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Just a final thought before nurse tucks me in. When i started this project I was going to use mahogany and pitch pine. Now its box, plate and tough stuff. The base I built was a mdf torsion box. That is going to have to change. A steel frame is, I can see, inevitable. Thankfully my ex racing buddy is a great welder so i think that a cream bun in his direction may be required. Thats for the future so good night and thanks.
Bruce
If you use the MDF torsion box mounted between a steel frame like I do now you'll have a very rigid machine:
Attachment 5253Attachment 5254
Mine is 18mm MDF on top, 9mm MDF underneath with 3x1 PAR pine in between ... convenient sizes at the time to fit the leadscrews inside.
Part of the reason why is you can make it so the height of the bed is adjustible, so you can still machine tall parts without compromising the rigidity (due to large overhang) when machining sheet material. That is also where the Z-axis design you have now drawn with the rails on the spindle plate is significantly stronger - compare the distance from tool to linear bearing blocks.
While trying to adjust the position of the z motor I realised that it would get in the way of the spindle mounting plate. Solution is obviously to mount the motor on the back of the gantry and use a small belt drive to run the z screw. This probably explains why i see it on many m/c's. Gosh max and jonathan i worked that out all on my own......guess it must be wrong then.
Bruce
Using a timing belt is a great idea for a number of other reasons. It enables the ratio between the stepper motor and ballscrew to be changed. This alters the region which the motor operates in within the speed/torque curve, which with careful selection will get better acceleration and or feedrate. For instance I found with my Z-axis by calculating to get an estimate and then trying various pulleys that 42:22 ratio was best, with the larger pulley on the motor. The other big gain is the timing belt 'seperates' the ballscrew and motor so the vibrations do not transmit so easily - in other words it damps the system reducing resonance. Again this improves the feedrate, so it's a good thing to do on the X and Y-axis too. If you put a 2:1 ratio on the X and Y ballscrews it should get better acceleration and less importantly top speed, but you sacrifice resolution slightly (in most cases negligibly) plus you've always got the option of swapping the pulleys round to get better resolution...
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got the cable today so i will try and blowup the spindle over the weekend:eek:
Wired up the spindle and did not blow it up. I have a link to youtube to prove it.:smile:
http://www.youtube.com/watch?v=C8bMG...ature=youtu.be
Bruce
Nice
It does always flash. Bear in mind if you run it in reverse without a cutter in but the collet nut on the nut has a tendency to fly off :naughty:
oops:redface:Quote:
Originally Posted by Jonathan
How can you get the readout to give rpm?
Just doing a redraw to get some accurate drawings after all the sketching.
Bruce
Assuming you've set PD144 to 3000 you just keep pressing the >> button until you get to RPM.Quote:
Originally Posted by motoxy
I generally leave it set on current - much more interesting as you can see if the cut is drawing too much power.
Thanks Jonathan. So glad I did not go down the kress route.
Okay its sunday afternoon and I have spent an hour chopping wood. You know when you get what you think is a great idea. You rush in and draw it up and think...eerr i'm not so sure.
I was concerned about getting good fixings in the box even though it is 6mm. Rather then pushing tubes through I came up with the idea of prespacing blocks along a threaded rod and pushing it into the box. Drill through and fix everything. You then have 4 end bolts to clamp up the sides.
Your thoughts???
Bruce
Just decided that that idea is pants. Think I may have a better one.
Probably just have a block fixed each end for location and fixing. Drill the opposite side of the box where the rail mounting screws are along the centre line just big enough to hold the nuts to lock the screws through the box. This should not have a detrimental affect on the overall strenght of the box.
I should probably now be thinking about buying some more parts. z rails and screw, motors and couplings. Then start getting some materials.
Well I think its about time to get my motors, drives etc. and couplers. I have looked at diycnc, zapp, cncrouterparts and cnc4you. Any others I should check out or any advice to be had? Probably have to buy the power supply in uk to avoid 110v.
Bruce
Last time I checked cnc4you was cheapest for steppers including postage (though it looks like that may have changed now) and eBay for the drivers. I'm not aware of any other places.
The drawing in post #98 - You should make the joint between the X-axis linear bearings and gantry sides stronger. Currently it's only aluminium angle which will bend at the corner relatively easily, and since the bearings are free to rotate upon the rails that will cause deflection. Perhaps you could use box section there, or better just add some triangular pieces to stiffen it.
Power supply - 500VA toroidal transformer plus bridge rectifier and capacitors is all you need. www.rapidonline.com are reasonably priced.
Hi Jonathan, thanks for the heads up on the angle. hard to think I used to be a designer.:redface:. Currently being checked over for memory loss problems which probably explains a lot.
I am going to start my build now. I am ordering material tonight as I think I can start moving forward now.
How easy is a self built power supply???
zapp have this as a kit http://www.zappautomation.co.uk/prod...547704f50af02c £316
Do you think these are to cheap or worth a punt http://www.ebay.co.uk/itm/2508624928...ht_3191wt_1110
Bruce
Thats it. Ally ordered.
Very easy to make a power supply. Connect primary of transformer to mains via a fuse, secondary to bridge rectifier (e.g. bit excessive but you can't go wrong with http://www.rapidonline.com/Electroni...ctifiers-29671) and output of rectifier to smoothing capacitors. Minimum about 10,000uF, 80V or greater. Switch on and check the output voltage and polarity is correct with multimeter just to be sure then connect it to the stepper drivers.Quote:
Originally Posted by motoxy
I tested a driver that looked identical to the ones you've linked to on eBay. I'd happily buy them if I needed some 50V drivers.
Edit to add:
Apparently it's not blatantly obvious this 4 line post isn't a substitute for proper research, so please note that this isn't a set of complete instructions but a general guideline.
Okay I have purchased most of my main electrics. Jonathan was trying so hard to save me money but to be honest I was not happy building my own psu. I decided that I would get all my parts from one source in the UK so I could have a warranty and tel support. cnc4you are the lucky recipients of my dosh. I had a long talk with Brian and feel very confident.
I have some parts being made by a very kind young gentleman, I wont mention that its Jonathan as I do not want to embarrass him.
So by the end of this week I should have enough parts to begin the build, again. Hopefully this time, after all your good advice, properly.
Ooo i'm so excited.:yahoo:
Bruce
Jonathan I,m sorry but I'm not happy with your reply and I've got to say something.:thumbdown:Quote:
Originally Posted by Jonathan
Your flippant answer regards transformer and capacitors/rectifier is very dangerous in the wrong hands and your putting folks in danger of either blowing up there drives and worse still potential to KILL them selfs.:surprised:
They need to know that yes while it's not difficult to build a transformer supply it does have to be done correctly and components correctly sized to give the correct output they require.
They need to know that the transformer seconderys need to calculated and sized correctly so when rectified from AC to DC they get the correct output so doesn't fry there drives.!
They need to know for stable performance the capacitence should be calculated in relation to V & A required, to say just use anything bigger than 10,000uF is far from ideal.!!
They also need to be aware of the very big potential to KILL them selfs if they dont treat Big capacitors with respect.
They should also be made aware of the need to build in a capacitor drain to be absolutly safe when working on the control box, and that regardless of whether the box is plug in the wall or not that with out a drain system built in then there at risk of being fately electricuted if touched in the wrong place.!!
They need to be made aware of other factors regards rectifiers, like they should really be mounted on heat sinks also how they are wired and they have positive and negative output.
Folks It's not difficult but it's not just simply grab any old transfromer and capacitors and stick it together with a recitfier like Jonathan makes it appear.!!
It needs to be calculated correctly for correct output and as always when working with electricty treated with utmost respect.
While I know how to size and build one I won't post the information in thread like this because of the potential for error then blame.!!
I will gladly help folks on a one to one basis via email or preferably on the phone/skpe because I can explain and control better that it's done correctly. Just won't do it in public.!!
The information regards sizing components correctly is available on the net if you search. But please be sure you fully understand before attempting other wise you risk the BIG possibilty of destroying your drives or Worse your self if you get it badly wrong.:confused:
EDIT: Jonathan dont bother coming back at me because you can't really and I'm not getting into another thread hi-jacking slanging match just needed to be made clear for the sake of others.
Bruce I'm sorry for wasting more of your thread space.:redface:
I'm allowed to have an opinion as well. Any DIY project like this involves an element of risk. I assumed that taking elementary safety precautions was contextually implied, and if I was wrong to assume that on a forum like this I apologise. I have added some wording to make this clear now.
Just for the record, the mains part clearly is dangerous, but for the rest of the PSU wikipedia sums it up nicely:
10,000uF capacitors are perfectly fine for motoxy, as I said before more would be nice. I can only put my hands up and laugh that you would argue about something this elementary with someone who studies electrical engineering and has the same capacitance in both of his PSUs working fine without problems.Quote:
Originally Posted by Wikipedia
If motoxy hadn't bought the parts already I would have happily soldered them together for free and sourced the parts, it would have taken at most 15 minutes.
So after that completely unnecessary attack on my post, you know what? I think I will bother.
No Jonathan shame on you because for this very reason you should know better.!Quote:
Originally Posted by Jonathan
I'll say it AGAIN BECAUSE YOUR A STUDENT AND OBVIOUSLY THICK AS SHIT. . . People read your posts and take your word as gospel.
If your going to post on serious stuff like electricty then please have some concideration for those that don't have much if any experience but a massive desire to try, which is great and I for one fully encourage in 99% of cases but with electrical issues then caution needs to exercised and advised.!!
Now go stick your tongue across them 10,000uF Caps if your so sure it will only tickle.. .:wave:
Thats the drivers, motors, bob and psu arrived. I guess I am going to have to tidy the workshop and get started.
Bruce
I know what your thinking, here's another of those that start a build log but do not build.
SURPRISE:yahoo:
I have started the rebuild. I have put registers into the top and bottom plates of the z gantry and started drilling and tapping to connect. The I used my home made
under the bench router table. I know it will not be with a tight tolerance but I kind of got the urge to do as much as I can on my own. That said its thank you to Jonathan for a fine pair of ball nut brackets and spindle mounts.
Do not expect this to be a speedy build. As you can see I have done 3 bolts so far.:whistling:
Well done Bruce.
Sorry to bring bad news, but you've put the joints on the plates the wrong way round. Normally people do it such that the top and bottom plates, to which the Y-axis bearings are mounted can move up/down a little then be bolted down to accommodate variation in the Y-axis rail spacing. You had it right in the drawing in post #87.
There shouldn't be any need to start changing things as long as the top and bottom sides of the plates are square to make the bearing plates parallel. If so then you just need to make the gantry such that there's a little bit of adjustment in at least one of the Y-axis rails. The other solution is leave the bigger plate on the Z-axis as it is and cut the smaller one to fit between and make that joint adjustable.
I know what your saying jonathan. I made an error in the design and only realised after I had ordered the material. I have given it a lot of thought and have a system to adjust the y axis. If it becomes a problem then i will order some more material. Budgets a bit tight at the moment so I will have to see how it goes. Thanks for keeping an eye on me.
Your worse than the Grim Reaper boy. . :naughty:Quote:
Originally Posted by Jonathan
Bruce he's correct but just shim if it's tight.!!
Shim (spacer), a thin and often tapered or wedged piece of material
That sums up most of my metalwork
Next step is the y rails. I routered out a register and then did it again. The rails edges are rounded and I did not go deep enough. Hopefully not to much wrong this time. Next will be drill and tap the rails in place.
Bruce
Bruce Having a register to work from is good idea BUT Becareful it can bite you with round rail.!!. . . . The base edge of round rail is often not very straight (Or Flat) so carefully check that
1: It's straight
2: The distance from rail to Edge is consistant along it's length.
If it is straight and consistant then you can work from the register when setting rails parallel if not then work direct from the round rail.
Thanks for the warning. My intention is to get as much straight and parallel as possible but when setting out the various components I will use a dti on the important surfaces.
Cor if i new what i was doing i would be dangerous:naughty:
quick update. Y bearings are in and the rails screwed into the box. I clamped the ends just to push it back and forth and thankfully there is no hint of binding. Mind you I am sure you will tell me what I have done wrong....:joker:
Bruce
Just thought you might like to be updated. Thankfully shimming will be at a minimum as most of the crucial measurements seem to be reasonably close less than 0.1 degree.
Still got to add pads to the base of the sides and bracing on the back.
Bruce
In case your wondering I have made sliding fit pads for inside the box. These have been threaded so the tie bars although going right through will not stress the box. Once I am happy with the build these pads will be locked in place with bolts.
Well Done Bruce,
Coming along well and looking good. Keep it up and it will be running in no time flat.
Michael
Just a quick update. Been busy and work is about to kick in. The y gantry is almost finished, probably another 6 hours should see it done. The z is waiting on Michael Marino's machine becoming available and then we can machine the recesses in the plates.
Going to see if i can coax my mate to do the welding of the frame for me. So it is progress just a bit slow. Would be quicker if i made less mistakes!:redface:
Bruce
Next update. Its now a rolling y chassis. The mounting plates above the x bearings will be cut down to size after i know where the ballnut bracket will be located. It does not look much since last time but I must have drilled and tapped 50 or so holes.
If all the limit switches are connected in series would it make sense to mount them all on this gantry as this would mean only one cable going from the gantry to the control box?
Yes With a bit of care and planning it's possible to use just 1 switch for each axis all wired in series. Doing it this way then yes it's possible to mount them all on the gantry.Quote:
Originally Posted by motoxy
Basicly you need some kind of ramp or bracket either end of each axis to trip the switches.
Confession time now bruce I forgot to do what I've got to do.!!! . . . Will do it ASAP promise. .:redface:
Jazz there is no rush.
I take it that these switches are homing at one end and limit at the other? Or are homing switches separate?
You will notice that i am entering another area of simple and possibly obvious questions. YOU HAVE BEEN WARNED!:smile:
Looks like Michael is nearly ready to start on my z plate. Once that happens then hopefully there will be another lurch forward.
Hugs and kisses
Bruce
NO for limit switch's to be any use then you need the switch to be tripped either end. Often 2 switch's are used per axis mounted static at either end but a single switch per axis can be used if fastened and travels on each axis then triggered by use of a ramp or bracket if mechanical. Optical or proximity type switch's are also good for this type of application as the can be triggered by static magnets etc.Quote:
Originally Posted by motoxy
Home switch's can be either separate or the limit switchs can be used as double duty. Mach3 knows the difference between when the switch is triggered as limit or home.!
Basicly the switch is always treated as a limit while the machine is working but then when told to home temporely disables the switch as a limit and treats the switch as a home switch then when finished homing goes back to being a limit switch.
Just to let you know that this build is not dead I am thinking about the base. Steel box is 50 x 30 and 100 x 50. I intend to fix 10mm ally plate on top with an overhang that will support the screw/ motor. and give it some protection from debris. Therefore the rail and screw are fixed together and the critical factor should be lining up the left and right plates. Fillets will be added on the build.I really ought to start setting up the electrics now but this part does make me a little nervous so listen out for some stupid questions soon. :confused:Bruce