Here we go again . . . MK4

[routercnc]

I managed to finish all 16 inserts, so another job done:


All the Y and Z axis material has arrived from aluminium warehouse. All fine except they sent me 5" round instead of 5" square. This is to make the block which holds the spindle. Quick phone call and they sent me the 5" square for free and told me to keep the round:


So onto the Y axis sides. Here is the CAM:


Laying out the blank:


Holes:


Profiled:


Holes tapped:


Then the corners had to be filed square to take the stepper bracket:


Edge holes drilled and tapped:


The second one was made the same way but snapped a cutter with the adaptive being effectively too aggressive. Actually it was my fault as I did not align the blank quite right and so the cut was too wide as the stock was not where the software thought it was. Anyway, we got there.

Couldn't resist a dry assembly to check it all fits:



There will be a piece of bent sheet over the front and rear, so checking this will fit flush to the stepper bracket:


Then onto the Z axis. Here are the raw stock parts:


Top plate being set up:



All for now.

[Nickhofen]

Wow nice work so far!!!

[routercnc]

Thanks for all the kind comments.

Onto the top part of the Z axis. Main holes roughed out.


You will notice that it is all offset to the right and the front. I made an error setting up the job and started to worry there would not be enough stock. In Vectric Cut2D the job always starts at 0,0. So you need to find the stock edge, go in say 5mm, and then zero out there. Then run the part which will give you a margin around the edge. In F360 I defined the stock in the software (which was 5mm larger than the part) and should have zeroed out on the edge of the stock. But instead I used my old method (by habit) and moved in 5mm then reset. The net effect was that the part was 10mm over to the right, and 10mm forward. Would it fit on?

This hole was supposed to be 5.5mm from the edge - looks like I might be lucky!


Counterbores done and used to hold the part:


Profile cut - ooh, just fits!


Then I walked in the 2 holes for the linear bearings. This is in case I ever make the power draw bar spindle and holds the chrome rails which the PDB mechanism floats up and down on.


When I was machining these holes I was removing 0.02 mm at a time (from the diameter). I noticed it was consistently taking away material from the half of the hole nearest me, and nothing off the other side. Now these are small distances, and within the 0.05 mm ballnut backlash so could be that, but I did lots of passes and spring passes one after the other and it always cut on the side nearest to me, as if it was progressing / loosing steps in Y- direction.

Here is the part trial fitted (on top of the sides which are still raw stock):


You can see that this also has stripes where the roughing stepped down on each pass, even though I did a full depth finishing pass. I checked for play in the Y ballnut and ballscrew mounting bearing and all was well. I pushed and pulled the spindle and all seem OK (well, as stiff as it always was anyway). I'll keep an eye on it as the final few parts need total accuracy !

[Zeeflyboy]

beautiful work, it's all looking so nice and chunky!

[paulus.v]

You can see that this also has stripes where the roughing stepped down on each pass, even though I did a full depth finishing pass. I checked for play in the Y ballnut and ballscrew mounting bearing and all was well. I pushed and pulled the spindle and all seem OK (well, as stiff as it always was anyway). I'll keep an eye on it as the final few parts need total accuracy !

Isn't your softwood spoilboard the problem? Holding that chunk of metal with only four small woodscrews... Just a thought, I don't have experience with similar setups.

I'm following with interest your nice work!

[routercnc]

Thanks Paulus,

All thoughts are welcome. I did wonder if it might move the part but after it was cut out I grabbed it and tried to pull it around on the spoil board but couldn't move it at all. It was pretty solid.
I've cut lots of parts out using this spoilboard method and not seen this result before.
Also before I started the profile cut out I marked around the perimeter with a pen, and the part had not moved relative to this outline.
For the bores I was also only taking 0.02 mm cuts which is very little tool pressure, just taking whispers of metal off, and yet it still seemed to be progressing in the -Y direction by a small fraction each time.

So at the moment I'm assuming this is a new electrical or mechanical problem that has developed. I've put this poor little machine through quite a workout considering it was meant for plywood and balsa wood, so anything is possible. Maybe it has finally figured out it is making it's successor . . .

I also thought about whether I was missing steps on change of direction, maybe somehow the step active high/low setting had changed? Next chance I get in the workshop I'll check that and I'll run some G-code moving the Y axis back and forth various distances and at various feedrates (without load), stopping back against a DTI, and see what happens. Then I'll take it from there, repeating with the spindle on (no load), then some edge cuts, etc. and see if it returns to DTI zero.

[routercnc]

Time for one of the side jobs. The linear carriages are buried inside the Z axis box so there is no easy access for greasing them. So I designed some remote grease nipple parts, turned from some 10 mm brass bar. Here are some of the almost finished parts (4 off assemblies required, so 2 bits to go . . .plus threads need tidying . . .):


First job was to check the thread size and pitch for these 20mm hiwin carriages - turns out they are M6x0.75 (M6 fine).


So I ordered an M6x0.75 spiral fluted tap and an M6x0.75 die. Quick check to see that I got it right (using the nipples which came with it):


I had some errors transfering the photos for much of the next steps (files were corrupt) so I'll have to skip a few. First part being turned:

.


Then screwed it tight into the carriage and scribed a line on the direction of the outlet tube, and a line perpendicular to that one. This is so the outlet tube points in the right direction (as you will see later), and so that I could align the centre in the vice (next op):


Then I made a fixture which would hold the part and used the perpendicular line to get it in the centre. The outer dia of the fixture was tight against the end stop. This all put the part in the same repeatable position, so I can machine 4 off flats and holes:


Here are the first 2 assemblies, tightened up and pointing the right way (phew!):


Trial fit:


View from the outside:


I'm just in the process of tidying the threads (undercuts, slight taper on first few threads, etc.) so they insert fully home. I've also got to add 2 flats on the outside near the grease nipple so that can be installed/removed with an M8 spanner.

The 4 upper carriages will have this system, but the lower 4 will have the bolts in until they need to be greased then an access panel will be removed from the underside of the Z axis (which keeps out the swarf as it is near the spindle), then the bolt removed and a long straight nipple extension screwed into each carriage in turn. So I only need to make one adapter for the bottom ones and keep it somewhere safe. That's the plan anyway.

[Neale]

I also thought about whether I was missing steps on change of direction, maybe somehow the step active high/low setting had changed? Next chance I get in the workshop I'll check that and I'll run some G-code moving the Y axis back and forth various distances and at various feedrates (without load), stopping back against a DTI, and see what happens. Then I'll take it from there, repeating with the spindle on (no load), then some edge cuts, etc. and see if it returns to DTI zero.

That was my first thought when I saw your post. I found the same problem on my current machine on the Z axis - didn't show up on simple profiling jobs but when I did some heavy-duty 3D carving, it rapidly showed up. It's probably only a single microstep per reversal so a bit of gcode that moves, say, 50 times in each direction and comes back to a dial gauge will show it up. The clue in my case was that the error was pretty consistently number of reverses times distance moved per microstep. At least it's a quick one to check and eliminate!

[routercnc]

I managed to finish off the remote grease extensions. The threads were tied up so the grease nipples now sit flush on the end of the tubes:


Then machined 2 flats (8mm AF) which were aligned to the flats on the grease nipple. This is to allow the tubes be inserted after the bearings are fitted, making it easy to fit/remove the Z axis - something which might happen quite a lot when setting the machine up:


Here they are complete:


The single straight one (left side) is to service the lower bearings and is fitted to each unit as required, then removed.

Then onto the Z axis. These are the large side pieces, each 30mm thick. I'm machining them as a pair to get whilst I get them to size. Outer dimensions on most edges are critical as they will hold a pair of Z axis rails and need to be parallel, true, and hold a tolerance on the dimension.

They are too wide to go on their side on the bed or vice, and too thick to sit flat on the bed, so had to set them up on the edge:


Dialled them in roughly to avoid having to machine too much material away


Tops machined flat - left a tiny bit next to the vice which I filed away by hand:


As the parts were too thick to machine the ends, I marked a datum on the left end (+0.5mm longer than final dimension), and one on the right end.


Then set up a parallel edge. This was so I could flip the parts over and rest the machined edge against this. Took a long time to set it all up and be sure it was good, but them machined the other side.


I was pretty relieved to get to this point with both edges parallel and part to size (96 mm). However what I didn't know at this point was that this new top surface was actually on an angle and it was more like 95.7 mm (!) on the other side. Don't know if the fixture slipped during machining or what. But it is out by way too much for the linear rails.
I think my recovery plan will be to re-machine both parts to 95 mm (1.0mm underside) , and then use machine epoxy behind one set of bearing carriages to fill in the ~1.0mm gap. This might turn out to be a blessing in disguise as this will ensure perfect alignment.

Then onto drilling and tapping the holes. Not much to report here, standard stuff tapped to M5. But I did make this tap guide from a bit of aluminium round. The last part of the hole is tapped to M5, then there is a 6mm clearance. This guides the tap into the thread perfectly. Might make so more for other sizes:



I didn't get a picture of the last ops but I basically machined the ends to final size using the datums machined on an earlier op. I had to flip the part to do both sides.

Once I sort out the edge machining problem, there are some straightforward holes / counterbores to come, then I need to figure out how to machine some detailed features onto the ends. I think I will cut a hole in the table the machine sits on and poke most of it through into the draw space underneath.
The final op after that is to drill an 18mm clearance hole about 200mm long through the centre of the part (ballscrew sits inside). I think I'll do that on the lathe . . . bit more thought required.