Build log at last

I welded this frame for a friend about 6 months ago but he has moved to a new house which doesn't have a garage so he give it back to me. Its made out off 60x60x4 box and the end plates are 10mm plate.He was going to use it to cut hard wood and really that is what i will be using it for but if i could cut aluminium every know and again it would be a bonus.The size of the base is 1000mmx700mm. After reading some other build logs i am not sure if i could get away with using one ball screw or do i need 2? The gantry i hope to build out off aluminium . I haven't bought any parts yet
Thanks in advance
Greg
1000mmx700
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1 ball screw
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2 ball screws
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I am starting to design the gantry and after reading the other build logs I think i will use Linear hiwin rails HGR20 or should i use HGR15 for the z axis?This is probably a stupid question but what is the difference between a HGH20CA carriage and a HGH20HA and could someone please confirm if the height off the carriage sitting on the rail is 30mm.Do you think I can use one ball screw on the Y axis or should i go with two? All advice much appreciated,
Cheers Greg

Greg From what I believe HRG15 on the Z is more than strong enough but the problem is that it would make it very tight on space for the ball nut and you would have to cut more out of the plate to accommodate it. There is not much difference in price between the two.

In my opinion at 700mm wide you could get away with one screw depending what you want to cut.

I have 15mm rails on the Z and wouldn't do it again - more like 20mm. Much stiffer and give better spacing to fit all the parts in.

I've always gone with 600mm max width for single ballscrew, above that twin ballscrews. One of my earlier machines was a single ballscrew at around 600mm wide and you could push on one leg of the gantry and move it a mm or 2 without much effort. In practice this was still surprisingly effective even in hardwoods cutting off to one side, but I'm sure it contributed to errors cutting aluminium. So it's close, and Clive is right in that it depends on what you want to cut, but I would say 2 ballscrews at 700mm for robustness personally.

HGH20CA etc usually refer to the carriage style - wide, long etc. so google it to be sure. Some people prefer the wide version for for the X bearings (which the gantry then sits on), where you often want a large area to connect into. Whereas on the Y and Z you need every mm so go for the standard/narrow ones.

Thanks for the replies, So 20mm rails for the whole off the machine , flange carriages for the X axis and HGH20CA carriages for the Y and Z .Will go with the 2 ball screws even though i only intend to cut hard wood but just incase i ever need to cut aluminium. I have had ago at the gantry, really i just stole Jazzcnc L shape design,Hope he dosen't mind .the front profile is 120mmx60mm and the back profile is 60x60mm the end plates are 20mm plate.
Cheers Greg
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I certainly like the double ball screw idea and placement, what i dont like is the possibility of adjustment and the fact that both end supports are enclosed by the frame. Make sure the ball screw assembly is shorter by 1-3mm than the distance needed and use a plate inbetween, so you could sand the plate and adjust accordingly, or use epoxy putty there, adjust and let it dry.

Just make sure you mount the rails perfectly, that will guide the ball screws and will greatly facilitate the final adjustments

I know you shouldn't buy anything until I have the design finished but i have been offered 3 X AM882 drives for £110 would this be a good buy and work well for this machine, With my knowledge off electrics not great i want to keep the electrics as simple as possible .After reading some more build logs am i right in thinking that 1610 ballscrews all round would be ok for this machine with Nema 23 Stepper Motor 3Nm all round or Nema 23 Stepper Motor 4Nm?
Cheers Greg

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Originally Posted by Gregor

I know you shouldn't buy anything until I have the design finished but i have been offered 3 X AM882 drives for £110 would this be a good buy and work well for this machine, With my knowledge off electrics not great i want to keep the electrics as simple as possible .After reading some more build logs am i right in thinking that 1610 ballscrews all round would be ok for this machine with Nema 23 Stepper Motor 3Nm all round or Nema 23 Stepper Motor 4Nm?
Cheers Greg

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Greg If the am882 drives are in good condition then they will be fine . 1610 on X and Y. 1605 on Z nema 23 are good as long as you get them with low inductance the 8 wire version. Zapp or cnc4you have the correct one's

Thanks for all the advice
I have made a start on the design off the z axis which i am not sure if i have worked out the travel right so any advice would be great,I change the profile for the Y axis L shape to 90x45 I think it was in a post by Jazcnc that I was reading that it is handy for fitting the Hiwin rails to. Here are some pics with the measurements
Cheers Greg
Attachment 20257
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Why have you gone for the square shape on the gantry sides as your previous post you shows it different. It might be better to show the z axis in more detail as you will need a cutout on the back plate and the front plate to accommodate the ball nut.

Sorry I posted the wrong pics here are the ones I should have posted.If my calculations are correct the spindle should be 25mm from the edge off the front off the gantry
Cheers
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If you have not bought your screws yet the Y screw could be made shorter and the pulley and the motor could be inside the gantry as you won't be using the full length of the screw.
Are to still at the drawing stage or have you started with the build?

Hi Clive
I have the base made which i welded for a friend but then he moved house and didnt have room for it so got it back but thats about it.I think i understand what you are saying something like this
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Cheers

Yes because the ball nut is in the centre of the z plate you could also put the screw on the back but its up to you.

edit When you order the screws make sure you make the F length about 30mm you can always cut it off but not put it back on:playful:

Gregor not sure you have done enough checking etc to make sure things will fit correctly.
I know for fact how you have it designed now the ballscrew won't fit on the gantry without lot of messing about. You'll also get clashes from Ballnut brackets etc which will result in loss of travel.

While my design works great there's very little spare room so if your going to copy how I build them you need to follow exactly of at least check for clashes etc. This means more detailed Cad model with accurate models of parts used.

How you have it now won't work very well. These might help explain better.

Ok Greg the master has turned up. Take notice, I don't think he will mind copying it is easier that doing it for one's self:joker:

So look very carefully at the pics you will learn a lot.

Hi Jazzcnc
Thanks,Nice machines .Yes my cam skills are crap .I see were you have the stepper mounted on back profile and I understand that were i have it wont work so i will move it down and make a bracket for it
Attachment 20303
I will probably get most off the parts from aliexpress and i have tried to get all the demensions from there but there drawings are very small and hard to read ,does any body have any links were i could get the measurements

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Originally Posted by Clive S

Ok Greg the master has turned up. Take notice, I don't think he will mind copying it is easier that doing it for one's self:joker:

So look very carefully at the pics you will learn a lot.

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Take no notice of this Man he's being too Modest he knows far more than he lets on.!!

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Originally Posted by JAZZCNC

Take no notice of this Man he's being too Modest he knows far more than he lets on.!!

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I was always told if you spout your mouth off. they know twice as much as you because they know what you know and what they know. Try typing that after a bottle of vino:beer:

Its Saturday night so that's my excuse.

Quote:

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Originally Posted by Gregor

I will probably get most off the parts from aliexpress and i have tried to get all the demensions from there but there drawings are very small and hard to read ,does any body have any links were i could get the measurements

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You can find Cad models of parts like BK/BF bearings. They are standard dimensions across manufactures with only slight cosmetics differences so provided you get right model they will be ok. If can't find Cad modles then just search for BK12 or BF12 which is the size for 16mm ballscrews and you'll get loads of dimension charts.
Same with steppers Nema23 is standard size for mounting only the length changes with model type.

Similair with ballscrews and ballnut. The size and dimensions of the ballnut are common standard dependant on style. You'll use flanged type so again you'll easily find dimensions for 16mm ballnut with only slight differences in length.
Ballscrew machining is again standard dependant on bearing type with only the very end dimension changing according to your spec. This is what Clive is referring to when says F dimensions. Same here type RM1610 end machining and you'll get loads of dimension drawings which will suit BK12 bearings.

Also when designing the brackets for the Motor take into account the centre distance between screw and motor along with pulley size for belt length and make sure you can buy belt the right length to give adjustment you need. Very easy to find there isn't belt size that covers for Centre distance.
These are the little hidden details which get missed and bite you in the arse after all parts are machined.

The one other area on this design which is close is the drop down bracket for ballscrew. Gets for tight when approaching the end bearings so pay close attention here checking for clashing.

Jazzcnc is that a homing limit switch at the bottom off the ballnut bracket?
http://www.mycncuk.com/attachment.ph...0&d=1483821869

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Originally Posted by Gregor

Jazzcnc is that a homing limit switch at the bottom off the ballnut bracket?
http://www.mycncuk.com/attachment.ph...0&d=1483821869

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Yes if you look at the Red machine you'll see better that there's washers at each side which act as targets for the switch. One switch per axis which shares Home and Limit duty's.