Hamzters newbie build

[Hamzter]

Hey,

I've been lurking on CNCZone for some time, and finally decided to take the plunge and build a CNC Router. I'm at a very early stage at the moment, just looking for the major components and I could do with a little advice from the experts!

Motors/Drivers/Power Supply - I've come across various sites selling the necessary components here in the UK, but they generally seem much more expensive than their US counterparts, am I just looking in the wrong place? The cheapest 'kit' I've found is £350 here, which is pretty steep, could anyone recommend any cheaper alternatives?

Leadscrews - I've found Trapezoid (pretty much the same as Acme) leadscrew on ebay, along with suitable nuts, I don't have any equipment to cut down the ends to fit in the bearings and couplers, alot of people seem to gloss over this subject on their builds, if I can't get the parts in this condition are their any other alternatives?

Apart from those I can't see any major hurdles, it's going to be a fairly modest sized machine due to space constraints, typical MDF construction with roller skate bearings. Looking forward to doing some building, itching to get started, thanks for any help

[CarveOne]

Originally Posted by Hamzter Hey, I've been lurking on CNCZone for some time, and finally decided to take the plunge and build a CNC Router. I'm at a very early stage at the moment, just looking for the major components and I could do with a little advice from the experts! Motors/Drivers/Power Supply - I've come across various sites selling the necessary components here in the UK, but they generally seem much more expensive than their US counterparts, am I just looking in the wrong place? The cheapest 'kit' I've found is £350 here, which is pretty steep, could anyone recommend any cheaper alternatives? Leadscrews - I've found Trapezoid (pretty much the same as Acme) leadscrew on ebay, along with suitable nuts, I don't have any equipment to cut down the ends to fit in the bearings and couplers, alot of people seem to gloss over this subject on their builds, if I can't get the parts in this condition are their any other alternatives? Apart from those I can't see any major hurdles, it's going to be a fairly modest sized machine due to space constraints, typical MDF construction with roller skate bearings. Looking forward to doing some building, itching to get started, thanks for any help

The only alternatives to turning down the lead screws to fit the stepper motor shaft is to use a coupler that slips over the lead screw on one end and has a hole on the other end to fit the motor shaft. These will have set screws to lock the adapter to the lead screw and motor shaft. These can be purchased or be made by a local machinist. They can be made of Delrin plastic or some suitable metal on a metal lathe.

For lead screws, just cut them to length with a hacksaw or chop saw, grind the ends square, and slightly bevel the edges so that the lead nuts will start on the lead screws more easily. Buy bearings with an inner diameter the same as the outer diameter of the lead screws. Buy shaft collars with set screws and use one on each side of the bearing. The set screws will be tightened against the lead screw to prevent lengthwise movement of the lead screws in either direction. You may want to put thrust washers between the collar and the bearing (each side of the bearing). DumpsterCNC.com (USA) makes the Delrin type of adapter/coupler. Delrin has enough flex to allow for very minor misalignments.

CarveOne

[ger21]

Originally Posted by Hamzter Leadscrews - ............. I don't have any equipment to cut down the ends to fit in the bearings and couplers,

Do you have a router?
http://www.cnczone.com/forums/showpo...5&postcount=83

[Hamzter]

Originally Posted by CarveOne The only alternatives to turning down the lead screws to fit the stepper motor shaft is to use a coupler that slips over the lead screw on one end and has a hole on the other end to fit the motor shaft. These will have set screws to lock the adapter to the lead screw and motor shaft. These can be purchased or be made by a local machinist. They can be made of Delrin plastic or some suitable metal on a metal lathe.

You mean attach the coupler directly onto the thread? I considered that but it could potentially slip, has anyone tried this?

[ger21]

http://www.dumpstercnc.com/acme_couplers.html

[CarveOne]

Originally Posted by Hamzter You mean attach the coupler directly onto the thread? I considered that but it could potentially slip, has anyone tried this?

I used the Dumpster 1/2-10 single start ACME to 1/4" shaft couplers on my first machine, a modified Solsylva 25x37. Their ACME couplers have threaded brass inserts instead of just threaded holes in Delrin. They clamp onto the ACME threads quite tightly.

For my second build with 1/2-10 5 start lead screws I machined my own adapters to fit over the ACME threads, provide a shoulder for one side of a 1/2" ID bearing, and reduces to 1/4" shaft so that I can use a 1/4" to 1/4" coupler. The adapters have a machined collar and set screws for the other side of the bearing. The adapter is a snug fit to the ACME screw and a roll pin is inserted through the adapter and lead screw. I could have used something simpler and off-the-shelf from DumpsterCNC instead. I have their 5 start couplers on hand and will use them on a future project.

CarveOne

[Hamzter]

Ah those DumpsterCNC couplings look great, they even have decent shipping prices for here Think that should sort me for the leadscrew, how about the motors? Any recommendations? I'd rather not go with a kit that requires a load of soldering, I've not done any in 5 years and I was rubbish at it then!

[CarveOne]

Originally Posted by Hamzter Ah those DumpsterCNC couplings look great, they even have decent shipping prices for here Think that should sort me for the leadscrew, how about the motors? Any recommendations? I'd rather not go with a kit that requires a load of soldering, I've not done any in 5 years and I was rubbish at it then!

There are lots of choices for motors. You'll need to figure out the motor torque for the size machine you want to build.

The best deal on stepper drivers as far as cost versus performance is concerned is the Gecko G540 http://www.geckodrive.com

CarveOne

[Hamzter]

OK, thought I better start doing some calcs, I might need a reality check on some of these, I have no idea what is achievable...

X Travel - 100cm
Y Travel - 60cm
Z Travel - 40cm
Cutting tool - 1/2" or 1/4" Router
Construction Material - MDF

Maximum Feedrate - 120 IPM / 3 meters per Minute @ 1000 rpm (this seems to be the maximum speed, but I'd be suprised if I got half that with the lack of torque)
Required Pitch - 3mm
This nicely fits with a Tr12x3 trapezoidal thread

Estimated Z mass - 10kg
Estimated Gantry mass - 20kg
Torque required to hold Z axis - 0.05Nm

Stepper resolution (full step) - 200/rev
Linear resolution (full step) - 0.015mm


Even at full step, this machines resolution would be more than enough, so I'll probably eventually gear this down, but at least initally I think I'm going to keep it simple (and slow) and drive the lead screws directly. I'm not sure about required torque though, anyone have any guidance? I'm thinking of getting some 1.86Nm (260 oz-in) motors, any thoughts?

[CarveOne]

Typical machines of this size use 260 to 305 oz-in steppers and do just fine with them.

CarveOne

[Hamzter]

Looking around I think £330 is about the going price for a full kit...

Steppers - £20 x 3
Drivers - £50 x 3
PSU - £50 x 2
Breakout - £20

There's two ways I can make this cheaper though, I've seen a board that combine the breakout board with 3 drivers, which would save about £60, but they're limited to about 2.5 amps per motor.

The other way is to get a single PSU, the motors I'm looking at have a maximum current of 4A (bipolar parallel) and I can get a 24V 14A supply for £55 that should work, would I find myself wanting a higher voltage supply though?

[Smiler]

Originally Posted by Hamzter Hey, Motors/Drivers/Power Supply - I've come across various sites selling the necessary components here in the UK, but they generally seem much more expensive than their US counterparts, am I just looking in the wrong place? The cheapest 'kit' I've found is £350 here, which is pretty steep, could anyone recommend any cheaper alternatives?

I have that kit and I have had absolutely no issues with it. Then again, when I bought it this time last year it was £235, shows how prices have rocketed. Still, at that price it is a very nice kit and those are 3Nm motors too, plenty powerful.

No soldering needed either

Jeff.