[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]

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]

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]

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]

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]

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]

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.

[Hamzter]

I've started blocking out the design now, and I've realised I have no way of adjusting the skate bearings. I'm going with a design very similar to this design, the only easy way of adjusting em is to shim the joints until all the play is removed. Any other suggestions?

[Hamzter]

Well I dumped the idea of having aluminium angle on the base, since I have no way of adjusting the play or making an accurate chamfer on the base for it to sit, instead I've replaced it with a pipe like in the JGRO design. In fact this thing now looks extremely similar to the JGRO, except in metric I've just got a couple of questions...

- What's the best way of attaching the components together? I was originally going to use cross dowels to screw the major joints together, but these might be a bit overkill, and I'm having trouble getting hold of some anyway. Are wood screws good enough?
- Some of the bases I've seen seem overkill in terms of support, mine's very minimalist at the moment, do you think it's strong enough?

I've already started cutting some MDF for the major components that won't change dimension, couldn't wait to get started Still tweaking bits, any crits are most welcome

[Hamzter]

Base is pretty much complete now, so far made with only hand tools plus a drill. I went with 33mm diameter steel pipe, with a 3mm wall thickness, that stuff is hella hard to cut, took 10 minutes to do one cut with a hacksaw! Still need to buy:

- Stepper motors, drivers, breakout board, power supply - probably 1.86Nm or 3Nm
- Leadscrew - going with Tr12x3 thread
- Couplers - going with DumpsterCNCs direct thread couplers
- Leadscrew nuts - will be using hex or square nuts, possibly replacing them with anti backlash ones in the future
- Bearings - regular deep groove bearings, possibly taper or thrust bearings for the z axis
- Control PC - my laptop doesn't have a parallel port so I'll be needing a cheapo PC, might be able to make this from components i've got lying around.

Crits/tips are most welcome!

[BobF]

Wood screws will not hold very well in mdf. Use 1/4" nuts and bolts, or t-nuts where you can. Glue the parts that you don't need to disassemble for maintenance.
Here is some cross-dowel hardware.
http://www.leevalley.com/hardware/pa...75&cat=3,41306

[Hamzter]

Well I've ordered all the mechanical components now, just gotta get the electrical side, I'm thinking of going with the RoutoutCNC 2.5A driver kit, mainly because it's a damn sight cheaper than most! This limits me to wiring my steppers up in series (1.86Nm @ 2.0A), but I think I'll be able to live with it. Along with that I'll get a 24V PSU (drivers are rated at 30V), which comes to about £205 + p&p, which is a damn sight cheaper than the £350 I was originally thinking of. Will post some pics later

[Hamzter]

Got the steppers up and running now Discovered that my parallel cable was actually only a parallel connector on one end and a funny, slightly larger connector on the other, so i ended up chopping the cable and wiring it directly to the drivers, took forever to identify all the wires with a multimeter tho! Sore fingers now from stripping all that wire...

Anyhow I've had a play with the motor tuning in Mach3, they seem to stall out at about 300rpm, they still seem to have torque at this speed so is it resonance that's preventing them going faster? I've not got anything attached to the motors yet, with a bit more inertia do you think they might go faster?

[Hamzter]

Time for an update, I've finished the gantry, so far I've made it entirely with hand tools apart from a drill. Unfortunately that limits my accuracy in places, and that means the bearings aren't perfectly aligned, I've had to shim them by running insulation tape around them until they run against the steel bars. Couplers should be arriving tomorrow so I can at last try some movement with Mach3!

[Hamzter]

Finished! Sort of :P Still got a few bits to do, but all 3 axes are working now. Probably took 40-50 hours to build, using only hand tools + a power drill, for those interested, here's what I bought and where I got em from:

3m 12x3 Trapezoidal Threaded Bar - Linear Motion
3x 12x3 Trapezoidal Square Nuts - Linear Motion
6x 12x3 Trapezoidal Hex Nuts (these were to clamp the bearings in place) - Linear Motion
30x Bearings - RS Components
4m 1 1/4" Steel Bar (for the bearings to run on) - eBay
1m 1" x 1/8" Aluminium Angle - eBay
4x MDF board - B&Q
3x Trapezoidal Couplers - DumpsterCNC
1x 320W Power Supply - eBay
3 x 1.86Nm Stepper Motors - Zapp Automation
3 x 2.5A Stepper Drivers (note this is only powerful enough for series connection) - Routout CNC
1 x Breakout Board - Routout CNC

I've still got to make adjustments to remove a bit of play, make a router attachment, build an electronics enclosure, add limit switches and a E stop button, so it'll keep me busy for a couple of weeks yet. For now I've just got a pen taped to it, which flexes a bit but is still pretty accurate More pics when I've got a router!