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  #181  
Old Sun 11 October 2009, 08:59
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
Quote:
Originally Posted by Gerald D View Post
Chopper, the oriental 7.2 behaves like a belt-drive at 7.2 ratio. For a discussion on the best ratio, there is no need to bring in a discussion of gear vs. belt.
Gerald,
there was no intension of discussing belt drives vs. the 7.2's
the only reason was for the loss that is generated through the gear drive which limits the 7.2's to around 700 to 750 ozin and all I am saying is if the 7.2's will drive the gantry with 700-750 ozin then the other reduction will be fine with a 50% loss of power since it will still have more than the 7.2's
and the reason I compared to the 7.2's is it seems to be the standard that is used here
//chopper
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  #182  
Old Sun 11 October 2009, 11:50
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
There is a serious misunderstanding of the amount of torque available from a "OM 7.2" motor/gearbox package. It gives a lot more than 700-750 ozin, but the spec says that you must not design your system to use that extra torque. Same goes for the belt-drive - the thin belts that most use for these reductions should also not be used at the torques levels that are needed on our routers.

For the OM 7.2, there is NO "loss that is generated through the gear drive which limits the 7.2's to around 700 to 750 ozin" That limitation is put on by the design engineer who needs to guarantee you long life running 24/7 under full torque.
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  #183  
Old Sun 11 October 2009, 17:02
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
Gerald,
if the engineers limit the torque it is for a reason, that being it will cause gear wear or failure, in other words the gear box cannot handle the load, so what good is a higher rating of torque if you cannot use it?
so the limitation of the 7.2's is going to be at the rated torque which is in the 700-750 oz-in range which quite frankly I could care less about.
but as far as the belt drives go the xl belts with .375 inch width have a breaking point of 390 lbs, which is equal to 74,880 oz-in
so if the operating range is say half of the breaking strength that would put us at 195 lbs or 37,440 oz-in which is way more than these motors can produce, I also have to believe that the operating strength of these belts would be closer to 75% of the breaking point which would be 292.5 lbs.
or 56,160 oz-in which is also way more than the motors will produce.
so I guess I will have to disagree with you that these smaller belts will not handle the load, the specs show that they will, and can handle the load what you have stated is incorrect.
//chopper
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  #184  
Old Sun 11 October 2009, 23:03
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Chopper, for belt drives, the engineers publish charts like this:


The bottom left corner of the chart starts at 0.1kw (100 Watts) and 100rpm., which would be quite a common situation for us with our routers. The engineers there deem it too much for a XL belt.

This is just a general example of what the supplier's (belt or gear) engineers put out in public. But we have seen that our router application happily runs beyond the supplier's spec . . . . . for both belts and gears.
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  #185  
Old Mon 12 October 2009, 09:35
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
A chart which says to limit XL to 180 oz.in torque:
http://www.torquetrans.com/pulleys/t...lt-pulleys.pdf

http://www.misumiusa.com/CategoryIma..._pdf/p2823.pdf

http://www.roymech.co.uk/Useful_Tabl...ing_belts.html

http://mechatronica.eu/en/design-man...%20(21-26).pdf
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  #186  
Old Mon 12 October 2009, 19:31
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
Gerald,
I have never found charts like that before,
but I also didn't see the charts list what belts they were testing,
and what I mean by that is what type of material the belt was made from and what type of material was used to reinforce the belt, unless I missed it....( the belts I am running are reinforced with Kevlar and are much stronger than the regular XL belt)
there is a lot of reading there and I am not going to go through everything,
what it comes down to is you may want to run a heavier belt so built a transmission with a heavier belt, not a big deal, I have had zero problems with the XL's I am planning on changing them out every so often which I feel would be good maintenance. I don't know if this is necessary I will monitor them, to see what happens, also the pinion will walk out of the rack before you could put enough force on the belts to damage them.
but the issue still remains with the back lash in the gear heads of the OM 7.2's
and this you cannot get away from with out switching out the transmissions,
I am only stating what I have done you can choose to use the information or not, it really doesn't matter to me my machine works and works well, with great cut quality that quite frankly I thought I would never get from this type of machine, I also know that it is not a fluke since I have had the same result on two different machines, the second machine had a bad chatter issue just as bad a Nils, if not worse, in fact it was so bad that when he cut a file and the machine would come back to zero it would not be in the same spot, which was caused by backlash, once the belt drives were installed the problem was gone, you can run a file over and over with 100% repeatability
and accuracy, on both our machines,( just the other day I ran a repeated file over and over the first few cut parts were not deep enough so I adjusted the depth and cut the rest of the pieces and set the first part back in the jig and it dropped right into the drilled holes with out even touching the sides of the existing hole) I know you cannot do this with the 7.2's,(I had them on my machine ) now maybe you don't want to or need to have that kind of accuracy,and again I really do not care but I thought why not make the machine as accurate as possible,
that is why I shared what I had done, I am not trying to mislead anyone
all I have to say is the proof is in the cuts,
also I want to ask if any one using there mechmate can get this quality of cut with there machine, I really want to know I mean no disrespect this is a request to see the cut quality comparisons if you need to know it was cut in 6061 .250 thick on the diagonal to the machine, ( with a Milwaukee router) I am quite sure that you will not see the 7.2's be able to accomplish this, again this is from my experiences, with having the 7.2's they seem to be tight at first but as they break in the backlash becomes apparent..I am not going to argue about belt vs 7.2's this will be my last statement on the subject unless asked, you can see that they work by the quality of cut produced,
//chopper
Attached Images
File Type: jpg pic-1.jpg (16.3 KB, 2040 views)
File Type: jpg pic-2.jpg (12.3 KB, 2037 views)
File Type: jpg pic-3.jpg (10.0 KB, 2043 views)
File Type: jpg pic-4.jpg (11.2 KB, 2053 views)
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  #187  
Old Tue 13 October 2009, 00:08
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Relax a bit Chopper. Nobody is saying that you have built a bad drive, and nobody is saying that the backlash in a geared motor can be ignored.

I do not understand how these marks. . . .


. . . . can be caused by backlash in a geared motor. Those marks are about 1/4" apart. (since been confirmed that material is 1/4" thick)

Did you see such widely spaced, very regular marks when you were running geared motors? I cannot recall that your "before" photographs showed anything like this.

Bear in mind that there are many other users out there with geared motors who are not seeing these wide apart, even spaced marks. (I don't call that "chatter")
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  #188  
Old Tue 13 October 2009, 09:03
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
Gerald,
mine were similar but not as deep,
the other machine that my friend has was very similar to this if not worse..
what I think happens is once the first pass happens it sets the chatter for the rest of the passes, the bit will follow the path of least resistance and that is why you end up with the chatter lining up from top to bottom, on different cut paths, I also believe that the equal marks along the cut path are generated by the tool, because it is say a two fluted up spiral bit it will grab or dig into the material at equal measurements, since the marks are about an 1/8 inch apart I would say he used a 1/4 inch bit two flute up spiral, but this is conjecture I cannot prove it.
ok I will back the springs of a little bit(relax)
//chopper
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  #189  
Old Wed 14 October 2009, 03:07
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Gerald,

The material I cut was .25" in the picture you have marked.
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  #190  
Old Wed 14 October 2009, 04:36
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Thanks, the post above has been edited.
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  #191  
Old Fri 06 November 2009, 18:37
salewis
Just call me: Stan #67
 
Littleton, NC
United States of America
Do you have the transmission plates available?

Stan
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  #192  
Old Fri 06 November 2009, 21:00
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
I can make them for you if you want or you can build them from the plans
//chopper
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  #193  
Old Sat 14 November 2009, 13:34
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
these bits are for the cnc machine world like a haas or equivalent,
also onsrud makes some look up there 83-300 series www.onsrud.com
feeds and speed are listed there, I want to throw out a disclaimer here I have done quite a few things to make sure my machine is tight... and backlash free,
without getting into a pissin' match I just want you to know that these cuts may not be accomplished with out the proper modifications to your machine excessive backlash may cause adverse effects like bit breakage etc. and always wear safety glasses, I also want to state that I have an extensive background in metal fabrication / machining / welding etc. which might give me a slight edge on experience in doing this type of work...... and here are a few pics of mild steel 1/8 inch
//chopper
Attached Images
File Type: jpg steel-1.jpg (8.8 KB, 2141 views)
File Type: jpg steel-2.jpg (18.0 KB, 2145 views)

Last edited by chopper; Sat 14 November 2009 at 14:03..
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  #194  
Old Sat 14 November 2009, 13:57
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
Quote:
Originally Posted by MetalHead View Post
What were your feed and speed settings for this? Also what kind and size of bit (Mill bit?) did you use?
I used a 1/4 inch shank with a 1/4 inch tool dia. the feeds and speeds may very from brand to brand, I used 20 ipm @ .020 cut depth, if you have a machine shop supplier near you or on line with a little looking you will be able to find some that work, just specify that you are doing high speed machining..
the bits I used are from my local supplier and it is there house brand that I used.
//chopper
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  #195  
Old Sat 14 November 2009, 13:59
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
Quote:
Originally Posted by Conrado_Navarro View Post
chopper
can you post the bit data?, brand, type, and where to order?

Thanks

Im a fan of your work!
I hope the above answered your questions also if not please ask I will help with what I can.
//chopper
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  #196  
Old Sun 15 November 2009, 05:45
salewis
Just call me: Stan #67
 
Littleton, NC
United States of America
Chopper, you mentioned "mods" to the MM, what kind of mods (beyond the 4:1 trannies)?

Stan
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  #197  
Old Sun 15 November 2009, 09:17
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
I modified the Z,
and the rack,
and the spider, but the most important thing is to spend the time to make the machine right, pay attention to the details and tolerances, make sure things are square, and parallel, etc..if you look under my build you can see some of the z and spider mods.
//chopper
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  #198  
Old Sun 15 November 2009, 11:16
lumberjack_jeff
Just call me: Jeff #31
 
Montesano, WA
United States of America
That is very nice work chopper.
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  #199  
Old Sun 15 November 2009, 16:11
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
Quote:
Originally Posted by chopper View Post
here are some more pictures. these are MM motor plates, kinda funny a MM making a MM,
these are .250 thick and are really smooth these pics are blown up a bit, you can reference to the quarter, I do not know how you can not believe that the 4 to 1 belt drives do not make a difference after seeing these cuts. I am getting better cuts in steel than most of you can get in wood,
//chopper
it has been brought to my attention that the above statement has upset some of you,...the statement I made was in no way meant to be offensive, but I can see how it could be taken that way even though it was not intended to be...( for that I apologize I am very direct and to the point and some times it is taken the wrong way)
all I want to do is show you all what is possible with your machines to think out side the box, to do what they say cannot be done, did I think my machine would cut steel ? or stainless steel? no way but I tried it to see that is all, and to my surprise it did,

as I stated before I have a background in metal fabrication, welding and machining..that allows me to understand what I am doing, and may also give me an edge.. when I was in metal fab we did a lot of work for demanding customers that required perfection, and I have brought those work ethics over into all the work that I do, the mech mate is no different, so what I am saying is the MM is what you make it, if you want to perfect it you can...(from the above posts you can see what is possible), if you do not that is your choice, some will be able to do this and some will not, that I am afraid is a fact, (but the ones who can shouldn't be held back by the ones who can not) and it shouldn't stop you from trying, and as time goes on your understanding will grow and so will your abilities, if you never try you will never know or achieve the impossible,

I also want to say that my belt drives are not the cure all for all the problems that are faced in the building of the MM ( they will not make up for a poorly constructed machine) if you do not spend the time to understand what you are doing or cheap out on parts, or decide that your rails are good enough, or compromise on the quality of your fabrication, you will be limiting your machine.....you and only you can decide what you do, so you can choose to limit yourself or not. but you cannot blame Gerald, myself or anyone else if your machine doesn't preform the way you want after all you built it.. the advise here is given freely you have to decide weather or not you use it and if you do you are responsible for the out come no one else.
with that said all I want to say is good luck on your builds..
//chopper

Last edited by chopper; Sun 15 November 2009 at 16:14..
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  #200  
Old Sun 15 November 2009, 16:15
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
Quote:
Originally Posted by lumberjack_jeff View Post
That is very nice work chopper.
thanks
//chopper
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  #201  
Old Mon 16 November 2009, 05:14
Robert M
Just call me: Robert
 
Lac-Brome, Qc
Canada
Send a message via Yahoo to Robert M Send a message via Skype™ to Robert M
Offended or not ( BTW as a woodworker by trade, I one of those exception who was not offended…) I can see by you direct approach why some where !
Among critics, one thing some of us can and should admit, we thank you for your contribution and the time it takes to share some of your result to us.
Yes I agree you should tame or change some of those words as it would get your message across smoother without changing the context, but on the other hand, as with many other here, we also have to understand where one wants to go when a statement is made ! It goes both ways !!!....and sometime ( personally I’d say most often…but that is my opinion) sometimes other tent to jump to fast as if it was a personal offence !
Well, for what my opinion is worth, I thank you for your contribution as other should also pad their back to contribute POSITIVLY to this great community that Gerald started !
Amicalement, Robert
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  #202  
Old Mon 16 November 2009, 07:23
jhiggins7
Just call me: John #26
 
Hebron, Ohio
United States of America
Chopper,

I agree with Robert. Please keep your unique and substantial contributions to this Forum coming!
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  #203  
Old Mon 16 November 2009, 09:30
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
Thanks,
I do not intend on going anywhere, unless I get into big trouble,
I just want to clear the air so to speak and I know that some of the stuff I say is taken the wrong way I am the first to admit I am no word smith, so I just wanted you all to know why I say what I say, but I will try to use a better choice of words in the future..
//chopper
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  #204  
Old Thu 19 November 2009, 12:05
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
OK folks - I drew these in Visio and exported them to DXF format. Can someone check me on the mesument and placement of the holes.

The motor plate holes seem to be to far to the right of the bracket, but I think I did all by the measurements.

I centered the motor drive shaft hole and the slave pully hole. I figured that was correct, but it was not on the drawing that I could see.
Attached Files
File Type: dxf Chopper Plate.dxf (19.9 KB, 224 views)
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  #205  
Old Thu 19 November 2009, 12:09
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
Chopper - you may have addresed this, how does the assembly come apart to replace the belt?

NM - I found it .

I attached it to the 45 degree angle on one side of the motor plate, you need to put these in a location that will allow you to put the big pulley in place and remove it if say a belt breaks, look at the pics for reference

Last edited by MetalHead; Thu 19 November 2009 at 12:11..
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  #206  
Old Thu 19 November 2009, 12:24
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
OK reading that led me to this mod to save welding , but it would add some bends.
Attached Files
File Type: dxf Chopper Plate 45 mod.dxf (21.4 KB, 242 views)
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  #207  
Old Thu 19 November 2009, 13:11
riesvantwisk
Just call me: Ries #46
 
Quito
Ecuador
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Chopper,

If I may Ask... what is the purpose of the bearing cups?

I am highly surprised that you could do the steal with it, amazing!
Good job, good pictures.. thanks

Ries
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  #208  
Old Thu 19 November 2009, 16:24
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
Ries,
the bearing cups or bosses hold the bearing that the shaft turns on,
the shaft that has the large pulley and pinion..
chopper
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  #209  
Old Thu 19 November 2009, 17:00
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
Quote:
Originally Posted by MetalHead View Post
OK reading that led me to this mod to save welding , but it would add some bends.
Mike, I see you have added "wings" to the design, I think this is a good idea..
however I do not know if it will work since the plate that goes onto the pivot point arm goes somewhat behind the plate, you would need to try this to make sue it will fit correctly.
I actually redesigned the plates to make them easier to build they remove the funky angle bended plates and replace them with straight ones, you could add "wings to these much easier, take a look and let me know what you think,
they also guard the pulley ( to keep fingers out and add a dust shield if desired) I also wanted to add that the hole in the bottom of the new Z plate is not to size I left it small so it could be drilled out to what ever size is desired ( I am using these on a plasma machine) so we will be drilling them to an inch size
//chopper
Attached Images
File Type: jpg belt drive motor plate pic.jpg (6.8 KB, 2286 views)
File Type: jpg pic z.jpg (5.3 KB, 2294 views)
Attached Files
File Type: dxf belt drive motor plate.dxf (47.7 KB, 233 views)
File Type: dxf modified Z motor plate.dxf (36.2 KB, 198 views)

Last edited by chopper; Thu 19 November 2009 at 17:12..
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  #210  
Old Thu 19 November 2009, 17:14
riesvantwisk
Just call me: Ries #46
 
Quito
Ecuador
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Quote:
Originally Posted by chopper View Post
Ries,
the bearing cups or bosses hold the bearing that the shaft turns on,
the shaft that has the large pulley and pinion..
chopper
Chopper,

in that case, is this because the metal is potentially to thin to hold the complete ball bearing?

I may sound like a dummy, but never did any metal working, just trying to understand

Ries
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