New Build Have Some Questions

[aussiecncer]

Hi all,

Ive been looking at the forum for god knows how long now and am really keen on build a plasma table. There are so many great builds on this forum. Low budget/High budget its really amazing what you guys can deliver.

I'm waiting on the sale of my other project which will fund this one. There is a pic below of it. This is what the table will be basically made to do and cut out parts for my buggy projects.

I have lots of questions so please any help would be greatly appreciated.

So for basics I'll list my plan so far.

4' x 4' footprint

Hypertherm Pmax45
4 Axis 620oz Bladerunner dragon cut kit from CandCNC
Ali Gantry Extrusion 50/100.I drew up 50/50 but think i'll change it.
V rails T3 with matching bearings.
Touch n go type Z axis

Now I'm throwing up in the air what drive i want for the XYZ. I've been thinking about using timing belt. I would like to go with the rack but i am finding it hard to get someone to supply it in Aus at the price range i have. Some can supply but its not good quality stuff.

I seen on this forum but, can't seem to find it, one bloke has used timing belt ran it along the length of the table a had it drive from one end rather than the gantry. It look like it worked really well. I've put a picture of the basic mockup of the design.

It starts with a 4:1 ratio reduction that drives a 5mm pitch 50.90 PD Timing pulley. It runs the length of the table to an idler(i guess you can call it that) and back. The gantry has the belt clamped and rather the motor and gantry move its just the gantry. The final IPM that i calculated(if i'm correct) at 800rpm was 400ipm.

So here are some questions for you:

1) Can i get enough accuracy from this setup for making parts for my buggy projects like the rear housing?

Main thing is i'd like the holes to be able to line up exactly. Most of the material will be 6mm(1/4") Taper is not an issue as I will counter the taper with smaller hole dia and drill it to the right size.

2) Are the V-Rail up to the job?

I'm waiting on quotes for Hiwin rail but most of the stuff is in the normal accuracy range and the lowest pre load on the blocks so i'm worries about paying $$$ for lesser quality stuff.

3) What is a desired cutting speed?

I'm not going to run a production shop so travel speed isn't an issue. From what i think i've calculated i can reach 400ipm @ Max rpm(800).

Here are some pics that will help explain the pulley setup and also the possible rack and pinion setup.





Some of the stuff i'll be looking at cutting. This was Laser cut from the closest profile cutter 700km away. You can see why i want a CNC plasma







The buggy



Any help would be greatly appreciated

Matt.

[country kid]

g-day mate.... welcome to the club... i also planed on making an edge buggie and that's the precise reason im building one !!!! do you have an alias on the edge forum? um sounds like you have the right idea... im looking to make the same thing... try TEA transmissions they have an aussie office for R&P or ebay... i like your design it looks like you got the KISS concept prity down packed. you would be looking for 0.5-0.25mm accuracy?
hope it goes well mate i will keep a close eye on this one

[aussiecncer]

Yeah i think i've seen ya on the forum. matt(boily) is my alias.

I'm looking at using some of the edge design to do my own. Looking at more of a trophy truck setup with the swinging rear axel and sheet metal suspension arms.

I've tried TEA and there the ones i'm waiting on for a quote on Hiwin rails. There rack and pinion gear looks alright but they are non hardened rail. Just 1045. So I'm not sure if that would be suffice.

The other thing i like about the timing belt drive is the mounting. It doesn't require so much in regards to drilling, tapping, shimming. The stock TEA supply is undrilled and could be a mounting headache.

I'll be looking into this brecoflex timing belt. Apparently it doesn't stretch or at least its very minimal.

What have you looked at so far?

[country kid]

yer ok iv seen you kicking around on there.... im still looking and thinking.... the one issue i have with the belt is belt+heat? so i haven't explored belts with that said if some of the more experienced guys say its ok i might go with what you have below or similar. if found some good lengths of hardened Rack on eBay but no idea about postage.. um i was looking @ the integrated v-rail by PCB linear over in America but no idea about international postage again. im favoring the R&P, as for the v rails these guys could be an option:
http://http://www.smallparts.com.au/
they have dealers all over aust. its the dual v stuff you were looking @? theres a few build on hear that used it i believe.
i don't want to be intrusive but could you email me a copy of your drawings once your finished? just as a starting point since your ahead of me?

[aussiecncer]

The "small parts shop" is where I've been looking the most. They have some decent prices and they seem to have some good gear. The pulley stock is a good idea for making the idlers and such. The only thing is there rack is quiet expensive at about $300 for a 1500mm length no pre-drilled holes.

The turn around for parts is very long though I'm not too worried as I'm not at that stage yet.

I looked into PCBLinears intergrated rail and even though it would be great to get i think by the time you pay for it and get it here you might as well have gotten Hiwin or similar rail. I have found distributors of PCB stuff in Aus but only for their bearings. No rails.

Yeah is the DualVee stuff i'm looking at. I've really looked in depth about every way to get some sort of guide way for X/Y. Cold Rolled Steel, Tool steel stock(only have 1m lengths), DualVee, Linear rails(Hiwin) I just wish they would get back to me with prices. DualVee seems to be the the way to go for a low/medium budget which is what i'm after.

Once I finalize my drawings I'll send them on and you can see if it'll suit what you need.

[country kid]

hmmm iv looked @ these guys for rack http://http://stores.ebay.com.au/HUB...=p4634.c0.m322 dont know about freight im waiting for a reply...
well i think i will go with V-rail for the cost and being in austrlia we really dont have antoher option for the cost? would getting the steel shop to cut a spline in a pice of 40*40 solid stock be viable? then run a square bearing in that?
the hewin would be quite dear?
i was thinking of using the utili track made by the same company as dual vee for the y axis...
that would be really good thanks mate.

[aussiecncer]

I've looked at this guy as well. DamenCNC - Mechanical Parts

I contacted him in regards to what type of Hiwin rail he supplies. The rails is that of the normal type(basically the lowest tolerances) but his prices are hard to beat with our $ trading so well. I still need to look into it and ask around a bit more about the rail but it could be good enough for what i need.

I think it ended up about $2k Aus inc freight for absolutely you would need for:

25m Rails
Z axis
Rack/Pinion

Which isn't bad. I figure if i can get away with $500-$600 each ZXY it would be worth it.

The only thing is the accuracy of the rails. That is the deciding point.

[Arthurmetal]

about timingbelt:
I used T5 (10 mm wide) timingbelt on my 4x8"table. Particularly on the x-axis, which has about 10" of belt there is some stretch. This limits my max. speed to 2200 mm/min. On full speed right angle turns I can see the vibration in the cutting path.
My choice for this timing belt was a low budget entry into cnc plasma cutting, but the first thing to be replaced by rack and pinion. I would either recommend r&p or else a wider and stronger belt.
regards, Arthur

[aussiecncer]

Thanks Arthurmetal,

I was lookign at using 15-20mm belt for the drive. I'm still looking at R&P. I think that my latest find will help relieve some of my funds and i'll be lookng into R&P.

I have a 96mm x 2600mm x 23mm thick gullotine blade from work that is not used as it was the wrong hole centres. They aren't using it and has been hanging around for a few years. Tolerance are good with in 0.01mm and the blade is hardened as you could imagine so i'm using it for my long travel.

I'm very pleased as this will help steer me in the right direction. Just need to clean the rust off it. Luckily it was put in the warehouse. Most of the rust is from moisture and dirt.

Cheers