlash, as the drive pulley reverses direction.
Keith
Last edit: 22 Apr 2021 05:18 by beefy.
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- Creative25
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22 Apr 2021 09:09 - 22 Apr 2021 13:54 #206775
by Creative25
Replied by Creative25 on topic Building a chain driven Plasma table.
I agree with you with today’s technology. It Needs a lot of stupidity for making pulleys and sprockets 1 mm out of center.
But still half of my sprockets were out by 1mm.
Maybe for some people the definition of a cam pulleys is A pulley where the pilot hole is not in the center.
As far as chain goes I m planning to do exactly what you suggested. Will post some pictures when I get there.
Just wonder about chain wear if it is the same as on a dirt bike. Worst case I got driving in dirt roads with lots of dust.
I got 3000km day with plasma you want to change it earlier so say 1000km
That is 10000000 meters how long does it take for the Gantry to travel this far?
But still half of my sprockets were out by 1mm.
Maybe for some people the definition of a cam pulleys is A pulley where the pilot hole is not in the center.
As far as chain goes I m planning to do exactly what you suggested. Will post some pictures when I get there.
Just wonder about chain wear if it is the same as on a dirt bike. Worst case I got driving in dirt roads with lots of dust.
I got 3000km day with plasma you want to change it earlier so say 1000km
That is 10000000 meters how long does it take for the Gantry to travel this far?
Last edit: 22 Apr 2021 13:54 by Creative25.
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22 Apr 2021 17:20 #206816
by Creative25
Replied by Creative25 on topic Building a chain driven Plasma table.
I am no thinking of adding a fifth axle since I already have a chuck available so I am wondering what is the most convenient place. Within the Table next to the water tray or on the side of the table?
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23 Apr 2021 22:59 #206895
by andypugh
Or a manufacturer working to produce _something_ at the lowest possible price, with no inspection and a workforce who either know no better, or are not encouraged to do the job right.
I suspect that your parts did not come from a local industrial supplier or reputable source, but rather were the cheapest thing from China / India / Aliexpress?
I do buy from such sources, I see what arrives as a piece of metal cheaper than I can buy raw materials which is already close to the right shape. And little more. Sometimes you get lucky.
Replied by andypugh on topic Building a chain driven Plasma table.
I agree with you with today’s technology. It Needs a lot of stupidity for making pulleys and sprockets 1 mm out of center.
But still half of my sprockets were out by 1mm.
Or a manufacturer working to produce _something_ at the lowest possible price, with no inspection and a workforce who either know no better, or are not encouraged to do the job right.
I suspect that your parts did not come from a local industrial supplier or reputable source, but rather were the cheapest thing from China / India / Aliexpress?
I do buy from such sources, I see what arrives as a piece of metal cheaper than I can buy raw materials which is already close to the right shape. And little more. Sometimes you get lucky.
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23 Apr 2021 23:17 - 24 Apr 2021 16:52 #206898
by Creative25
Replied by Creative25 on topic Building a chain driven Plasma table.
The sprockets came from a reputable company. I would not mention the name.
But I guess it is made in China. But at least they should check the quality.
It is time Europe and America gets weaned from outsourcing from China. Western companies have become so dependent on China that they can do whatever they want.
The cam pulleys are from China.
Shipping from China is cheap. And why should I buy locally if it comes from China anyway.
But I guess it is made in China. But at least they should check the quality.
It is time Europe and America gets weaned from outsourcing from China. Western companies have become so dependent on China that they can do whatever they want.
The cam pulleys are from China.
Shipping from China is cheap. And why should I buy locally if it comes from China anyway.
Last edit: 24 Apr 2021 16:52 by Creative25.
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28 Jul 2021 18:41 #216140
by Creative25
Replied by Creative25 on topic Building a chain driven Plasma table.
Hi to all
Just want to share, found a cheap plug for the CPC Port of my Hyperterm Powermax 45.
www.aliexpress.com/item/1005002589682498...1.0.0.42094c4djpcp0q
Just wander what cable would be good to connect to it.
I am thinking of a Cat7 Network cable. Would this work?
Just want to share, found a cheap plug for the CPC Port of my Hyperterm Powermax 45.
www.aliexpress.com/item/1005002589682498...1.0.0.42094c4djpcp0q
Just wander what cable would be good to connect to it.
I am thinking of a Cat7 Network cable. Would this work?
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28 Jul 2021 18:50 #216142
by andypugh
Replied by andypugh on topic Building a chain driven Plasma table.
Cat5/6/7 only has 8 cores. How many do you need?
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28 Jul 2021 19:23 #216144
by Creative25
Replied by Creative25 on topic Building a chain driven Plasma table.
I only need 6 cores.
Just concerned they may be a bit thin. Do they break easily if flexing a lot?
Just concerned they may be a bit thin. Do they break easily if flexing a lot?
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28 Jul 2021 20:37 - 28 Jul 2021 20:41 #216147
by andypugh
Replied by andypugh on topic Building a chain driven Plasma table.
You would certainly want to be using stranded CATn cable, but they can take some flex.
If you are running the cable to the head, then look at drag-chain rated cable.
www.rapidonline.com/Drag-Chain-Cable
I just noticed that Rapid don't have any any more. Conrad do, though: www.conrad.com/p/faber-kabel-035356-drag...ld-per-metre-1152195
If you are running the cable to the head, then look at drag-chain rated cable.
I just noticed that Rapid don't have any any more. Conrad do, though: www.conrad.com/p/faber-kabel-035356-drag...ld-per-metre-1152195
Last edit: 28 Jul 2021 20:41 by andypugh.
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29 Jul 2021 09:24 #216203
by Creative25
Replied by Creative25 on topic Building a chain driven Plasma table.
CAT cable is only for Cpc port.
Thinking of using Mike cables for sensors.
And automotive cables for Stepper Motors. Do I need to shield the cables for the Stepper Motors?
Thinking of using Mike cables for sensors.
And automotive cables for Stepper Motors. Do I need to shield the cables for the Stepper Motors?
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