ok, first attempt using sketchup 8

[deannos]

yes it will be a pair of leadscrews on the x axis, not sue on how to attach them yet.

[JAZZCNC]

Hi Dean,

There's pro's and cons to both portrait and landscape designs. Landscape is good for reasons like only having one long screw on Y axis rather than 2 long screws on X axis which is a problem with large format machines, space saving and easy loading are just a bonus IMO.
The down side is that you need to really beef up the gantry and your choice of 45mm profile fastened to a single plate will leave the machine very weak IMO.
Nothing wrong with the format great for light duty wood use but I would seriously look to beef up the gantry.

If you must use profile then why not use 45x90 sandwiched between 2 plates like the pics below.
The wider profile helps with ridgidity and mixed with the extra plate it would be very strong. Plus It has the advantage of protecting the screw with just a slot for the Y aixs ball nut mount bracket which is covered with simple brush draft excluders but still allowing ballnut bracket to slip by.Access is simple by unscrewing the rear plate.
The slot is easy cut into the plate by drilling hole either end then simply running circular saw up each side.

Keep up the good work. .

[deannos]

Jazz,
Is the plate with the slot still ali or wood, i'm confused with cutting with a circular saw. If i did beef the gantry up this way would i then be able to cut anything other than light wood, would it be able to mill aluminium if required

[JAZZCNC]

Jazz,
Is the plate with the slot still ali or wood, i'm confused with cutting with a circular saw.

Yes it's Ali plate and yes it cuts very easy using hand held circular saw used for cutting wood so long as it has a TCT tipped blade, preferably with a thin curf.
There are purpose metal cutting blades as well but can be expensive and not required if just doing the odd bit of Ali cutting.
You could use a jigsaw but the hand held makes quick work of it and cuts a nice straight line.(Better if you use a guide or piece of wood to run against)
The hand held will cut 10mm plate in one pass just lower the blade in nice and slow and push at a slow feed. Make sure you use goggles and long length sleeves because the chips burn like crazy.

You can even cut Ali with hand held router if you take shallow depth pass's. Thats how my first machines gantry sides and Z axis where cut, I made a MDF template then used TC 6mm straight top bearing guided wood bit and cut around the templates in 0.25 pass's.!! . . . Scarey shit at first and took awhile to do but it worked ok.

If i did beef the gantry up this way would i then be able to cut anything other than light wood, would it be able to mill aluminium if required

With this setup you'll be ok for anywoods really so long as your not expecting to cut 20mm in one pass.!! and my comment about light wood use was aimed at your first design mostly.
Regards cutting Aluminium then yes it will but you'll need to be sensible, don't expect it to take 2-3mm depth pass's or even 1-2mm. You'll be in 0.25-0.75mm Max area for acceptable results. That said this is still usable thou and if your realistic with DOC/FEED rates etc then it'll be ok.

[deannos]

If you must use profile then why not use 45x90 sandwiched between 2 plates like the pics below.
The wider profile helps with ridgidity and mixed with the extra plate it would be very strong.

Jazz,
I don't mind whether i use profile or not is there something else i could use

[JAZZCNC]

Jazz,
I don't mind whether i use profile or not is there something else i could use

Well seen as your using steel for the frame then I'd probably look towards using that. Simplest way would be an I beam RSJ type beam.
Would get 180x100 for about £30 if your buying steel for rest of machine. You can buy 1500mm length from Metals4U for £37 plus postage.

This would be an easy option and plenty strong enough for your needs, easy to fasten rails, screws etc.
You will need to make sure you get a nice straight and flat piece then may still have to do a bit of cleanup with grinder/sander and straight edge to make it's flat but it makes a very strong gantry. (Don't be fooled into thinking profile is always straight or flat.!!)
The weight will be slightly higher but to be honest for a wood router if mixed with a strong spindle/big router the extra weight can be an advantage and allow deeper cuts which offsets the slightly lower feeds.

The other way is to use 80x40 box section in a similair setup to the Cad model using profile, just slightly cheaper than profile at £35 for 7.5mtr.

[deannos]

Well seen as your using steel for the frame then I'd probably look towards using that. Simplest way would be an I beam RSJ type beam.
Would get 180x100 for about £30 if your buying steel for rest of machine. You can buy 1500mm length from Metals4U for £37 plus postage.

.

I like the idea of using the RSJ, less for me to do. I assume i wouldn't need to box this in and it can be left as is, would it need support or stiffeners at each end.

[JAZZCNC]

I like the idea of using the RSJ, less for me to do. I assume i wouldn't need to box this in and it can be left as is, would it need support or stiffeners at each end.

Here's how I'd go about it.! . . .Miniumum welding and very strong. I've drawn it with welded corner braces but this could be built without any welding what so ever just drill and bolt if you used 19mm plate for the corner brackets.
Personally I'd weld 5mm plates in the corners and proably a few extra braces across it's length round the back side to just help reduce resonance but again these could easily be bolted, just weldings quicker.
I'd also probably incorparate a thin detachable cover plate on front with slot in it using brush's like in other design just to protect the screw from debris, esp if main use is wood. For the little extra work and expense it will save the screw big time. You could use flexible consertina type covers but they are expensive and can be akward to setup.


EDIT: OR you could just cut a slot in the RSJ and mount the screw on back side and cover with thin plate, something like clear perspex so you can see workings.!! Added pic (RSJ4) with slot in couldnt be arsed to alter sides or move motors but again you'll get the idea.
It will weaken the gantry thou and some extra bracing along it's length would be required.

[Jonathan]

The torsional stiffness of I section is very poor compared to RHS or box section and clearly the ganty twisting directly leads to tool deflection (proportional to the extension of the Z-axis) parallel to the Y-axis. For the same mass you should be able to make a much stronger gantry with RHS, or an equally strong but much lighter gantry. The difficulty is the position of the Y-axis ballscrew is sub-optimal, but you should be able to get it close to between the rails. That's why people often use two pieces for the gantry with the ballscrew between. That also allows adjustment to get the rail mounting surfaces parallel.

Routercnc's spreadsheet posted a few years ago on this forums lets you compare the sections easily.

With this setup you'll be ok for anywoods really so long as your not expecting to cut 20mm in one pass.!!

I've done that in plywood...pretty scary at first but the second cutter survived!

[JAZZCNC]

thats one nice no nonense design jazz,:tup: mind if i pinch it:naughty:

Nope go for it Chip all my ideas are some bugger else's anyway. . . Just Jazzzzz'd up. .:heehee: