Let The Fun Begain, New build on the Table.

[Bush Flyer]

The next question That I have is about stepper motors and drivers. What is the advantages to having separate drivers for the stepper motors to having all drivers on one board?
I think I will buy the four separate drivers but wanted to check before sending a order.
Now I will buy nema23 motors but what holding torque should I buy 3.1Nm. or will 2.2Nm work just as well, with the RM1605 ball screws I have. Now I know That it would be better "faster" to drive it with belts and pulleys to change the ratio but at this time it will have to be direct drive. I can change it at a later date if I don't like it.
I will be cutting Balsa and ply 98% of the time but I will require the CNC to cut 3mm aluminium and some hard wood now and again.
I have been reading builds on the forum but it seems that most talk about speed but why? I would be happy as long as it does a good accurate job, if it takes a bit longer to cut I don't mind.

[Jonathan]

I have been reading builds on the forum but it seems that most talk about speed but why? I would be happy as long as it does a good accurate job, if it takes a bit longer to cut I don't mind.

For every material there is an optimal speed (feedrate) at which to cut it and a minimum speed. Optimal is hard to define - it could mean the speed which obtains the best tool life, the highest material removal rate or numerous other factors. The reason we're concerned with maximising the feedrate is if it is too low, you wont be able to cut some materials. Again, weather you can or cannot cut a material with a particular machine is hard to define - for example you could cut aluminium really slowly with a file, but that doesn't really count. For example, since plastics exhibit poor thermal conductivity, they need to be cut with a (relatively) high chipload, to reduce the heat generated by the cutting. Since the spindles we use generally operate best at high speed, this necessitates using a high feedrate to cut plastics otherwise at best the tool life will be poor and at worst it simply wont work. There are ways round this (e.g. using tools with less flutes, use a different lower speed spindl), but in general it's a much better option to choose a drive system which will meet the requirements you expect from these materials.
Even if you don't end up needing the high speed available, the fact the machine is capable of it is advantageous since the machine will be more reliable at lower speeds - e.g you can pretty much guarantee if you've chosen motors/drivers which will move the machine at 10m/min they will never stall or have problems at 5m/min.

In princible there's nothing wrong with having several drivers integrated into one board, so long as they're reliable and suitably rated. The problem is in reality none of them will output enough current/voltage for what you need, so trying to get one to work will not be reliable. Just forget them and please don't post more pictures of TB6560 drivers ;)

You can try Irving's motor calculation spreadsheet (just search that on the forum) to work out which motors would be best. I'd advise using the common 3Nm motors with a 75V power supply. The difference in price between this and other options isn't that great, and it's the best performance you can get without spending a lot more money. I think CNC4You is currently the cheapest place to get the motors and eBay/aliexpress for the drivers.

[martin54]

Yes I though about buy a chop saw. But it would take money away from my CNC budget. I don't mind taking three days to cut a part of aluminium as I can only work for short periods anyway.

They are not that expensive & although it would have been another expense which might then mean the overal build took a bit longer it would have been a useful addition for cutting wood & aluminium to size prior to machining in the future. Why take 3 days to cut something when you can do it relatively quickly & then spend the rest of the time doing something else which is more productive.
Have you been to or do you go to your local Pain management centre? If you don't then it might well be something worth looking into. They will be able to help you in all sorts of ways, not with just being able to do a bit of work but pretty much every aspect of life.

[Bush Flyer]

Looking really good. Any estimations on how much you think this project will cost?

Just wondering.... Where did you source the aluminium extrusion from? Thanks

To get it up and running I hope it will not be more than £1500. I tried to work out what It would cost then added 22%, I cost the bolts at about £40 but it has cost £59 in bolts so you need to add about 22% to what you think it will cost I have done this with everything that I have made and it's stood me well. It will always end up at the higher price.

[Bush Flyer]

Well I now have Artcam express and Mach3 licence bought and its seems to be running well, The only concern is the stepper motors get hot after it has been running for 45 to 50 minutes is this normal the axis all run free so there is no binding in the bearings etc.

[Jonathan]

The only concern is the stepper motors get hot after it has been running for 45 to 50 minutes is this normal

Motor case temperature up to 80°C is considered acceptable.

[Bush Flyer]

That's Fine its below that I measured the two X axis motors at 71 degrees the Y axis was 68 degrees and the Z was not worth measuring, so all good will just test again after I have a long cutting job to do.
Thanks Mike.