Post up a link to the servo manual and we may be able to give more guidance
I discarded the Chinese servos due to some worry that will be difficult to tune. Decided on Mitsubishi servos with very good specs, from fleabay. But could not find a good looking ones, or were expensive/ yeah, sellers know/, or were incompatible with mach3 /again sellers know and try to fry you/ .
Yesterday i payed for 4x SAMSUNG SERVO MOTOR DRIVER CSDJ-04BX2 and CSMT-04BB1ANT3 motor 400W. Absolute encoders 2500, auto tuning, max 450khz pps, in and out encoder signals, and so on.
Here is the manual:http://www.cnczone.ru/forums/index.p...e=post&id=8233 section6.1 and on
my head hurts from reading 10 different servo manuals :-)
Hi, long time i put this off, but now that successfully finished my first build i am back on the track with my machine build.
Now i have all the electronics, motors and major part/linear rails and ball screws/ sleeping at my garage. This time i will build it much faster.
Having learned a lot from the first build, i reconsidered many things and am trying to finalize the drawing stage, so i can buy the steel profiles next week.
Many changes were done, simplifying, strengthening and all this having in mind the common materials here in Spain.
1. Decided that the machine will be on no long legs. It will rest on the floor.
-I work alone so lifting heavy materials will be a problem in the future. As it will be multi functional, there will be removable plasma torch and 1000x1000x100mm removable water bed also, for the not so rare cases i need some parts from steel done until i make my self proper plasma table.
This is how it will look:
2. I wanted to avoid as much as possible laser cut pieces/$$$/ and use instead the profiles themselves as i would do the cutting at home which saves me quite a lot in fact. Only 3 types of steel will be used-100x100x4/the darker ones/, 100x100x3/ the lighter gray/ and 60x60x4/ the gantry verticals and reinforcement pieces/
The gantry support legs from 100x100x4 / so i can reach and screw the HIWIN blocks to the plate/:
The ball screw end supports from 2 pieces of UPN100 soldered together. I have the believe that this part is very important to be extremely sturdy in all directions as there wil be very heavy pull there, starting from the tightening and later when the gantry accelerates and so. Additional 2 100mm thick plates for reinforcement,one bellow and one for the face of the beam, so there will be no further doubt there :-).
3. The rotating ball screw nut
Attached to 10m steel plate via screws , the plate is soldered directly to the gantry sides. I couldn't help and add 2 ribs to the plate, just in any case.
basically the 30T HTD 5 pulleys are 90mm center to center, so 330m belt will fit according to this calculator http://www.bbman.com/catalog/belt-le...alculator.html
The problem here is that the servomotors have much larger central cylindrical part, so there is no more that +-3mm up and down for adjustment. that means the calc has to be very exact with servo motor, as oposed to steppers where i achieved +-6mm adjustment in both directions.
The other thing is that i can not find Alu pulleys HTD5 30t. Only steel, i am not sure but it could impact the inertia as its 3 times more heavy.
4. Back to the gantry. In a way i am proud of it
Now the gantry is where i took liberties with the design, hopefully for good. As i said before there is extremely small overhang. Unluckily there was no 120x100 profile available, though when i started the drawing they said that there is . So i redesigned it again. 100x100x4 and 60x60x4. As i started the gantry from scratch and put a lot of thought in there, i believe it will not only be very successful but in the future will serve as an inspiration to all that want the benefit of closed aluminum gantry but don't have the means or money and go with steel. I mean - take away half of the reinforcements and vertical reinforcements /remember-i will mount impact hammer/ , and it still will be heavy duty normal gantry, couple this with the gantry sides like i did them, and you will have cheap very nice gantry that you need a way to cut the profile and solder +2 plates for the HIwins.
In short I believe that's the ideal High Heavy Duty DIY gantry. I hope you will like the design idea. Hidden and short screw, motor inside, all cut from profiles including the sides. In a normal HD variant, there will be less vertical profiles, less support triangles and one less profile each side of the gantry sides.
FYI : On this picture bellow you can see that the distance i left from front to the vertical supports is 100x100 -60x60/inside verticall supports/ = 40mm. But if the ball screw supports have to be mounted on the vertical bars, no additional plates as i made them, then the distance must be 43mm. Even so the vertical supports will protrude at the back only 3mm which can be masked by soldering, so 100x100 and 60x60 is ideal combination for HD Gantry
This is how i envision a normal HD gantry, that will be comparatively very light for what it is and no need to go in the servo territory. I would like to hear critics or opinions on this :-):
5. The Z
This is on what i am checking and working today. have to check again if the cheese holes are right on spot.
As i said above, with servos i can not design a plate with more than 3mm of movement in both directions to tighten the belt. So i had to do something i dont like and split the Z motor plate to be able to additionally adjust the belt. Still have to calculate again the exact length. And so the days go by...
Will update the Z pictures, when i finish counting cheese holes :-)
6. The machine bed
Some changes here. Instead of vertically soldering 3 x 2 /100x100x3/ profiles i decided to lay them all in one plane, so the distances between them are very small-200mm. So the bed is really strong, even using cheap bed material.
Quite a long post, but i am excited
Last edited by Boyan Silyavski; 25-07-2014 at 12:56 PM.
You have been busy with CAD, nice drawings, what cad package are you using?.
And great to see you have assembled the parts and drives....
How do you intend to join all the steel sections and the vertical bracing? By welding?
From memory you are going to use this machine with an impact hammer to make musical instruments.
Will it be an air operated hammer similar to one of these? https://www.google.com.au/search?q=a...w=1215&bih=817
I was using a small one hand one last week to break up some concrete. they cam deliver quite a blow, You can turn them down by using both a pressure and flow regulator. the settings will depend on what sort of material you are acting upon. even at a low setting the energy released is significant.
Tubular steel is very strong no doubt, however it can vibrate, particularly if the hammer is set to oscillate near the resonant frequency of the frame. Without very sophisticated FEA software it is hard to conceptualise just how a structure will behave. however you may find it advantages to consider the issues involved in advance and if vibration turns out to be a problem have a means of increasing the mass of the structure and what sort of damping measures you take to reduce the amplitude to an acceptable level.
Here is a link to an excellent paper on concrete filled steel structures used in machine design. http://www.mech.utah.edu/~bamberg/re...e%20Design.pdf
Last edited by John McNamara; 25-07-2014 at 01:38 PM.
Now the question of the day is having in mind all the servos are 400w, do I drive all 1:1 or 2:1 ??? The x y encoders are 2048 and the z is 2500 ppr ,all the screws are xx10 and 1605 for the z
The servos will accept 100000 pps at step mode
Last edited by Boyan Silyavski; 01-08-2014 at 08:35 AM.
Last revision. Can not find a weak spot that is not bombproof. Starts to look more and more like a mill .
1. Decided to drivel all 20:30t, only the Z is 20:20t. This after exausting 3 day calculations, belt lengths,inertia, tooth engagement, speeds, etc. and at the end -common sense.
This is a separate thread of its own. I believe this the wisest decision between speed, acceleration, precision.
2.I decided to redesign the Z as it bothered me, especially with this long 1400mm belt. At the end common sense also helped here. At the end raised a bit the overhang without compromising anything so much. I design like this-until i see perfection at every detail.
So the Z. Tried to design it like a Russian tank from WW2. All plates are 20mm Aluminum.
- it would be covered against dust from all sides
-The cheese . The additional holes at the front are for mounting extra things, like: 3D plastic head, plasma torch, engraver, light and so on. The front plate on the moving box is separated in 3 parts. The lowest one is for the case when a so high object is machined that the spindle has to be all in, hence from there access to the nut of the spindle. the second part allows exchange of the spindle. The upper one stays there forever.
-The linear movement and where is placed. I even decided against using it for the hammer. the idea of making a precision machine and the trying to brake it seems less and less attractive. So this one will make the other which will be purpose build 5-6 axis, but anyways as i have 2 ball screws i decided to fit them.
-Reinforced the motor plate, this will hold the drag chain too. The belt now is very short as i like it, no extra pulleys and 6-7 teeth engagement each ball screw pulley. So seems ok to me.
The rotating ball nut assembly. 20:30t hence 1.5:1 driven. Compromise due to common sense. At the end precision and power at the same time is the aim.
2048 encoder on the motor, so more or less 20m/min. I see on the motor specs that it can go up to 4500rpm, just the curve is straight till 3000rpm. The resolution will be ~0.003mm on all axis , 0.001mm on the Z/ 1605 screw and 2500ppr encoder/. That without any artificial gearing or micro stepping which is not needed it seems. Thats good, cause the Galil board is not micro stepping board.
Can't wait to see this come together, keep up the good work. :)
I see no point in having 2 ballscrews to drive the Z axis.? Whats the thinking behind this.
Your just making the motors work harder and increasing costs for no practicle gain.? You'd be much better spending the money on a second ballnut and creating Zero backlash.!!
Originally Posted by JAZZCNC
Yeah, what i was thinking, you got me there . I started the design half an year ago, and learned a lot during this time.The thing is that i wanted not only to have 2 ball nuts but also 2 extra ball screw supports, " 4 is better than 2 " to resist the vibration. Thats why the double ball screw. Also the double ball screw saves on the total Z length.
Now i am not so sure. Still its not too late. Now i see that i could have made the ball screw machined so that it accepts double support at the ends. I have an extra ball screw at home, longer, i mean. Then the only thing that needs changed will be to buy 2 longer Hiwin rails to compensate. Have to rethink that. There is still time.
Now going this way of thinking i start doubting if i should not make the whole z axis 100mm longer and have travel of 300mm instead of the 200mm as its now. Could just raise the vertical bars on the sides of the base with 100mm without compromising any integrity. They are ~80mm high right now. the thing is would i really need that extra 100mm and for what?