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GeorgeD
13-08-2010, 03:22 PM
How much weight can a mid range stepper motor handle?

Basically I want the motor to push up a certain weight using a leadscrew to drive the weight upwards.

The information is that the motor will not be constantly operational all the time ie it will be idle more than operational for upwards lift and fine adjustment ofthe intend load.

This is for my project that I wish to make with a view to selling them on ebay and dependin how well they sell?

:wink:

Ricardoco
13-08-2010, 03:37 PM
How much weight can a mid range stepper motor handle?

Basically I want the motor to push up a certain weight using a leadscrew to drive the weight upwards.

The information is that the motor will not be constantly operational all the time ie it will be idle more than operational for upwards lift and fine adjustment ofthe intend load.

This is for my project that I wish to make with a view to selling them on ebay and dependin how well they sell?

:wink:

I've had this dilema myself, I simply got a torque rench on its lowest setting and tried to turn the screw and kept upping the setting untill it turned before it clicked then i read the scale on the torque rench, this gave me a NM reading as a guide and then went hunting for a stepper that had a higher NM spec, i expect there many more scientific ways of working this out, however i did this 14yrs ago and it is used a lot and has never failed!!

Rick

GeorgeD
13-08-2010, 03:59 PM
How do Rick.

Basically I don't want to give too much away on this(Chinese might be lookin? :heehee:) but the pushing weight will be in the region of 8 maybe 9 kilos,thats about the weight of 4.5 bags of sugar? but there will be some slight resistance in terms of down force from the intended item being pushed up.

Ricardoco
13-08-2010, 04:10 PM
Well all you must remember is Kg is a measure of weight and a newton is a measure of force (I think lol) but if you convert the 9Kg to 9Kgf this will give about 88.25 newtons. if that helps at all lol


How do Rick.

Basically I don't want to give too much away on this(Chinese might be lookin? :heehee:) but the pushing weight will be in the region of 8 maybe 9 kilos,thats about the weight of 4.5 bags of sugar? but there will be some slight resistance in terms of down force from the intended item being pushed up.

Youve just got to go with force measurements thats why i used the torque rench as it gets a bit complicated if you start trying to convert force over to weight and visa versa i suppose thats why newtons measure is still in use today...

GeorgeD
13-08-2010, 04:14 PM
Now listen here,Isaac.:whistling:

irving2008
13-08-2010, 04:43 PM
So George, what you're suggesting is a knee-mill style of bed lift for a CNC router?:whistling:

Incidentally the Nm rating of a stepper motor has very little relevance to its operating capabilities. The figure oft quote is the holding torque, when it is stationary. Except for some specific applications this is rarely the case, as torque drops of with speed.

In answer to your question F = 2*pi*T*e/p where p is pitch in m, T is torque in Nm and e is efficiency, or T = Fp/(2*pi*e). For a ballscrew e=.8, for trapezoidal e = .3

So for a 5mm pitch trapezoidal screw, lifting a 10kg weight (100N force) a torque of 100 * .005/(6.28*.3) = 0.27Nm is needed at the actual working speed.

Then you have to consider if the motor can hold the weight up when it is stationary. For trapezoidal the efficiency is low so there is relatively little push back.. But with a ballscrew with a long lead (pitch), typically 5mm or bigger, that weight will push back on the motor, so as soon as the power is removed or reduced the weight will fall... this may or may not be acceptable... There are formulae to work this out, but I'll leave that as an exercise for the reader...


Oh, you have of course checked the Euler buckling loading for your chosen screw?

GeorgeD
13-08-2010, 04:56 PM
Oh, you have of course checked the Euler buckling loading for your chosen screw?

Bucklin won't occur,Irving... the screw is too short.

I'm a bit constipated at the mo,so I'll go work it out with a pencil.

Robin Hewitt
13-08-2010, 09:40 PM
I don't want to give too much away on this(Chinese might be lookin? :heehee:)

I used to make things until a very nice chap from Kowloon 'phoned and offered to make them for me. It's wonderful, but there is a learning curve.

I also got cloned in Taiwan. You know when they are going to clone you, terribly polite, you get a friendly email enquiring about your patents. Hit my Asian sales for six but I'm still going.

Web sales depend on web forums talking about you, last weekend I got a sudden rush of orders from Slovakia which was unexpected.

Produce a quality product then strive to improve it :smile:

Good luck.

routercnc
13-08-2010, 09:57 PM
If the range is small, add 2 springs in tension, pulling up, to take some of the load. Set them pointing outward at 45deg or so, so that they give a gentle pull all the way through the range. Either do some maths, or use trial and error. Important thing is:
Springs do not go slack at top
Springs do not go so tight at the bottom that there is more load on the leadscrew than there would have been without them

This will also reduce self wind (rhymes with mind not thinned!)

Set it so that without the leadscrew connected the load hangs about halfway down. Then add the leadscrew and motor. This is a bit like an industrial assist, sometimes called zero g assist. Some Z axis routers (mechmate??) use this idea.

GeorgeD
14-08-2010, 07:01 AM
How do,Robin.

I have already taken a patent out on this device but only a buttons one.

The design is so simple that I cannot believe it has not been manufactured,the operating devices are available for this type of design but are in excess of 70 and up,eck that first figure is what I'm going to knock this device out for? including the operating handheld unit.

I've seen a shiny metal bar(Chrome) go for $60 in the states and that only has one function. :surprised::heehee:

Ross77
15-08-2010, 01:17 AM
George, the Chinese have no respect for patent or copyright, if I'm not mistaken but a patent only gives you the right to defend your design so it would cost in litigation..

Anyway they are also very clever in that they let you think of the idea, prototype and develop it, prove theres a good market for it ........ and THEN RIP YOU OFF..