#1 They give a little more support but it's not a game changer and using the narrow type is ok if you have them or can't fit the wide ones in. If no obsticles then I'd always use the wide if possible, the price difference is nothing.
#2 Depends what your doing but Don't waste your money on Aluminium bed if your mostly cutting woods because most of the time you'll have spoil board on top. For the main base a good grade ply wood sealed is fine. Then put spoil board on top of this and surface that.
If you need the flatness of Tooling plate or surfaced aluminium bed and plan on using coolant all the time then you'll need something that's stable so spend the money but IME most the time you'll have spoil board on top. And probably screwing into it.?
Most common question I'm asked is "What do I use for work holding" the answer is "Anything that Works".!! . . . I'll Clamp, screw, bolt , stick or suck and often some combination of few of them just to get a job done. Thou by far the most common is screwing down into spoil board.!
Dean - Thanks for clearing things up for me, I will be doing some aluminium work on it but was going to go down the route of using a mist rather than flood cooling, will this still be OK with the ply wood sealed base and spoil board setup? Also, probably a silly question but what are the typical depths for the ply wood base and spoil board? Just checking as I want to make sure I leave enough space bellow the spindle.
DigiSoft - Thanks for the link, I remember seeing it previously. Really nice build!
Provided you seal very well then yes with Low qty mist then yes Ply will be fine. Problem then comes from your Spoil board. Even Low volume Mist still creates mositure which gets into spoil board which isn't sealed. Often MDF is used for spoil board because it's cheap.
Really if your planning on using any wet kind lube often, even with air, then you'll want something that's resonably stable.
Depths are usually a multiple of sheet sizes so 18 or 25mm etc.
I had a resin impregnated board on the floor of my trailer. It seemed indestructible. I was wondering if that would make a good base as it is waterproof.
Going back to your sketch in post#19, I would extend the side pieces forward so it matches up along the whole side of the X bearing plate. You can then pickup another bolting point on the front X bearing between the 4off vertical bolts for the X bearing.
This side piece extension would be triangular in shape and fill in from the top of the gantry down to the end of the X bearing plate.
It would then (optionally) be triangular back out to the ballnut mounting point, or just go straight back.
This would provide much more support for the gantry onto the bearings for not much effort (apart from a bit more material).
Dean - Cheers for the advise. I swapped over the carriages for the narrower ones on the x axis and drew up the frame as per the setup you recommended using 4mm external rads on the section. Only thing I added was the box section running along the back (between the two x rail support sections) to let me mount a bearing for the belt onto (same as yours on post #7 here).
Routercnc - Thanks for the great idea, I updated the design with the following adjustments:
- Extending the plate 20mm short of the full bearing plate to keep standard sizes (200mm width x 300 height)
- Instead of being triangular back to the ball mount, I made rectangular cutouts on each side as any other way caused it to clash with the aluminium x axis ball-screw bearing supports and as a result, reduce working area.
I am going to try get access to a mill for this, but if all else fails are there any other options for cutting the steel plates?
Gantry weight (just side plates and box section) is coming out at roughly 17.5kg @3mm wall thickness. When put together with Z axis, spindle and motors, will this handle OK with the one 3.1Nm motor on the x Axis?
Also, I checked the z extension using the 25mm tall bed/spoil board and the below image shows the spindle end going slightly into the bed at full extension. Would it be worth changing the 100 x 50 box section under the x axis rails to 120 x 50 or maybe higher?
Last edited by examorph; 30-01-2016 at 03:35 PM.
Now here's the beauty of this system if you have one already and want to try using Nema 23 3.1nm motor then it's not going to cost you a fortune if doesn't work.
Use nema 23 motor with 1.5:1 Ratio (if using 10mm pitch screws) to increase torque and if it doesn't work then just replace motor with 34 and bore the pulleys to fit new shaft size which will be same or larger than 23. Depending on how you make the motor mount then you may need to alter or change this also.
68Vdc is at the bottom end you'd run nema34 motor and top end for nema 23 so will still give you decent performance so very little risk or cost involved.
I wouldn't sacrifice Strength having too large an extension or hieght for the few times you'll probably need full extension.
Dean - Cheers again for the help, good to know I can cut thru 10mm steel plate simply with an angle grinder! I haven't ordered anything yet so good spot on the motor, will get in the 6.1Nm to be on the safe side. Do you have any recommended suppliers as I dont think CNC4You do this and also, will it work fine with AM882 Drives?
I lifted up the spindle slightly but think this, like many other things might have to be one which gets put right during the build.
Do you think I am in a position now where I can start getting some of the linear motion stuff in from Fred Lee and start looking at local suppliers for the frame materials? If so, could you please cast your eye over the below list to make sure I haven't cocked anything up?
Linear Rail -
2 x Hiwin HGR20- 300mm linear rail
2 x Hiwin HGR20- 600mm linear rail
2 x Hiwin HGR20- 1000mm linear rail
12 x HGH20CAZ0C Hiwin block
1 x SFU / RM 1605-L250mm Overall length- C7 ballscrew with a ballnut with end machined and increase dimension F on end machining to 25mm for pulley
1 x SFU / RM 1610-L650mm Overall length- C7 ballscrew with a ballnut with end machined and increase dimension F on end machining to 25mm for pulley
2 x SFU / RM 1610-L1050mm Overall length- C7 ballscrew with a ballnut with end machined and increase dimension F on end machining to 25mm for pulley
4 x BK / BF 12 support for ballscrew
Some things I am not too sure about are if the reference is right for the narrower carriages, if the Z0 pre-load is what is normally gone for and also if the end machining info is right?
Hi, a bit of advice.
I see sth strange in this machine. May be i am wrong, but before buying and spending and cutting material, better do a continuity check. Element by element the way you will mount it together and check if thats possible and the difficulties.
I do that with whatever i build and in spite of that some times is difficult in real life to mount things together, there was an element in my first machine that cleared mere 1-2mm or it would not enter. Even that i have checked that 10 times .So dont use just copy paste, Hi but move the elements as they will be moved in real life.
My rule of a thumb is to leave clearance holes at least 1.5mm bigger in diameter, better 2mm. Cause the paint, the welding, etc... And when you weld, aim at precision, dont be in a rush. I have welded 1 meter machine under 1mm precision and 3 meter machine around 1mm. Its not a joke. And it was one of the first thing i welded. By the way 250A mig is best for home fabrication and costs about 350euro on ebay. Later when you can could change gun and cable with a brand one. Thats what i did.
Buy more material and use extra cut to size pieces as hard stops so you could achieve precision mounting. later you would use them for sth. And steel is cheap.
You need light preload, not 0 preload for the bearing blocks. Wider block serve nothing more than easier to mount usually for the gantry legs. On Z almost always the normal blocks are a must. Make sure you buy the long carriages.
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