Questions on using a moving gantry style mini-mill...

[JAZZCNC]

#1 With cutters less than 3mm I work on 30% diameter DOC.

#3 Wouldn't use tabs I'd use Onion Skin of 0.1mm. This gets rid of any chance of bed damage and removes risk of lifting.

#4 Rough and Finish passes. I'd use Large tool for Pocketing and Roughing then use small tool for Finish pass and corners cleanup etc.

[Davek0974]

Thanks Jazz, more good tips.

0.6mm DOC on a 2mm cutter sounds reasonable.

I had seen onion skinning used on the woodworking forums but how do you go about cleaning it off on a job like this or is it easier than i think?

Rough and finish - large and small makes sense, would use the same process for shapes like the large oval or just use the large tool staring to finish?

Thanks

[JAZZCNC]

I had seen onion skinning used on the woodworking forums but how do you go about cleaning it off on a job like this or is it easier than i think?

The part breaks out easy. Often it breaks out clean but even if the 0.1 skin is left on in places it just snaps off clean. Then quick whip round edge with De-bur tool and done.

Rough and finish - large and small makes sense, would use the same process for shapes like the large oval or just use the large tool staring to finish?

Depends on Job really. If could get away with using same tool then I would but if Got to use small tool then it pays to use large tool to hog away material quickly then finish with small tool at full depth.
Often people try to avoid tool change and use same small tool but this fasle economy in several ways.?
Large tool will do it in fraction of time and with much less wear which more than offsets the tool change time. The small amount of material left also means the smaller tool is much less likely to break and also wear is less.

All it means is you have to think a little differently when you Cam the part and order the toolpaths are generated when large amount of tools are used.
Instead of having a operation which roughs then finishes in same toolpath before going to next area meaning lots tool changes. ie: Pocket operation then profile operation.
Instead you just have each operation do the roughing with large tool then create a separate set of operations for the finish passes with small tool.
This way when post processed all the Roughing passes are done before the Finish passes so only one tool change for all operations.

Hope that makes sense.?

[Davek0974]

Thanks JAZZ,

I was unsure if the onion skin would be enough to hold the part for the finish op's, have been messing in sheet cam and running simulations etc, seem to have it sorted i think but i can now re-order the processes to do all the roughing first.

What sort (if any) lube/coolant do you use on aluminium? I have enough parts in now to build a pressurised fog-less system but just wondering what people put in them :)

Back to the CAM, shapes like the odd shaped internal part on my drawing, I have roughed out the bulk with a 5mm tool, that leaves of course 2.5mm rads in all the corners, are you saying to finish cut that with the 2mm tool in one pass?

Do lead-ins and outs feature or forget them for the minute?

[JAZZCNC]

What sort (if any) lube/coolant do you use on aluminium? I have enough parts in now to build a pressurised fog-less system but just wondering what people put in them :)

I use WD40 type lube but oil/parafin mix will work.

Back to the CAM, shapes like the odd shaped internal part on my drawing, I have roughed out the bulk with a 5mm tool, that leaves of course 2.5mm rads in all the corners, are you saying to finish cut that with the 2mm tool in one pass?

Yes will be ok in this case because your now side cutting and the tiny amount left won't hurt anything. However it's not recommended to use same size tool as the radius. ie: 2mm Rad use use 1.9mm or smaller Dia tool. This means the tool won't be cutting on two sides in the corner so won't chatter or snag and break the tool. Which can happen on really small tools. Larger tools just usually leave mark in corners and make horrible noise.

Do lead-ins and outs feature or forget them for the minute?

Well they are all part the process really so should happen anyway. For instance you'll ramp into pockets for roughing to safe tool wear but radius arc into the Finish pass if enough room for better finish. If cam program allows I always let the lead out go slightly past the lean In point as well to remove cross over point.

[Davek0974]

Thanks, lead ins and outs pretty much like the plasma then.

Radius makes sense, already use the different rad rule on the Bridgeport as that can get a bit vocal when it wants to;)

Will apply to this as well, I was going 5mm rough and 2mm finish which fits ok i think, don't really want to go below 2mm unless really needed, but there are some features that are 2mm on the job so can't use bigger.

Been researching fluids and seems pretty much anything goes, even Methylated spirits, but paraffin and oil mix seems popular - pretty much WD40 without the waxy residue ;)

New power supply arrived today, will test it out tonight ;)

[JAZZCNC]

Will apply to this as well, I was going 5mm rough and 2mm finish which fits ok i think, don't really want to go below 2mm unless really needed, but there are some features that are 2mm on the job so can't use bigger.

Unless Rad is critical then it's worth changing rad in Cad just 0.1mm makes difference to small tools and in most cases doesn't make jot difference to part. When designing I nearly always make my none critical rad's 0.1mm over size for this reason because most tools I'm using are round numbers.