Cool Panel Cover Logo #107 - Dakovo, Croatia

[marko cro]

Man, im loving the way it moves.
its 666.66 mm per sec, with microsteping 1600. I am amazed with the power it has.
Still some fixes needs to be fixed, but that will come in a couple of days.
Maybe this week I can get serial number

[parrulho]

Easy move, very fast! Nice machine.
I like the way you put e-chain on Z.

[marko cro]

Thanks Paulo,

It looks very nice, but there are some problems. Making it square X to Y and when motor overdrives,it skips some teeth, and it needs to be pun in 90 deg again.
If not in 90 °, then the pinion is causing problems. Still looking to solve that problem.

[marko cro]

Some problems encountered today. As i have forgot to put screws to fix the motors as in picture:

I had some speed reduction, and a lots of vibrations. Made the some blank cutting and vibrations were major. Can this be the only reason for vibrations, or it can be the less strong tension springs?
Help needed.

[pblackburn]

You will need enough lbs of force to keep the pinion riding in the track and not wanting to ride out when resistance is met with your router/spindle. If the rails are smooth and the spacing is correct between the V rails your vibration will be minimal if not nonexistent. If you are seeing vibration then I would suspect something is binding and the vibration you are seeing is the breaking free moment. Make sure you are not clamping the shield or seal of your bearing with the spacer or nut you are using. Easy way to check this is to remove the springs and let the steppers hang. Then press with you hand on the gantry and Y car. It should not take much effort for it to free wheel to the end stops after you give it a light push. If the gantry of the Y car is riding up on the rails it will cause weird things also so check that. Make sure your pinion is tight and not loose or rubbing the side of the c channel or tubing. These are only some things to look at.

[marko cro]

Hi Pete, thanks for helping out.

When i remove the steppers from pinion, movement is very light and it slides with very little force. Nothing is rubbing on anything and the bearings in V wheels are ok.
I belive the force in the steppers moves slightly steppers itself as they are fixed on only 1 screw, and not on 2 like in the blueprints (the one circled red in the picture above is missing and I think there is the problem.
Also to point out, the V rails are the weakes links of the whole machine, and will look to repalce them as soon as possible.

[pblackburn]

You are using a plastic (delrin, teflon, nylon,etc) washers with the pivot bolt and slot bolt. The bolts in both places should be used for stability.

[Surfcnc]

Marko

1. two bolts are needed
2. a PTFE or other washer is required on both bolts (as per the plans)
3. lubrication and adjustment of both joints is also advisable
4. check the pinion is both square and fully engaged into the rack
5. check that the the opposite sides of the X axis and Y axis is also secured with a spring, bolts etc
6. check that the V rollers are free to turn and not binding on the central hub of the rollers.
7 check your motors are tuned correctly by disengaging the pinions from the racks and run them without moving the machine.
8. it is unlikely the pinions moving on the stepper shaft would cause the "vibrations" you are explaining.
If the pinions are moving, they could however cause problems with the cut quality later down the track.

You should not need to replace the rails unless they were made badly in the first place.

Regards
Ross

[smreish]

The vibrations you speak of I found were all rack/motor relationship on my machine.
- square to rack seated pinions
- lube the rack!
- tension on the springs NOT to tight, but not to loose - to tight caused my machine to shudder (like a really low rumble and vibration)

[marko cro]

Thanks Ross and Sean,

I have lots of nerves wasted on the tuning the rails tightening the screws, but now it seems stupid of me and lesson learned.
However, I want to put permanent solution into machine, and I was thinking something like this http://www.ebay.com/itm/2-Set-SBR20-...item3cc84a9469 on all 3 axis.
What would i get in precision and in the quality of the machine as whole.

I am very close to buy the whole package, but want your opinion before any final purchases.

Thanks,

Marko

[pblackburn]

All I can say is dust is the enemy of caterpillar type bearings.

[pblackburn]

This is another option

Many people have using the type you have shown. It can be done but mind the dust. It plays havoc on the bearings. Wood is a very destructive byproduct. Bellows are always an option for those systems. Also the wiper on the bearing will be a deciding factor. Not all manufacturers are equal in this. These will require some recalculation on the mounting plates if they lift the mating parts to high.

I am just saying....Do your homework and it will play off but don't rush to a hasty decision when yours may still be salvageable.

[marko cro]

Thanks a lot Pete,

Wasn't thinking about the dust much.

I believe that those linear bearing do have dust wipers installed on them. As i don't know those kind of bearings, I believe they could last for a year at least in conditions with dust collector and cleaning. I am just assuming out loud, with no valid ground.
I will work on the SW design and see if it checks out without and major workaround of the motor and rack and pinion setup.
Also, was thinking about doing the X and Y 1st, and DIY the Z slide.
I think my rails are ok, but the welding the gantry welding was a bit off, and the setting up the wheels is a PAIN. Some wheels have grooves a bit deeper and it makes it a son of a ..... to setup.
Any thought about precision and some vibrations advantages with these bearings?

[pblackburn]

As far as alignment, they will need to be true. You have to be careful bolting them down that you do not create a bow. There are different options for the bearings, oilite bearing or caterpillar ball bearings. They run extremely true if mounted properly. I have used many of them in industry.

If your gantry is twisted you can twist it back with some large C clamps. Mine twisted while welding and I followed the instructions to a T and was clamped down everywhere. That is the nature of welding. It is a science to weld and know how the steel will react, not cause to much tension to break the weld after the part cools.

I am sure you can correct the problems with the gantry. This may require you to modify and shim the Y rails if it is out to far to compensate with the adjustment built into the Y car.

I had to adjust the Y car and gantry both on my build.

[pblackburn]

I forgot, the bearing in you picture need grease, grease collects dust, dust loves grease, vicious cycle. If you have great dust collection, it will not cause much of a problem. WD40 will clean the rails but will also thin the grease in the bearing so you will have to regrease. You have to be really careful when putting these bearing on and off the rails. A custom insertion tool will add in the transfer of the bearing onto the rail else they will fly everywhere. Trust me, I have done that on more that one of our robots.

[pblackburn]

Here is one that is already cutting and is currently being upgraded

[Surfcnc]

Marko the beauty of the Mechmate is you can do what ever you like.
I have a little experience with the recirculating ball linear bearings and lubrication, constant lubrication, is the only solution to the ingress of dust into the bearing.

While it might seem strange, ensuring the dust inside the bearing is wet with lubricant is probably equally effective as trying to have the bearing always perfectly clean.
The already wet dust keeps the dry dust out and maintains some degree of lubrication.
Either way constant lubrication of this type of bearing is a necessity. Periodically use air to flush out old lubricant and dust and start the process again.

The tolerances of the bearings to the rails can be highly variable depending upon quality.
The linear bearings in the Ebay advertisement are the short type.
A long version that has is two short bearings end to end in the one unit is also available and may help to reduce some of the long term wear on the rail and to further restrict any movement.
Bread loaf style rails and their linear bearings are more expensive but usually more accurate, best to do a cost/benefit on your options before purchasing anything.

As Pete suggests the bearing rail combos have alignment tolerances, any misalignment will need to be accounted for with some vertical and horizontal adjustments in your bearing to gantry mounting solution. Simply slotting or some over sized holes might suffice but you must make allowance for it.

Good luck.

Ross

[marko cro]

Thanks guys for your help so far.

To explain, my gantry is not bent in the normal way it bends. I have 2 mm of extra distance between wheel base from one side to other.
That gave me lots of problems, but that was my mistake, and i cant unweld it and redo the cutting.
Due the uneven distance of the wheels and some imperfection in depth of the wheels (also there is the different angle problem), there is the hard path to align it all straight and without any problems.
What I had in mind is this adapters made from aluminium (if bolted to gantry), or steel or iron if welded to gantry.
Not sure about these adapters from aluminium will hold and be rigid enough if I bolt them in 4 places.
What would you suggest in this situation?
Here are some pics

[pblackburn]

When you say " I have 2 mm of extra distance between wheel base from one side to other." Do you mean the tube lengths are a different? Most cutting discs are only 0.030" thick so you could cut it apart and re-assemble.

I prefer bolt to weld when it has any piece that is a wear part. I would weld 1/4" (6mm) steel around the areas I would like to bolt my adapter plate(plate that would receive the bearing) to. This way you could flat head bolts to secure the bearing to the adapter plate and then bolt the adapter to the 6mm plate that is on the tubing. This would give a secure but removable bearing. This will require accuracy and precision. I do not know the tools you have available. This means your adapter plate would have to look different than what is in your drawing. These type of bearings require precision and accuracy for mounting. Being off a little it will still assembly but causes premature wear.

I am not trying to scare you away from it, just trying to give you the information for you to plan for.

Like Ross said, "Marko the beauty of the Mechmate is you can do what ever you like."

This is a very true statement.

[marko cro]

You are Johnny on the spot.
I have measured tubes and they were perfectly the same, and now there is 2 mm difference. But never mind for that now, as with this new bearings, I think i will be on right track.
Thank you again for great help in this matter.
I was talking to guy from ebay and he agreed to cut to certain sizes which i require.
The only thing is what i need to do is this adapters, and they need to be done with precision, but I can trust nobody in my small crappy to do it for me.
I was thinking to weld 6 mm steel plate to connect both tubes of the gantry for more rigidity, and then screw the adapters with bearing blocks to it. What do you think about it?

[pblackburn]

The main thing is to ensure perfect alignment. There are many ways to do it. This is only one way I will discuss here. Maybe someone will chime in with other examples.

If I had no one to trust and not the means to use a mill. You may be able to do your rail assembly including the bearing on the rails. Cover the rails with a weld blanket to protect them from weld spalls. Place a non-conductive shim between the adapter plate and the plate it is to be bolted to, this is to stop the flow of electricity through the bearing. Secure it with clamps and wood between the clamps to stop the flow of electricity through the clamp and and through the bearing. And begin light tack welding until you can disassemble and to do the final welding of the plates. Take extreme care to ensure you do not let the flow of electricity go through the bearing to ground. This method would make sure your alignment was correct.

But don't let any off the bearings rest on the gantry without having an isolator between them. A little weld current will make little marks on the bearing. You may not feel it at first but it is the beginning of destruction.

I have welded many rails up this way, but check, check and triple check before striking the first arc. You can not take it back. Trust me, I have made that mistake.

Another option is a slot in the mounting plate welded to the gantry to give you some adjustment side to side. But you want to try to mount the plate so the bearing will run as true as possible on the rail. You do not want it 15° off to the side.

[marko cro]

Thanks Pete,

I will try to aling it best as I could. Was thinking to to adapter from aluminium, but maybe it will be easier to do it when I have some movement in the machine.
I have removed most of the vibrations from the machine and it was the rack and pinion not beeing squared made the vibrations.
This is my 1st drawing , just done.
What the community thinks about it.
Disregard the letter above, not sure what is wrong with my drawing there, but will resolve it right away.

[marko cro]

Happy Easter guyz,

Not an Pen plotter anymore

Some pictures.




Shorten video cutting
Feedrate is put to 76 mm per sec, but i reducet it at 50 %, due the DIY drill bit.
The wood is oak, and some radius were off by a 0.1 of mm
Comments welcome
http://youtu.be/-aHpcM6UJbQ

[pblackburn]

Makes dust, that is success.

Just a suggestion. Mount your spoilboard. You would be amazed how much it stiffens the machine

[marko cro]

Hi Pete,

It was Easter time and I didnt even planned to work on MM.
I would bought it already

[pblackburn]

Looks good though. The real question is for you, are you satisfied? Thanks for the video and pictures. It helps everyone.

[marko cro]

Thanks
I will have to check what are the diagonals after spoil board and another one on top of the base spoil board.
The Z level roughing is a good way to do after profiling some parts, removes the imperfections when drill bit enters material.
Still lots of learning to do, and lots of drill bits to acquire, and LOTS of fun!!!
Any suggestion about drill bits, what should i go for if I want to do aluminium profiles reliefs.

[Andrew_standen]

Congratulations, cutting wood !
Good luck
Andrew

[danilom]

Marko ....

drill = burgija

router bit = glodalo

[marko cro]

JUST MAKES NO SENSE !!!
To explain my statement.
My rack and pinion problems has reached its peak. After 1 week of setting it up to square, I found out, that only it has NO vibrations when pinion is fully engaged on rack, but with an angle.
When its perfectly squared, i have vibrations, but aligned on one side or the other, with teflon angled spacers, works perfectly.
My only reasonable idea is that rack and pinion are not match, but they are and I am stupid as a wheel.
Pictures will come shorty, along with video of machine working.
The more I know, i know how less I know, but now its as less I know, im happier.
Another thing in this setup will be wear or the rack and pinion, but without vibration it doesn't have to wear fast.
Like I said, I am DUMB! Its miracle that I can use toilet by myself.