fresh start 8x4 build

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first of i would like to thank you guys especially a few certain people because i knew nothing about cnc and ive learned alot and still enjoy learning more and more everyday. i will be updating new pictures on this thread from drawings to practical.

cutting area of 8x4 sheets of all types of wood and some cases of plastics. frame is made up of 90x90x5mm box sections and will be all welded and bolted to floor.
The 2 box sections that the gantry is sat on are 100x100x10mm, gantry is roughly 70kg with 20mm aluminium plates all round. x axis are 3000mm r2525 ball screws both sides with rotating nuts both on nema 23 3nm 840oz motors. the y axis is running on 2010 screws 1450mm running with another nema 23 3nm 840oz. The z axis is 450mm with total travel height of 200mm on a 1610 screw and all axis on dual linear profile rails.

as for electrics so far im going to use em806 drivers so any tips on whats the best power supply to get to run those steppers at best performance?

looking forward to good and bad crits.

Ash

Ash Look closely at the gantry and you'll see common Gotcha.??? ( 2 exam points deducted If I got to tell ya . .Lol)

Also I'd add lower rail between the diagoinal braces it will stiffen the frame for when being moved etc.

are you talking about bearings not flush with the rails? and thanks Dean ill add those supports on frame.

Ash

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Originally Posted by reefy86

are you talking about bearings not flush with the rails? and thanks Dean ill add those supports on frame.

Ash

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No keep looking. Getting warm thou

I would put the Z axis within the footprint of the gantry, by swapping the end cheeks over. I just puts the forces on the X axis slides acting downwards with gravity and cutting not putting twisting forces on the gantry. Also you could reduce the floorspace of the machine, without reducing the cutting area.

Cheers,

Rob

is it the fixed bearing blocks on z axis? if it is im sure someone said to have the blocks fixed and the rails moving. im still looking though lol

thanks rob, ill alter them now and Dean i take it thats what you were pointing at :)

Stab in the dark how are you going to access the bearing blocks bolts under the gantry

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Originally Posted by Clive S

Stab in the dark how are you going to access the bearing blocks bolts under the gantry

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2 points to Clive. . :yahoo:

Aw c'mon Dean and Clive, you just use a very short hex key :barbershop_quartet_

you have me thinking now lol. are those bearing blocks not designed to screw from plate into the blocks? thats how the design is by bolting from underneath into the blocks.

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Originally Posted by reefy86

you have me thinking now lol. are those bearing blocks not designed to screw from plate into the blocks? thats how the design is by bolting from underneath into the blocks.

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The bearing blocks are threaded and you bolt dowm into them. Your design cannot access them without removing the gantry profile first which makes setting the gantry square very difficult. You'll want to access them and leave lose fit while tweaking gantry square then tighten them.

dont know if im being stupid but what i had in mind was to only bolt the top alu profile untill its square then had the bottom.

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Originally Posted by reefy86

dont know if im being stupid but what i had in mind was to only bolt the top alu profile untill its square then had the bottom.

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Sounds like a plan to me :thumsup:, use the top one like you say, then add the bottom beam once your happy with everything else.

If the machine turns out like what you have in CAD (post 1), it will be a very nice machine indeed, I look forward to watching this one unfold and you seem to be in good hands.

Will you be doing all the work yourself Reefy?

.Me

thanks lee, im a newbie on all this so the only credit ill take is actually listening to good advice. ill be getting the frame welded by an experienced welder and then have a friend help with the heavy lifting ect and then everything else is on my own.

Ash

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Originally Posted by reefy86

dont know if im being stupid but what i had in mind was to only bolt the top alu profile untill its square then had the bottom.

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The way I see it is if you tighten the top one how will you get the bottom one in position. As Rob suggested you could rack the end plates back then you could access the bearing blocks and move the spindle back between them.

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Originally Posted by reefy86

dont know if im being stupid but what i had in mind was to only bolt the top alu profile untill its square then had the bottom.

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Sounds great in theory and will work treat in Cad but can tell you in practise it will be pain in the arse and you'll struggle to get linear rails to align and be parallel.
Fraction of degree error on wide machine shows massively at other end and you'll want easy way to adjust without affecting other areas of machine.

Then you have the fact that really you want to be bolting the bearing plates to the lower profile to stiffen the gantry.

Would be lot easier and stronger if you made the bearing plates longer and bolted to gantry. Also like whats been suggested you also want to move the gantry back to better balance the gantry on the bearings. Plus will bring the cutting area more into the machine foot print.

i just roughed this out but is this what you suggest on the bearing plates? made the plate longer so can access bearing blocks and the aluminium profile is bolted to center of plate.

Ash
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Ash easiest way is to have two plates. One bolts to the bearings and other is bolted to and part of the gantry. These then bolt together with the lower plate being threaded for bolts passing thru the upper plate and in location that is easy accessed. This way you can place gantry on bearing plate then lock into position when square. Then drill ream fit dowel pins to lock in place if wanted or just have tight fit.
Tight fit works well when first setting up and learning becuase if you bend the machine out shape can easily get back square by lossening bolts starting again.

slap in the face lol. thanks dean :)

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Originally Posted by reefy86

slap in the face lol. thanks dean :)

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Was not my intention to slap ya mate.! . . . . I'll keep stum if you like.?

I slapped my own face for being dumb I meant lol

update :)

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I love this forum. Had planned to make my x cars for the gantry in a similar way. After reading this I have to rethink to ;)

Or all this is just an indication that at the end you fill finish with too much spindle Overhang on gantry. My criteria is that in a good design, when looked from side, the bit should stay in the bearing spread or the sall called gantry side legs. Or at least not be too far in front of it. I don't see what you will be saving here? 5cm of rail?

you mean keeping spindle bit more or less as centre to the bearing blocks or centre to the side plates as much as possible?

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I mean D4 to be so long /260-300mm/ that router bit stays inside it. Its called -overhang/ how far from X rail is the spindle nose. There is center of gravity also. The nearest the bit to the center of gravity, the better. Ideally all should be designed so that is perfectly balanced .

you could read basic info about forces there http://www.cncroutersource.com/do-it...NC-router.html


But you could do it out of this concept as you like, if using Hiwing 20 rails and carriages. They are so strong that overhang is not a problem. Just i like things to be perfectly balanced and engineered






http://www.cncroutersource.com/image...4Davn5U1nm.jpg

thanks boyan, from spindle nose to x axis is 151mm, d4 as you describe is 215mm.

Ash

im hoping im slightly correct but are these images right?

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Hi, just answered your PM but could not upload pictures there. Just saw what you have posted as images .


In short - NO. Dont despair, but this is not right. You will figure it out :-).

Lets see:

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This is how its the right way:


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Look at the ideal/ my machine is on the extreme side so not necessary so much / but hence is nice for illustration:


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Also this is the correct way, i would say the perfect way for the Z plate, so its naturally reinforced by the rails and the plates at the back and

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And finally, design so much travel and space brackets so that at lowest position of Z axis the spindle still reinforces the Z plate. Ignore that the spindle is small , because its small one 0.8kw and Z axis real travel is 180mm . NOrmal 2.2kw or 3kw spindle is much longer. This just to illustrate eventual max. Position:

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Originally Posted by reefy86

update :)

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Much better, I would bolt those extra plates to side plates (2 more bolts)

Withe regard to the long carriage rails on top of the steel frame, are they staying there or being moved to the side of frame?
I would have thought side mounted rails on angle would allow for adjustment, due to distortion of the frame during welding, if they stay on top shimming will be required.