Motor selection for metal cutting job

[Abrabaracurxis]

Hi,

i need to select a motor to cut small diameter pipes (less than 5mm) 1 mm thickness. i have to do around 400-500 cuts per hour what parameters do i need to consider in the selection? or better by what criteria should i google... dont really know what to look for ...

... and i dont have much experience in this kinds of jobs so this probably sounds stupid but if i fix several pipes togther can i cut several at once? (im thinking to use some kind of coolant)

thanks

juan

 

[MikeHalloran]

You can buy machines to do this, you know.

If you really need to homebrew it, there's a lot more to it than just picking the motor. You first have to decide exactly how you're going to cut the metal, because the various methods available have vastly different torque and speed requirements.

Before you can do that, you have to decide how big a burr you can stand, and how you're going to remove it or prevent it.

Before you can estimate that, you have to know what metal you're planning to cut.

At 500 cuts an hour, you also have to devote some attention to how you'll feed the long tubes into the machine, how accurate you need the cut length, whether you need to vary it, how you'll feed the long tube, whether it's permissible to scar the tube, and how you'll get the short tubes out of the machine and on the the next operation.

Oh, and what the machine is supposed to do when it gets to the end of a long tube, and has to get rid of a leftover piece that is too short to use and may be too short for the machine to handle in a normal way.



Mike Halloran
Pembroke Pines, FL, USA

 

[waross]

Do you want to use a band saw, a reciprocating saw, a circular saw or an abrasive wheel?
Try Googling "cut off saw" You may want to consider an air clamp instead of a screw vise. You can probably cut bundles. The main factor is supporting all the tubes. If there are some loose tubes inside the bundle you will have issues. The challenge will be to clamp the bundles so as to both support and restrain them. It's a challenge that I'm sure can be met.
And I agree wholeheartedly with all the good advice that Mike gave you.
The portable cut-off saws with an abrasive wheel may be too slow. You can fabricate a version with higher horsepower but that means much higher cutting pressure on the work piece. Your small pipe may deform if you use a high power abrasive wheel with high cutting pressure.
yours

 

[itsmoked]

Or water jet.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[MikeHalloran]

Or a rotary shear. Sort of like a pipe cutter, but the wheel is inside out. No chips, no waste, very fast.



Mike Halloran
Pembroke Pines, FL, USA

 

[Abrabaracurxis]

Hello first of all thanks ,

Mike, well i don't have to homebrew it but some other guy in the team is looking what is in the market. So i am exploring the posibility of building it. The idea is to recicle some scrap that is produced along several stages of the process. We are looking also to get rid of the problem that causes the most scrap but we have right now lots of scrap that needs to be recovered. The scarp is steel conduit pipe, we are running some tests to know what kind of steel it is.
We have to come up with something that
1. is automatic,
2 real easy to handle,
3 with a 0.5 mm presison,
4 able to produce pieces anywhere between 5 cm and 1.5 m and of course at the lowest price.

I am going to feed it with scrap with lenghts ranging from around 10 cm up to 2 m.

the feeding, positioning and disposal mechanism are not a problem right now we got that under control. Also, the burr is not a problem because at 25mm from the ends the plastic is removed. Once the machine process a batch of scrap (the scrap is sorted before feeding it) an operator comes and picks it up and thats it.

Waross
Until now i had considered only the abrasive wheel solution. I think is the easyest. Thanks confirming i can cut more than one pipe. I'm thinking to use neumatic clamps to fixit and be able to cut. I'm trying to cut 2-3 pipes at once in 3 seconds and the whole operation take about 9 seconds. I can regulate of fast it aproach the pipes with no problem...

But still the only thing i need is a high horse power motor? like 1.5-2 HP? how many RPM do you recomend? (well i supose the RPM i will get them when i discover what kind of steel is)...does it have to be three phases or i can do it with one?

well this is our firs project has freelance and motors are not my strongest skill so thas is the only issue that worries me...

thanks for your help.

juan

 

[MikeHalloran]

Huh? Five millimeter o.d. x one millimeter wall thickness, steel conduit? Three millimeter i.d.? Coated with plastic? And you've got piles of long scrap pieces that you want to cut into shorter usable pieces? And just cutting them to length changes them from scrap to product? Why are they considered scrap now?

In the metal trades, 2HP is a very small motor.




Mike Halloran
Pembroke Pines, FL, USA

 

[itsmoked]

How can an abrasive wheel be worth the filth and the hassle of changing and paying for it regularly??

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Abrabaracurxis]

Mike,

Five millimeter o.d. x one millimeter wall thickness, steel conduit?
>>Yep

Three millimeter i.d.? Coated with plastic?
>>Two coats inner and outer

And you've got piles of long scrap pieces that you want to cut into shorter usable pieces? And just cutting them to length changes them from scrap to product? Why are they considered scrap now?
>> They call it scrap because they can't use it like it is right now.

In the metal trades, 2HP is a very small motor.
>> OK, i will be looking for something bigger, i think i need high torque, right? not just high spedd...

Itsmoked
How can an abrasive wheel be worth the filth and the hassle of changing and paying for it regularly??

>>well to be honest an abrasive wheel is what they use. Im considering now a circular saw.

thanks

juan

 

[Compositepro]

Work out a way to efficiently clamp large bundles together. You could cut several hundred pieces in one cut with a half horsepower bandsaw. We do this with 1/4" aluminum tubing and use stretch wrap to bundle the tubes. It is labor intensive for a short time.

 

[waross]

Hi markus506
Motors;
Induction motor speed is slightly lower than the syncronous speed. For an 1800 RPM synchronous speed the motor speed may be 1750, 1775, 1780, etc. depending on design. Theyb are often refered to by their synchronous speeds even though they only aproach but don't reach synchronous speed.
Most common is 1800 RPM. Next choice will be 3600 RPM.
There are no higher synchronous speeds at 60Hz.
There are 1200 RPM, and slower but they will not be appropriate. To heavy and too expensive for this application.
Single phase or three phase, depends on size and availability of three phase power. You can have almost any size motor in single or three phase. If the motor can be fed from a 15 or 20 amp circuit on an extension cord then single phase is probably cheapest. Above 1.5 or 2 horsepower the cost differential will be small. Above 5 horsepower three phase will probably be more economical.
BUT, it depends on your site conditions.
Three phase motors are a little more dependable than single phase motors, but on a cutoff saw, either one should last years.
Your people will be in a better position to estimate the cost of installing one versus the other. If the choice is close, go three phase.
respectfully

 

[Abrabaracurxis]

Hi waross,

thanks there are abailable single and three phase available so ill go three phase... in the other hand if i use a saw the RPM will be relationed with the number of blades in the disc right?

Compositepro
if you don't mind in the machine you have, what is the horsepower?

thanks

juan carlos

 

[waross]

Hi Abrabaracurxis;
That would be teeth in the disc or blade.
respectfully

 

[MikeHalloran]

A saw just makes bigger chips than an abrasive wheel. For your material, you need very fine tooth blades, and because it's steel, you can't run them very fast.

If the material is all the same diameter, and the coating is not real thick, a rotary shear could cut it clean, with no wasted stock, and no swarf or chips to get rid of.

At a slower pace, a close- fitting shear die could do the same, probably for less investment. Depending on how much out of roundness you can tolerate on the cut edge.



Mike Halloran
Pembroke Pines, FL, USA

 

[itsmoked]

Mike; I'm not picturing a rotary sheer at all.. Got a link to one?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

Probably something like this.
High speed tubing cutter

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[jraef]

Probably something like this.
High speed tubing cutter

or this
high speed tubing shear

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[itsmoked]

I seeeee. Thanks jraef.

Not at all what I was picturing from Mike's [blue]"Sort of like a pipe cutter, but the wheel is inside out"[/blue] description.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

Thanks jraef
respectfully

 

[MikeHalloran]

I was thinking of a machine that's even faster than what jraef showed you, but I couldn't find any pictures. Anyway, you get the idea that it's possible to cut a lot of tube without producing a lot of chips.





Mike Halloran
Pembroke Pines, FL, USA