Printable View
Hi!
Im putting together my first 4-axis CNC. I was thinking of using a Gecko G540 kit but its quite expensive and i wonder if there are any other kits out there with a good price/performance ratio?
eBay is full of them but its hard to know which ones are good.
Anyone with a recommendation? The size of the mill is roughly about 1000x600 mm.
I live in Sweden so anything from UK or Germany would be nice...
Thanks
I don't think that any of the experts on this forum would want to specify hardware based on your specification! There are too many people who have bought the wrong items at the beginning of a project and created a lot of problems for themselves. Often, they have bought cheap kits from eBay/China, and suffer from poor performance or unreliability or both. Once you have finished your design to the point that you can safely specify the hardware, then a couple of good UK-based suppliers that I have used are Zapp Automation and CNC4You. They probably will not be as cheap as you might find via eBay for what sounds like similar kit, but they are good people to deal with and sell decent quality goods. There are others but I only have personal experience of these.
So, get a good understanding of what you are trying to do (what do you want to cut, home/industrial use, etc), get a design put together, and post on this forum for comments. You will get plenty of useful advice!
Neale is correct it's a little premature to be recommending or even thinking of buying anything yet if you haven't even designed the machine.
The Gecko G540 is a nice bit of kit but it does have some limitiations like restricted to 3.5a motors and still use all it's features, Plus restricted to less than 50Vdc for running motors.
Machine your size if robustly built will most likely be best run on nema23 motors which if sourced in Europe will most likely be 3Nm and 4.2 and for best performance you'll want to run them on 75-80V drives with 65-70Vdc PSU.
The G540 can run 4.2a motors but you loose the Idle current reduction feature which means the motors get hot when at stand still. Also your restricted to aprox 42-45Vdc to leave a safety margin for back EMF.
So my advice is to look at individual drives and don't buy anything yet. Save and wait until you need them then buy good quality Digital drives along with correctly sized PSU.
If you do want a decent all-in-one drive that's slightly higher spec than the Gecko then look at the Leadshine MX3660 which is only 3 axis but as 60Vdc digital drives along with inbuilt BOB and spindle control. http://www.zappautomation.co.uk/elec...ng-driver.html
Thankyou for your comments guys.
I have been thinking about this for a long time and i have a design. I fell pretty Confident about the design (mechanical engineer) but i do have to admit that im not that good with the Electronics part and i havent done my homework calculating how much torque i need and so on.
I was kind of hoping for some Quick advises and your comments above was very enlightning, especially the part about idle current reduction.
I was looking at zapps page and i would like to get my parts there but i got a bit confused and didnt know what products to choose.
The design looks like a machine thats called "high z 1000" if you want to check with Google.
Size would be about 1000x600 mm. The machine should be allround, Wood but also alu.
So, if you got the time i would gladly take some further recommendations. 4-axis, idle currrent reduction would be nice and so on.
Thanks
So are you saying you don't need or want input with the mechanical design, but you do need input for the electrical parts ?Quote:
Originally Posted by JW1977
Well sorry to say this but if your copying the Heiz high Z 1000 then you do need help.!! . . . It use's unsupported round rail and as got flimsy Z axis.Quote:
Originally Posted by JW1977
It may well look ok and scratch it's way thru aluminium but it's far from ideal and much better design could be made that isn't much more work.
Suggest you post your idea or drawing.!
It was a bad idea to bring up the High Z. Should have stuck with just saying 4-axis machine.
I can say this much that im going to use supported rails mounted on 2 pcs of alu extrusions. These two sides will be held together by two (dont know the English Word for it) but two end pieces, watercut alu... Theres much more, i will post something when ive got something solid.
I got this, im sure of it... If not, ill ask you guys... ;-)
EddyCurrent; Yes, i will gladly take some advise for the Electronics part. Thats why im here...
Regards electronics then really it boils down to one standard setup for this size machine to get best performance and it goes like this.
3Nm 4.2a 8 wire low inductance Nema23 motors wired in parallel.
75-80Vdc digital drives
65-70Vdc PSU
16mm 10mm pitch ballscrews on X & Y
16mm 5mm pitch on Z axis.
Good quality BOB
And if you want the very best performance and reliabilty then external motion control card to get away from parallel port.
Yes you can calculate the torque required and probably get away with lower NM motors and possibly use 50Vdc drives along with smaller PSU but the above setup won't cost much more and will be well on top of the workload giving maximum performance while at same time giving redundencey which prolongs life of components as they are not working near there limits all the time.
*JAZZCNC*
Brilliant answer! Now i got something to work with.
Im gonna check out the Zapp site to start with...
Thanks!
Hi there, fellow swede!
I agree with what jazz says, trust that guy.
I'd suggest getting the leadshine am882 drives. I recently finished my build (check my blog at tumblebeer.com) and I used a mix of dm542a cheap drives from an old build and the leadshines, and I can tell you to never ever use anything but digital drives. My leadshine motor spins happily and completely quiet at 3000rpm at only 36v, while the analog drives are resonating and screaming at barely 500 rpm.
As for motion control, I'm using a plcm-e4 from purelogic and I'm very very happy. No need for an external bob, it's packed with optocoupled inputs and mains relays.
Thanks for the vote of confidense.:thumsup:Quote:
Originally Posted by Tumblebeer
Think you've got to really experience the difference by using cheap drives to appreciate how much more performance good digital drives give. It's not just the speed it's the smoothness and motor heating, or lack of it.!
Combine this with decent motion control card and like you know it takes the machine to all new levels of performance.
Hi there! :peaceful:
Thank you for the input. Im still trying to figure out what procucts i should use.
The Gecko 540 solution felt like a pretty solid turn-key solution but of course limited compared to JAZZCNC´s setup above.
What do i need? I dont want to spend more more money than necessary right now but i dont want to spend it on junk either.
Tumblebeer, what did you start with?
The "what do i need" question was me thinking out loud btw :distracted:
I'll start with reiterating the same advice pretty much everyone that has built something gives others: Buying cheap stuff usually ends up costing more than buying more expensive stuff. I know, you've heard it before. Yet everyone, including me, think themselves above this one fundamental rule. I'm not. You're not. No one is.
I started buying http://www.ebay.com/itm/2-4-phase-Ne...item3f1fba0066 together with mid range inductance 3nm steppers. I used a 36V powersupply.
When I built a new machine, I added another stepper, for the dual x-axis setup. This time (putting the new stepper on the y-axis), I went for a http://www.cnc4you.co.uk/index.php?r...product_id=362 together with an am882 from aliexpress.
Right now, I'm about to throw the old drivers in the trash and get 3 more am882's. The difference is huge between them. I mean really huge.
I haven't tried the geckos, but from what I've heard people are quite pleased with them. However, I haven't heard of anyone driving a slightly binding, quite heavy carriage at 15000mm/min at only 36 volts. My leadshine driver can do that. Also, I've seen a version called am882h, that takes ac input. No idea if it's any good, but it should make the power supply slightly cheaper and simpler.
As for using a motion controller, I'd recommend getting one. It'll make everything so much easier. You get smoother and faster motors from the clean pulses, you can use a modern computer (even a laptop) to run the machine, you can use a 100m long ethernet cable instead of a 1.8m parallell cable. Less than an hour ago, I added a crosshair laser to my machine, took me 30 seconds to hook it up to one of the relays on my plcm-e4 and I could control it from mach3. Doing that from a printer port would require an expensive bob, and you'd still be limited in the amount of pins on your db25.
I realise I'm rambling a bit here, but perhaps I got my point across. Get a motion controller, get digital drives. If you want to go my route, I'd say buy
4x http://www.cnc4you.co.uk/index.php?r...product_id=362
4x http://www.aliexpress.com/item/FREES...820280286.html
(or http://www.aliexpress.com/item/FREE-...347654950.html)
1x plcm-e4 http://www.purelogic.ru/shop/elektro...i_ethernetusb/
and either build a toroidal linear psu (should be slightly better) or buy a 70-72vdc switched psu with some overhead (should be good enough, cheaper and easier).
Ok i can see your point.
About the plmc-e4. How much is it and where can i get one? Is it russian?
Im a bit afraid that ill get in the Electronics part over my head with a "russian" plc.
Im still a bit confused about BB, motion controllers and so on.
Is it right that the plmc-e4 is a more advanced bb and motion controller in one? Whats the difference if you compare that one with the G540 bb for instance? If you got the time i would appreciate the "CNC Electronics for dummies "version of it all. I got the driver and motor part thats no problem.
I just found the PLCM-E3 at Zapps site. Price was ok to. :smile:
Ok Well there's No such thing as Dummies around here just the Un-enlighted.!!. . . So lets start turning on the lights.!!Quote:
Originally Posted by JW1977
It all starts at the PC.? We need some way to communicate with the electrical components that make up the machine ie: Drives. The Machine Control software ie: Mach3, linux CnC etc all do the same thing in they convert G-code files into electrical output pulse signals. They also monitor incoming signals for things like Limit switches, E-stop etc. They also control External devices like Vacuum, coolant etc using general Outputs.
Now how these signals are produced and recieved can be done in a few ways. Most common is the Parallel port because it's free and part of most PC's.
Because the Drives are controlled with electrical pulses the quality and frequency of these pulses plays an important role in how the machine performs. If the pulse signals generated are poor quality then the drives don't ilke this and because the drives control the motors this passes down the line so poor performance.
Equaly the frequency of the signal plays a important role in the performance. The Frequency or number of pulses over certain time period dictates the overall speed that can be gained from the drives/motors for a certain amount of micro stepping set in the drives.
This all gets deep quickly so Without getting too deep now this all means that what ever produces the physical pulses has a big affect on the machine.
The parallel port is free but limited in both the quality and how many/fast the pulses can be produced over a certain time period or frequency. It's also limited in how many channels(axis) of signals it can output and recieve but will get to this later.
So the next step up is to use an external Motion control card that does the same Job but much better with dedicated circuitry to give much much higher frequencys and higher quality pulses. Often they also give more Channels of outputs and inputs known as I/O.
Now we need some easy way to connect or access these outputs and input signals and this is where the Breakout board comes into the eqation.
Most motion control cards only provide access to it's signals with a connection or multiple connections similair to the parallel port pins and this makes life very hard for connecting wires etc.
So here's where the BOB comes into play and makes wiring easy. They are essentially just distribution or I/O connection devices with some of the better ones providing features like protection for the PC with optoisolated connections and Charge pump in case PC connection is lost so it Stops any signals and the machine. They also provide other features like Spindle control and on-board relays to turn on/off external devices thru outputs.
Now while BOB's appear simple devices they are also very very important and THE largest source of trouble on any machine. Because they are an intermediate for all the signals then if the BOB is of poor quality it doesn't matter how clean or fast the signals recieved they will get distroted or lost before they reach the intended device so not something to skimp on which often happens.
Some motion control cards Like the PLCM-E4 (not the Plcm-e3 which is just a motion control card and needs a BOB) and the much much better CSlabs devices come with inbuilt BOB's. This takes one aspect or area for trouble out of the equation. Also to be considered is the Voltage that I/O can handle.? Better boards will let you use 24V logic which is much better for electrical noise immunity which doea plague some machines with cheaper BOB's which only allow 5v.
Now regards I/O then Motion control cards offer many more Inputs and outputs compared to the Parallel port. With the PP you only have so many inputs and outputs and by the time you have used up those needed for motors etc you'll be left with 5 inputs and 2 outputs.
This for some machines can be limiting and restrictive and if you need more then another parallel port and BOB are required.
Compared to Motion control cards that will offer 16 or 32 inputs along with 10-12 general outputs and 3-4 Analog input/outputs for controlling speed of external devices like VFD's or pumps etc.
So as you can see the concept is easy enough to grasp you have signals along with inputs and outputs which flow like below.
MOTOR OUTPUTS (MOVEMENT): = = CONTROL SOFTWARE - - MOTION CONTROL DEVICE- - DISTRIBUTION DEVICE - - DRIVES - - MOTORS
INPUT SIGNALS = = EXTERNAL SIGNAL(ie:E-STOP) - -DISTRIBUTION DEVICE(motion control)- - CONTROL SOFTWARE
GENERAL OUTPUTS= = CONTROL SOFTWARE (M) COMMAND- - DISTRIBUTION DEVICE(motion control)- - EXTERNAL SOURCE(ie: Vacuum)
That's about all there is too it.!! The tricky part is buying the kit which plays nice together and gives good performance. Unfortunatly the ones which play best often cost more. . .Lol
Allright, it feels like im getting closer. :welcoming:
After some research i found that the Aliexpress price for the AM882 drivers are really good. I think im gonna go with them...
Stepper motors are not hard to find. Maybe ill take Tumblebeers recommendation-link even there...
How much is the PLCM-E4 and where can i get one?
Are there any alternatives with a good price/performance ratio?
Btw, i really appreciate your help guys!
Yes slowly slowly it will start to sink in but can I just say it's not a good idea to buy the electronics first. Really they are the last thing you should be buying. Decided on what to buy now so you know dimensions etc but don't buy them as your just wasting warranty while they are sat on the bench. Build the frame first then and get rolling chassis then buy them electrics.Quote:
Originally Posted by JW1977
Those steppers Tumble linked to are fine but don't think all steppers are the same,.!! Even thou some will be same frame size or Nm rating there can be one important difference which plays a big part in performance.!! The Inductance rating.?Quote:
Originally Posted by JW1977
Cheap motors which you may find on Ebay etc can have very high inductance which affects the speed you'll get from them so check the spec before buying.
There quite few cheaper motion control cards but they tend to use the USB port which can have problems with noise and lost connections. They also tend to be built using cheaper components so not quite as reliable or stable. Ethernet is by far the better choice and gives best performance for not much more money really so I'd fully recommend you stay away from USB based cards.Quote:
Originally Posted by JW1977
I've used most Motion control cards and I can tell you the best by far is the Cslabs products but they do tend to cost more money, thou you get what you pay for.
That said the PLCM cards are OK thou I've not used the plcm-e4 yet only the E3 but suspect it's much the same just with built in I/O board(BOB).
Then there's the ESS Smooth stepper from Warp9 in the US. The ESS just pips the PLCM cards in terms of performance ESP when used with a quality BOB like the PMDX 126.
Again like Digital drives you do to some degree get what you pay for and with pulse and signal handling being very important to performance and reliabilty then IMO it's worth spending that bit more in this area.
Go with the CS labs unit! it has been pretty straight forward and i think a lot less to go wrong if its your first time. Im so glad i did as you can get some great support from people around these parts hay jazz ;)
Bad news is that if you want to use twin motors on X (or even if you want to allow for upgrading to two motors in the future), then as far as I can see you need the very expensive CS Labs board, the IP-S, not the IP-M. Have I understood this correctly? The ESS seems to be a reasonable choice - as long as you never need manufacturer support, and the PLCM kit is great if you read Russian! Not sure of the status of the E4, and the E3 needs a BOB, as does the ESS. This all makes choice of a driver trivial by comparison...
Yes your correct Neale. For slaved Axis you need the IP-S version which appears expensive but for what you get it's really not and it's truely amazing bit of kit for the money. Nothing comes close to what it offers or quality in this price bracket.Quote:
Originally Posted by Neale
That said Yes for General DIY it's on the expensive side and the others are more than good enough at this level.
The ESS is OK except Warp9 are rubbish with support.!! .. . Not a little rubbish but TOTAL CRAP.
Purelogic who make the PLCM are actually very good at support and will sort any issues you may have in very short period of time really.
This Software support shouldn't be trivilised or under valued really as these device all run off Plug-in software inside Mach3 and it's the quality of the plug-in that makes or breaks these devices. So if you have any troubles or conflicts then being able to get software support is priceless.
The CS labs software and support is excellent with very few bugs and if they are any or Mach3 changes breaking the plug-in which often happens, then they get resolved and dealt with very quickly. They will work one on one with you get conflicts resolved
Pure logic PLCM are ok but not the same quality plug-ins or support but still ok and will work with you.
Warp9 on the other hand won't lift a finger unless half the ESS users in the world jump up n down screaming and even then take 2yrs to do it.!!
The BOB is often the weak link used with most Motion controls and unless you use a decent BOB then really I don't see the point.! It's like having 1000HP engine running on knackerd tyres.! . . . Pointless if you can't get the power down.!!
Building the machine first and then complete it with the electronics is really the most logical way to go and i am gonna take the advice and do so also.
It was my original thought but i have been thinking of this for a long time and got a little carried away and just wanted to by everything that i need fast...
Its easy to get carried away if you want the best parts and start reading and learning. Ive learned a lot only from this thread and i thankyou for it.
For example, low inductance motors, Ethernet connected motion control board, digital high voltage drivers that must be working well with the data of the steppers and many other things...
Im still a bit confused about the motion control detail though. I can se why people like the Gecko G540 kit as it seems like an overall mid-level good compromise.
I know that what Im about to ask is a topic for a whole new thread but im in the market for a small lathe. Im gonna use it for the cnc build.
The budget is about 5-700 GBP and Im counting on some work and money above that to make it perform better. Ive been Reading about the Sieg C3 super, Warco and the Amadeal lathes. They seem pretty much the same but brushless motor and high weight is +....
Considering the above, which one? ��
Sorry for changing the subject back and fourth, its just me but a question regarding the Electronics came to mind...
In my world its easy just to overdimension for example the steppers and the motors so that they should be able to cope with whatever i through at it.
Someone once told me that it isnt so and that the best thing is if the performance of the machine is optimised to what you should use it for... Which is right?
The optimum range of anything is where it operates in the central linear region of it's performance graph. If you oversize then it's not working hard and is in the lower non linear region of the graph, if you undersize it will work at the upper non linear region of the graph.
Yes but a Porsche 991 works damn well to go shopping with. Question is, are there any disadvantages doing light work with a muscular cnc... Someone once told me so but i cant remember why...Quote:
Originally Posted by EddyCurrent
I can imagine that if things are oversized they will use more energy to overcome their own inertia and losses than the energy used for light cutting. If this is the case I would expect the machine to be, 'not in control'.
A bit like trying to using a 50kg computer mouse for fast game playing.
Adding larger motors can easily cause your machine to move slower, even though it may have twice the power at slower speeds.Quote:
In my world its easy just to overdimension for example the steppers and the motors so that they should be able to cope with whatever i through at it.
.........................................Question is, are there any disadvantages doing light work with a muscular cnc
Generally, the bigger the stepper, the slower it's capable of spinning.
Steppers are rated at their holding torque, when they are not spinning. The faster they spin, the less torque they have. With larger motors, the torque falls off more rapidly. If you gear them to spin slower, where they have more power, then you give up resolution.
I've seen cases where people have purchased large, inexpensive motors on Ebay. These motors are often too slow to get out of there own way. In most cases, these same people end up buying new, smaller motors. I've seen motors 1/4 the size make the machine 4-5x faster.
The best performing stepper motors will always be the smallest ones that meet your requirements. You should be choosing motors based on performance requirements.
Ok well first the G540 isn't a motion control card at all, it's just 4 drives combined with a BOB. The drives are limiting regards motor amps and while they are nicely made they can't match the AM882 in performance terms. I've used both and I wouldn't buy another that's all I'll say.!Quote:
Originally Posted by JW1977
For a family of one maybe but try taking 4 kids and all the baggage that goes with them.!! You need a Porsche Cayenne for lugging kids and baggage around.Quote:
Originally Posted by JW1977
Think of the CNC machine as either Porsche 991 when optimised giving great performance at what it does best but limiting at other things.! OR . . Cayenne is still a Porsche and supposedly performance vehicle which will get your there with all your baggage and kids safely but not very excititng and rubbish around the nurburgring.!!
The Cayenne is the one with the Big engine not the 991. It's oversized and under performs because it's optimised for ever lugging kids around. This comes at a cost in both performance and Expense.? Your paying for performance vehicle which fails to deliver.!
The tuned and optimised porsche 991 does ONE job well and thats going fast. It's limited at moving kids but was never designed for that purpose so wrong to expect it too.
Now this gets more complicated with CNC due to way steppers work. Large steppers bring an all new set of problems which to get performance from requires expensive drives and motors.
This is why it's best to target the machine use and design to that with a generous safety margin and nothing more. More is less really is true when it comes to steppers. Anything above the safety margin is just wasted money.!
Ok, i understand... Ive spent the last days designing the gantry and i will soon order the parts.
Thanks again for all the input. Ill be back 4 sure!
Btw and of topic.
I testdrove the new 991 Carrera S a couple of weeks ago. Bl... H... it was nice! :friendly_wink:
Hi jazz cnc
Have you used the mx3660 or the mx4660 in a build?
I am currently planning my mechmate build in the uk (and being electronic s shy,but willing to learn) I have been looking at these options.
Just interested I hear others experiences with them.
Thanks
Hi Macwood welcome to the forum, You do realise that this post is getting on to being 3 years old. But in the absence of Jazcnc I have used the mx3660 on a small mill and found it fine. It is a 3 axis driver but is only really suitable for powering the steppers up at about 50V.Quote:
Originally Posted by Macwood
How many motors will you be using on the the machine without the spindle? Also if you have not bought any motors or drives keep away from kits of parts as they are never matched.
I suggest you start a build log to keep all your questions in one place as that helps others when trying to answer.
Hi Clive
Thanks for your quick response on a Sunday!
Yes I realised it's an old thread ,but thought I'd ask.
I'll be running 4 motors, 1on the x, 2 on the y , and 1 on the z.
Would like the option to add rotary indexer later perhaps.
I have bought nothing yet, except steel for the table.
I will be starting a build log, more then likely on here and on the mechmate site also.
Best Mac
Quote:
Originally Posted by Macwood
And on vacation:stupid: Well if you are running 4 motors two slaved, then forget the mx3660. I hope you have done your homework re the Machine you are attempting to build. Have you had a read through some of the build logs on here? It would help if you said what size machine and what you want to be able to cut with it.
Have you decided on what software you will be using.
Ha! I’m on my holidays too.
Still doing my homework... been lurking in the back ground for some time now. Have decided that If I don’t start asking more questions I’ll never make a start on it.
I think I make a proper start and post in the introductions.
Enjoy your Vacation.