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Rogue
01-09-2011, 04:02 PM
Assuming there are no clearance issues with the table/nut, are there any disadvantages to mounting the motor under the table, parallel to the leadscrew?

Another of my soon-to-be-infamous-for-low-quality example images:

4426

(not sure if the picture worked, ISP is being a pain today)

I'm hoping that a pulley system of some form would be suitable to belt-drive the leadscrew from that location.

GTJim
01-09-2011, 04:50 PM
IMO I dont see any problems with mounting as drawn as long as the spindle protudes enough for a pully, and I think it keeps things tidy.

Jim

Ricardoco
01-09-2011, 05:19 PM
IMO I dont see any problems with mounting as drawn as long as the spindle protudes enough for a pully, and I think it keeps things tidy.

Jim

here! here!

and if you think your drawings are basic i do all mine in paint!!! so you will never win that competition.....

Jonathan
01-09-2011, 07:13 PM
IMO I dont see any problems with mounting as drawn as long as the spindle protudes enough for a pully, and I think it keeps things tidy.

You could mill a pocket in the shaft side of the aluminium to accommodate the pulley if there is not enough space.

Pulleys are definitely good plan as they will let you change the ratio allowing the stepper motor to be put in the right region of the speed/torque curve. You can also swap them round to get more resolution if required.

AdCNC
02-09-2011, 12:22 AM
This is similar to what i did with my first machine.

http://www.mycncuk.com/forums/attachment.php?attachmentid=1862&d=1269125465

Plenty of pics on my build

http://www.mycncuk.com/forums/showthread.php/1638-My-First-Attempt-Of-A-CNC

Rogue
03-09-2011, 11:28 AM
Sorry for the delay in replying. Had ISP issues for a few days and my posts seem to intermittently require moderator approval (though I think it's when the post includes links).

Jonathan: I think I'll be looking at some kind of pocket, but I still haven't started to research the pulley systems yet so I don't know what I will need in terms of size and clearance.

AdCNC: Awesome build. This axis isn't fixed to the main structure though, it will be the X axis unit mounted on the Y axis.

Jonathan
04-09-2011, 09:32 PM
Jonathan: I think I'll be looking at some kind of pocket, but I still haven't started to research the pulley systems yet so I don't know what I will need in terms of size and clearance.

I used XL pulleys , but HTD 5mm pitch is better. I've found 1/2" wide best to be fine. It's best to use reasonably big pulleys to reduce belt wear. In general minimum 5 teeth engaged with belt.

ADCNC: like the setup with the coolant etc...

Rogue
04-09-2011, 11:14 PM
Just to prove how slowly my brain works... by 1/2 wide do you mean I need to accomodate a diameter of 1/2", or it will protrude 1/2"(+bit sticking out for setscrew) from the mount?

Jonathan
04-09-2011, 11:23 PM
I meant the width of the timing belt should be at least 1/2". You can calculate it ... but that works fine for me so etc.

I would want the shaft to stick out as far as you can get it to as it depends on the pulley, where the setscrews are and the position of the other pulley.

Rogue
05-09-2011, 12:10 AM
Fair enough, so until I settle on a firm number I'll pencil in 1 1/2" clearance from the surface of the mounting block for the pulleys. I suppose judiciously placed idlers would also help with increasing the engagement with the belt.

Is belt something that can be shortened easily, or will I be confined to designing around what is available?

Jonathan
05-09-2011, 07:27 AM
Idlers shouldn't be necessary. I made the mount with the holes for the stepper motor slotted to allow tensioning the belt and different size belts and pulleys.

You can't change the lengths of timing belts - the only way is to buy a different length. You can work out the length with something like this:

http://www.sdp-si.com/cd/default.htm

Also:

http://bearingstation.co.uk/products/Belts

JAZZCNC
05-09-2011, 07:49 PM
Assuming there are no clearance issues with the table/nut, are there any disadvantages to mounting the motor under the table, parallel to the leadscrew?

Another of my soon-to-be-infamous-for-low-quality example images:

(not sure if the picture worked, ISP is being a pain today)

I'm hoping that a pulley system of some form would be suitable to belt-drive the leadscrew from that location.

Hi Rogue,

I often use timing belts on machines and in the configuration you plan on using.
I've built several machines which use's them on all axis inc Z Axis and they work great without any issue's. They have all the bennafits Jonathan states plus they have one other little known plus. They help reduce resonance, which if bad can affect motor performance.
I've found 20 tooth 15mm wide HTD to be the best for 1/1 connection. They wear the best and easy available at any bearing company. They also have the best size boss on the pulley for using a decent sized grub screws or small bolts for gripping the shaft.

If you want to up the ratios's say 2/1 or 3/1 then 15 tooth is about the smallest I would use on the driven side using steppers, thou be aware the boss size is too small for decent grub screws so you have to then drill between the teeth and make sure the head of the screws is below the surface.

Also be aware that a lot of company's supply the pulleys with a small pilot bore which you then bore to the size required. Drilling with a decent drill press is possible but very easy to get wrong and create runout and if done this way then I'd recommend drilling smaller and reaming to exact size. . . Job best done on a lathe.

Jonathan
05-09-2011, 07:55 PM
Yes they do a good job at reducing resonance.


Also be aware that a lot of company's supply the pulleys with a small pilot bore which you then bore to the size required. Drilling with a decent drill press is possible but very easy to get wrong and create runout and if done this way then I'd recommend drilling smaller and reaming to exact size. . . Job best done on a lathe.

Get them delivered to me and I'll bore (or ream) them to the right size on my lathe for you. Just pay me the postage...it's only a 5 minute job, if that.

Rogue
05-09-2011, 08:31 PM
I've found 20 tooth 15mm wide HTD to be the best for 1/1 connection. They wear the best and easy available at any bearing company. They also have the best size boss on the pulley for using a decent sized grub screws or small bolts for gripping the shaft.

If you want to up the ratios's say 2/1 or 3/1 then 15 tooth is about the smallest I would use on the driven side using steppers, thou be aware the boss size is too small for decent grub screws so you have to then drill between the teeth and make sure the head of the screws is below the surface.

The stepper & ratio issue is something I've yet to address. I need to work out the benefits of the various ratios first. I'm pencilling in 1:1 until I've had a good think over a hot cuppa.


Get them delivered to me and I'll bore (or ream) them to the right size on my lathe for you. Just pay me the postage...it's only a 5 minute job, if that.

I may well avail myself of your services, though it might be some time away. Thanks!

Jonathan
05-09-2011, 08:57 PM
The stepper & ratio issue is something I've yet to address. I need to work out the benefits of the various ratios first. I'm pencilling in 1:1 until I've had a good think over a hot cuppa.

Smaller pulley on stepper = better resolution, which is generally not that big a benefit.
Larger pulley on stepper = higher speed, up to a point which I've not yet managed to reach.

The main thing is as you increase the speed of a stepper motor the torque to start with is fairly level, then drops. You want to size the pulley such that the motor is operating mainly in the region before the torque drops off.

Also I expect a smaller pulley on the stepper motor will get better acceleration.

Just for example with a 13T pulley on my Y-axis stepper, and 12T pulley (bit too small really) on the 10mm pitch screw I get 36,000mm/min (1417 ipm). Changing the 13T to 30T gets about 55m/min (2165 ipm), and changing to 42T gets 60m/min (ipm = lots). Clearly the 42T pulley isn't worth the extra <10% speed given the significant reduction in resolution. Microstepping the stepper motors to artificially gain resolution is really only cheating yourself after about 1/4, maybe 1/8 of a step. The accuracy of micro-stepping depends on the motor and what it's connected to. In general apparently it is not that accurate, but still use it for general smoothness.

You can do some pretty impressive things with 10mm effective pitch as I'm sure JazzCNC will soon demonstrate...

JAZZCNC
05-09-2011, 09:00 PM
The stepper & ratio issue is something I've yet to address. I need to work out the benefits of the various ratios first. I'm pencilling in 1:1 until I've had a good think over a hot cuppa.


If you haven't bought the screws yet then I'd go with 1/1 and get the correct pitch screws best suited to your needs. Mainly for simplicity.
2/1 will double the torque but half the speed and so on. 1/2 will double the speed but half the torque and so on.
One of my machines use's 1/2 with a 20mm x 5mm pitch screw which effectivly gives me a 10mm pitch screw but with reduced torque, the plus side being it's a simple belt & pulley change and I have full torque and high resolution but at half the speed, It works good.
2/1 is usefull if you have small Nm steppers which tend me able to spin faster than larger steppers but with lower torque couple these with a high lead screw and smaller steppers can be made quite strong.

JAZZCNC
05-09-2011, 09:07 PM
You can do some pretty impressive things with 10mm effective pitch as I'm sure JazzCNC will soon demonstrate...

How would you like me to do that Jonathan.? With my little Aztec friend. . Lol

Jonathan
05-09-2011, 09:24 PM
How would you like me to do that Jonathan.? With my little Aztec friend. . Lol

Yep, that's just what I was thinking. I'd like to try one of those on my machine.

Rogue
05-09-2011, 09:30 PM
If you haven't bought the screws yet then I'd go with 1/1 and get the correct pitch screws best suited to your needs.

"The correct pitch screws" should really read "what I manage to find when I have the cash in my hand".

Realistically, C7 1605 screw is what I'm looking at: 20 each for X/Y axis, not sure how much it would cost to get the ends turned down though. No idea about ball nut yet, whether to wait for longer and save for proper ballnuts, or look for a cheap alternative and later replace.

My build is influenced by the fact that I've just completed a course and I'm trying to get back into the workforce, hence not putting down lots of hard cash in one go. I'm hoping to be working again by the time the design phase is finished and the purchasing begins :whistling:

JAZZCNC
05-09-2011, 09:44 PM
Personally I'd go with 1610 it's a better all round pitch. Not sure what you mean by only buying the screws and sorting the nut later because it's normal to buy the ballscrew and ballnut together.
RE: Turning. Even thou I have a good lathe and capable of turning my own screws I dont bother and buy them pre-machined from china, It's just not worth me doing it my self for what they charge.

I'd save and buy the ballscrews before buy cheap and replace later as it's often more than just quick swap over job due to the differant way the connect or work, Plus cheap acme lead screw is rubbish and good quality acme lead is more expensive than ballscrews from china.!!

JAZZCNC
05-09-2011, 10:05 PM
Yep, that's just what I was thinking. I'd like to try one of those on my machine.

Ok just for jonathan Here's what 10mm pitch gets you.!!

Johnathan if you want the code your welcome to it, or any body else for that matter. It's a 17mb file thou and over a million lines of code, If I remember correct it took about hour n half.
I did another after that but with the Welsh dragon on the back side but didn't take any pics. . . . Looked good thou.!!

Enjoy and the pics don't show all the detail or do it justice. . . 150mm diameter 10mm Ali plate cut with a 6mm 90deg carbide chamfer/spot drill.

Jonathan
05-09-2011, 10:10 PM
Ok just for jonathan Here's what 10mm pitch gets you.!!

Was amazed when I first saw that - I still am.


Jonathan if you want the code your welcome to it, or any body else for that matter. It's a 17mb file thou and over a million lines of code, If I remember correct it took about hour n half.

Yes please! I've got some aluminium that size so why not...I believe you did it with a 6mm spot drill, 90? As better excuse than most to finally buy some spot drills I guess.

I agree that 10mm pitch is definitely the way to go if you want good feed-rates.

JAZZCNC
05-09-2011, 10:22 PM
Was amazed when I first saw that - I still am.

Ye me too I must have looked at it for days and every time I saw a bit more detail I'd missed.
It's also mesmorizing to watch the toolpath do it's stuff the bloody thing bounce's all over the place, so much so when first started cutting I very nearly stopped it because I thought it had FUBARD.




Yes please! I've got some aluminium that size so why not...I believe you did it with a 6mm spot drill, 90? As better excuse than most to finally buy some spot drills I guess.

No better excuse IMO. . lol . . . . . I'll dig it out and send your way.

Rogue
05-09-2011, 10:29 PM
Personally I'd go with 1610 it's a better all round pitch. Not sure what you mean by only buying the screws and sorting the nut later because it's normal to buy the ballscrew and ballnut together.
RE: Turning. Even thou I have a good lathe and capable of turning my own screws I dont bother and buy them pre-machined from china, It's just not worth me doing it my self for what they charge.

I'd save and buy the ballscrews before buy cheap and replace later as it's often more than just quick swap over job due to the differant way the connect or work, Plus cheap acme lead screw is rubbish and good quality acme lead is more expensive than ballscrews from china.!!

Ah, I don't think my post was as clear as it should have been, my apologies.

I'm planning to go for ballscrew+ballnut, but I noted that, depending on where you look, there seems to be a big jump in price from the ballnuts without preload/zero backlash to the ones that do have it (which I would think are preferable). Going cheaper would get me running sooner, and having a working (albeit lower precision) machine to play with while building up more funds is preferable to me. There also seemed to be suggestions for ways to increase the effectiveness of the lower end ballnuts, though now that I think about it, they may have been talking about the acme setups. Hmm.

As for turning the ballscrews, I suppose that's a matter of perspective. If you have the skills and equipment but your time is money then yes, turning the ends down to fit the bearings probably is better left to the supplier. Would I do it that way? Ask me in 5 years :smile:

1610 rather than 1605, you say? I shall run that though the collection of calculations I'm building up.

The following picture is a rough mockup of what it's running - working area was originally planned at 200mmx200mm for the table, will have to be bigger simply to fit the stepper in the location parallel to the screw. The gantry will be close to the table but large so the X can run up quite high and still be supported, for reasons discussed elsewhere. "Scale" is a dirty word as far as this picture is concerned, don't read too much into it. The XY will not be completely seperate from the gantry, it was just easier to draw that way!

4466

Rogue
05-09-2011, 10:33 PM
Ok just for jonathan Here's what 10mm pitch gets you.!!

That is several steps beyond awesome, and something to aspire to in the future. Is there a drool icon? If not, why not?

JAZZCNC
05-09-2011, 10:44 PM
As for turning the ballscrews, I suppose that's a matter of perspective. If you have the skills and equipment but your time is money then yes, turning the ends down to fit the bearings probably is better left to the supplier. Would I do it that way? Ask me in 5 years :smile:


Not really I have the time, equipment and the skills but ballscrews are hardened and the indexable tips required cost me nearly as much as what I get charged.
So to me it's not worth the hassle and all thou unprobable still possible risk of error.

RE: 1610 or 1605. I should clarify this depends on the intended use of the machine. If your going to use it to cutt intricate jewelry or want very fine detail then the small pitch is better but for a general allround machine then 10mm pitch works best in my experience.

Rogue
05-09-2011, 10:51 PM
All round, I'd guess. If I understood the earlier posts correctly, if I had a system for changing pulleys I could get the higher precision if needed, at the expense of speed? If so, this is one of the things that interest me about pulley systems.

Jonathan
05-09-2011, 11:02 PM
RE: Turning. Even thou I have a good lathe and capable of turning my own screws I dont bother and buy them pre-machined from china, It's just not worth me doing it my self for what they charge.

That's precisely what I thought. I would machine a ballscrew if someone asked, but it's just not worth is with linearmotionbearings2008 prices on eBay.


All round, I'd guess. If I understood the earlier posts correctly, if I had a system for changing pulleys I could get the higher precision if needed, at the expense of speed? If so, this is one of the things that interest me about pulley systems.

That is correct. Lets say, for example, you have a standard stepper motor so 200 steps per revolution. The travel per step on a 10mm pitch screw will be 0.05mm with direct drive or 0.1mm or 0.025mm depending on if 2:1 or 1:2. Using microstepping will get finer resolution up to a point.

Though I would normally advise 10mm pitch screws (I probably did earlier!) since this is such a small machine it may not make a lot of difference...having said that the main thing is getting high acceleration, otherwise you'll run out of travel before it hits top speed and has to decelerate. To do that a 2:1 (bigger on stepper) with a 10mm pitch screw would be ideal since the motor has to input only a quarter of the kinetic energy into the screw when accelerating compared to a 5mm pitch screw.

Your 'system' for changing pulleys is just an allen key plus a bit of space.

JAZZCNC
05-09-2011, 11:23 PM
Agree with what jonathan says just one thing to point out 2:1 10mm pitch is effectivley 20mm pitch. If you can live with this loss of resolution then it's a good way to go.

What's your main intended use.?

Edit: Jonathans comment about accelleration is even more important if you plan to do lots of 3D and intricate V carving. 3D and intricate carving is very time consuming, esp vcarving, with lots of very small moves required with the Z axis dancing around all over the place. The problem with low accel is the commanded feed rate actually never get's meet and therefore the cutting time increase's. On very large 3D jobs this can run it several extra hours or even days.!!

Jonathan
05-09-2011, 11:32 PM
Agree with what jonathan says just one thing to point out 2:1 10mm pitch is effectivley 20mm pitch. If you can live with this loss of resolution then it's a good way to go.

What's your main intended use.?

5mm, 10mm .. . it all depends on what motor is driving the screw. If it's a 3nm motor then clearly a different ratio will be optimal when compared to using a 1nm motor.
If you're using it for PCBs then you'll want good resolution, so probably best to use swappable 1:2 pulleys. Can't really thing of anything else that would require it. Maybe engraving, but generally for engraving it's relative position that matters more than absolute which means microstepping is more valuable.

Rogue
05-09-2011, 11:40 PM
Right, the "intended use" question.

1: PCB milling (from one extreme...)

2: Panel making for instrumentation - aluminium and as-yet-undetermined plastic, <5mm layers, mostly cutting external borders, internal holes for switches. Engraving text. Nothing intricate.

3: Small components as needed for above, odd little brackets etc. Aluminium mostly.

4: If possible, larger aluminium pieces. The "low gantry, tall Z" design is because there might be the occasional taller but narrower piece. (...to the other)

Ideally making new bits to improve the mill or make a bigger, better, shinier one!

I don't expect it to handle steel but you can flippin' well bet I'll give it a try to see what happens :naughty:

I'm hoping that I'll be able to make it stronger/more sturdy by leaving the gantry to handle Z. It also means I can consider adding a counterweight system later if I get adventurous or drunk. I have no idea if it needs one, I just always thought they looked cool. Not... ehh... a proper "technical" answer, I know :redface:

Rogue
05-09-2011, 11:47 PM
if you plan to do lots of 3D and intricate V carving

Engraving would be flat text for a control panel, nothing fancy. I might need to do something fancy every now and then to try and justify it to my wife, but thankfully she has low standards. Well, when it comes to husbands, anyway :whistling:

JAZZCNC
05-09-2011, 11:49 PM
Maybe engraving, but generally for engraving it's relative position that matters more than absolute which means microstepping is more valuable.

Ermm. . . Not a good idea IMO realying on micro stepping. Really it's horse's for course's when you get into the finer engraving area and resolution rules. So it's finer pitched screws all the way but at the sacrifice of speed. . . . If I intended main use as engraving then fine pitch's would be used for the resolution not M-Steps.

Micro stepping is good but mainly for smoothing motors.

JAZZCNC
05-09-2011, 11:53 PM
Engraving would be flat text for a control panel, nothing fancy. I might need to do something fancy every now and then to try and justify it to my wife, but thankfully she has low standards. Well, when it comes to husbands, anyway :whistling:

Scrap the last post then. .:rofl:

Rogue
06-09-2011, 12:04 AM
Micro stepping is good but mainly for smoothing motors.

This is one of the things which I need to get my head around as well. From what I read, microstepping is good... but it's bad. People report motor problems disappearing when they start to use it, but from what you say it seems to be an inferior way to achieve good resolution. I'm assuming that there is a middle ground somewhere that I need to find (not too fine a pitch, not too many divisions for microstepping).

JAZZCNC
06-09-2011, 12:26 AM
This is one of the things which I need to get my head around as well. From what I read, microstepping is good... but it's bad. People report motor problems disappearing when they start to use it, but from what you say it seems to be an inferior way to achieve good resolution. I'm assuming that there is a middle ground somewhere that I need to find (not too fine a pitch, not too many divisions for microstepping).

Depends on a few factors really and the drives being used also play a big part to how micro stepping is implimented.

10x micro stepping is about the max usable and beyond this is just pointless unless you have a very high pulse width which is beyond the capabiltys of the std parallel port. . . It's gets complicated so wont go there.!

Generally micro stepping should be used but mainly for motor smoothing at lower speeds IE: small tiny moves and lower rpm's but after a point micro stepping becomes an inderence more than a help and this where the drive comes into play.
A good drive will use a technique called morphing where it changes from micro stepping to full stepping along the power curve. This also brings resonance into play and why belts can help.
Poor drives without morphing and usually mid band resonance compensation can suffer from resonance issue's caused by the vibration frequency's that interfear with signal performance and affect the motors making them run really badly and sound dreadfull. . . . Belts act as a natural damperner.

Good drives like Gecko's etc use morphing and Mid band resonance damping and this really does make differance.

If you work on the principle that micro stepping works but mainly to help with motor smoothing at lower rpm's but with the side affect of slightly improving resolution ( too a point) then you wont go wrong. Just don't relay on it soley to give you the resolution you need.
Like I say the good drives do make a big difference.

Go to the Gecko site and read the FAQ section it has some good info on how morphing and micro steeping works.

Rogue
06-09-2011, 12:46 AM
I... ahh... won't go into my original driver plans which involved a PIC and some fairly shaky ASM :whistling:

I was actually looking at the linistepper kit originally, again on the grounds that I could probably put a set together for the cost of a single Gecko in the short term. I know "short term" is a dirty word on this board, and knowing my luck unipolar motors will have a whole extra set of problems attached to them :rolleyes:

JAZZCNC
06-09-2011, 01:26 AM
In my experience with helping folks who have try'd to make your own drives and use oddball steppers etc becomes false economy with the end result being wasted time and money.

Good for the experience but with the same result. . Inferior performance and poor reliabilty . . ending in scrapping and buying "Proper drives an motors".! . . .BUT. . .By no means let me saying this put you off thou because it's all a good learning experience. . . Keeps you out of mischief as well. . Lol

Rogue
06-09-2011, 01:43 AM
...Inferior performance and poor reliabilty...

Another reason I'm glad my wife has low standards.

I've got some odd steppers lying around to play with for PIC projects, though I had grand dreams of extending functionality in ways that isn't actually needed or, indeed, useful.

Steppers are far enough down the line that I'll hopefully be better placed to source better components. I plan to make up some linistepper drivers anyway, whether or not for the CNC, as there's always mischief to be gotten into!

Jonathan
06-09-2011, 07:01 PM
Ermm. . . Not a good idea IMO realying on micro stepping.

I'm not saying rely on it, just it might help. Clearly the result will be slightly distorted.

I already mentioned about microstepping accuracy (or rather lack of) in post #15...

One thing I'm going to try and do with my stepper driver design is make it effectively run using microstepping, for smoothness, yet only require the number of pulses for whatever microstep division you choose. Effectively it will move through each of the microsteps for every step pulse.

JAZZCNC
06-09-2011, 11:15 PM
I'm not saying rely on it, just it might help. Clearly the result will be slightly distorted.

I already mentioned about microstepping accuracy (or rather lack of) in post #15...


ye I know Jonathan and wasn't really picking up or discrediting your referance about microstepping more pointing out for high resolution operations like engraving etc then it's better to use the correct pitch screw.

Rogue
17-09-2011, 08:14 PM
I've been bouncing some of these shapes and ideas around and I'm left with the feeling that, while the idea really appeals to me, I'd end up with the combined table element somewhere in the region of 170+mm deep if I try to fit the motors in the way planned. For some reason that just doesn't feel... right. I have no idea if there is a mechanical reason for this to be wrong, it just seems odd.

This design lark is harder than it looks, especially when you have a tendancy - nay, burning desire! - to reinvent the wheel at every opportunity :confused:

JAZZCNC
17-09-2011, 08:29 PM
Don't sound over deep to me but it would really help if we had a nice pritty drawing to look at.:whistling:

Rogue
17-09-2011, 09:34 PM
Oh I do love making pretty drawings... one on the way then, if not in the next hour then tomorrow!

Rogue
18-09-2011, 12:42 AM
Right. Cobbled something together while the rest of the family were subjecting themselves to XFactor :whistling:

4549

I've had a glass or three of wine so you'll need to excuse a few glaring errors (yes, one of the motors is physically inside a wall as I forgot to "carry the one" while doodling numbers on the back of a fag packet...). One side is missing for visibility, and because I realised another "carry the one" error made it physically impossible :redface:

For size reference, the big blocks along the bottom are 80x80, the others are 80x40. My initial idea for the top table was to use L brackets to connect to the blocks on the rails of the bottom table. No idea if they would be suitably strong enough but it seemed like a good idea at the time (cue cutaway of top table showing L bracket)

4550


I've not put in the Z, just roughly indicated where the spindle would be. I also want to think about what I can do to make the gantry stronger, bracing etc, for most mass and rigidity within my capabilties - so no welded steel tubes or fancy epoxies :cry:

Rogue
18-09-2011, 12:46 AM
I also realise it would be flippin' hard to clean as it, but I have plans for tackling that as well! That will be another thread later on in the year!

JAZZCNC
18-09-2011, 09:51 AM
Hi rogue,

Ah ah I see what you mean know.? . . . Just a quicky as it's early and I'm on way to motoX.

I would scrap the top moving portion as it's too bulky, overly complicates and add's no extra strength or bennifit over the Z axis running across the fixed gantry in the usual way.
Would be cheaper due to less materials and less work.

Yes triangulate and brace the hell out the gantry and base frame.

If you have a need or want an idea for capabilty to have a high Zaxis but with absolute max strength at the cutter, so very little tool flex then let me know and I'll post a suggestion.? . . . If not then won't waste my time. . Lol

Ok time to jump on a road bike to go race dirt bike.!! . . . . .Arg I hate road bikes but got to get there fast.!!

Rogue
18-09-2011, 12:31 PM
If you have a need or want an idea for capabilty to have a high Zaxis but with absolute max strength at the cutter, so very little tool flex then let me know and I'll post a suggestion.? . . . If not then won't waste my time. . Lol

All suggestions welcome! If there is no real benefit to the design then I'm not obsessed with keeping it. I just thought it was easier to make the table area "solid" than it would be to make the gantry "solid".

blackburn mark
18-09-2011, 02:06 PM
This design lark is harder than it looks, especially when you have a tendancy - nay, burning desire! - to reinvent the wheel at every opportunity :confused:


:lol: hahahahahah!!!!!!!!!!!! its a problem for sure lol..... i excuse myself the trait because you never know, i might actualy be a genius and unravel a never been seen before solution to an age old problem... alas... it never quite seems to be the case though:wink:

it still beats watching the X-factor though

Jonathan
18-09-2011, 02:32 PM
it still beats watching the X-factor though

Anything beats watching the X-factor.

baccus61
16-04-2012, 06:02 AM
Hi guys, It's always a toss up as to how to go about building one of these new fangled things. Whether to fix the gantry or fix the table. I would prefer to fix the gantry myself but then you need twice the room for the table to move underneath it, but it is the strongest method. My gantry's have been moving due to space limitations but your design looks to be relatively small so fixed gantry would probably be the way to go.
On large gantry's it is a good idea to have a greater pitch for the long axis screw due to whipping if turning too fast so to move the gantry/head a certain distance the quickest way possible this method is good. You do sacrifice resolution though but you may not need 0.000001 tolerances. (arbitrary amount)

I have 10mm pitch ballscrews on my Y axis because that was the largest pitch available at the time for the price and my X axis has a 12 start 50mm pitch acme screw with matching anti backlash nut. I have geared this acme screw down to 3:1 which gives me 120 steps per mm which I think is fine for my wood working. Remember that the steppers might be out by a few arc minutes per step but they all come back to the same point after 1 full rotation. There might be small inaccuracies in that 1 revolution but geared down 3:1 it makes them smaller inaccuracies again. It all boils down to how accurate you need it to be.
Temperature comes into play if you have a very big machine as well and if your milling wood then also humidity plays a part.

What would you expect the tolerances to be for PCB routing. I've never done this but I would expect you wouldn't need anything better than 0.002" (But I may be wrong)

You could probably mill Steel, Aluminium, etc but you would only be able to use a very small chip load as your strength and vibration absorbing qualities of the gantry just wouldn't be there. You could do it but it would take ages to achieve something easily done on a bigger machine. Potentially you could mount a diamond wheel to your spindle and grind your jobs but the time taken would be an issue. (you would probably want that 1 year of your life back :-) )

Fixing the gantry will give you the greatest stability and if braced properly then you will have a fine little machine to work with and with the quality of all the parts available today you can't go wrong.

If you need to put bigger things under the gantry then make the table adjustable by being able to drop or raise it. Shouldn't add too much to the design for a small router.

The Chinese spindles are very good value for money if you are after one, and compared to the wood routers, they will give your ears a much needed rest and make your neighbors happy at the same time.

Rogue
16-04-2012, 05:02 PM
I have a plan in mind for bracing that involves a wrap-around... err.. thingy? Shell? I'll let you know how it works out. I'm moving back to a fixed gantry so the need for keeping everything under the table is less urgent. I still intend to do it, though for other reasons.

At my wife's request I've put everything non-essential on hold after a (or more specifically, another) job fell through at the start of the year. Until I'm earning again, I need to step back for the sake of my wallet and my sanity :saturn: