Thanks routercnc for that stock-squaring video https://www.youtube.com/watch?v=tW8HNAlUXxU
How serendipitous that I found your link to the video almost totally by chance. Enjoyed the presenter's humour also.
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Thanks routercnc for that stock-squaring video https://www.youtube.com/watch?v=tW8HNAlUXxU
How serendipitous that I found your link to the video almost totally by chance. Enjoyed the presenter's humour also.
Some overdue updates . . .
To finish off the machining of the ballnut blocks. Chamfered 2 of the edges:
Attachment 21038
I swapped the 3 jaw over to the 4 jaw chuck and dialled it in using the bore I'd machined out on the CNC. Got it to within 0.05 mm, so pleased with that.
Attachment 21039
Drilled it out using a range of twist drills up to 25 mm, then bored it out to size
Attachment 21040
Three more to go:
Attachment 21041
Then used the CNC to spot out the 6 ballnut holes, then drilled and tapped then on the drill press:
Attachment 21042
Then onto the mounting holes on the underside. Again CNC spotting the holes, and then drilling and tapping the M8 holes on the drill press:
Attachment 21043
Checked it with a spare ballscrew - fits OK:
Attachment 21044
_________
Then onto the side support plates - spotting out all the holes:
Attachment 21045
Attachment 21046
Drilled out, counter bored, and tapped:
Attachment 21047
__________
Next parts are the tram plates. These connect the Y axis box structure (which contains the Z axis), to the Y axis bearing plates and allow the Z axis to be aligned in multiple planes to tram in the spindle. The adjustment will be made with M10 cup end grub screws before the main bolts are then tightened. I'll put a screenshot of the updated design in the future post.
Cutting them out:
Attachment 21048
Spotted, drilled, counter bored and tapped:
Attachment 21049
Here they are trial fitted to the side support plates (which then sit on the bearing blocks).
Attachment 21050
________
Then onto parts of the Y axis box structure. Started with some eco-cast from aluminium warehouse. Nice and flat and in good condition:
Attachment 21051
Attachment 21057
Marking out the holes with a 3mm drill bit:
Attachment 21052
Then machined out the pockets which will take the 4off Z axis profile rails. I did a very fine finish pass with large overlap on the bottom of the pockets to get them as flat as possible. There is some adjustment when everything goes together but best to get it close as possible:
Attachment 21054
Quick check:
Attachment 21055
Cutout, drilled, counter bored, and tapped:
Attachment 21056
Next parts were the triangular supports. No photos of these being machined as I wasn't happy with first one. As the design was just a simple triangle I used tabs to hold it in place. But these left the usual witness marks on one edge which didn't look very nice. I tried to sand them out but wasn't happy.
So I started again and added some internal cutouts to add a bit of style, but more importantly allowed me to hold the part in the middle while I machined all the perimeter away:
Attachment 21058
Still needs holes drilled and tapped in the sides, but decided to do a trial fit. It connects the tram plates to the side support plates:
Attachment 21059
Attachment 21060
A work of art, very nice :)
It's very satisfying when you have made a pile of bits and they just all fit together perfectly :)
Great thread - always really interesting to see how people go about making the parts rather than just seeing the finished product.
Super chunky looking parts there as well. I dunno what it is about a nicely machined chunky piece of alu but it's just damn tasty!
Managed to cut another one out this morning:
Attachment 21070
Another trial fit showing both triangular supports:
Attachment 21071
Just 2 more to go for the other side.
Here is the current design for the Y/Z axis. You can see the tram plates (small grey rectangular plates) I mentioned earlier which will allow me to tram the spindle relative to the larger green bearing plates underneath.
Attachment 21072
Initially I will put the WC spindle in the main housing and drive it direct. It might stay this way depending on how much better it is than today.
But if not, the following pictures show the alternative full feature version. The parts will be made to accept either set up.
Main feature is a home made spindle (Tormach TTS drawbar style with R8 collets), driven by the WC spindle via a pulley with different ratios, plus the addition of powered drawbar.
Attachment 21073
Here is a rear view of the pulley drive from the WC spindle, which is connected via a sliding frame to allow the belt to be tensioned:
Attachment 21074
This view shows the Z axis with power draw bar. This will give a simple push button tool release. I don't have pneumatics in my workshop so this is electrically driven via a stepper, through a pulley reduction drive, and finally through a ballscrew. Quick calcs show this should have enough power/torque to overcome the pre-load on the belleville washers (part of the drawbar retainer) to release the tool. The whole PDB system floats on sliding bearings so that it squeezes the drawbar against the spindle shaft, rather than loading up the bearings.
Attachment 21075
Attachment 21076
Here is an underside picture showing the spindle which bolts in via the lower flange. It is also held in place with the clamps further up the main body, which are also used to hold the WC spindle in direct drive mode:
Attachment 21077
Here is a cutaway view of the spindle showing housing, bearings, draw bar and collet system. At the top you can see the pulleys for the drive and the belleville washers which hold the tool in place by pulling up the R8 collet, which in turn squeezes the 3/4" shaft of the tool holder. Google Tormach TTS for more info.
Attachment 21078
(The power drawbar assembly is not shown in this drawing)
Still some finessing to do (e.g. tube connecting AC bearings in nose to upper bearings not in correct alignment etc.), plus still have to convince myself that I am capable of machining the spindle in the correct steel (oversize by ~0.3mm), get it hardened, then grind the bearing journals and the R8 taper to all be parallel and aligned again as they will be distorted. I'll need to make a fixture for my lathe to hold a die grinder or some other idea.
This is the biggest part of the project, the most risky, and the main reason I may just stick with the direct drive set up. But the attraction of big torque boost, the ability to run larger cutters, and the quick tool change keeps me interested.
Very nice, look forward to seeing the spindle progress.
Now thats the most out of the box z design i have seen recently. No shame in using 8x Hiwin bearing blocks and 4x rails plus a couple of motors apart from the Hf spindle. How would you align all that stuff in place? Each piece must be carefully machined to a tight tolerance.
Ok. I know that you will patiently make it. Obviously not your first machine :encouragement: 2 questions:
1. Wasn't it simpler and better using BT30 spindle and servo motor on a fixed gantry?
2. So much effort in all places but gantry will slide on round open cage bearings? No square supported ones? :cower:
Boyan - in the first post ;)
Quote:
Originally Posted by routercnc
Thanks Boyan. This is probably about version 5 of the Y/Z axis design with all sorts of combinations tried out, some with single Z ballscrew, some with pulley driven ER straight shafts, and other options. Eventually the desire to have the option of pulley driven spindle (for lower speed, higher torque), much larger cutting bits, and the ability to add a PDB drove me to this design.Quote:
Originally Posted by Boyan Silyavski
I wanted to make the stiffest Z axis I could as it is all won or lost here. The 4 rails and 2 ballscrews is as stiff as it can be (in concept terms) so went with that. I thought a lot about the alignment of the bearings as you cannot just machine everything and bolt it together. The Y axis box structure has slip planes to allow it to be pre-loaded up to the bearings to squeeze them together. I'll let you know if this plan works !
1. I agree fixed gantry would be even stiffer, but I needed to maintain a very large cutting area for wooden panels. If it was just smaller metal parts then you are correct. So this requirement has forced a compromise. Fixed gantry would have a very large working footprint and I don't have that space.
I also looked at lots of spindles including buying off the shelf BT30 etc but they are very expensive with PBD. In the end I decided to allow fitment of direct drive WC spindle (the hole is 80mm diameter), with the option of making a spindle later.
2. As Zeeflyboy has pointed out this has already cost a lot to make, plus there is more cost to come (more Z axis rails, more aluminium plate, more steppers and drivers, pulley hardware etc.) so the ~£200 profile rails on X will have to wait. Agree it is a weak point, and will also give some loss of accuracy. For now they will have multiple blocks per side, not the usual 2, to get the best out of them. But the rail supports which they run on has already been spot drilled ready for profile rail. A simple adapter plate to the gantry will then allow the upgrade.
I to am following this with interest. Have you decided on the size and number of the bellevilles? Also could you give more details on the drive arrangement for the PDB as I am making one for my mill but using an intensifier (small jack) to give a 7:1 advantage with 12 belleville washers. From a post on the Zone by SDMQuote:
Here is a cutaway view of the spindle showing housing, bearings, draw bar and collet system. At the top you can see the pulleys for the drive and the belleville washers which hold the tool in place by pulling up the R8 collet
Hi Clive,Quote:
Originally Posted by Clive S
I'm only 50/50 on making the spindle+PDB as it is quite a risky project, and could well end up just using the WC spindle as direct drive. But in terms of spec for the PDB system I've not finalised on all the details. It does seem quite hard to find definitive numbers on things like tool pre-load.
I'm away from my home PC at the moment, where all the data is, but from memory I'd put in the same number as the Tormach PDB kit shows (~6?) since I would be using the same R8 collet style. I've read that the load applied using the Tormach PDB kit is OK for general work but could be on the low side and an aggressive cut could pull it out of the taper, so I could need more. They don't want to share the spec details (understandable) for the bellevilles so no more data than this. I can add more than this without a problem.
I've downloaded a calculator to work out loads depending on series or parallel arrangements and also give the total travel until it bottoms out. This is where the tricky bit is to ensure the loads and travel all work out.
I had allowed for 10mm total travel of the drawbar to release the tool, of which 6mm is used to remove the pre-load off the taper, and the remaining 4mm is to push it out and hopefully release the tool.
The mechanical drive system needs a lot of force/torque, so the 7:1 jack you are thinking of is a good start. I currently have a geared down stepper driving a 1605 ballscrew. I did look at a 1204 screw to get more ratio but the axial forces are very high and I didn't want go that route in the end. Again from memory it needed at least 8 Nm to turn the ballscrew. That's all I have for now.
Thanks for the info. From what I have read (and I am no engineer) a R8 collet requires a holding force of about 2400 lbs to be safe. I am using part No. D2315162 washers from Belleville Springs 2 in P and 6 in S this give a free stack height of 28.5mm and a flat height of 24mm. 75% deflection height is 25.13 mm with a load of 12337N.Quote:
I've downloaded a calculator to work out loads depending on series or parallel arrangements and also give the total travel until it bottoms out. This is where the tricky bit is to ensure the loads and travel all work out.
I had allowed for 10mm total travel of the drawbar to release the tool, of which 6mm is used to remove the pre-load off the taper, and the remaining 4mm is to push it out and hopefully release the tool.
The guy on the zone recons 0.5mm will release the collet after the pre-load has gone.
The setup requires about 180Kg on the jack to give me 1260kg
I would be interested in the link for the calculator
Hi Clive,Quote:
Originally Posted by Clive S
I got the info together last night but no time to post out. Similar to your findings.
R8 needs 2500 lbf (11,000 N or 1,100 kgf) to hold it, maybe a bit more to be safe
Used calculator on this website:
http://www.meadinfo.org/2009/07/bell...ck-design.html
Used washers (())(( to get 15,000 N when flat.
Release distance was about 0.3mm (between holding load and flat load).
Looked at data on this site:
http://www.leespring.co.uk/browse_ca...=&pageNumber=8
part 500-125-1125
This was a quick look, I think it could be refined.
Mini update -
Cut out the 3rd bracing piece:
Attachment 21222
Final one under way:
Attachment 21223
All 4 profile ops done:
Attachment 21224
Then onto the side ops. I need to machine several side features starting with 2off 6.8 pilot holes (to later take an M8 thread). Bit nervous as I'm trialling fusion 360 for the first time as it can do these pilot holes as spiral bores. Done a few aircuts and all seems OK from a cutting point of view (apart from that G28 as mentioned in another post).
Here is the fixture:
Attachment 21225
Luckily I had planned ahead (!?) and the first triangular brace I made with the poor surface finish could be used as a support. It will be sacrificial as one of the ops will cut into it.
The vertical angle is held by the precision vice, with a backstop at one end. The part just drops in and is then clamped. I was just about to hit cycle start and I was called away ! So it will have to wait . . . .
I've been busy with other projects but back on it again and ready for some updates. I've had to re-read the last few posts so see where I'd left off so apologies if I repeat something.
Last time I left you in suspense over the holes in the side of the bracing pieces. Here they are being machined:
Attachment 21557
All 4 pieces machined:
Attachment 21558
Two of the holes need to be M8 tapped, and one is a clearance + counterbore. Here is the counterbore being done.
Attachment 21559
Bit nerve racking for 2 reasons. Firstly the pilot hole was machined blind on the other side, so I had to hope I'd got it all lined up so that the counterbore appeared in line with the hole. As you can see it was all OK:
Attachment 21560
Secondly, part was a bit close to the chuck. I'd measured it and knew it would clear. Clearance is clearance as they say but still glad it went OK. . . .
Attachment 21561
Then tapping the M8 holes on the bottom:
Attachment 21563
All 4 parts done:
Attachment 21562
_____________________________
Then back to the side panels. They needed holes on the sides which is always a bit more awkward. Got them dialled in:
Attachment 21564
Attachment 21565
Machined the holes and noticed that the top edge had a slight climb to it across the width with one edge 0.05 higher than the other. I guess this is reaching the limit of my current machine when cutting out a profile. So I took a very light skim to get it square again. This needs to be square to make the whole box square:
Attachment 21566
Repeated for the other one, then placed them machined edge side down onto an assumed good reference surface (lathe cross slide) to get them level with each other and then clamped them together:
Attachment 21567
Then machined the other edge, by taking a minute skim off, and then machined out the holes:
Attachment 21568
Then tapped the M8 holes:
Attachment 21569
Final dry fit of everything:
Attachment 21570
More to follow . . .
The tram plates also needed holes in the side. Here was the set up:
Attachment 21571
These holes needed to go all the way through the part, which is quite wide. The cnc machine can bore about 20mm into the hole, so the rest would need to be drilled out. But I didn't trust the drill not to wander so machined the bores on BOTH sides of the part using this fixture. Then drilled it out on the pillar drill from both sides until it met roughly in the middle. Guaranteed to get a straight hole !
Attachment 21572
Then counter-bored to hide the cap head and cleaned up:
Attachment 21573
_________________________________
Onto the Z stepper mounting plate, which will hold to the 2 stepper motors. First time using Fusion360 so a bit worried about how it would turn out (didn't need to worry as it turned out and have not looked back). Exported the part as an IGES file from my CAD programme and used F360 for the CAM. Very impressed with it. Here is the part to be machined:
Attachment 21574
As you can see I was still using a profile method to cut it out (hangup of using Vectric Cut2D), but have since learnt much better methods.
Holes:
Attachment 21575
Profile:
Attachment 21576
Stepper holes drilled and tapped, and done:
Attachment 21577
More to follow . . .
Next up was a little job I'd been putting off until I'd got to grips with F360. These are going to be inserts which fit inside the extrusion to connect the bed uprights. I'm sure there are many ways to make these parts but I decided to get some practice on adaptive tool paths. Here is the first of 16 parts:
Attachment 21583
It all started with a large 8mm sheet:
Attachment 21581
I then machined 2 edges so that the parts would be the right length:
Attachment 21582
Then over to the chop saw to rough them out to width:
Attachment 21584
Attachment 21585
Next part tool a while - machining the 3rd edge on each part in turn:
Attachment 21586
Not sure if this is good practice or not but the 4th edge I did in small batches:
Attachment 21587
All to size . . .
Attachment 21588
Then 6.8 mm holes machined (ready for M8 tap):
Attachment 21589Attachment 21590
Now onto the angled sides. I made a fixture to hold the parts which had 2 datums for alignment:
Attachment 21591
Attachment 21593
Attachment 21592
The fixture was dropped into the vice each time and aligned in Y (fore/aft) by eye as this is not critical. It only needed to hold the blank in the correct X (left to right) and Z (up and down) position.
Then a 2D adaptive to rough it out. I had intended to do a cleanup but this doubled the machining time and the parts fitted fine with just the roughing:
Attachment 21594
The adaptive took about 2.5 minutes which was not too bad. I've done 8 parts, 8 to go . . .
Nice work following with interest:congratulatory:
Lovely work as usual, well done!
It's mechanical porno!! ;)
Cheers guys. It's very satisfying when it all works so glad you are enjoying it too.
For anyone thinking about jumping to F360 then I'd say don't hesitate. Its a powerful bit of software and is daunting at first but start simple and go from there.
I managed to finish all 16 inserts, so another job done:
Attachment 21624
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:
Attachment 21626
So onto the Y axis sides. Here is the CAM:
Attachment 21625
Laying out the blank:
Attachment 21627
Holes:
Attachment 21628
Profiled:
Attachment 21629
Holes tapped:
Attachment 21630
Then the corners had to be filed square to take the stepper bracket:
Attachment 21631
Edge holes drilled and tapped:
Attachment 21632
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:
Attachment 21633
Attachment 21634
There will be a piece of bent sheet over the front and rear, so checking this will fit flush to the stepper bracket:
Attachment 21635
Then onto the Z axis. Here are the raw stock parts:
Attachment 21636
Top plate being set up:
Attachment 21637
Attachment 21638
All for now.
Wow nice work so far!!!
Thanks for all the kind comments.
Onto the top part of the Z axis. Main holes roughed out.
Attachment 21750
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!
Attachment 21751
Counterbores done and used to hold the part:
Attachment 21752
Profile cut - ooh, just fits!
Attachment 21753
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.
Attachment 21754
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):
Attachment 21755
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 !
beautiful work, it's all looking so nice and chunky!
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.Quote:
Originally Posted by routercnc
I'm following with interest your nice work!
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.
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 . . .):
Attachment 21764
First job was to check the thread size and pitch for these 20mm hiwin carriages - turns out they are M6x0.75 (M6 fine).
Attachment 21758
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):
Attachment 21759
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:
Attachment 21760
.
Attachment 21761
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):
Attachment 21762
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:
Attachment 21763
Here are the first 2 assemblies, tightened up and pointing the right way (phew!):
Attachment 21765
Trial fit:
Attachment 21766
View from the outside:
Attachment 21767
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.
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!Quote:
Originally Posted by 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:
Attachment 21786
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:
Attachment 21787
Here they are complete:
Attachment 21788
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:
Attachment 21789
Dialled them in roughly to avoid having to machine too much material away
Attachment 21790
Tops machined flat - left a tiny bit next to the vice which I filed away by hand:
Attachment 21792
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.
Attachment 21793
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.
Attachment 21794
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:
Attachment 21795
Attachment 21796
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.
Looking great and coming along nicely!
Cheers Lee.Quote:
Originally Posted by Lee Roberts
If I get a chance I'll post up a more detailed set of measurements and photos of the long side parts I'm making. Having measured them on my 'surface plate' they are out by more than I thought so I've spent the last few days working out what to do, including starting them again.
They need to be accurately made because they take linear rails on both sides.
Current plan is to use the lathe to square up the parts. I've got a couple of fly cutters on order which will go in the chuck, then I need to make a raised platform which sits on the cross slide (toolpost removed) which will hold the work. I'll then feed they work by winding the crossslide past the chuck and square up the edge. I have a ground straight edge which will sit behind the other edge of the path so when it is flipped over the freshly machined edge will sit against it and mean that the second edge will be parallel to the first.
Only problem is that the cross slide had about 110mm travel and the edge is 310mm long so I will need to index it along the ground reference edge 3 times. Will this give an accurate long edge or will it give an edge with 3 facets? I will find out !
Anyone with a better idea as it won't start work on the raise platform until the weekend ?
OK here are the detailed measurements showing how far off 96mm width the parts were (!). I think they slipped / tipped in the fixture, which I couldn't tell as I couldn't see the ref surface they were sitting on during the machining.
Attachment 21817
Attachment 21818
They are out along the length, and across the width. Annoying but there we go.
Current plan is to machine them square again (but obviously they will be undersize for width). Here is a sketch of what I'm thinking of attempting on the lathe:
Attachment 21819
I've bought some 5mm thick aluminium strips which I will superglue and bolt to one of the edges using countersunk cap screws, setting them well underflush. Then I'll machine the edge back to get the part 96mm wide, using the lathe again, and then remove all of the screws (except the ones at the far ends which will hold the strip on, along with the glue). I can then attach the rail. Should look like this if all goes well:
Attachment 21820
If it doesn't work then the strip can come off and I'll try something else. Thought about epoxy levelling all 4 surfaces, which I think can be done if I start on a level surface and do it in the right order so they all end up parallel to each other.
Another option is to do both sides but use steel strips instead. Then get them ground in pairs on a surface grinder so they are parallel and flat to each other.
I knew this bit was going to be challenging, but it must be right otherwise it will bind or not track straight up and down.
Progress has been slow because this has turned out to be more involved than planned.
I started by making a raised platform for the lathe. This was to hold the part whilst I used a flycutter to trim and true up the long edges, ready to take the add-on strips. Here are the long T-nuts being made:
Started with the drawing and some stock:
Attachment 22126
Machined to size:
Attachment 22127
Finished:
Attachment 22128
Trial fit in the cross slide, plus made up some simple spacer tubes:
Attachment 22129
The top plate (a large offcut) was bolted and shimmed using shim stock on the spacer tubes until it was as flat as possible:
Attachment 22130
Attachment 22141
Then a straight edge was dialled in:
Attachment 22131
Edge skimmed back:
Attachment 22132
Glued and countersunk screws used to add the extra strip:
Attachment 22133
Ready to try again, this time a different set up which shouldn't move!
Attachment 22134
Skimmed it all down to 96 mm trying to get within 96.00 - 96.05 everywhere. I used the height gauge to check progress and wrote the heights on the part. Here is it getting close.
Attachment 22136
I also left a machined edge on one of the sides for the rail to align to.
Attachment 22135
Attachment 22137
Attachment 22138
Hopefully that will be good enough for the rails to run on.
Machined the counterbored holes:
Attachment 22139
Ready for the end features . . .
The part was too long for the machine so only one thing for it - cut a hole in the table:
Attachment 22143
The profile pieces which make up the bed are not accurate enough to be used as a support. The sides are not flat and are not perfectly square to the bed (since that was skimmed by the machine). So I made up a 'tramming' plate:
Attachment 22144
I bolted it at the bottom, then used a screw at the top to dial it in. Here you can see that before the screw starts to be tightened there is an uneven gap to the part I am machining (which is held at 90 degrees to the bed via the precision vice:
Attachment 22145
Screw tightened until it made contact:
Attachment 22146
I made up a strap clamp to hold the part and bolted it to the tram plate. Then it was ready to dial in by running the indicator up the side and adjusting until it was vertical:
Attachment 22147
Then the features were machined:
Attachment 22148
Took the part off and put it on the lathe, then used a centre drill (as a scribe) to mark along the edge (part not shown in photo):
Attachment 22150
Then removed it and used the height gauge at 15mm (part is 30mm thick) to scribe a line. I was relieved to see it was exactly the same height as when on the lathe which meant they were both at the same point.
Attachment 22151
Basically this meant I had got the lathe platform at exactly the right height, with the centre of the chuck in line with the centre of the part. The next op on the lathe is to drill an 18 mm clearance hole (for the ballscrew) about 190 mm deep into the part.
But that is on hold until I machine the end of the second part. Before I took the first part out I had added a backstop to pickup the edge. This meant it was in the right position. Here is the second part set up for the same end machining:
Attachment 22149
Getting closer now but this bit is taking ages . . .!
Well you are certainly putting in the attention to detail - hopefully it pays off in the end with a nice and smooth machine.
Good to share your techniques too, always interested in how people approach certain problems or use equipment in creative ways.
Thanks Zeeflyboy. I hope it is smooth, especially the Z axis which needs to be accurate and aligned so that the 4 rails don't bind up.Quote:
Originally Posted by Zeeflyboy
Some more progress on the long side parts of the Z axis. I finished the end machining on the other side piece:
Attachment 22190
Then it was over to the lathe to bore the 18mm clearance hole for the ballscrew to go inside. Here is the first one set up and a pilot hole being started at the bottom of the large counterbore:
Attachment 22191
Worked my way up using larger drills and then removed the chuck and dropped in the final 18mm bit. This has a 2MT on the end so needed MT3-2 and MT4-3 adapters to fit in the MT4 headstock taper:
Attachment 22192
This went OK but I ran out of travel on the carriage so needed to re-position the work closer to the headstock end. By doing this the 2 'tabs' on the end of the work (which were to stop it sliding under the pressure of the drilling) couldn't be used, so I ran without. I noticed after a while that the work had moved on me ! - so, I drilled and tapped some holes and mounted it directly to the plate, using the strap clamp I'd made earlier. This was much better. You'd think I'd have learnt by now that clamps can't hold work pieces and stop them sliding if the tool pressure is high.
Attachment 22193
I had originally intended to bore from one end and make it a blind hole. But the drill was not long enough and although I could have bought a longer one I decided it was just as easy to drill from the other side and go right through. I'd just put a nice blanking cap on the bottom to stop the chips going up inside and landing on the ballscrew (it is right next to spindle where the chips will be flying around).
Problem with that was that the drill bit was not quite long enough and left a small ring of aluminium where the 2 holes met (the blank ring about half way down the hole):
Attachment 22194
I managed the clean it out with my longest a round file and all was well. Repeated on the other part and big holes finished. I checked the ballscrews and they fit without touching the sides.
There is one small tapped hole to put in each of these parts, plus the blanking cap, and then they are done.
________
Spindle Block
Had a great surprise recently. The spindle mounting blank was too large to fit on my machine so I'd called in a favour from someone with a bridgeport sized / type CNC machine. I only asked him if he could machine it to size, then I would do the rest including somehow doing the 80mm bore in the middle. To my delight he gave me this back:
Attachment 22195
Attachment 22196
I couldn't have done that on my machine so I was very pleased to say the least! Now it still needs lots of M12 holes drilled and tapped in the side, some M8 in the front (for the clamps), and the bore is at 79 mm, so needs opening out to final size but that has really given me a head start on it.
The M8 and M12 holes are easy to do, just setting up time etc. The bore will need to be done by putting the part on the lathe cross slide and then I'll need to make up a line boring bar which will run between centres using a dog drive off a drive plate. I've seen this done but not done it myself so I might do a practice piece first.
Couldn't resist a quick dry fit just to check it was going to fit together:
Attachment 22199
edit - just noticed the spindle block is upside down in the photo ! I'll make sure to turn it around before machining the mounting holes in the side.
There are a few jobs to do on the main spindle housing. Boring pilot holes on both sides of the block:
Attachment 22255
Then the pilot holes for the M8 taps for the spindle clamp brackets. Spindle block is so big I had to get inventive on the fixture to machine these parts:
Attachment 22257
Then onto the tapping 16 off M12 taps and 4 off M8 taps - took a while !
Attachment 22256
Quick assembly check:
Attachment 22258
Then noticed that some of the bolts were loose on the current machine. Wondered why it had been chattering more recently - was worried the small 15mm profile rails had worn, but then spotted this:
Attachment 22272
So I had to dismantle the Y axis and tighten them up. 2 bolts had come right out, and one more was loose. The rail has also lost a bolt. I guess that is what happens if you ask a machine designed for wood to plough through endless 20 mm aluminium plate for months on end. Used loctite and tightened them back up. Also doesn't help that on 15 mm rail they use M3 bolts which are very small and you can't put much torque on the heads.
Then onto making the spindle clamps:
Attachment 22260
Attachment 22261
Attachment 22262
Attachment 22263
Attachment 22264
Although I've got to bore out the spindle hole on the spindle block, I thought I'd check everything was going to fit together. Aligning first rail to master datum:
Attachment 22266
(note the rails are slightly too long - have marked them up for gentle grinding back to length)
Dialing in the second rail, ref the first:
Attachment 22268
Attachment 22269
Then checking the vertical alignment showed that the 2nd rail was ~0.05-0.1 high towards one end. The large side plates they sit on will need the M12 bolts loosening and knocking round slightly when this goes together for real.
Attachment 22271
Coming together:
Attachment 22267
Then discovered a problem! The whole assembly is ~2 mm to big! The plate at the top of the photo should be flush with the side plate but is clearly too high.
Attachment 22270
Bit of head scratching, and checking the drawings couldn't find anything I'd made which was out of spec. Then checked the profile rail and carriage and they were ~2 mm taller in total than the drawings I'd down loaded from Hiwin. I know it has been mentioned on this site many times but check the hardware before committing the drawing and making the other parts !
Luckily this is easy to resolve, just take ~2 mm off one the side pieces and everything will be back in line again. I'll leave that till later because everything has to be set up to get it all very parallel otherwise the rails will bind.
Onto making parts for the lathe to bore out the main spindle housing to final size . . . more to follow
Damned fine work there!