Fixing a BEEPload of backlash
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- Опубліковано 26 чер 2024
- The X-axis of my Proxxon FF500/BL mill suffers from excessive backlash.
In this video I identify the cause and solve the problem, thereby improving the quality of this machine.
Music:
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I like how methodical your approach is to every endeavor you take and that you make due with what you have on hand
Thank you Victor 🙂
Really nice tight tolerances now, what a great upgrade.
Cheers 👍💪✌
Congratulations, Michel!!! I am from Brazil, have some Proxxon machines (Lathe, Milling) and enjoy your videos. Basically I face the same problems with my Proxxon here. Your contribution is inpiring!! Thank you.
elegant solution to the problem ! Ill keep it in mind when I get around to doing my mill, best regards, Steve
The grey cells are coming up with some clever ways to get things done, good job!
It is interesting that proxon had not used an adjustable bronze split nut to compensate for backlash as it wears. Nice video as always
Not clear if this was the original nut or a previous owner's replacement. My Proxxon came with adjustable split nuts.
@@TheBakafishI bought this mill new 4 years ago, so the nut is original. Which Proxxon machine do you have? How old is it? I've read that Proxxon has made improvements here and there (including replacing that ridiculously bad aluminium nut in the PD400 with one made of bronze), and maybe they'll improve their ways even more.
@@Michel-Uphoff okay, I was just guessing because I agree that the top nut seemed to be inferior brass compared to the bottom which looks like bronze. I have a very old PF-230? It uses bronze nuts, that are split as I have been suggesting and use set screws to adjust the preload.
Thanks for this, my mill is 72 this year, has had a busy life but is still only just 50 micron of backlash. That said I need to explore what is going on. Brass versus bronze? Different melting points, but for me the definite would be a chemical spot test. Needs care though, I once mistook cobalt for nickel.
@@johnsherborne3245 I would like to put that piece of metal under an XRF analyzer. Who will volunteer? (just a bit too expensive to purchase for myself)
Excellent video. No need to further investigate, brass has the tendency to transfer to the mating surface, bronze does not.
The master at work, nice video, thanks
Very nice work sir
Great workmanship once again.
Thanks!
Terrific upgrade Michel, Well done!!
Thank you Colin 🙂
It seems quite evident to me that from your hardness tester results, there can be no mistaking that proxxon used two different materials. Not something you'd expect for the price they want for it now! I have their miniature table saw and the die grinder.
Very impressive! I have the same machines, but couldn’t do that sort of accurate work on them.
Really, why not?
Ever a pleasure, Michel!
Bloody nice job on that sir! I like it a lot. I'm going to revisit my X axis nut on my 25 year old Warco WMT300 lathe/mill combination machine. It has a very weird trapezoidal 20 mm X 0.1" ( 10 tpi) thread. I made a new nut in brass (which was my big mistake ) but due to a chipped tooth on a change wheel, I mucked the first one up and left it for a few months to ponder how I could do the job without ruining a second one. I decided to make a tap first and used a piece of steel from a Range Rover anti roll bar as this is good steel, a bit hard to machine but I managed it. The second nut was brass as well, (big mistake) and I managed to make a usable nut with only about ten thou of backlash. I also cut my leadscrew to swap it end for end using the unworn tailstock portion to even out the wear in it I made joining sections at either end to put the leadscew back together in its proper orientation with the machined bearing and driving potions back in their proper places.mi also cut 30 mm off of the very end of the unworn part of the thread as a go gauge and the tailstock joining piece was made 30 mm longer to restore the length of the screw. This has worked ok but after two years of hard work I have a lot of golden sheen glitter on the leadscrew and around 25-30 thou of play again. I'm not sure if I have enough room to do the half nut idea as you have, but I'm going to see what I can do to replicate your idea, this time in bronze if I can find it. We have now no engineering suppliers locally as all the engineering firms seem to have disappeared here on the London/Essex border. We used to have a brilliant engineering supplier about three miles from me but they closed their doors more than ten years ago now. A great pity that as they had been in business since before the Second World War. I'm going to watch this carefully again making notes and screenshots to replicate your half nut idea, if you don't mind. Sorry to be long winded lol
You could try: www.metals4u.co.uk/materials/bronze
might be an idea to dril in an oilhole from the t nut slot in the tables surface down intoo the capture nut for the leadscrew to be able to drop a little oil in there once in a while using a siringe and a needle
Dobra robota :)
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Well done as usual Michel. Proxxon may have used aluminium bronze which is hard enough for nuts but can still wear out over time.
The unknown "yellow material" (probably brass) has a hardness of Hv 137. Aluminium bronze generally has a hardness of around 200 Hv (180-220)
Aluminium Bronze or Ampco as it more commonly called in the States comes in a variety of alloys of varying hardness and wear characteristics. In my opinion it is generally too hard for applications like this as it will cause excessive wear on the screw unless care is applied in choosing the alloy. Ampco the company that first marketed Aluminium Bronzes in the US actually had as it's first product an Aluminium Bronze alloy that was used to produce cutting tools for machining steels.
Prachtig hoe je dit weer oplost Michel !!!!!
Dankjewel 🙂
Thanks for sharing. Will you ever upload somewhere a writeup of your calculations?
Which calculations are you referring to?
Nice video 👍😀
Was that 0,7 mm backlash ?... that will ruin a part if you are not careful 😢.
A bronze split nut is a good way to solve a problem like .
Offcoarse there are different solutions or materials you can use.
But bronze is self lubricating.
Specially if you use bearing bronze .
Michel, I meant to also ask, Do you find that mounting the machinist vice parallel to the bed allows for less headaches? I have a mini mill and until I saw this video, I had blinders on about doing so. Everything I do so far is small, yet I still put myself into a bind when dealing with stock that goes beyond the reach of the mill, not the vice. For some reason, I see parallel mount to be a better, less troublesome on mini mills which lack the depth movement. Thanks again for that one especially!
When necessary I mount the vice perpendicular to the bed, but usually I go for parallel. This installs very quickly and does not require any alignment. I have carefully measured the bed's T-slots in the past and they are within one or two microns of parallel. I insert a very precisely fitting parallel standing up into the front T-slot, and a second parallel lies against it. I press the side of the precision-ground vice against that and tighten it. I have never been able to detect a deviation greater than a few microns and mounting the vise in this way only takes half a minute.
For the small workpieces I usually make, the orientation of the vise is not important at all. I also like that the vice does not protrude from the front of the bed.
I noticed you have increased the volume of your narration and the music compared to the machinery sounds. Thank you. I really enjoy your videos so thank you for sharing with us.
How did you mill the nut if you had your mill disassembled?
After determining that the nut was the culprit, I reassembled my mill so I could make the new nut first.
I do like the idea of simply making things a bit smaller. What was that thread type 60 degree? It seems to me an Acme style tread would be the best option for such a task. This looked much different from my vantage point.
It's M16x2
@@Michel-Uphoff My Proxxon uses trapezoidal (metric) threads, are you sure that's really M16?
@@TheBakafish yes M16x2 top angle 60 degrees. Maybe the top of your threading is flattened, so it looks like trapezoidal? Acme and standard trapezoidal thread has a top angle of 29 and 30 degrees.
At 22:50, what is happening with the side cutters? What are you putting in and cutting? At 22:56, what is happening with the small hex key/Allen wrench? Is that an Allen wrench?
... Thanks for taking the time to share this with us!
I've put tiny plugs of plastic (POM) in the M3 hole, to prevent marring the flange nuts when I tighten the M3 set screws. As mentioned the purpose of these M3 screws and plugs is to prevent the flange nuts from loosening.
The use of brass for the X axis may have been a consideration given that the X axis generally sees more use.
One thing l was surprised by was the X axis leadscrew is a 60° thread form rather than a 30° Trapezoidal thread form. I have a 9x20 knock off of the Emco and the leadscrew is a 5/8 Acme so a 16mm Trapeziodal is or was doable.
Ideas for eliminating or reducing backlash to the minimum.
1) A split nut that can be adjusted to reduce backlash as much as possible.
2) A two piece nut with a floating adjustable nut half that is loaded via one or two Belleville Washers. This may or may not solve the problem. You would need to be careful of generating excessive wear on the lead screw and nuts. And take care that any cutting forces do not exceed the capacity of the system used to takeup the backlash. Not that a mill this size should generate a lot of cutting forces.
3) Or go all in and switch to ball screws.
The shop l served my apprenticeship in had a Kearny and Treker S-15 Universal. That featured hydraulically loaded nuts on the leadscrews.
Yes, it's a regular M16x2 thread. Why would one consider the more wear-prone brass when the nut is used more often?
II expect that the x-axis will now be, or can be obtained, free of play for years. If not, I will consider installing ball screws, or purchase another mill.
@@Michel-Uphoff
From the other posts evidently Proxxon previously used an Aluminium nut. Now depending on the alloy Aluminium can have reasonable wear characteristics. Anodizing can improve that. The company l retired from was in the automotive industry. At one time they made practically everything in the drive train, all of the sheet metal stampings etc. certain things they bought. A smaller manufacturer cannot make everything. But one of the online repair tools used in the engine division was a honing tool used to repair 6 cylinder engine blocks whose crank bore was just slightly off due to the block getting twisted in the boring fixture. The bar was made of aluminium and anodized. The anodized OD and ramp surfaces for the honing stones held remarkably well. The test in the blocks was from wear on the surfaces the blocks were clamped against. If twisting started to show up the pads would need to be replaced. Every feature on the blocks were measured off of the pan rail and two .7500" locating holes in the pan rail face.
@@mpetersen6 Such a hard anodised layer can be extremely wear resistant. The column of this mill is made of anodised aluminium, and there is still no wear visible on the ways. But that nut was in the lathe and made of plain not anodised aluminium. I understand from a viewer that this cheap nut has now been replaced by one made of bronze.
@@Michel-Uphoff Yes.. anodised nut will last, but will hog the screw :)
I don't know where people get the patience to struggle with cheap Chinese lathes and mills. But I really like your tool grinder.
Thank you. My lathe and mill are made in Germany.
nice cleaning up the leadscrew, thats nice thing for tapered tread. the bronze splitnut should not be cut a whole. better leave a few mm for easy adjust and extra stability, and keep wel oiled. thicker oil ore grease wil give you much longer use of it. it was bone dry.
It's well lubricated. Didn't show that on video.
I don't agree with leaving a part of the nut uncut. Ultimately, this leads to unbalanced wear (the play on the fixed side is not eliminated during adjustment). The nut is very stable, including the top, because the flange couplings fit very accurately into the nut parts, so it's rigid enough.
@@Michel-Uphoff I agree, partially cut nuts are common because they're easy to make and less parts in assembly but they do lead to uneven wear as Michel points out.
Not saying that your choice of splitting the nut lengthwise won't work, but traditionally to deal with backlash you split the nut so that you can apply forces on opposing shoulders of the screw. Consider this if your solution ends up being unsatisfactory, I suspect you will have trouble keeping it adjusted.
That is the well-known "El Cheapo" solution. In that solution, both threads are at an (increasing) angle to each other, which causes unbalanced wear. I don't think it's better than mine, all the half nuts work with the applied principle. Besides this, there was insufficient space for the cheap standard solution. I don't think there will be any problems with the adjustment. There is now 0.8 mm free space to pull the two nut halves together as wear progresses. This 0.8 mm has also been taken into account as free space at the peaks and valleys of the threads.
@@Michel-Uphoff Maybe you have misunderstood or I haven’t explained it properly. I have high precision ground Japanese ball screws that use dual (split) nuts that are preloaded against the opposite sides of the groove, so inexpensive or expensive the solution is effective to reduce backlash. The concern I have with your solution is that it is acting on multiple vectors of the thread, and it is very likely that the pressure required to engage the threads enough to reduce the backlash will end up binding the screw as there won’t be adequate clearance with the major diameter. When new it should work well, but wear will affect the faces far more then the peaks and valleys and clamping it tighter will just bind it and not help with the backlash. I also still believe the screw is trapezoidal, metric nuts of the same pitch will fit, but the cross sectional profile is truncated for strength. I could be wrong, not trying to take anything away from your excellent work, just trying to give you some alternative perspective.
@@TheBakafish High precision ball screws are a completely different chapter and cannot be compared to a traditional screw thread. As explained elsewhere there is adequate clearance at the crests and roots to allow for a total of 0.8 mm adjustment.
@@Michel-Uphoff It would atleast be a long while before it needs another adjustment.