Luke11CNC Build Log ,I'm so naïve

[luke11cnc]

Looking at the price list Jonathan I may go with 20x20mm so I have 5 or 6 mill worth of surface trimming so it should last me quite a while

what do you think ??

James

[Jonathan]

It makes sense to use thicker, so yes 20mm. However I'd be inclined to use wider than 20mm strips (only 67% with 20mm and 10mm gap) for additional strength. It's less work to 40x20 compared to 20x20. If you went to maybe 40mm wide you can get two bolts side by side in each strip which should be stronger - less twisting? Not sure...

[luke11cnc]

good point Jonathan

James

[JAZZCNC]

Jonathan: Yes I do always put something between the bed and part. Depending on the job at hand.?
If it's a non critical job that the top surface be exactly parallel to bed or thru drilling then I just use any thing to hand that resonably flat IE MDF off cuts.
If it's more important it's parallel to bed but doesn't need to be exactly 100% perfect and doesn't have any drilling involved then I use a 1mm thin ridged card board I bring from work that doesn't compress.
If it has to be exactly 100% perfect and must cut thru or involve drilling then I have several sized 15mm HDPE slabs that I clamp to the bed then surface. MDF is no good for this because the minute you cut the top layer it turns into a shape shifter and no matter what folks think MDF aint flat or parallel thickness.
To be honest 60% of the time the card board is used 30% MDF 10% HDPE.

That said regards MDF.? I've just been given an MDF type paper product sheet that is resin impregnated. It's used to make the cubicles in swimming baths and shower area's. It doesn't swell no matter how wet, even when submersed under water. This I know to be true because this sheet was outside for 8mths.
I've just used a piece as a spoil board and it machines like plastic and surfaces with a perfect finish because of the resin.
Really it's the perfect product for a long lasting disposable bed topper.! . . thou I do understand it's very expensive.

James: (Or anybody who's interested)

Here's how I did it. (It was a bit tedious but worth it) . . . . Material 1"1/2 x 5/8 (38.1x15.88mm)

Using a 90Deg spot drill in the spindle find the centre of bed and scribe boxsection. Then mark the first strip exactly in the centre then bolt down exactly in the centre of the bed lining up with scribed mark.
Then using a 8mm spacer working out both sides bolt down each strip to bed. Then using a 8mm twin flute end mill create a climbing milling toolpath to cut the 10mm slots in 2 depth pass's, didn't want to use a 10mm endmill as it would have been cutting on both sides and required much less DOC taking longer and leaving a worse finish. . . .(Yes I know the 8mm cuts on both edges but only on the way up not down.)
Reason I did it this way was because I have some machine clamps that use 45mm centres. They could have been just butted with a 10mm spacer but there are other bennifits to machining the slots for me(see below). . . . Plus the strips arn't exactly straight.!!

Doing it this way I know exactly that all my slots are exactly parallel to the X axis. Across the very top (Yaxis) and down the outer edge (X axis) as a strip that bolts on top of bed and acts as referance edge, which again is machined parallel and square. I've made some 45mm wide aluminium strips (various lengths from offcuts) that have a 3mm notch down the centre with the edges machined parallel that fits tight into the slots and can be used as positionable reference edges anywhere on the bed ( WHY.? Because I like to cut in differant parts of the bed to save wear on the ballscrews from always cutting in the same spot.)

James I would go with the 3/4 or better still 1" the little extre expense will be worth it.

[luke11cnc]

Thank you Jazz

Yes I will go 11/2x1
James

[Jonathan]

Useful ... yes MDF is not flat, but then again it depends what tolerances you're trying to work to. That resin impregnated sheet sounds worth looking in to.

For me to cover my bed with 1.5x0.75" and 8mm slots would cost £475 even taking into account the 7.5% discount they give you for spending too much! Not really happening, though it would be a big advantage I can't really justify spending what my lathe cost on the router bed, could get a 60W laser and power supply for that :naughty:. I guess I could just do half the bed (1000*910mm, or 2000*455 but probably the former) and leave the other half MDF. As long as I skim them both equally that won't loose much, except it means I'll start using one end of the X-ballscrews much more than the other but that's not the end of the world. Would put a sheet of 3mm aluminium underneath half the bed to act as a coolant tray.... got a spare coolant pump.

Anyway, I'm going a bit off topic there. I've put the slot in the mount as requested and the Z-axis is very close. Done a little wiring on the control box too.

[JAZZCNC]

Useful ... yes MDF is not flat, but then again it depends what tolerances you're trying to work to.

Yep thats why I said "Job dependent"

. I guess I could just do half the bed (1000*910mm, or 2000*455 but probably the former) and leave the other half MDF.

Yes thats not a bad idea. . . I actually do put MDF full length down one side sometimes for jobs that are awkward to clamp or drilling and obviously don't need flatness.
The good thing about MDF is that it's easy to screw into and for small parts that need profiling some times it's easier because the slots don't line up and make clamping hard if not impossible. Thats why the more and closer the slots are together the better really because it gives you more % chance of always dropping on a hole or something to latch onto with clamps or bolts.

Has you probably Know full well Jonathan the bed and imparticular material clamping is an often un-thought about side of building a machine and can be a right pain in the arse. I can honestly say that yes while it was expensive other than the water cooled spindle it's the best upgrade I've made to my machine by far and wished I'd done it 2yrs sooner, makes work holding so much easier and far more accurate/repeatable.

[Jonathan]

The good thing about MDF is that it's easy to screw into

That's exactly why I'm hesitating. For almost all the parts I make I screw the aluminium down enough for the router to spot/drill the holes then use those holes for screws to clamp it properly and stop things flying when it is cut out. With the aluminium bed it's more difficult since I would clearly have to make the holes align with the slots which isn't always possible... never straightforward is it!

[JAZZCNC]

Ye I used to think like that but belive me it is far better and you still can use MDF spoil boards for quick or awkward jobs. The only difference is I don't ever have to surface the bed when it's critical to flat and true. I find because of 45mm centres 90% of the time find a suitable hole or pocket. Drilling is the most trouble some for me but I often pocket holes anyway(If not loads holes) so it's not a big deal.

One of the things I will often do when cutting several jobs that all have different needs is mix both MDF, HDPE and my card board spacer trick and use offsets G54, G55 etc.

I have my bed divided up into area's and have spot drilled small registration dot's so I know the 0,0 of each offset. Then I just fasten each particular job down using which ever method best suits the job lining the board up with the ref marks, line the material up with the corner of the board then in CAM/code I always have the part just in from 0,0 stand back and let it rip.
Depending on the jobs and time etc I don't always do it in one large piece of code, sometimes I'll have seperate code for each job just with the different offset coded in. This way I don't lose too much time unclamping re-clamping etc and can set the next job off straight away because I've set up the next offset while the previous job was cutting, just set the Z0 which is a 10 second affair with tool probe and away it goes again. . . It's quite efficeint.
The other good thing about clamping MDF or HDPE boards is because of the accurate and parallel tracks and offsets I can easily remove and replace the board with work still attached. Sometimes I'll do really long jobs that can be 15-20+ hours long so some times don't want to leave the machine on unattended so pick a suitable point to stop the code but then some times find I need the machine for something else in the mean time.!. . . doing it this way I can clear the table for the new job but still be perfectly back in position and carry on at anytime.

Like I say " FOR ME " it really has been a good improvement and worth the investment but everyone has different needs and ways of working.

[luke11cnc]

So sorry for not updating sooner but Im still smiling and It's been a busy day today as I'm trying to get ready for Christmas

Really BIG BIG thank you to Jonathan for wiring up the CNC machine and letting Luke help you solder and strip wires

well the machine is working and cutting well But I do need to screw it down as vibration is clearly a big issue Please let this be a warning to any one thinking about building a CNC a simple table design is not going to cook it.

I will follow up with a video as Luke took one on my Phone and I will also upload some more photo's as soon as I tidy up the garage (still looks like a bomb has hit it)


I have booked Jonathan to give Luke and myself 3 to 4 hrs training on the machine (don't want to break it!!)

any way I'm happy just sit and look at it and reflect on the journey taken with my son

James