Fear not!!! All will be revealed.... I'm working on the Y axis right now... I'll post pictures of the entire set-up and how it all goes together as soon as I can.

Best Regards,
Julian (Fozzy The Bear)

 

Sorry Guys!! Been so busy building that I haven't had time to stop and update the log for a few days..... Lots of new things to add here. Will be doing an update in a couple of days time.

Best Regards,
Julian (Fozzy The Bear)

 

Build Continued.......

Egor... The monster needs more parts!!!! Fetch the shovels!! ..... :twisted: Mmwhaaaa Haaa Haaaa Haaaaaaaaaaa!!!! :twisted:

Well I promised an update and this is a genuine monster of an update. You'll see what I mean as you read on....I just haven't had the time to write this up for the last week... I've been far too busy actually working on it. Progress is pretty good, given the metal mangling I'm doing here.

First of all I have to offer some thanks to my good friend Mike Hogan, without whose advice and the use of his fabulous and very large machine shop, which is stacked to the gills with every vintage machine tool you could possibly imagine needing, and without his assistance and skills, this probably would have been impossible. So thanks Mike!!

Lets start with the outside of the case:

You can see some of the new bits here. I've added a tubular steel rail to the front of the case at table height. This will carry the machine fences to keep heavy materials straight on the bed and was machined with an 8mm slot in the top for the fence restraining bolts... You can also see the alloy support rail for the table top in this photograph. The table will eventually be screwed to this rail and another one at the rear, using countersunk machine screws.

At the right hand end of the main wooden case is the new metal case that houses the repositioned motor for the Y axis:

This is made from Alloy U-channel which significantly strengthens the end of the case. The cover was made from a sheet of alloy that I salvaged from a freezer that we were throwing out some time ago. It's one of those bits that I tend to keep in case it might come in useful for something one day. I'm a bit of a hoarder of bits like that. This time it did come in useful. At the moment I put a brushed alloy finish on it, but I might get the tools out and do some 1930's style circular polishing on it, if I get the time.

If we lift the lid off you can see what's in there:

On the left is the new Y Motor position on what would have been the original outer case. On the right you can see the new access hole put in place to make removal of the X Motor easy to do. I was originally going to fit the power tool in this case as well. However, I've now decided that it's best placed in the same position as a MKII on the rear of the machine. Simply because it puts less strain on the flexible drive shaft. (sorry Mark, stealing that idea from the MKII)...

Lets move on to the inside of the machine...:

First of all I tried the rubber hose connector in this position, but I just found too many problems with it. No matter how it was tightened up it had a habit of pulling the leadscrew out of alignment. Not an ideal situation. SO! Here's the new drive coupler, attached to the motor and to the 3/8" Acme threaded bar. I looked at buying one, and then had a heart attack when I saw the price. so I grabbed a bit of hexagon Brass bar and machined one up to fit 1/4" at the motor end, and then machined the end of the lead screw down to 1/4" to fit in the other end. This is not a flexible coupler. Some of you may see that as a problem. I don't... why?... Because the alignment of the motor and leadscrew has been set accurately to within 1.5 thousandths of an inch... No wobble here!!.

At the other end of the Y Axis leadscrew there's a 6mm bore thrust bearing:

This is firmly against the side of the case.... and consists of a track machined onto washer, a ball race cage and a second machined washer. This image is so hugely enlarged, that it's difficult to appreciate how small these bearing races are. They are absolutely minute!! making very little surface contact area and hence almost killing the friction out completely.

If we look at the outside of the case at that end:

You can see a knurled knob for manual movement of the carriage when the power is off. This is screwed onto the end of the leadscrew and locked in place with a small grub screw... underneath the knob, is a second thrust race, which pre loads against the case and the first thrust race we looked at. This stabilises and fixes the position of this end of the Y Leadscrew.

OK! Time to start looking at the Z and Y leadscrew drive on the carriage.:

You can see the new Y drive plate and nuts here... and you can also see some of the Z drive.
Because of the accuracy of the re-machining on these parts the rubber pipe coupler worked fine on the Z axis.. This is because the leadscrew is completely retained and restrained from any adverse movement.

Lets take a closer look at the Z drive and bearings.:

at the top and bottom of the leadscrew are another set of those thrust bearings. These almost eliminate any friction, and are part of why we are getting 75IPM from the Z drive.

On the top of the tool carrier block, you can see where the 3/8" ACME screw passes though. Inset into the top and bottom of the block are a machined down ACME nut... These were reduced in diameter on a stub mandrel in the lathe, so that they fitted between the linear bearings. They screw in place down and up the leadscrew into a pocket formed with an endmill. Once in place they are rotated to adjust them and locked there with a grubscrew though the rear of the block. Using two nuts this way means that there is zero backlash on the Z drive, but it still moves with very little friction.

The two threaded holes in the face of the block are for mounting the tool carrier...

Now lets take a look at the Y Drive:

Alignment accuracy was an absolute swine with this.... It had to line up precisely with the leadscrew or it would jam up. Very difficult to achieve.

The mounting connected to the carriage has a slight slot in it to accommodate the nuts, then the feed carrier is bolted to it with a nut in each end. Between the nuts is a bronze collar, and a spring, which pushes them outwards. They can't turn in relation to each other because they're restrained by the feed carrier block. So the spring tensions them both in contact with the driving faces of the leadscrew. They're then locked in place by a setscrew that you can see at the right hand side of the block. The left hand set screw was not in place at the time of the photograph as I was still adjusting it. This arrangement was a little bit complex to manufacture, but provides automatic anti backlash.

The alignment is critical!! if it's a fraction out of true the whole thing locks up. The tolerances are to within 1.5 thousandths of an inch. To put that in perspective for the non engineers, that's about half the thickness of a single human hair.

Fully assembled and running free the smoothness of the carriage is really spectacular to see.

The advantages to all of this.... 1) much less friction means that more motor torque gets carried to the cutting head, instead of being absorbed in the machine. That's why we got 75IPM on the Z...
2) Much more stability in the machine and hence more accuracy on smaller parts and cuts....
3) It's keeping a twisted bear amused

I've yet to power up the Y axis, but i suspect that we should get some very decent torque and speed.

More updates to follow.... Working on the rollers now.

Best Regards,
Julian (Fozzy The Bear)

 

WOW!

 

Amazing work Fozzy! I like it.

 

That is like a MK1.5 on steroids, only better. I'm humbled by the ingenuity and the workmanship. Good show, Fozzy.

 

Amazing work Julian, the engineering that has gone into your build so far is unbelieveable .

The tolerances that you're working too are extremely tight. Do you envisage any problems with the MDF expanding due to changes in humidity? I have mine in my garage and the MDF definately moves/warps very slightly depending on the weather conditions. It doesn't cause me any noticable problems, but i'm not working to thous of an inch.

Si.

 

Thanks for the compliments guys.... I do appreciate it....

Now on to this question.... Yes It was something that initially concerned me a great deal. So I've kind of designed around that possibility. First of all before beginning the build all the MDF was sealed with waterproof PVA. It kind of sets and prevents any humidity penetration. So that partially cures any problem. Secondly, I designed around the issue. So anything which is likely to suffer from changes in humidity is in areas where it won't change the tolerances.

There are parts that can cope with it. For example, the linear bearings can actually cope with shifts in the distance between the rails of up to 10 thousandths before they even begin to show signs of it and probably twice that before it becomes a problem.

Other than that, most of the other high tolerances are in the metal components anyway. Although we do have some dissimilar metals, steel, aluminium, brass etc etc differential expansion is really not a problem in something as small as this. It does become a problem in large rigs... In fact I've encountered a metal expansion problem on a Camera Motion Control rig, where we had intentionally dropped the set temperature to well below freezing. Consequently the metal parts had contracted to the degree that bearings started to seize, especially the plain bronze bushes which contracted onto the stainless rods.

I know that's a long answer but I hope it indicates that I did consider the potential problems. To be very honest, the tolerances are tight now, but as the machine runs in they will slack off by quite a lot.

Thanks for the question... It was an interesting one for me..

Best Regards,
Julian (Fozzy The Bear)

 

Thanks for the detailed explanation Julian, it sounds like you've got everything covered. I didn't realise that you'd sealed the MDF with PVA, that should be more than adequate to overcome any issues.

The reason that I asked was that I raised the bed of my phlatty by cutting a sheet of 2mm HDPE to fit and screwing it to the MDF. A couple of days later when I went to use the machine the drive rollers made a horrible noise. This turned out to be because the bed of the machine had warped significantly due to the expansion differences between the MDF and the HDPE, causing the drive roller to catch the MDF :roll: . I cured the problem by slotting the holes in the HDPE to allow for some expansion and I also gave the MDF a couple of coats of sanding sealer. To date i've had no more problems, but I just thought i'd ask the question so you didn't run into similar issues.

Si.

 

Ahh! Yeah!! I'd guess the sanding sealer would do a very similar job to the PVA..... That's the good thing about MDF in its raw state. It soaks everything up like a sponge.

Best Regards,
Julian (Fozzy The Bear)

 

Is PVA the common white glue? I'm probably just going to put a few light coats of clear polyurethane on mine.

 

Thanks Randy,
Yes, anything to make life easier later on. Having those two holes in the case frame just makes it real easy to get a screwdriver to the stepper bolts. You can't really tell in that photograph, but there's about an inch of clearance at the back of that Y stepper, so if I do decide later on to change the steppers out for something larger, then they can be an inch longer without too much trouble.

Best Regards,
Julian (Fozzy The Bear)

 

Thanks Mark,
But it's only due to the quality of your original design work that made this possible at all.

Best Regards,
Julian (Fozzy The Bear)

 

Build Continued.....

This is just a quick log update for today.... I'll be posting a bit more during the course of the next few days...

The base cabinet is now more or less complete (except for its access doors). It was tricky because it houses a few bits an bobs and I needed the space under the printer to clear the Z motor and the flexible drive to the tool bit. The Power tool is now mounted in an alloy frame on the rear of the machine and the main drive roller is now properly in place, and running on ball race bearings. Before I connected the motor you could spin it by hand and it'd stop turning about two mins later.

On to the bits and bobs to be finished off right now. Filling in the access holes at the back of the printer, because I don't need them and because the dust extraction system won't work with them open. Still need to fit the pressure rollers, and still need to wire things up. But I may be cutting the first foam before the end of next week if things go to plan.

Pictures to follow in a couple of days......

Best Regards,
Julian (Fozzy The Bear)

 

Build Continued.....

Just thought I'd post the case design sketch.... The doors and front panels are missing in this sketch as I was working out the internal layout. The colours are representative only of the separate parts and are not the colour of finished items. Obviously the walls of the finished cabinet are also not made of glass... They were done this way in the sketch to give me a clearer view of what was going on with the layout inside. But I though you guys might like a look....

The computer is the blue box at the left hand side and the monitor sits on the extended top at that end.. still have to design a case for that part.



Best Regards,
Julian (Fozzy The Bear)

 

Wired up the steppers today.. as far down as the base of the cabinet, where the driver board is living inside the sandwich box mod.. I forget who it was that came up with that one, but many thanks to them it's a perfect solution in a high humidity environment.

Also picked up an HP Flat Panel Monitor today... Fits very neatly on the end of the printer... Total cost £3... that's about $5 USD. Got it from a local reclamation place that sells loads of stuff like that off, that people have taken to the tip.... It astounds me what people actually throw away when it still works perfectly. It's in a pretty nice condition too. No screen scratches or anything, in fact the case is pretty good as well. The image is way better than the CRT I was using on there.

Should have all the steppers running for the first time tomorrow.... I'll post the speeds we get.

So close, I can almost smell the foam dust!!

Best Regards,
Julian (Fozzy The Bear)

 

Build Continued......

Its Time To Animate My Monster Egor..... Time For Little A Jolt From Dr Frankenbear's Electrodes..... Throw The Switches!!!! MMMWWWAAHHHH HAAA HAAA HAAA HAAAAAAAAAA.... :twisted: ......... Its Alive! My Monster Lives!.....

OK so this is just a quick update really.... mostly because I'm a bit busy right now... Finished up the wiring yesterday. Still needs tidying up and a few cable clips here and there, but it all went in. The computer fits very neatly in the base and driver board in its sandwich box mod also fitted in neatly down there.

The Results of all the work are great!! Really pleased with the torque and speed so far.....
ALL AXIS' A STABLE 75 IPM ON THE STOCK 90 Oz Steppers !!!!!

I will be taking Randy and Crash's advice and knocking that back a bit probably down to 70 IPM for 100% reliability on the cuts. But right now it plays a very nice rendition of the Tetris Theme

After perfect performance outside of the machine the Z Axis decided to give me a couple of problems to solve inside the machine. Nothing major, just a couple of sticky spots that didn't want to work themselves out. So I pulled it apart and got the magnifier out... It seems that because the ENCO ACME Threads are rolled threads rather than cut threads, they do have a very small ridge where the rollers started and stopped. I suspected that this was the cause of the problem so I put both lead-screws in the lathe and polished them up with some very fine grade emery cloth. Re-assembled everything and badabing! Everything was running like a Swiss Watch!

The X Axis roller will run at stupidly high speeds partly as a result of the ball race bearings I fitted to it.... I'm debating now whether it wouldn't be possible to add a gearbox to that to give it even more torque at output speed. I didn't measure the limits of the IPM Speed because it was so high that it would have been pushing at least 300 IPM

The Y Axis I think is running at the practical limit for the 3/8" single start ACME thread... If I push it too high the limit seems not to be the limits of the motor but the limits imposed by resonance of the ACME bar... Might upgrade that later to use a 1/2" or even 3/4" thread. But right now it's still producing the same 75 IPM I got on the Z Axis so I'm happy!

Didn't get time to take pictures yesterday... But I will do today If I get a few mins...

Still loads to do... Still working on the pressure roller mods. Still have to make the tool carrier and tidy up a few bits like a lid restraint and locks, the vacuum system plumbing and odds and ends like screwing on the alloy corner protectors, need to make a stand to fit the end of the machine to take the keyboard and mouse etc etc etc.... I'm aiming for Saturday or Sunday for the first cuts.

Pictures to follow.....

Best Regards,
Julian (Fozzy The Bear)