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Danny
27-10-2011, 09:02 PM
Hi My names Danny i have some work background in using 2d cad cam ( lectra) top spin cutters for cutting fabric and some skills in solidworks. I have been interested in home building boats and have designed and built my own craft designing it in SW using sheet metal functions to create flattened patterns, i am currently making a 17 ft Thames skiff from plans purchased from Selway fisher. i am looking for a DIY solution for drawing 1:1 scaled lines directly onto 8x4 sheets of plywood .
Being a novice to cnc building i have a very simple an probably unrealistic idea of what is required:
i would like to build a vertical mounted (to save on space) x y plotter that's cheap and easy to build so i can jigsaw out patterns .
Is this possible ?
What should i buy?
Can i make this happen on a shoestring?

blackburn mark
28-10-2011, 12:14 PM
that sounds like a lot of work just to get markings for you to follow with a jigsaw..... it "MIGHT" be only a little bit more heart ache and pain to build a lightweight router to do the cutting for you that will at the very least be as acuraite as following lines with a saw... (a cnc router is really only a plotter with a bit of backbone)

if your only ever going to cut woods with a max thickness of say 2" it needent be a heavy monster of a machine and mounting it verticaly should still be an option.

plenty of people build usable cnc machines with less experience than it sounds like you have.... with a lots patience and the guys on this forum you should be able to get there

ps: we were or are all novices at building cnc's so dont be thinking your going to get a roasting for asking daft questions :smile:



Can i make this happen on a shoestring?

that really depends an what "you" mean by "shoesting"
http://www.ebay.co.uk/itm/CNC-Kit-3-Axis-Driver-1-86-Nm-NEMA-23-Motor-PSU-/180738281785?pt=UK_BOI_Industrial_Automation_Contr ol_ET&hash=item2a14d75139

180 driver steppers and power supply.... it wont be fast but it should get you there

http://www.ebay.co.uk/itm/3-linear-rails-SBR-set-4-ballscrews-4BK-BF-4-coupler-/250515980037?pt=LH_DefaultDomain_0&hash=item3a53ea7f05

this is a tipical kit from linearmotionbearings2008 on ebay.... there are other options but lots of us have splashed a little exta cash and bought from this guy (you need to do some research to find a price for the sizes that you are after) however, considering that you where happy to follow lines with a jigsaw you may be able to find a much cheaper option for screws and rails that would match your jigsaw skills for acuracy :)

now you need to have a look at frame options.... aluminium extrusion, easy to use and a bit pricy.... steel box section needs welding

do you have access to a lath and welder ?

do a bit of research and get some drawings up so we can pull them apart :smile: and you should soon start getting a feel for how much blood sweat time and cash its going to take :eek:

Jonathan
28-10-2011, 01:47 PM
if your only ever going to cut woods with a max thickness of say 2" it needent be a heavy monster

Unless you try cutting it in one pass :eek:

If you're only using it for plotting them a timing belt drive (instead of ballscrew) would be fine since the force on the pen is very small compared to cutting. With the stepper kit that Mark just linked to and belt drive it could still be fairly fast as the distance moved per revolution for a belt drive is high ... so the motors don't need to move at a high rpm to get a good feedrate. You just sacrifice resolution which isn't a big issue for a plotter.
I wouldn't advise those motor or that driver for an actual router though - you'll only get fed up with how slow it is and want to upgrade.

I was going to mount my machine on the ceiling originally (so at a funny angle) as that would take up less space and the swarf will just fall away and clear more easily.


now you need to have a look at frame options.... aluminium extrusion, easy to use and a bit pricey.... steel box section needs welding

Doesn't have to be welded, but that's the easiest option. A frame made from wood should be fine for a plotter. Can get away with one of the cheaper bearing options.

John S
28-10-2011, 02:39 PM
What about thinking outside the box ?
Print your drawings onto film then project them onto the 8 x 4 sheet then go over them with a felt tip, even if you do a series of dots you can later link these.

You will have to play about with the focal length but a simple test would be to project a 300 mm square and measure it.

Jonathan
28-10-2011, 02:43 PM
What about thinking outside the box ?
Print your drawings onto film then project them onto the 8 x 4 sheet then go over them with a felt tip, even if you do a series of dots you can later link these.

Surely the lens will distort the image? In theory you could compensate for that on the printout ...

blackburn mark
28-10-2011, 03:19 PM
Surely the lens will distort the image? In theory you could compensate for that on the printout ...

i did include the idea in my first post but scrubbed it because of this.... iv just had a quick google though and can only find refrence to the "key stone error" which can be dealt with by mouting the projector so it its projection is square (or use the onboard correcter that you find on most machines)
needs more google time :)

njhussey
28-10-2011, 03:27 PM
Or you could simply print the drawing as a tiled PDF and use spray mount to tack them to the wood...depends on how often you're going to be printing like this I guess!

JAZZCNC
28-10-2011, 07:19 PM
Is this possible ?
What should i buy?
Can i make this happen on a shoestring?

Nobody can truely answer this accurately without knowing the length of the shoe string.!! . . .If your thinking 300-400 then forget it it's NOT do-able and don't let anybody tell you it is because there just pissing up your back.!!. . . . but . . . If you set a sensible realistic Minimum budget of around 800 - 1000 drivers etc but NOT PC or software then yes it's easily do-able.

Like Jonathan says timing belt driven machine will work out the cheapist option to do what you need, but he's wrong(Sorry jonathan) about the resolution not being a problem with belts.! . . I've built a few belt driven machines to do similiar light weight jobs (cutting out Hypalon for RIBS) and without gear reduction the low resolution becomes a problem with tight radius and medium to intricate detail work.
The problem without reduction when cutting/drawing small Radius,circes etc or intricate detail the feeds needs to be low otherwise the corners get clipped and because of the high effective pitch using direct drive it makes the motors work in a low speed range they don't like. This cause's them to run rough also because of the Low resoulution the action is jerky.
The amount of reduction will depend on the diameter of pulleys used but from expeinece at least 3/1 is needed to be usable and keep the motors working in nice range they like.

Must say thou if your going to the trouble/expense of building a machine then it's a absolute no brainer to let the machine cut the plywood rather than draw it.? . . . Belt drive will easily be upto the job of cutting ply wood if a decent design and job is made of the build.

Danny
28-10-2011, 10:31 PM
Hey thanks for all the good feedback, my shoe string is around 500 quid at the moment ,

The reason for pen plotting is because the type of shapes i am interested in cutting are to be faired on the job (clinker boat planks).

Being able to draw on an 8x4 accurately has great DIY potential for allot of budding designers, you also have the option of plotting on paper laid onto the sheet, this then allows accurate patterns for cutting out all kinds of materials, im an upholsterer by trade and have sewn up anything from car headlinings to tents, boat hoods bla bla , i work in the furniture industry where allot of money is thrown at big cnc kit often burdened by service contracts and sytem updates, cat and mouse situations with sofware compatibly, Journeymen asking why they cannot just pick a hand tool up and crack on happens too. extraction of cad patterns and lines into the real world is more the issue for me, i can see low a cost cnc plotter going into all kinds of projects and small business solutions allowing the craftsman not be be burdened with the chance of
measurement mistakes.

Funny enough i have too considered image projection but came to the same conclusion about scaling and accuracy.

I have one last idea id like to put forward that may keep the cost down if only i knew how to achieve it , how about a small robot plotter that runs over the surface on a sheet , although you would have to lay you sheet down it would perhaps be compact and portable! so the sheet could be anywhere temporarily , onsite cnc plotting for builders shop fitters now there's an idea!
Printing out detailed lines onto floors..

Could i convert an old scanner to move and draw lines perhaps.

Thanks guys for all the advise, its good to purge the mind of mad ideas!

Jonathan
28-10-2011, 10:47 PM
Minimum budget of around 800 - 1000 drivers etc but NOT PC or software then yes it's easily do-able.

This is only 2D or 2.5D so the free version of Cambam should be fine. I used it a lot.


but he's wrong(Sorry jonathan) about the resolution not being a problem with belts.! ... the low resolution becomes a problem with tight radius and medium to intricate detail work

I meant not a problem with belts for a plotter, but if you've done a plotter and it's wasn't then fair enough. There was a plotter at school we dismantled that was belt driven without further reduction...and the rapid prototyper, laser cutter.
Hmm, a cheap low power laser to burn the outline into the wood would be a snazzy way to do it! Might be easier than finding a pen that'll work consistently?
Given these parts seem to be for a 17' boat/canoe (?) I doubt there's going to be many tight radii or engraving! But still there's no point theorising unless we actually know, and it's clearly better to do it as well as you can afford to start with.

JAZZCNC
28-10-2011, 11:51 PM
I meant not a problem with belts for a plotter, but if you've done a plotter and it's wasn't then fair enough. There was a plotter at school we dismantled that was belt driven without further reduction...and the rapid prototyper, laser cutter.


Yes on small printer type plotter this would probably be fine because of the small Diameter pulleys but on a machine this size the diameters get large so obviously the circumference does giving a very large pitch.!
Take for instance a 20T pulley which really for 8ft machine is about as small has you'd want to go then direct drive pitch is 97mm.:eek: . . . . It's bit like putting F1 engine in a dumper truck, it will carry what ever you want and go like fuck but the bastard won't stop or go round corners. :dance:

Danny
29-10-2011, 10:01 PM
So just to recap

Im building a wooden constructed belt driven plotter using these parts from:

http://www.ebay.co.uk/itm/CNC-Kit-3-...item2a14d75139

ive read some of the other posts and the talk is very technical is this kit above simple enough for a novice like myself, i have rebuilt engines but electrical jargon is scary to me ,but i can follow instructions well, should i bow out gracefully i wonder.

belts and pulleys what sizes would you recommend and were from.

free software from cambam ( can i just import dxfs and this software will control the pen as well as work out the tool paths?) obviously the pen will need to move in and out somehow Via the z control i presume.

do i need any other parts ? timber is not a problem the rest is.. has anyone got pictures i can take inspiration from i have some ideas but sure they will be way off what's really needed , if i new what to import from 3d content central into solidworks
i could assemble a plotter for you guys to giggle at !

wiatroda
29-10-2011, 11:18 PM
Totally agree with JAZZ .
If that's going to be pen only there is no point to mess with ballnuts and screws. Belt is defenetly a way to go. I wouldn't drive it directly but made some reduction, but of course direct drive will work as well.
eg belt 3M pitch belt driven with 15 tooth pulley gives you 45 mm of axis movement per revolution of driving pulley. Reducing it further 5x gives you 9mm/rev. Driving it with stepper (after reduction) @1/2 step (400 steps/rev) gives you 0.0225mm resolution. I think its enough for your boat drawing or even for cutting
Driving it directly with 15 tooth pulley @1/2 step will give you 0.1125mm resolution
Just some example calculation -hope it helps

NB70
30-10-2011, 10:24 AM
Here's a simple and cheap large format plotter:


http://www.youtube.com/watch?v=LKrNT0V0KXI

Build instructions are here:

http://makezine.com/makeitlast/

http://blog.makezine.com/archive/2011/02/make-it-last-build-3-rigging-up-your-drawbot.html

blackburn mark
30-10-2011, 11:30 AM
ive read some of the other posts and the talk is very technical is this kit above simple enough for a novice like myself, i have rebuilt engines but electrical jargon is scary to me ,but i can follow instructions well, should i bow out gracefully i wonder.


hi Danny, the reason i bought this kit was because its cheap and like you im not to handy with the electrickery
i just followed the instuctions thay came with it and i was up and running, im not saying its simple but with those instructions and this forum you will get through it if your willing to stick at it and push on to the end :smile:

using timing belts is a winner of an idea to keep the price down
i get mine from here
http://www.beltingonline.com/polyurethane-timing-belts-182/synchroflex-4/synchroflex-t-series-73/?zenid=m9vl012e5ki95toch08jpn8j62



( can i just import dxfs and this software will control the pen as well as work out the tool paths?)

not quite... you will import your dxf and use this sofware to create a file (g-code) that will have your tool paths feed rates etc and insruct your machine via mach3 sofware

im gessing you will be able to twist somones arm where you work and get them to help you with g-code ????

if your willing to use AutoCad to do your drawings it may be worth reading robins thread and trying his RCAD
http://www.mycncuk.com/forums/showthread.php/3884-RCAD-by-me?p=25432#post25432

it may offer a simple alternative to G-code and is driven through a usb and might just be an absolute winner for avoiding the complexaties of CAD to CAM to Mach3

Jonathan
30-10-2011, 12:18 PM
You could try the method where the board is supported with it's longest edge on the floor and a cable, up to 8+4=12' long supported at the top corners with a motor and pulley. The pen is suspended in between, so the cable makes a V-shape. By adjusting the length of the cable by spinning each of the motors you can get the pen to move to any position within the board. It's simple trigonometry to work out the relationship between pen position and motors. Then you enter those formula's into mach3 and it will run it as normal...
A standard belt driver plotter will probably be better, but since you're going to have to buy steppers and drivers for either you could try this initially as you only need a piece of string and a pen...

Edit: Wrote this post 2 days ago but forgot to press send!

John S
30-10-2011, 12:31 PM
Interesting link on the belting Mark.

Pulley pricing between T5 and HTD5 is pretty even but 6 metres of HTD belting is 94 against 45 for the T5

Something to bear in mind when pricing a job up

[edit] but HTD is cheaper all round when using stock belts, it's just the open length thats cheaper in T5

Jonathan
30-10-2011, 12:43 PM
Pulley pricing between T5 and HTD5 is pretty even

I guess that's because there's a similar amount of material and machining time involved in each. It's the same process just a different cutter? Edit: I suppose the same could be said for the belts!


but 6 metres of HTD belting is 94 against 45 for the T5

Shame we can't also make the belts.

Good link anyway ... still want to find somewhere which sells HTD belts with steel tension members.

http://www.bearingstation.co.uk/

Something to bear in mind when pricing a job up[/QUOTE]

wiatroda
30-10-2011, 01:24 PM
I have some surplus belt leftover from my belt driven CNC I made some time ago. Don't have too much pictures, in fact non, I think - they disappear in stomach of our samoyed puppy together with 2GB memory card.
3M 15mm wide and 5M 25mm wide-
ebay auction no 300608706166 and 300615411815
Pulleys and belts I buy from bearing boys (http://www.bearingboys.co.uk/) good price, selection and fast delivery

John S
30-10-2011, 01:53 PM
Good link anyway ... still want to find somewhere which sells HTD belts with steel tension members.

[/QUOTE]


The link posted by Wiatroda,

http://www.ebay.co.uk/itm/open-end-HTD-25mm-wide-5M-pitch-timing-belt-CNC-linear-motion-/300615411815

Is for steel reinforced.

JAZZCNC
30-10-2011, 04:41 PM
eg belt 3M pitch belt driven with 15 tooth pulley gives you 45 mm of axis movement per revolution of driving pulley.

My experience is 15T is too small for a machine this size.! Problem being the number of teeth in mesh is on the lower safe limit. It will work ok but the belt wears prematurely.
Obviously a plotter has very little work to do so the load is light meaning it won't be so much a problem but if it was to be used for cutting wood etc the force's will eventually tell there toll.
IMO for the sake of few more quid, and it literally will be 1 or 2 per pulley, and seen as gearing is required either way then it's just not worth not doing.!

Jonathan
30-10-2011, 04:41 PM
The link posted by Wiatroda,
Is for steel reinforced.

Sorry I meant standard 'circular' belts, not cut belt like that...


IMO for the sake of few more quid, and it literally will be 1 or 2 per pulley, and seen as gearing is required either way then it's just not worth not doing.!

Where do you get them for that price? Not worth making my own for that money.

m_c
30-10-2011, 09:52 PM
Sorry I meant standard 'circular' belts, not cut belt like that...

Dare I ask why you want steel?

Danny
31-10-2011, 11:21 AM
Thanks for all the tips guys i can see im not going to be short of advise and thats a good thing, my next step will to knock up a cad drawing for you guys to rip apart!

JAZZCNC
31-10-2011, 03:04 PM
Where do you get them for that price? Not worth making my own for that money.

Sorry Jonathan thats does read miss leading doesn't it.!. . . I meant 1 or 2 more.

Danny
05-11-2011, 03:45 PM
Hi there can you tell me if there is any issues with using fixed rack of teeth rather than belts , can you drive the stepper motors along a rack of fixed teeth ? just wondering if its cheaper im looking a allot of belt for an 8 x 4 could i half the amount needed by switching to a fixed rack set-up?

JAZZCNC
05-11-2011, 05:35 PM
Hi there can you tell me if there is any issues with using fixed rack of teeth rather than belts , can you drive the stepper motors along a rack of fixed teeth ? just wondering if its cheaper im looking a allot of belt for an 8 x 4 could i half the amount needed by switching to a fixed rack set-up?

Hi Danny,

What I think your referring to is (R&P)Rack & pinion.!
There are no issues as such and it's often the prefered setup for longer length machines due to technical issues like whip etc with using screws, also it's slightly cheaper.

If by halfing the amount you mean only using R&P on one side then NO Bad idea.!! . . With a machine of this width, even thou the load will be light, you will potentially suffer from racking which could cause sticking and inaccurecys. Driving from one side is bad and not recommended even for machine of this light duty. . . . Drive it from the centre and it will be ok.

That said R&P does come with it's own set of requirements.!!. . .It still needs gearing for resolution thou not quite so larger 2:1 - 3:1 max, larger motors are needed because it's quite inaffecient this also means larger more expensive drives which in turn require higher power supplies.
On a techinical side it's far less efficient than timing belts with much more backlash (Timing belts are very low to zero backlash) and it's noisy as hell.

IMO for your light weight machine needs you won't get better or cheaper than using timing belts. R&P will certainly be far more expensive and perform far worse on a techinical basis.

Don't know what machine design you have in mind regards belts but let me just point out you don't need looped belts.? . . . Just a single length fixed at each end and looped around 2 rollers and the drive pulley is all thats required up each side.

If you look around you tube you'll see what I mean something like this http://www.youtube.com/watch?v=VPlyTTFo6w0

m_c
05-11-2011, 05:54 PM
Jazz has covered the pros+cons of each pretty well.

Belts should work out far cheaper, and remember you can always buy a longer belt and cut it into two.
You also don't a wide belt given the relatively low forces needed.

For example, in the old HPC catalogue I've got here, they do upto 2500mm belts in HTD5, which could be cut to give you one side of the long axis, along with enough for the short axis, then you just need a shorter belt to cut open for the other side.

JAZZCNC
05-11-2011, 06:52 PM
For example, in the old HPC catalogue I've got here

If your buying from HPC then you have too much bloody money.:rofl:

Find a local bearing dealer they will more than likely have belt on the shelf and sell you the exact lengths you need. . . I find they like to dealing cash with things like belt n bearings as it's easily lost.:whistling:

m_c
05-11-2011, 07:35 PM
You got one of those bearing suppliers aswell? :heehee:

I know HPC isn't cheap, but their catalogue is a very handy reference to have. I've only ever bought one item from them, which nobody else could supply quickly, and they weren't that much more expensive than the other options.

Danny
06-11-2011, 09:36 AM
Ok im going to summarize the parts so far.


Im building a wooden constructed belt driven plotter using these parts from:

http://www.ebay.co.uk/itm/CNC-Kit-3-...item2a14d75139

i need to choose the correct belt size as in width i take it i can use smaller belt for
the shorter Y and wider for the longer x ...say 10mm / 25mm?
15 tooth pulleys ok?

Are these steppers man enough?

http://www.ebay.co.uk/itm/CNC-Kit-3-...item2a14d75139




3M pitch belt driven with 15 tooth pulley gives you 45 mm of axis movement per revolution of driving pulley. Reducing it further 5x gives you 9mm/rev. Driving it with stepper (after reduction) @1/2 step (400 steps/rev) gives you 0.0225mm resolution. I think its enough for your boat drawing or even for cutting
Driving it directly with 15 tooth pulley @1/2 step will give you 0.1125mm resolution

JAZZCNC
07-11-2011, 12:19 AM
Ok im going to summarize the parts so far.


Im building a wooden constructed belt driven plotter using these parts from:

http://www.ebay.co.uk/itm/CNC-Kit-3-...item2a14d75139

i need to choose the correct belt size as in width i take it i can use smaller belt for
the shorter Y and wider for the longer x ...say 10mm / 25mm?
15 tooth pulleys ok?

Are these steppers man enough?

http://www.ebay.co.uk/itm/CNC-Kit-3-...item2a14d75139

These links don't show up for me.?

Regards pulley size I really wouldn't use 15T see post #21 for reason why.! . . . Belts are great but there are some things that must be done correctly or premature belt wear leading to failure is very easy. . .These things are: 1: Correct belt width appropriate to load 2: Correct pully size regards Tooth engagemant 3: Alignment 4:Tension

Danny
07-11-2011, 11:19 AM
Thanks Jazz sorry for the dumb questions its getting a little clearer to me bit by bit, yep those Ebay links have gone now ill hunt down the Seller and try and find a new one, looking at the shaft coming off of these steppers there must be a way of connecting the pulleys?

JAZZCNC
07-11-2011, 03:37 PM
Thanks Jazz sorry for the dumb questions its getting a little clearer to me bit by bit

Don't worrie one bit about Asking Dumb Q's I for one fully encourage it and pritty much sure they'll have been asked before.!!


looking at the shaft coming off of these steppers there must be a way of connecting the pulleys?

When you buy pulleys most often they have just a pilot bore in the centre and come with a Boss on one side. This Boss is drilled & tapped, often in 2 places, then a grub screw inserted which clamps to the motor shaft which often have a flat on one side, if not it's a good idea to grind a small flat your self. The centre pilot bore is then machined to suit the motor shaft.

You have to be carefull regards motor shaft length and the thickness of the motor mounting plate.? If the plate is too thick you won't have enough shaft sticking out the other side.
Often with steppers you'll find the shaft is realtively short so doesn't allow the shaft to pass all the way thru the pulley.? one way to get round this is to either machine away the boss or turn round the opposite way then drill between the teeth for the grub screws. If done this way you must ensure the grub screw is below the surface and no sharp edges from drilling & tapping other wise it will damage the belt.

If Machining pulleys etc is a problem just ask.

These pics may help.?

Jonathan
08-11-2011, 12:05 AM
This Boss is drilled & tapped, often in 2 places, then a grub screw inserted which clamps to the motor shaft which often have a flat on one side

I'll add it's a good idea to put a small brass bar in the tapped hole between the grub screw and motor shaft as the brass, being a bit softer than steel, will stop the motor shaft getting marked/burred. If you don't it can cause problems trying to get the pulleys off. I would also threadlock the grubscrew to stop it working loose.
Brazing rod is a handy source of brass bar the right diameter...I just part off lots on the lathe then try and find them.

JAZZCNC
08-11-2011, 12:29 AM
I just part off lots on the lathe then try and find them.

Your a sick sick boy or sadist not sure which.:rofl:

Belt hole punch pliers and thin brass sheet is much easier.:whistling:

Danny
01-12-2011, 01:55 PM
After much deliberation i have finaly come to the conclusion that i should be building a router first that will take up to 8 x4 sheets an then have a pen attachment, so am willing to increase my budget accordingly , i have a simple vid for you guys to giggle at , tell me your thoughts! im thinking of running the belting round the entire H frame and am looking for suggestions to how to fix the H frame to while allowing x y movement. http://youtu.be/6QkyB0GB6Ok

JAZZCNC
01-12-2011, 03:16 PM
Hi Danny,

I think you'll find the cost of belting will make using looped belts of this length un-economical. You probably won't find made up looped belts of this length unless large and expensive widths so will need continous belt with connecting plates. Last price I got for a good quality belt was 12mtr, there are cheaper but when it comes to belts you don't want cheap-O otherwise your in for a world of pain.!!
If plan on driving direct from pulleys off the stepper their will be a couple of issues.

1st Resolution will be low so some reduction will be needed, thou not massive if your just plotting.

2Nd The belt tension required over this length will put very high lateral loads on the stepper causing premature wear. Better if you drive direct from shafts with bearings at either end then drive the shaft with small belts under low tension to the steppers, this will also make it easier to create the reduction.

I would give Rack & pinion a look, I think you'll find it works out just as cheap with less hassle and much stronger if you ever want to upgrade and use it as cutting router.

Jonathan
01-12-2011, 05:19 PM
Perhaps another problem with belts that long is them vibrating/resonating? Just a thought...

Swarfing
02-12-2011, 12:41 AM
Danny

look at using the belt in this configuration, you wont need so much and will be easier to tension.

http://www.youtube.com/watch?v=vETkf1sqo3M

Swarfing
02-12-2011, 12:45 AM
Oh another thing look at using HTD8, for some reason this can come out cheaper than HTD5 in cut lengths. I got mine which is HTD5 plus pulleys from ERIKS in Swindon and the truth is at 165 i could have bought screws