Leadscrews, timing belt, or damper?

[Ranscon]

My machine is a homebuilt 24 x 48 router table. Built from MDF with steel reinforcement. The gantry is possibly 30 pounds. Moves quite freely with minimal friction. 425 oz/in steppers from Keling (kit) 4030 drivers, c10 bob, 24volt PS, 1/2"-10 tpi single start Acme leadscrews, delrin nuts, 2.4 ghz computer, Mach3 control software, not sure what the best motor tuning settings to use are but have tried different microstepping and the best I can get reliably is 44ipm so I'm running at 40ipm to be safe.

If you have any suggestions on motor tuning and microstepping please let me know!! Resolution is important but not critical as I primarily use this machine for wood routing.

If I cannot work this out with tuning I will try one of the following methods.

I'm trying to decide on the BEST (and least expensive) Method to get my machine running faster.I am aiming for 100ipm reliably with possibly a maximum of 150ipm or so.

The torque curves are quite confusing to me. When I ordered the steppers, I called John(keling) and told him what I was working on and what speeds I was looking for. Why did he recommend the 425's over the 270's (which have double the torque at higher speeds)? I know it wasn't for the $ as there is only $10 each difference.

Would the 270's run my machine better? What are the advantages to having the bigger motors if they have 1/2 the torque? It just doesn't seem right at all to me.

Fist option is Dampers:
I have seen a video somewhere here but cannot find it now with a machine comparison running with and without a damper on the stepper. How would I determine the size and weight of a damper? Is there a DIY way to build one that works? I've seen one made with a bolt and washers which looks a bit dangerous to have in the open but I guess it could be enclosed. I would prefer the one that looks like a big washer or flywheel.

I've also considered going with a timing belt system.
If I went with a 2:1 system it should put me at 80ipm and a 3:1 should do 120ipm without any other changes correct? I would have to put a 30tooth pulley on the motor and a 10tooth on the leadscrew correct? Would this hurt the torque of the motor by changing it to a lateral load? Any other side effects of this? Does anybody have a drawing of a setup like this?

Thirdly, I guess I could change my leadscrews.
What would I need to go from 40ipm with 1/2" 10tpi acme's to 150ipm? If I go with 1/2" 5tpi's that should double the speed correct? what if I were to use 10tpi's with 2 or 5 starts? what would this do for my speeds?

And Finally, Which of these methods would be the best to keep reliability high and price reasonable? Thank you very much in advance for any helpful information you can provide me with, Jeff.

[harryn]

Hi, I am too much of a beginner to advise on motor tuning, but here is a little to get you started.

I looked in the "stepper motor" section of the forum and ran a search for "damper". This thread will get you started on that path.

http://cnczone.com/forums/showthread...ghlight=damper


Perhaps before you spend to much time targeting 150 ipm, it would be helpful to try to run your router "hand driven" to see what speeds make sense for the router + bit + material combination. I was very surprised that in this mode, my Bosch router with 1/2 straight 2 flute bits was very happy at 300 - 400 ipm - kind of an interesting experience.

[ger21]

The cheapest thing would be to try a damper.

http://www.cnczone.com/forums/showth...639#post256639

However, it's very unlikely that you'll get 150ipm out of the 1/2-10 acme, as that's 1500rpm.
You could gear the screw to spin that fast, but it'll probably start whipping which would cause other problems.

For best performance, those motors should probably be driven at a much higher voltage than those drives will allow. Switching to 36V would possibly improve performance by up to 50%.

I guess that if you want to spend as little as possible, I'd first try dampers, which may get you more speed, but you really should either gear your screws to spin faster, or switch screws, probably to 1/2-10 5 start. And go with a 36V power supply.

[Ranscon]

Thanks for the info and ideas. I'm going to try the dampers first.(excellent link Harryn and Gerry). I have a piece of 1 inch thick very dense plastic (used to be a bathroom partition wall). I'm going to try the 9 rattler design with 1/2" steel rod plugs. Does the diameter of the holes make much difference in noise or performance? 9/16" or 5/8"? If this can get me closer to my goal, maybe I'll change the screws next to get the rest. I'll let you know how it works out. I may be able to make the dampers later today. Thanks again, Jeff

[Ranscon]

I put a homemade damper on it today made of 1" hdpe with nine 5/8 inch holes and used two 3/8" sling shot balls from Walmart in each hole. With one ball each it stalled out around 70ipm and now with two balls the first stall out is at 80ipm. Used to stall at 48 and I ran it at 40 ipm with no problems. I figure I should be able to run it reliably at 60-65ipm now. Does this sound about right? Jeff

[harryn]

Originally Posted by Ranscon I put a homemade damper on it today made of 1" hdpe with nine 5/8 inch holes and used two 3/8" sling shot balls from Walmart in each hole. With one ball each it stalled out around 70ipm and now with two balls the first stall out is at 80ipm. Used to stall at 48 and I ran it at 40 ipm with no problems. I figure I should be able to run it reliably at 60-65ipm now. Does this sound about right? Jeff

That is quite an improvement. I guess it is all in how it sounds - does it still sound "good" or "bad" ?

[Ranscon]

Can Hardly hear it when running even with the cutter off. Only hear it rattle when it first starts a move from sitting still. How loud are they normally? I may be getting more flywheel effect than damper? Either way, it definitely helps.

[BobF]

At 40 ipm you were turning 400rpm. At 60 - 65 you are turning 600 - 650 rpm. If you changed the screws to 1/2-10 5-start you would increase your gearing by a factor of 5. At 400 rpm you would get 200 ipm. 600 rpm would give you 300 ipm.
2 revs per inch * 200 full steps * 4 microstepping = 1600 steps per inch, plenty of resolution.