New build – input/comments appreciated

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Originally Posted by Christian Knuell

Seeing it from this perspective you'd be right - but my personal opinion is that limit switches are not only unnecessary but even give a deceiving sense of security they cannot provide:

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I agree upto a point but here are some cases they are required. Servo's for instance will just take off at full speed if there positioning system fails or gets interupted. So in this case they are very much required.

Also with small fast router machines it's very easy to jog from one side to the other which can result in banging into end stops etc often. Esp when first learning. Again I agree a machine that breaks with just a small limit crash is Crap but enough of this banging and eventually damage will occur so best avoided and for just a few sheckels more is it really worth not having.??

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Originally Posted by Christian Knuell

What sometimes makes sense is reference switches to automatically home the machine. But even though they can make life a bit easier in some situations they are rarely necessary:

[LIST][*]Usually you clamp your workpiece just anywhere on your machine and need to touch it off anyways because your machine has no eyes.

• In this case knowing machine zero is absolutely pointless - it is just a set of numbers without any meaning for the actual machining process.
• Only in case of step losses it can safe you a little time to get back to the correct workpiece zero - if your workpiece isn't destroyed anyways which will most likely be the case... And a machine losing steps regularly enough to make you want homing switches is again just crap or badly set up ;-)
• But even in this case you can usually just touch off again (if the reference edges are still available)...

[*]Reference switches are only necessary if you have things like tool changers, tool length sensors or fixed clamping devices on your machine. [*]And: if the switch isn't precise (or a chip gets in between) machine home will also be imprecise accordingly. Many cheap homing switches are much worse than touching off the workpiece.

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This I mostly Disagree with.!!

Homing switches are THE most useful thing you can put on your machine. I'll give examples to why.

Only yesterday I was cutting parts in large expensive sheet of aluminium when the cutter broke. The part wasn't damaged but it was my last cutter so the Job was stopped. The corner of the material where I choose Work Zero had been cut away. So how without Home switches do I get back into absolute position when my reference point is gone.?
Yes I could go back into Cam and choose some hole to re-reference from etc but this all costs time and effort. Home switches provided resonable quality remove all this hassle.

Example #2 Same large piece of material and Large Job with multiple parts nested into material. So large I don't have time to do in one sitting. Again Zero ref has been cutaway. Home switches allow me to pause the Job or break the Job into smaller jobs and still quickly get back into position.

There are other examples like power cuts or PC crashes etc that back the need for Home swithces but again for the small cost it's silly not having them.
The only thing is that if you need high accurecy homing then you need Good Home Switches. I find even your Cheap Chinese Proximity switches are more than good enough for 99% of Routers or DIY'ers using Milling machines.

So for the Small cost and the fact Limits and Homes can share the same switch it's Stupid not to have them.!!

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Originally Posted by JAZZCNC

Every thing neil says is correct .

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Was me not Neil :rolleyes: but agree with you on use of the term 'absolute'.

I ran without homes and limits for several months, then added some switches (but never got round to wiring them up) and one day jogged into one and smashed it to pieces and banged into the end stop. Makes you realise how powerful these machines are and to keep your hands out of the way.

Just got round to adding limits and homes so should be OK now.

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Originally Posted by routercnc

Was me not Neil :rolleyes: but agree with you on use of the term 'absolute'.

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Doh I blame coolant fumes.!!

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Originally Posted by routercnc

I ran without homes and limits for several months, then added some switches (but never got round to wiring them up) and one day jogged into one and smashed it to pieces and banged into the end stop. Makes you realise how powerful these machines are and to keep your hands out of the way.

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Ye try snapping a 12mm Carbide cutter by hand.!! . . . Even a small machine will snap one like a carrot.!!

Thanks - lots of really useful info. I know a lot more about limit/home switches now.
So 3 switches it is. Based on the above, I cannot really see why you would want to use separate home switches - unless you want some very special home position?
And let us switch tune:playful:. I have updated my model with a single Nema 34 motor for the Y-axis and an adjustable mounting flange, as suggested by Silyavski. Is 20T pulleys/idler pulleys ok for this, or should you choose larger ones?
http://www.mycncuk.com/attachment.ph...id=16168&stc=1

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Originally Posted by ngundtoft

Is 20T pulleys/idler pulleys ok for this, or should you choose larger ones?

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Yes they will be fine arranged like this with nearly half the teeth engage. Don't want to go too large other wise the extra interia starts to affect things.

I have been thinking about how to design a holder so that you can route dove tails at the end of boards.
This is not a function I will be using every day, so it should be simple and it should not compromise the machine in other ways.
I read the thread by EddyCurrent and how he has done it. It looks good and stable and I am sure it works very well.
However, I don’t want this function to interfere with the precision of the bed, so I am not too happy with the removable plate. Also, for handling, I find it somewhat impractical to have this opening in the middle of the machine. All that is needed is a jig that will hold the work piece in an accurate and repeatable position. So I was thinking of placing it at the end of the machine, as shown in the model. You simply fasten the work piece with one or two clamps. I may have to extend the cantilevers/ rails to get sufficient overhang for the spindle or alternatively reduce the length of the frame, since this machine is already getting fairly large.
http://www.mycncuk.com/attachment.ph...id=16169&stc=1

I remember Jazz showing (it had a red frame I think) a design that did just this, it could take panels etc on the front to rout the ends. This is one thing that I'd on my list for mk2.......

Something like this works well for holding boards on end.

Slots with Pockets on backside.

Attachment 16170

Thanks JAZZ. This is actually a brilliant design. It is simple to make, it can be removed from the machine when you are not using it and the width it can accomodate is adjustable.

The only thing that may not be optimum is the thickness of the material you can clamp. I remember using this type of clamps (although much smaller) and the reach is not so big. I tried to find the reach for similar types. I only found this specification for a single one and it was 3". I am not sure if that means it will go from 0 to 3" or if it is just the maximum. Maybe you can use this type of lever clamp instead (although they are quite expensive):
http://www.mycncuk.com/attachment.ph...id=16171&stc=1

There are many ways to do this and many types of clamps to help but the simple and easy way's are often the most affective. In this case it would be a simple spreader bar which is bowed so when clamping wide boards pressure is applied in the centre.

I was only really offering simple example of how to do it but not really being specific regards clamping etc.

Excellent start !

One point.
A tiny nema 23 stepper, on my machine, moves my bed mill, effortlessly.
The bed is 1600 mm wide, 60 mm thick on ribs, tool steel.
Mass is 200 kg, with upto 200 kg of stuff on it.

The "right" way to do it is drive the moving bit at 1:3 with the stepper with HTD belts.

This provides better overhead, much better acceleration, better accuracy, and about the same speeds.

If nema 23 steppers dont work, get ac brushless servos, at 130€ each, or 290€ for servo motor, driver, cables, encoder, everything.
They cost == the same as 34 size steppers, and
-5x more accurate
-5x better acceleration (more than you need)
-3-5x top speed (too much. You wont want all the speed).

The top speed is not important,
the cutting speed is very important,
accuracy is vital,
and rigidity is everything.

Just my experience.
Modern brushless servo motors are
-not noisy, (IMPORTANT),
-dont backdrive and activate with back-emf (VERY IMPORTANT),
-wont take off if the cables get cut or disconnected,
-have anti-jitter circuits,
-can be used with differential connections (less sensitive to noise)
-have a disable-input on them.

Best,
hanermo

Building cnc stuff since 2002, mostly full-time.

Yes, and thanks for great input JAZZ, it is just me, whenever I am working with something I always start thinking if it can somehow be improved - even if it is great to begin with.
Actually, I think it will be very rare that I need to clamp very thick material, and if so I could clamp it to the frame with normal wooden clamps, or even make some kind of spreader bar as you suggest. So I will use the toggle clamps - and they are cheap too.
http://www.mycncuk.com/attachment.ph...id=16173&stc=1

Thank you hanermo.
I am really impressed to hear that a Neme 23 can move a 200kg gantry - even with some gearing. So my measly 60kg gantry should not be any problem?
I have not really considered servo motors because most DIY people seem to be using stepper motors, and it is my empression that servo motors are more complicated to use and much more expensive. Also, I think you can get a Nema 34 and driver cheaper than 290 Euro (cannot find that symbol).
I am convinced that brushless servo motors are excellent - maybe I should look more into that.

Euro symbol is along with dollar and pound, one more to the right.
€ alt-5 on most keyboards (.fi),
€ alt/4 on .en
alt-5 on .es

The nr1 imporant piece of gear is the motion controller.
The Pokeys for example, with hardware MPGs ! and thats crucial, move my machine with an MPG as well as a 100 grand Haas.

The MPG is wired directly into pokeys, no USB.
MPG wheels cost about 30€ each, and I put one on every axis of every machine.

Pokeys supports 3 at once with Mach3, and will likely support more (they sort of tole me they can).
CSLabs also told me that they can support dedicated MPGs.

Trust me, dedicated wheels like on a lathe, where the same MPG, in the same position, always moves the x axis, is the dogs danglers.
Just like manual, but clean, fast, 10x more accurate, perfectly repeatble.

Important point !
A usb MPG cannot be good as .. ! Because the USB has variable latencies (to 1 ssecond 100.000 less).

On a Pokeys, the engine runs at 125 kHz,
so every 0.01 ms, it checks if it needs to move an axis.

This makes it "feel" like its solidly connected to the machine.
Huge difference.

Ah - thanks for help with € - it is on the 5 key, but not marked.
Did not know that motion controller (MPG) is so important. Is it so much better to have separate ones for each axis? It seems that many of them can be used for all axes. What does "100 grand Haas" mean?.
I did look at the Pokeys Electronics (controller and BOB) - what is your impression with that?
With respect to servo motors - what specifications should you be looking for if you want to replace Nema 23 or 34?

MPG is nice but it's not required for general use and on a machine used mostly for wood ie: router then individual MPG's are wasted money to me. On lathe or Milling machien with lots of setting up etc then yes I'd probably consider them but not on wood router.! One is enough and then it's more of a luxury than needed.!

Same goes with servos for me with Small/Med router based machines like this. The price difference is 3 x that of Decent steppers. AM882 or Em806 Digital drives with 3-4Nm steppers will be less than £100 per axis and they easily push 60Kg around at 10,000mm/min or more with 10mm pitch screw which is plenty fast enough for any DIY machine.

The good part about dedicated MPGs is that they work like a manual machine.
Ie you are never switching on the pendant to a given MPG.

It makes the machine extremely productive for one-offs, for manual use, and for setups.
Most faster than any manual every made.

The 2 best controllers I know of are;
1. CSMIO. Very good, expensive full-on (1000€ and up, industrial).
2. Pokeys. Very good, cheap (150 € ish).

Both have excellent drivers, excellent support, and good features.
Use ethernet !

It may be instructive to note, I am not mentioning anything else, I have stopped using 3 other solutions.
The others that may be good are machmotion and something else, .. no personal experience.
Use ethernet !

Ethernet is galvanically isolated and has very low latency.

??
I found an Em808 at 115 €.
Add 130 for motor, 30 for proper cables and connectors, == 275 €.

With the servo at 290€, ..
Seems about the same price to me. And you need to make the fussy cables.
No ?

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Originally Posted by JAZZCNC

The price difference is 3 x that of Decent steppers. AM882 or Em806 Digital drives with 3-4Nm steppers will be less than £100 per axis ...

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The average cost of the Haas machines I worked with, and sold, were 73k€, approx 100.000 $ at the time.
100 grand.
Haas is a large, very succesful, builder of large industrial machine tools. Nr in the the USA, nr 1 by nr of machines, in the world.

Disclosure: I used to be their sales manager for Spain.

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Originally Posted by ngundtoft

What does "100 grand Haas" mean?.

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Hi Hanermo2. Thank you for your input, I will consider an MPG - it sounds like a nice feature. But you are way out my league. I am building this machine because I cannot afford to buy a similar machine (and because I think it is fun). Obviously for professionals and companies a difference of a few hundred € per axis is no big deal, but for for my little private project it makes a difference. Also buying one or three MPG's makes a difference.

A small update to the dovetail jig. Since you can easily remove the vertical braces, I figured that you could just clamp thicker things directly to the base plate with clamps - same system as used in the Festool worktable (you can use the same clamps). If you are normally routing items that are not so wide, you can also have one of the vertical braces fixed tightly as a fence to ensure that the work items are perpendicular to the bed.
http://www.mycncuk.com/attachment.ph...id=16174&stc=1

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Originally Posted by hanermo2

??
I found an Em808 at 115 €.
Add 130 for motor, 30 for proper cables and connectors, == 275 €.

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Hannu I didn't say EM808 I said EM806 and the AM882 which is pretty much the same drive can be bought for £50 add £25 for 3Nm nema 23 and that's well under £100. I fit these all the time to routers and they easily handle what is required for router machine this size.

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Originally Posted by ngundtoft

A small update to the dovetail jig. Since you can easily remove the vertical braces, I figured that you could just clamp thicker things directly to the base plate with clamps - same system as used in the Festool worktable (you can use the same clamps). If you are normally routing items that are not so wide, you can also have one of the vertical braces fixed tightly as a fence to ensure that the work items are perpendicular to the bed.

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If it was me I'd have a combination of 3 things.
#1 Clamps as shown.
#2 Matrix Grid of Threaded holes for clamping Odd shapes with mill type clamps.
#3 several larger holes for Festo type clamps for deep items.

Oh and I forgot to say I'd get lift those bottom rails up about 75-100mm to create short stumpy feet for levleing and lose 2 of the diagonals wich are not required. Less welding, less chance of heat distortion.

Yes, good idea JAZZ. Some holes with T-nuts would increase the possibilities for fastening things. I actually thought that I extended the legs under the lower frame, but apparently I didn't. Also eliminated the lower beam I inserted for mounting the dovetail jig. I removed 2 of the diagonals since they are not required.
http://www.mycncuk.com/attachment.ph...id=16175&stc=1

Yes, I agee on the costs.
Many of my choices would be different if I did not do things for commercial uses.
Haas has the lowest costs in the industry.

A servo amplifier (ie driver) (just electronics) costs 500€.
The same from yakawa or siemens costs 2500€.
The ones I use cost about 350 for the same size, circa 1kW.

Like I said, the MPG wheel is only 30 or 40.

If money was no object I would go for the servo motors.

Do you have a link to a good MPG for 30 or 40€? The ones I found were approx. twice that.

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Originally Posted by ngundtoft

Yes, good idea JAZZ. Some holes with T-nuts would increase the possibilities for fastening things.

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One of the things you'll probably use in vertical position is lower bracket or shelf like setup to help support and locate material when clamping. This makes repeat work like dovetails much easier and the Thread holes come in use full for things like this so I'd take them all the way to bottom.

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Originally Posted by ngundtoft

Do you have a link to a good MPG for 30 or 40€? The ones I found were approx. twice that.

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Depends if your just talking about the MPG pulse generator like hannu probably is or what people often mistakenly call MPG but should call Pendant with all the other controls on it.?

Here's 2 of the MPG pulse generators. 25 pulses per Rev and 100 P/R. 100 is most commonly used I think.!

http://www.aliexpress.com/store/prod...540014466.html

http://www.aliexpress.com/store/prod...506063450.html

Hi JAZZ - yes absolutely, some way of fitting an end stop is very practical. I also realised that the "overhang", or working distance from the face of the dovetail jig, is only 91mm. So maybe I should extend the Y-axis rails by 50mm or so.
Thanks for the links. If this is the type that hanermo2 uses, I guess that you will need 3 - or maybe the Pendant type is just as good?

It seems I am getting close to having a mechanical design that will fulfill my requirements. However, there is still one point on my list that I need to look into. I would like to have some kind of adjustable bed. I will mainly be working with wood, so I think an MDF plate will be sufficient for that, and also with wood the fairly long Z-axis will not be a problem. But for aluminium I think it will be good to lift the bed for better stability. This bed could be smaller and also have provision for clamping the work material.
Something like this:
http://www.mycncuk.com/attachment.ph...id=16184&stc=1http://www.mycncuk.com/attachment.ph...id=16185&stc=1
If anyone has come up with a mechanically good construction for raising/lowering the bed, I would love to have some info/links.

Right, ok, now I get it. I misunderstood.
Spot on.

I have a 10-pack of new 2M542 stepper drives, cost 45€ each. Very good drives, I removed the gecko (251) drives from service. Less noise, no back emf, differential (I used single-ended).

These pair well with the cheap 23 size steppers, and are, as you said, ok for lots of smaller machines.
Well under 100€, as you said.
For small machines with nema 23 motors, that type of stuff is good, and cheap.

Its only once you go to larger steppers and higher voltage/current drivers the cost goes up, and is then about the same as servos.

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Originally Posted by JAZZCNC

Hannu I didn't say EM808 I said EM806 and the AM882 which is pretty much the same drive can be bought for £50 add £25 for 3Nm nema 23 and that's well under £100. I fit these all the time to routers and they easily handle what is required for router machine this size.

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I have started looking at the electrical side of the project. I noticed that GTJim switched to the PMDX-126 BOB, and has a setup very similar to my own. Since the Pilz safety relay PNOZ X9 seems to be available from eBay for reasonable prices, and I do not have much experience with these relays, I have based my diagram on the very nice drawings that GTJim has made.
I have a few questions though:

• You can connect the stepper drivers to the BOB as open collector (common anode) or PNP (common cathode). Has anyone noticed any differences (with eg. noise) by using one or the other type?
• The stepper drivers have Enable signal terminals – which output terminals from PMDX-126 should you use?
• The stepper drivers also have alarm signal terminals – if you would like to use this function how should it be implemented? Should the relay cut power or activate the K pin (machine hold function) on the BOB?
• GTJim has implemented a limit override switch – what is the practical use for this?
• Can you use the K1 or K2 relay (in PMDX-126 for controlling a vacuum cleaner?
• I also noticed that GTJIm uses a separate time delay relay for the power supply (1 to 10s). But this is not really required. I noticed that the Pilz safety relay has an on-delay of approx. 150ms (PNOZ 10) which is perfect for this use. 1 to 10 s is way too long time and only results in heating up the resistor. I could not find a data sheet/wiring diagram for Pilz PNOZ X9. Does anyone have a link for this?
• I am not sure if I should use single or 3-phase connection to spindle motor. 3-phase operation can be implemented by using a contactor controlled from the Pilz safety relay.
• Mains power indicator – since the other power supplies have indicators I think that this one is not really required

#1 No difference really take you pick.!
#2 Any spare output you want to use. Then set Mach3 Enable output to that pin number.
#3 Use the Fault Input.
#4 Because when you trip a limit then you need to temp override that limit to drive off the switch.
#5 Yes
#6 Google is your friend try this.! http://www.is-com.ru/files/PNOZ_X9_en.pdf
#7 Can only use three phase if it's a Three phase Input which it won't be unless you asked for 3 phase input VFD. If single phase Just use R & S or R & T both work.
#8 This so you can see it's powered up on the outside of the control box. Personal choice but I prefer to see if box is powered so it doesn't get left on.

Great - thanks a lot JAZZ. I have made changes according to your input.
1. Will keep as is.
6. Google must be a better friend of yours than mine :encouragement: - I could not find it, so thank you for the link.
7. From the datasheet for the Huanyang HY02D2223B it looks like it can be used both for connection to single phase and 3-phase.
8. Yes, I was not so clear here. I intend to put the LEDs for the three power supplies on the front of the control box and I think that would really be sufficient