Thread: Chinese company... cnc parts

I think most people have gone with a known brand (Gecko) to drive their systems.
For $600 you seem to get a bit.

If your uncertain, google each part number and read the issues that people have come across.
I did just that and I noticed that the breakout board is 5V and i read someone running a new PC had issues because the serial port on new machines rund 3.3V (CMOS, not TTL)

Thanks Mike, I will do that.
I have looked at some Gecko drivers. The g540 only handles 4 motors and I need 5. Which Gecko driver/s would your recommend?

Good to see someone doing a hot wire machine.

I have quite a few designs i have drawn up over time and will be looking to settle on one after building a manual benchtop machine to figure out exactly what size i will need as dont need a really big one. I am hoping to run both a shaped wire with turntable and straight wire on the manual machine i designed, as it will be used to make both round and square molds for my decorative concrete mixes. So watching you build will be interesting to see the results.

Your frame looks quite nice, maybe post the link to the build details too. Motor size will depend on the final wight of the towers but couldn't see too much of an issue with the smaller motors if most of the weight of the towers is held by the linear rails and the bearings are smooth running as there are no huge forces acting upon it like a router would. You could even use a gearbox setup on the smaller motors as it would multiply the torque by the gearbox ratio. Nema 23 gearboxes can be found on ebay and other places quite cheap.

As for electronics, try to go for some geckos as stated above. Homann designs has some nice G540 kits with 4 nema 23 steppers which could work well for you depending on which way you go with the end design.

Will you be using AC or DC voltage to power the the nichrome wire? Multiple wire setup? What style linear rail? What is the intended final use of the machine....just signage or anything else?

Daniel

Not sure where your 5th stepper(Guessing Rotary?) is but just thinking if your not keen on the G540, you could go with G251 drivers for nema 23 steppers or G201/203 for nema 34 steppers with a decent breakout board and, depending on cash and needs, maybe a smoothstepper for extra I/O pins on a second port.

As twistedfuse said .

This will be my first CNC build and I am having fun already. I just finished drawing this diagram. The v-groove wheels (red) will ride on v-rails (black). The lower horizontal 80/20 extrusion (grey) will be easily adjustable so that the wheel/bearings can be tightened against the rails and adjusted for parallel. The towers I left transparent so you could see the basic arrangement of the parts. I weighed my tower parts on some digital scales and each tower extrusion weighs 16.2 lbs. The small stepper with pulley will weigh another 4 lbs, and each carriage with 4 wheels will weigh about 2 lbs. The aluminum linear rail will weigh about 3 lbs with the hardware. This machine will usually be used with a single wire so add another 2 lbs for the bracket and spring. However, sometimes, I may want to use multiple wires and for that I plan to attach a 1.5" x 1.5" "gantry" brace between the two towers. That piece weighs 9.2 lbs so each motor, working synchronously will be carrying half that. Each of the two aluminum multiple wire attachments will weigh about 4 lbs with the wires and a couple of extra v-bearing wheels.
That comes to about 27.2 lbs for each tower in single wire mode and about 35.8 lbs with the multiple wire attachments.

I foresee that the rails/wheels will roll very smoothly and the machine is going to be moving very slowly most of the time, except I may step it up a bit for jogging. So, do you think a 600 to 800in/oz motor with Gecko drivers will be enough to move the x axis? or overkill? These are the rails I will be using Open Rail - $250 "Kickstarter Pledge"

Oh yes, the fifth axis will be for a lathe/turntable because, In addition to sign work, I plan to build foam monuments and parts, finials etc. and architectural moldings and things like fluted columns.
Thanks for looking and for the help thus far! Here is my side view diagram...

CNC is definitely alot of fun but can soon become an obsession. lol.

Can you post one with the tower sides shown as well. My concern is due to the height of the tower, to ensure smooth travel, the bearings will need to be wider than shown but it depends on bracing. Stepper size will greatly depend on the smoothness of linear components and if you run reductions but wouldn't think you would need anything more than 600oz/in direct coupled and have a feeling, since your running them slowly, will be overkill. Rememeber, the weight of towers and cross truss etc will rest on the upper v-bearings, bottom ones are just alignment, and as long as everything is smooth, will be able to be glide along with small force. The motors really do surprise you in just how much of a punch they can pack. If your worried, just design the motor mount/brackets to be suitable for both nema 23 and 34 configurations, then start small and upgrade later.

Its good to see you have thought out the machine well. Having the extra options will definitely be worth it. Keep up the good work.

Daniel

Attachment 238413
Daniel,
The two wheels at top, would be 6" apart on center. The top wheels would be 12" on center from the lower ones. By loosening the bolts connecting the lower extrusion to the T-slots in the legs, the lower extrusion would be slid downward. pulling the top and bottom wheels snug against the rails, then adjusted for parallel. Any wear or play could be easily adjusted again at any time. I placed the wheels only 6" to give the x axis more travel because I wanted at least 9' if possible.. The only problem I see at this time would be from an event such as the hotwire hitting the foam. To couteract that possibility, I want to try installing limit switches on each side of and very close to the wire assembly so if like the power supply to the wire goes down and the wire hits the foam, it would immediately stop the motor/s. What do ya think?

hotwire woodworkforum3.JPG

It is a good idea of the bottom rail being the adjustable one for slack etc and it will work....however a couple things to take into account are:

How fiddly is this proceedure going to be. By adjusting the rails against fixed bearings, the rails will need to be mounted perfectly level end to end each time so contact pressure is applied along the length and surprisingly this can be a task and a half. I would personally look at possibly doing a few sketches to see if you can come up with a design where the lower bearings are adjusted and the rails are mounted permanately. This way it is a one time setup of the rails/frame, extra support along the length(see below)and the adjustment is in the towers which could be easier. I have seen v-wheels adjusted in many ways which may be useful for you. Simple ways are having the lower bearing bolts in adjustment slots, eccentric screws to having the lower set ride on a spring loaded plate.

Thinking about the design some more, also realise that as there are no centre leg(s) there is the possibility of sag across the rails which means the centre will be slightly different from the ends where it is connected to the legs. Although it might not seem like it, a foam block does have some weight and having no structural support towards the middle could see extra sag. This could cause unwanted noticable sag cuts during cutting and depending on your accuracy needs might not be acceptable. Consider adding an extra leg, possibly two, along the length of each side to counteract it. Also if you choose to fix both rails, add braces between the lower and upper rails too. The internal structure of the 80/20 help heaps but it will be worth doing some calculatioins to see what the sag is going to be with the max size block you expect to use. This sag could be negligable and might not affect your machine/cuts but just in case i thought i would mention it.

Eitehr way i am not saying your design will not work but just realise there are trade offs both ways and it is probably more time involved than you first thought to align it, however either way you go it will take time and it should not need to be adjusted regularly.

Daniel
P.S Are you going to add leveling feet to the leg extrusions for compensation in the floor space.

Thanks Daniel,
I plan to put bracing in the center, just not sure which way it will be attached yet. There will also be a brace attached between the two bottom extrusions traversing the full width of the machine. This will be to counteract the tension forces of the wire as it pulls the towers inward. This should prevent any lateral deflection of the two bottom extrusions. The braces you mentioned could be attached between these bottom braces and the bed extrusions of the machine. It just so happens that I have some of those adjustable leveling feet, which came with all of this load of second-hand parts, and had thought about putting those on the machine but wasn't sure if I would need them. I will do that..
Thanks again!
Wayne

Wayne,

That sounds great then. Look forward to seeing the updated piccys.

Curiosity get me.....Where do you come across a bunch of second hand 8020....cause i really need to come across some for a few up and coming projects or varying sizes.

Daniel

From a factory my bro-inlaw works at. They were throwing it out and just gave it to him and he was going to haul it off to sell for scrap. I bought it off him for $375. A once in a lifetime thing I guess. I had also worked at the same factory ,over 13 years ago, as a supply clerk. While I was there, we threw out thousands upon thousands worth of unwanted supplies, most of it textiles and printed paper goods I suppose but a huge pile of it was unwanted machinery, furnishings and hardware. When I first began working there, the mechanics were building a prototype CNC quilting machine. The thing was made of steel and very large. No telling how many thousands of dollars were spent on it. But they never got it to work right and ended up scrapping it too. I certainly hope I don't have the same misfortune with my little project.
Anyway, check with your local factories etc. You make come across a good find.

If you want to be able to adjust the lower bearings to set up the machine, you can mount them on eccentric spindles. An 8mm spindle can give about 2mm adjustment range by rotating the eccentric in the frame with an allen key, then locking it is place with a locknut. Alignment of the rail is still critical however.

Nice!!!! Doubt ill find that around here but you never know. I spoke to the local scrappers and they had my number but doubt they would actually call. If you get a second in a lifetime and have nothing to use it on just give me a call.....lol.

Out of curiosity though, have you already bought the v-rails and bearings?

Oh and never worry about not getting it running as i will be watching and pushing you along as well as many others here. If i dont reply for a while just pm to prod me along...lol... as i get slack sometimes.