New build – input/comments appreciated

[routercnc]

Agree with Lee - nice design. Will do just want you want it to !

Some other minor things to think about:
Z travel is quite long - I guess you need that much to do the speaker cabinets if they are partially assembled? If you want to cut aluminium then you will probably need to raise the job towards the cutter to limit the reach of the tool and keep the stiffness up. Some thick packer plates or wooden blocks should do it but you can add those when you are ready.

At the bottom of the frame I'm not sure I'd do the diamond in the base legs, may be just a diagonal across from one corner to the other, and I'd probably add adjustable feet to level it.

That's it really . . .

[Blackrat]

looks good

i think you might struggle with alignment with the y rails running top and bottom , maybe placing on the front face will be easier .... my first machine was like that ... just a thought :D

[ngundtoft]

blackrat - sorry for mixing up the X and Y axes. I expect that you mean the X axis according to my new drawing? Maybe it is better, but it will also reduce the effective Y-axis work length. Anyone to comment on this?

JAZZCNC - with respect to extending the top rails (Y-axis), I am not quite sure what you mean by "placing gantry in space using a short cantilever"?[*]With respect to BOB - I have noticed that you are not happy with cheap Chinese boards - and very understandable so, if you have had bad experience with them. My reasoning was that the signal "processing" (Smoothstepper) is the critical part and that the BOB is really a fairly simple device which is not so likely to fail or give problems. A concern with the PMDX 126 (which is undoubtedly very good quality) is that it does not have controller for spindle and pump.

[JAZZCNC]

100% agree with Lee (No I'm not sucking up so you lot can shut up before you say it.!! ) Let this be a lesson to others on how to go about starting a CNC build.! . . . Well done Sir A-Star +.!

I do have some suggestions for you thou. Other than turning the motors outward which is a must do.!

Put some ends on the gantry it will greatly stiffen it up. I would also think about lowering the ballscrews has they are vunerable up there and some form of protection from chips etc.
This can be achieved by making the gantry narrower so it's just extends past the sides of the machine. The gantry ends then extend down past the top rail 3-5mm away from the steel and on the inside of the ballscrew. The gantry sides can then be bolt to the gantry and the bearing plates making gantry slightly narrower and a very strong structure.
This then allows you to place the ballscrews lower down out the firing line of chips protected by the top rail and damage from dropped materail etc.
The gantry side being on the inside of the screw makes alignment and setup of the ballscrew much easier. More importantly it narrows the restriction from the moving part the gantry and allows you to cover the screws easier with covers for protection. If your not sure what I mean ask and I can provide examples.

Also think about extending the top rails past the ends of the machine.? If done at both ends this can gain you back some cutting area and full access to work area by placing gantry in space using a short cantilever and at other end allow gantry to pass the front of machine so materail to be clamped on the end and edge machined or over height material.
I suggested this to Eddy at time he was designing and he didn't take up on it to only later end up cutting lumps out of his bed so could edge machine material ie: dove tails etc.

Only other change to frame I would make is to remove the back plate on the axis which moves acreoss the gantry. It's not required, it adds weight and very little strength. Can make the building much harder has the mating edges need to be perfectly 90deg otherwise it can twist and bend the bearing plates. Profiled linear bearings don't tolerate this very well and will bind.
Nice strong Drop down bracket will work just has well be much lighter, cheaper and easier to build.

Electrics then the only thing I would change is the BOB. For get the cheap chinese stuff you'll only regret it. I wouldn't use DIYCNC stuff either if your going with Smooth stepper. Honestly there really is only one BOB worth using with the ESS and that is PMDX 126.
All the others will at some time give you trouble or restrict the machine performance. Pay the extra at the begining and you won't regret I promise you that, which can't be said for the others. Trust me on this I've used most if not all of them.

What I've suggested are just that suggestions and what you have drawn so far would work great but some of those things I've suggested I think you'd find would probably be on your bucket list for Mk2.!!

Well done and if you build with the same careful attention then you'll have nice machine.

[njhussey]

Wow, well researched and thought out!!!

I'd definately do what Jazz suggests and extend the rails, I wish I'd done it now (mk2 will have them like that!!) not only to cut dovetails but to put a 4th axis etc. I can vouch for putting sides on the gantry and extending them down below the rails, makes aligning the ballscrews easy (make your frame as square as possible, will make aligning easier...less shimming!!)

Looking forward to seeing this build...

[JAZZCNC]

blackrat - sorry for mixing up the X and Y axes. I expect that you mean the X axis according to my new drawing? Maybe it is better, but it will also reduce the effective Y-axis work length. Anyone to comment on this?

There is no right or wrong it's how you view the machine. From the front it makes more sense to call long axis Y.

JAZZCNC - with respect to extending the top rails (Y-axis), I am not quite sure what you mean by "placing gantry in space using a short cantilever"?[*]With respect to BOB - I have noticed that you are not happy with cheap Chinese boards - and very understandable so, if you have had bad experience with them. My reasoning was that the signal "processing" (Smoothstepper) is the critical part and that the BOB is really a fairly simple device which is not so likely to fail or give problems. A concern with the PMDX 126 (which is undoubtedly very good quality) is that it does not have controller for spindle and pump.

Argh but your assumption that the BOB is fairly simple device is mistake often made. BOB is actually the single largest cause of trouble and strange happenings with CNC machines.! Cutting corners here is recipe for trouble believe me.
The thing you have to realise is that the BOB handles all the signals and if it's low quality with slow opto's or poor circuitry then those signals get strangled, distrorted and weakened. There's no point having an external motion card which gives nice fast crisp pulses if the BOB is going to bottleneck them and distort the signals.
Like anything in life the CNC machine is only good has the weakest link and cheap BOB will be just that then some.!!

The PMDX 126 does have Spindle speed controller daughter board pmdx 107 with Relays for controling pumps etc.

With regards to Cantilever overhang then like this.
Attachment 16024 Attachment 16023

[ngundtoft]

Can you please tell me what these profiles are called and where you can buy them. It looks like they are approx. 100mm high in the first of your pictures. I have searched the net, but I have not found the same profiles.


One more question - what distance approximately should you aim for between the tip of the spindle and the bed (steel frame), in the down position?

[JAZZCNC]

Can you please tell me what these profiles are called and where you can buy them. It looks like they are approx. 100mm high in the first of your pictures. I have searched the net, but I have not found the same profiles.

In the first picture It's an equivalent to ITEM profile size 120x80 with 8mm slot. Called Profile 40 I-Type Slot8 from Motedis in Germany.
http://www.motedis.co.uk/shop/Slot-p...60bnk0tfjmi0i0
You will need spacers with this profile for the BK/BF12 blocks as the slot hole spacing doesn't match.

The smaller narrower machines use 45x90 Profile B slot 10 and they do match the BK/BF12 blocks.

Other option is don't use BK/BF blocks and machine the bearings directly into the gantry sides and buy slightly longer screws.

One more question - what distance approximately should you aim for between the tip of the spindle and the bed (steel frame), in the down position?

Hard to answer because it depends on several factors like longest tool length and Max material size your likely to want to cut. Best way is to make a call on the max material thickness and the longest tool your likely to need and Add together plus 10-20mm extra.

For the amount of Z axis travel then I wouldn't go past 200mm with 150-160 giving a good balance of range and strength. The longer it has to extend the more it flexs so keeping short will be stronger but could limit you at some point with longer tools.
Too long and your weakening the machine. No point having 150-200mm travel when your only ever using tools that extend from spindle 50mm and cutting material less than 50mm. All your doing in this case is introducing risk of higher resonance which affects surface finish and accurecy.

This is why people who want a wider material cutting range opt for the adjustable bed because they can keep the strength and still have option of cutting thicker material with longer tools. The machine in Post#9 has this feature so can accept 150mm thick material and cut thru it with 150mm length for making mortice and tenions in 6" Oak beams or V-carve/relief the face of 310mm thick beams.

In normal day to day use the bed mostly stays in one middle of the road position.

[kingcreaky]

Well done sir.. Salute.

only thing I can suggest, is, instead of driving each shoulder of the gantry with its own stepper motor, connect the two ballscrews with a long belt to one stepper. you wont regret it. That way you can calibrate it square once, and it remains mechanically fixed that way going forward.

I think a few of the boys have done it, most recently mr njhussey look at his thread

matt

[Neale]

..and once the machine is set up and working, you'll use it to remake components to look better? That's what I keep telling myself!