Need expert guidance on rookie DIY build.

Hey guys, this is my first post so firstly I would like to say how happy I am at stumbling across such a well put together forum.

I am an absolute rookie in the field of cnc machining. However I have a big appetite for learning new things, so I will try doing as much of my own research as possible in between reading of your replies.

Basically I have a scenario where I would need to build my own cnc milling machine with selective requirements.

These are the requirements of the machined product:

- The slot will be 12mm diameter, with varying lengths.
- The material will be 5mm thick mild steel with a varying O.D. of 48mm to 114mm CHS.
- The length of material will be in the range of 1400mm to 3000mm.

The requirements of the machine so far will be:

- able to cut 5mm thick mild steel
- able to rotate along A axis of 0-359? degrees.
- able to work on material diameters of 48 OD chs to 114 OD chs
- able to work on material lengths of 1000mm to 3000mm.
- 3 axis (X,Z,A) (note: I will not need Y axis as I plan to keep the cutting tool centralised above the CHS at all times and let the X axis and rotational A axis do all the movement. the Z axis is simply for varying material diameters and for the cutting depth.)
- Would need to be cost effective.
- would need to be reliable. (the intention is to machine hundreds of these parts so reliability is a major factor)
- and finally, accuracy could be +/- 1mm.


I hope I have supplied enough information for the time being.

I look forward to, and appreciate any replies on this matter.

Many thanks in advance.

Steeki.

Interesting requirements. Any chance of explaining the purpose of these parts, especially given the low accuracy requirement.

Some clarifications please:
1. Is the slot axial or radial to the CHS, or continuous in both e.g a spiral?
2. You say the slot is 12mm dia. Do you really mean width? The sides of the slot are perpendicular and the slot is centred axially on the workpiece's rotational axis.
3. Is this a one or two man operation? 3m of 114 x 5mm CHS weighs 23kg and is bulky.
4. How close to the end of the material does the slot have to be machined?

Given the length of the parts I would consider buying an off-the-shelf mill with required rigidity and throat capacity then building a custom material transport. I'd envisage a series of v-rollered supports for the bulk of the workpiece, some form of hollow hydraulic chuck to clamp/rotate the workpiece, fixed to the table of the mill for fine X movement and a feeder mechanism to give the bulk/rapid X movement.

You would need something like this :



https://www.youtube.com/watch?v=JKHXxLvsAMA

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Originally Posted by irving2008

Interesting requirements. Any chance of explaining the purpose of these parts, especially given the low accuracy requirement.

Some clarifications please:
1. Is the slot axial or radial to the CHS, or continuous in both e.g a spiral?
2. You say the slot is 12mm dia. Do you really mean width? The sides of the slot are perpendicular and the slot is centred axially on the workpiece's rotational axis.
3. Is this a one or two man operation? 3m of 114 x 5mm CHS weighs 23kg and is bulky.
4. How close to the end of the material does the slot have to be machined?

Given the length of the parts I would consider buying an off-the-shelf mill with required rigidity and throat capacity then building a custom material transport. I'd envisage a series of v-rollered supports for the bulk of the workpiece, some form of hollow hydraulic chuck to clamp/rotate the workpiece, fixed to the table of the mill for fine X movement and a feeder mechanism to give the bulk/rapid X movement.

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Firstly, cheers for taking the time to reply mate. Appreciate it.

As for the product, it is something I prefer to keep as tight-lipped about as possible. But the slot will be of spiral shape (or helical?). It will cover no less than 90 degrees of the work piece and will be mirrored on the opposite side.

Yes apologies, width would be the right term. (I think I said diameter because currently I have to drill two 12mm holes and link them up by using a cutting disc.)

It is a one OR two man operation, of course depending on the size of the material needing slotted.

I have decided I will be using a 12mm slot drill so the start of the slot will always be 9mm away from the edge of the material, regardless of length or diameter. (15mm to the centre of the first cut)

I am on a really tight budget which is why I have listed my requirements to build a DIY machine solely for this purpose.

I am a fabricator by trade, so any structures would be easily rattled together. Its more the motors, electrics etc etc that pickle my head.

Steeki.

No problem, I like an intellectual challenge :)

How long are these slots? I just a little concerned how you'd move 3m of tubing under cutter and still have rigidity and repeatability since you can't necessarily take a 5mm deep cut, it'll need several passes.

Would a pipe threading machine convert ? extend stroke length, mount Z above, control rotation.

or this ?
http://www.jgsfab.com/tubepro.html

Do you want to cut thru slots in tube or pocket slots for say Key ways etc.? . . . . This will make a huge difference to how the machine needs building regards strength.
If just thru slots then plasma is the simple way just like the link eddy provided if it's the latter then something similiar would work but would need Major strength and clamping at the cutting head.

Quote:

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Originally Posted by silyavski

You would need something like this :

https://www.youtube.com/watch?v=JKHXxLvsAMA

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If I had the money, this would be my machine alright.

Quote:

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Originally Posted by irving2008

No problem, I like an intellectual challenge :)

How long are these slots? I just a little concerned how you'd move 3m of tubing under cutter and still have rigidity and repeatability since you can't necessarily take a 5mm deep cut, it'll need several passes.

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The slot will be a maximum of 300mm from the end of the tube and no more. so that is the basic cutting area.

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Originally Posted by EddyCurrent

Would a pipe threading machine convert ? extend stroke length, mount Z above, control rotation.

or this ?
http://www.jgsfab.com/tubepro.html

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Thats a brilliant job that. would be exactly what im looking for, minus the engraving tool. Although The chuck looks a bit small for my application.

On this note, what type of chuck is this? One with a through bore hole and clamps around the workpiece? This would be the first part of my jigsaw.

Quote:

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Originally Posted by JAZZCNC

Do you want to cut thru slots in tube or pocket slots for say Key ways etc.? . . . . This will make a huge difference to how the machine needs building regards strength.
If just thru slots then plasma is the simple way just like the link eddy provided if it's the latter then something similiar would work but would need Major strength and clamping at the cutting head.

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its thru slots mate. Ive decided to use a 12mm slot drill to mill these slots out. Im guessing here, but maybe it would be cheaper to put together than plasma? Also running cost maybe cheaper? All I need is my machine set to a constant speed and feed rate as the material will never change, nor will the thickness.


I will try and draw something up to explain it better. Im sure we could all understand a few drawings :smug:

http://www.mycncuk.com/attachment.ph...id=13602&stc=1

Apologies for the very basic drawing using MS Paint. But it should show what I have in mind regarding the machine, and what is required for the product.

Could I use the likes of a handheld mini drill as my cutting tool?

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Originally Posted by Steeki

Could I use the likes of a handheld mini drill as my cutting tool?

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5mm steel, 12mm slot drill!!! I don't think so. G.

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Originally Posted by GEOFFREY

5mm steel, 12mm slot drill!!! I don't think so. G.

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Right. Okay.

So what could I use?

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Originally Posted by Steeki

Could I use the likes of a handheld mini drill as my cutting tool?

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I wouldn't think so, also this needs thinking about more because it now seems overkill to build a 3 axis machine for such a simple operation.
It's made more difficult due to the pipe being steel, if it was wood for example I would make a larger tube to go over it, this larger tube would have the required slots already cut in it then I would use a router with a guide bush to follow the slots while cutting the workpiece tube inside, if you follow my drift.

Plasma is what you need. The forces to cut steel, even with Slot drill are much more than you probably realise if your suggesting to use Dremel type spindle.
The spindle will need to be slow spinning with plenty of torque. The Milling head will need to be very strong and clamp the pipe tight to handle the forces involved.

While Plasma cutter will cost more than spindle the cycle times for jobs will be much faster if you used plasma and the overall machine strength can be lot less as there are no cutting forces involved saving money on the build. These two things alone will outway the expense and pay back down the line.

No brainer to me Plasma is the way to do this.! . . . . . Just look around every machine doing this job uses Plasma or Laser.!!!

I agree with Jazz. With a slot drill you'll need a couple of fixed steadies either side of the cutter and you would have to traverse a 6m bed, to machine a 3m length, which would have to be extremely rigid over its full length.

With plasma the work holding is much simpler, the workpiece is static in X supported on some v-rollers which are easy to fabricate, the lightweight plasma head moves in X along a 3m rail, probably using rack and pinion drive, so relatively easy and cheap to build.

Righteo. Yous are the boys with the experience, so I will take heed.

So my machine will still need to be 3 axis, right?

I do recognise that practically every other pipe profiling machine out there uses a plasma or laser. But as I am a rookie in this field I was simply making an assumption based on.. well nothing really.

So plasma it is.

What is the cheapest plasma cutter available, capable of cutting 5mm mild steel?

Cheers,
Steeki.

Sorry for not being around guys, I've been doing some research and a lot of re-designing of my product.

After the advice obtained from this forum, I've concluded that plasma cutter is the way forward.

My new machine will be required to cut the same type of slot as above, but on a standard chs post size of 139.7 x 10mm @ 1810mm long. So therefore as my post will be the same length, and diameter, I'm really only looking at a 2-axis machine.

Whilst I have been redesigning my product, I have also been gathering together some spare parts to make an a-axis. - which is why I am back on here for some advice.

So far I have a 125mm self centring chuck (which just about grips my work on the inside), with a 32mm solid bar spindle welded out the back of it, at a length of 185mm.

I have two bearings with square housing which I will bolt to the opposite ends of a box section casing. (Each to the sides of 10mm plate, which is welded to the 120mm box section.)

The next part is where I need the help. I'm lead to believe I will need a Nema 23 stepper to rotate this chuck and work piece (post)?
The chuck and spindle weighs about 10kgs and the post weighs approx 58 kgs, although the majority of its weight will be supported using ball bearing rollers. Speed does not need to be fast.

As for the drive type, im not sure whether to go for a belt and pulley system or chain and sprocket?

Any help would be greatly appreciated.

Thanks again for your time guys.

Steeki.

Anyone? :concern:

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Originally Posted by Steeki

Anyone? :concern:

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So what do you want to know because you haven't exactly asked a question other than saying your not sure which linear system to use.?

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Originally Posted by JAZZCNC

So what do you want to know because you haven't exactly asked a question other than saying your not sure which linear system to use.?

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I would like to know if a Nema 23 stepper motor is the right choice for this application, and if so, how would I attach this to my 32mm diameter spindle? Also if I could get some advice on whether to turn this a-axis with belt and pulley system or chain and sprocket?

Cheers.