Precision Roller Chain

[plasmachad]

Is Precision Roller Chain a good options when looking at a table to buy . My last table had v groove just asking because I really don't know

[CNCCAJUN]

Trucut Plasma seems to do very well with precision roller chain.

Ask those guys . . .

Steve

[beefy]

My 2 cents on using chain.

The chain wants to be stationary like a rack, and the sprocket moves along the chain. This way you don't get chain slap, you could even have the chain resting on a base. I stuffed up and have moving suspended chain 2.5 metre long. The chain slap is terrible and can affect the cut when the feedrate is higher.

[WyoGreen]

My Router CNC machine is chain drive, and it works fine. Of course it is low speed. I wouldn't want to run it at the speeds that Plasma machines sometimes reach on thin metals.

Steve

[beefy]

Here's some considerations before going the chain route.

If you are having a dual drive on your long axis, you need the two chains to be exactly the same length for the same number of links. I bought two brand new chains and laid them out next to each other and one was slightly longer than the other. It's not surprising really when you consider how many links you get over a certain length. The precision in the manufacturing of each link will have to be quite high for the two chains to end up exactly the same length. So maybe you need to get the new chains out of the packs and lay them side by side to make sure they're exactly the same length.

Then wear comes into it. Have you had a bicycle. It always seems just a matter of time before the chain becomes slack. Its' basically wearing and "stretching" (as many describe it), the length of the chain has increased. This in itself is not a big deal because you can normally adjust your steps per inch in the controller software. What I see a potential for, is chains not wearing equally, so even if you started with 2 chains exactly equal in length, as they wear a bit they could become unequal lengths. For most cuts it may never be noticeable and may only be an issue for a larger cut where you want everything nice and square, but thought it's worth mentioning. I don't know of a way to calibrate individual slaved axis. Mach for instance just slaves the two motors and send identical steps to the slave motor.

Unlike a rack which is one solid piece of metal, a chain is made up of individual links. Therefore if cutting is concentrated at a certain part of the chain, e.g. say you did most cuts in the middle of the table, then there's going to be more chain wear along a certain length of the chain. The chain could wear and "stretch" at that area only. That can't happen with a rack, it doesn't "stretch" when it wears.

Just Google about transmission chain and wear/stretch.

These are just my calculated thoughts so anyone can decide for themselves. Many people have chains and are perfectly happy with them.

[muzza]

I had similar concerns with the "precision roller chain" on the Trucut system when I initially looked at it. Rather than link to the whole thread with a lot of other stuff I have copied my relevant question and reply from Trucut. Ross and I did have further discussions and I have to say that he pretty much convinced me that the way they utilize the chain was a good drive method. I did however decide to go "the build it myself route" with rack and pinion basically because I am more familiar with it.
Murray

Hi Cindy,
Main thing I see about your design I don't like is the chain drive. Why? probably more because I'm not too familiar with it and everything I have ever had with any sort of chain drive has meant wear and maintenance. Yes a rack and pinion will also wear and I have minor wear on my Y axis rack already but it is quite light for the work it does. The way I see it a chain is made up of many individual parts being each link, a thou of wear or stretch in each link equates to 100 thou or a tenth of an inch over a 100 link chain. Maybe I'm wrong and linking it back to my agricultural upbringing too much but that's what puts me off chain drives. Years ago I built a mandrell bender and it wasn't until we changed it from a chain drive to a gear drive that we could get the consistency and repeatability that we needed.

I like to think I have an open mind, don't take my comments to heart or as criticism but more feedback of my opinions and that's all they are, my opinions, I have been wrong before and expect I will be many more times in my life, he who has never failed has never tried.

Murray

We run chain because it is basically maintenance free. It's been used on all sorts of machinery for many years. It is typically run dry on motorcycles with little maintenance. We do a lot of machine maintenance for local industrial clients and one of the more common requests is rack and pinion replacement. On larger machines that can cost upwards of $100/foot. The amount of wear will depend on how much it gets used and often the machine is cleaned. Look at it this way....You have a steel rack meshed with a steel pinion engaged with compressed air with no lubrication. Throw some plasma dust on the rack and you're looking at about a 2 year rack life on a table....not to mention the noise they make when they get some wear on them.

Roller chain is designed to run in harsh environments with little to no maintenance. Accuracy and repeatability is the same and offers zero backlash. Resolution is determined by pinion sprocket diameter. The only thing that will change that is a change in the pinion diameter....no different than R&P. That chain we use is designed with an 1100lb working load. Used the way we use it, is only exposed to less than 10% of that, which means it never stretches. We have machines that have been running for 10 years with the original chain. It just never wears.

We've been in this business for about 15 years and have built machines using ball screw, lead screw, R&P, linear servo and roller chain. Roller chain is by far the most economical from a purchase price and maintenance perspective. Ball screw with a driven nut would be 2nd choice. Linear servo is very cool, but VERY expensive. Most or the $500K+ fiber laser machines are now using linear servos.

Gantry overrun can occur if the motors are undersized and/or machine acceleration is set too high. A properly designed machine will not overrun because the designer would have...or should have...taken things like gantry weight and primary and secondary drive reductions into consideration when designing the machine. A Koike Mastergraph gantry weighs around 3000 pounds and it stops on a dime. The smaller hobby machines use aluminum so they can get away with smaller motors and drives, which cost less.

[I Lean]

I use rack and pinion with zero issues--but I'm curious what the attractiveness of chain is? Is it cheaper than R&P?

[cindy carlisle]

Roller chain is by far the most economical from a purchase price and maintenance perspective.

[acourtjester]

I have used chain drive on the tables I built and it is cheaper the when driving the longer X axis. I use a cross shaft to connect the 2 sides driving a chain on each side. This mechanically locks then so there is no syncing of 2 stepper motors. This also reduces the need for an extra motor, driver, and power supply plus wiring. There is no need to home the table to correct any racking of the X axis that some report when using a 2 motor X drive system. I have built both 4X4 and 4X8 table and am building another now that may be 5X10 have not decided yet but it will have chain drive.
My 2 cents worth.

[cindy carlisle]

There are over 500+ TruCut CNC owners who are more than Happy with chain. Just this past yr so far we have had 8+ repeat customers "HAPPY CUTTING"

[Creative25]

Doing a comparison with motorbikes.
I had a Yamaha TT 600 with 45 horse power. One cilynder.
Chain totally underdesigned extreme vibrations driving on dirt roads and on dust. Lack of lubrication. The chain lasted 3000 Km that is very bad.

Comparing to plasma. That is cutting about 820 meters per day for ten years.

On plasma, Chain is over designed and
There are no vibrations. So it should last much longer.

[adbuch]

Doing a comparison with motorbikes.
I had a Yamaha TT 600 with 45 horse power. One cilynder.
Chain totally underdesigned extreme vibrations driving on dirt roads and on dust. Lack of lubrication. The chain lasted 3000 Km that is very bad.

Comparing to plasma. That is cutting about 820 meters per day for ten years.

On plasma, Chain is over designed and
There are no vibrations. So it should last much longer.

[acourtjester]

I used chains on my DIY tables and have a shelf for the chain to lay one to stop any flopping.