Pulleys, belts, bearings, shaft suppliers

[DeviousMW]

I need to build a couple belt based gear boxes
to reduce my steppers. I figure 3 or 4 to 1 reduction.
For those of you who have done this.. can you suggest
decent, if possible cheap, suppliers of these components?

The shafts on my steppers are 1/2" I plan on mounting a
timing pulley directly on the shaft driving a belt to a much
larger pulley which drives a shaft supported by two roller bearings to the pinion on the gear rack.

Thanks,
DeviousMW

[SORCHEROR]

what torgue are the steppers,and what are they going on?they have 1/2 shafts,they must be powerful,do you really need to reduce them,you will loose top end speed,larger motors perform better at low speeds,depending on your drivers,which drivers?the larger pulleys are costly,look at Mc carr masters to start
steve

[SORCHEROR]

whoops,thats Mc Masters Carr

[massajamesb]

Look up Hubbard cnc on Ebay. He has quite a few belt, pulleys, etc. and is pretty cheap, and a heck of a guy.

[DeviousMW]

Originally Posted by SORCHEROR what torgue are the steppers,and what are they going on?they have 1/2 shafts,they must be powerful,do you really need to reduce them,you will loose top end speed,larger motors perform better at low speeds,depending on your drivers,which drivers?the larger pulleys are costly,look at Mc carr masters to start steve

There are dual 640oz steppers driving the X axis. I was told by multiple people that I need to gear down at least 3 or 4 to 1. The gantry weighs about 100 lbs. I was going to use a 20 tooth pinion on a 20 deg 20 PA rack. I obviously was fast rapids but plenty of tourqe to change direction rapidly
and a high level of resolution. I'll be drving the steppers with Gecko drives and Mach3.

Whats the best way to caculate the best gearing for a stepper for a plasma table? (using imperial measurements).

Mike

[SORCHEROR]

what kind of screws will you be using ball or lead screws,or maybe rack
ball screws would be best,if you use lead screws i recomend a bouble start
with 8 or 10 pitch for higher rapids,i would not go more than 2:1 on the ratio
the faster a stepper turns the less power it has,personally i would go direct drive,since you have geckos,use a 54 volt supply min.maybe 70 volts,thats where you will get alot more top speed,100 pound gantrys not much if they are on linear guides or some kind of roller bearings,if it moves smooth it almost would roll itself,only have to worry about direction changes
with too much gear reduction im worried you will loose steps when trying to make a dir. change at real high rapids,remember the more gearing gives you more torgue only at low speed,less at high speed,by the amount of gearing,3:1 will give you 3 times low end torgue,but 3 times less top speed torgue,keeo that in mind,also with a heavy gantry,are you running two motors to move it on that axis?i would,that makes a differnce,the load is split between the two,just a thought
steve

[Torchhead]

I assume since this is in the Plasma section, this is primarly a plasma table. Ballscrews or leadscrews and plasma cutting don't mix.

The most used linear drive method is rack and pinion and the most used R&P is the 20 deg PA 24 tooth pinion and rack.

Since a R&P drive gives you a speed increase and a torque and resolution decrease, a belt reduction (at least to get back to unity) is recommended.

Depending on how you drive them a 640 oz-in stepper can easily give you 700 RPM. If the pinion has about a 1" PD then the load moves over 3" per rev. That offers you speeds of 2100 IPM (speed you can't use). A 3:1 gets you back down to reasonable rapid speeds of 700 IPM and offers 3 times the torque and resolution.

Direct coupling leadscrews works good because they actually provide the increased torque and resolution....often by a factor of 5 or 10.

If you use screws on a plamsa machine plan on spending a lot of maintenance time on leadscrew cleaning. Simple covers don't help much. Only bellows type covers will keep them clean.

www.sdp-si.com has rack and pinions and just about any other gear, sprocket, bearing, pulley or linear component you need but I don't know how their prices compare. I do know they don't stock nearly all of the items in their catalog and have the mfg's drop ship from their warehouses. Be careful on their shipping if you order multiple items or they will charge you for shipping on each item shipped from a separate warehouse.

There is a good source for pure rack that has been given but I can't find my link right now.

Tom Caudle
www.CandCNC.com

Tom Caudle
www.CandCNC.com

[DeviousMW]

Originally Posted by SORCHEROR what kind of screws will you be using ball or lead screws,or maybe rack ball screws

No screws.. strictly rack and pinion for the X axis. 700 IPM is pretty sweet
so a 3 to 1 reduction is in order I guess. Do you think these steppers
will have enough torque after being geared down to change directions rapidly enough to eliminate drifting and make precise cuts?

Thanks,
Mike

[Torchhead]

Originally Posted by DeviousMW No screws.. strictly rack and pinion for the X axis. 700 IPM is pretty sweet so a 3 to 1 reduction is in order I guess. Do you think these steppers will have enough torque after being geared down to change directions rapidly enough to eliminate drifting and make precise cuts? Thanks, Mike

If you are doing a dual drive with belt reduction in the gantry those 640's will have plenty of torque. From "slippage" I think you meant the deviation from the actual drawing toolpath to the actual cut path based on machine dynamics. Control software will attempt to not command your machine to do something it can't, so machines with poor acceleration trying to make a sharp turn cause the software to roll the corner (like swinging out on a turn). For nice sharp turns you need the ability to deaccel and accelerate a mass quickly and that takes torque. In plasma you want to do all of this at as close to the normal feedrate as possible or you get corner flare on the cut and ususally a head plunge from the THC, if you use one. Some slowdown on tight turns is unavoidable.

Anti-dive keeps the voltage spike on the turns from diving the torch but is only available on THC's that are integrated with the toolpath control software.

Tom Caudle
www.CandCnc.com

[DeviousMW]

Does the THC300 integrate with Mach in this way.. or I have to go the mp1000 route to get that kinda feedback?

Thanks,
Mike

[Torchhead]

Both products work the same way with MACH. Major difference is that the MP1000-THC lets you preset the target tip voltage (manually in MACH, At the MP1000-THC or from a materials chart) so you can have different pre-programmed setups. It also has better tracking and on-the-fly adjustment. There is no communication to the THC300 from MACH.

Additionally all of the MP1000 series products have a full Port 1 breakout for motor signals and advanced I/O. (you don't need to buy another breakout card for Port 1) The MP1000 is the only product that comes with a separate Table I/O card that can be mounted at the table for connecting all the Homes, Limits, E-stop and Feedhold and has three high current relays for outputs (besides the torch relay)

Tom Caudle
www.CandCNC.com

[Torchhead]

Originally Posted by Torchhead There is a good source for pure rack that has been given but I can't find my link right now. Tom Caudle www.CandCNC.com Tom Caudle www.CandCNC.com

Found it: http://www.stdsteel.com/gear.htm