Weight of my gantry is *45Kg*or*100lb*

Hi all.

I am having some weight issues with my gantry. I wish to use stepper motors that are direct drive to a rack via pinion. The weight of the gantry is 45kg or 100lb at the moment. I then have to add on the stepper motors, a rack and bits and pieces. So basically it is HEAVY!


As you can see the in the photo I have used angle iron to support the round bars on which the truck slides along. The weight of one round bar support (ie 2 lenghts of angle ) is 12kg. So I have two of them which is 24 kg.

I am thinking that I can save weight buy using aluminium angle as supports.

Maybe I should just use some aluminium shs and bolt on some of those duel'vee guides and use the groved bearings. If I was to do that, then I would eliminate the heavy steel angle iron and also the heavy round bar as well.

The idea of me reducing the weight is so that I can use small/cheaper stepper motors.

What do you all think of this?

Also what size steppers would I need to drive this system. It is only for a plasma cutter so there will be no contact. It is going to be driven on one side only. I have been thinking of using stepper motors in the 400oz range. Could I go smaller or should I go bigger. What speeds could I expect to reach.

Cheer Peter

hi
With the motors that possess (270 oz) , the force on leadscrew, of my cnc mills, is 305 kg = to 2998 newtons!!!! , (push gotten with leadscrew of 2 mm, with bronze dual nut ).
or 152 kg with leadscrew of 4 mm
hi

The table is horiziontal and runs with no friction, the only thing your motors need to do is accelerate the thing, not lift it. After all, you can push a fork lift with tons of load and more friction. Don't worry about the weight.

Cheers,
Sven

45 kg is not extremely heavy. The gantry on my router weighs about the same and I use 270 oz steppers 1:3 geared on a 3/4 inch diametre pinion. It accelerates to 500ipm within 2 inch of travel. If you use 400 oz steppers I think you can direct drive a pinion up to 1/2 inch diametre with roughly comparable speed & accel.
The number of theeth is not relevant in these parameters, only diametre. However, pinions with less than 12T are said to run less than smooth.

John

My gantry is easily that heavy. Maybe 150 pounds with the Z and router. It rides fine on just 4 roller skate bearings. I am using a rolled ball screw and nut. The weight is only an issue to accelerate and to decelerate, but it works well with 270 oz. motors. I get 70 IPM easily and can get a little more. The X is the slowest axis though, because of the weight.
When I watch the thing moving quickly back and forth, its hard to imagine that it weighs as much as it does.
Those little steppers are amazing. :wee:

Thanks everyone. That's AWESOME. I was thinking of using like 400oz steppers. But maybe now I can get buy with some smaller ones. Meaning that provided that they are under 3AMP max draw, I can runn Xylotex or other cheaper board.

Limbo: Yeah 500imp in about 2 inches of travel! That's brilliant. I can slowly see the power of these little motors now.

Yeah The gantry although it is very heavy, It realy just glides along quite easy.

Umm, Do 270oz steppers have a current draw of less that 3Amps ?

Quote:

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After all, you can push a fork lift with tons of load and more friction

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hhehehehhe LOL you made my day!

I have two forklifts and I cant push either of them with no weight and 3 guys pushing them...

but the steppers are probably good ;)

Quote:

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Originally Posted by miljnor

hhehehehhe LOL you made my day!

I have two forklifts and I cant push either of them with no weight and 3 guys pushing them...

but the steppers are probably good ;)

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Pallet truck, mini stacker, hand lift... It's still a fork. ;)

http://www.swforktrucks.co.uk/hpt.jpg


Cheers,
Sven

The 270 oz steppers from automation direct have a max current draw of 2.8A. I run them at 2A with a xylotex board.

BUT:

They need to be geared to drive a large pinion. I think the largest practical pinion size for direct drive with these steppers would be around 1/2 inch. To have more than 12 teeth on such a small pinion you end up with 24 pitch rack. This is probably much smaller than you planned for, or would want to use in a production environment.
Without gearing it might be better to stay with the 400 oz steppers.

John