How to calculate stepper torque?
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So according to that thread I am able to move even my double extruder carriage (~700gram) with 0.9 degree slim stepper with max acceleration 1689.65mm/sĀ²(now default in firmware 500). That could be a truth?
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@briskspirit said in How to calculate stepper torque?:
So according to that thread I am able to move even my double extruder carriage (~700gram) with 0.9 degree slim stepper with max acceleration 1689.65mm/sĀ²(now default in firmware 500). That could be a truth?
Yes. With my motors and moving my 4kg (yes 4,000gms), the theoretical maximum acceleration is about 750mm/sec^2 so I'd say that with a mere 700gms but smaller motors, 1700 mm/s^2 is entirely plausible.
Of course, that's just what the motors are capable of. Whether the rest of the machine can handle it is entirely another matter. Also, you can't accelerate the melt rate and extrusion of filament that quickly so you'd likely set print accelerations lower to say 500 but use 1200 - 1500 mm/sec^2 for non print moves (if the frame can handle it).
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@deckingman My point is to make Y gantry lighter, so I want to change X motor to lighter one. From 34mm to 25mm body (Also switch to 0.9 degree)
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@briskspirit said in How to calculate stepper torque?:
@deckingman My point is to make Y gantry lighter, so I want to change X motor to lighter one. From 34mm to 25mm body (Also switch to 0.9 degree)
That's fine - I'm not arguing with you. You asked if max acceleration of 1689mm/sec^2 with a mass of 700 gms could be true and I said yes. I used my own 4,000 gms with bigger motors juts to illustrate the point.
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@deckingman Sorry, I am not arguing too... This is the lack of my English language knowledge )) I just wanted to say that I am not trying to reach max acceleration possible, I just want to understand if it is real to move 700 grams X carriage with slim Nema 17 (13-16 N/cm) with printing speeds up to 100mm/s and any reasonable acceleration rates. I thought that Nema 17 slim will be too small for that...
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@briskspirit said in How to calculate stepper torque?:
@deckingman Sorry, I am not arguing too... This is the lack of my English language knowledge )) I just wanted to say that I am not trying to reach max acceleration possible, I just want to understand if it is real to move 700 grams X carriage with slim Nema 17 (13-16 N/cm) with printing speeds up to 100mm/s and any reasonable acceleration rates. I thought that Nema 17 slim will be too small for that...
Ah OK. Well looking at it another way, your mass of 700gms is about 17% of my mass of 4000 gms. My motors are 59Ncm. Taking the lowest figure quoted for your motors of 13Ncm, which means they have 22% of the torque that mine do. So you are moving 17% of my mass with motors which have 22% of the torque of my motors so it looks entirely feasible that those motors will be OK.
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@deckingman Thank you, will try! How many teeth on your pulleys? What printing speed do you use?
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@briskspirit said in How to calculate stepper torque?:
@deckingman Thank you, will try! How many teeth on your pulleys? What printing speed do you use?
20 tooth pulley. Normal printing speeds up to 100mm/sec but I have gone as far as 300mm/sec (but you need multiple melt chambers to attempt that and even then, it's not good print quality). Non print moves are always set to 350mm/sec.
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@deckingman I will try 16T pulleys , because right now I have strange 17T pulleys with 94.*** steps per mm
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@briskspirit said in How to calculate stepper torque?:
@deckingman I will try 16T pulleys , because right now I have strange 17T pulleys with 94.*** steps per mm
That's odd - in two ways. Firstly 17T pulley is really strange - never seen one and didn't know they existed. Also, are you running 0.9 degree steppers now? If so, the steps per mm should be doubled. For info, using 16x micro stepping and 1.8 degree motors the steps per mm are 80 for a 20 tooth pulley and 100 for a 16 tooth pulley. So a 17 tooth pulley would be about 90. But if you use 0.9 degree motors, the steps per mm should be 160 for a 20 tooth, 200 fpr a 16 tooth so about 180 for a 17 tooth pulley.
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@deckingman No, I am still on 1.8 degree steppers with 17T pulleys, so right now I have ~94.118 (EMF calculator tells me the same value). Already ordered 16T from ZYLtech.
There is lots of strange decisions put into my printer 17T pulleys(some of them are plastic), 17T pulleys as idlers, T8*8 lead screw, weird Chitu board and etc...I've teared down my printer and waiting for parts + WiFi board on Monday-Tuesday.
Hardest thing to do : I have T8x8 without coupler, it is glued to a rotor. So right now I am trying to soak it in acetone to soften epoxy/CA glue(some green glue, could be green Loctite so I will need nitro methane to un-cure it...) So I want to change lead screw to T8x2 screw inside my stepper motor. Option number 2 is to drive a new screw with regular stepper through a coupler or through belt/pulleys assembly and that will be complicated as this is the only one printer I have to print parts)) -
@deckingman You can get timing pulleys with practically any tooth count you could ever want in the industrial market.
http://shop.sdp-si.com/catalog/?cid=p346&filter=&sort=undefined&view=table
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@phaedrux But why somebody decided to put 17T on a printer? That what I was thinking about a few days in a row... Why not 16 or 20, which will give even quantity of steps per mm..
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@briskspirit Because someone had a ton of 17T for really cheap!
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@phaedrux said in How to calculate stepper torque?:
@deckingman You can get timing pulleys with practically any tooth count you could ever want in the industrial market.
http://shop.sdp-si.com/catalog/?cid=p346&filter=&sort=undefined&view=table
For sure - but I meant that I'd never seen or heard of a 17T pulley in the context of 3D printing.
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@deckingman You'd be astonished what lies inside some of the cheaper knock off printers out of China.
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@phaedrux That's why I decided to upgrade mine
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@deckingman the Makerbot Replicator 1 and a huge number of Chinese clones/derivatives of it used 17t GT2. So, at least a hundred thousand printers in the wild with them.
I don't know why MBI used 17t originally (probably cheap sourcing a truckload of them like @Phaedrux mentioned) but the clones kept it for a long time to maintain firmware compatibility with a stock printer JSON config file in the Sailfish/Mightyboard ecosystem.
There might have been some sensible driver for the selection at the time... maybe somebody wanted a particular pitch diameter to match a legacy T2.5/MXL pulley or idler bearing or something. Or wanted the smallest pulley that would fit a 1/4" shaft or something. Who knows.
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One learns something new every day.........
