Updated to Rack and Pinion from Chain Drive #62 - Fort Wayne, IN USA

[Gerald D]

The stepper motor will also "slip" if something is stuck. From that view, the chain is as "safe" as the rack&pinion.

A lot of people use the same principle with a timing belt instead of chain.

[WFY]

Hi Collin,
First of all nice job on the machine. One thing to keep in mind on the chain drive is over time the chain will stretch. We used the same type of chain on the inboard racing boat to couple the engine to the prop shaft. After about 6 or eight races we would have to change the the double roller chain for a new one because of play. It is a lot more load than you will get with a MechMate stepper but roller chains do stretch. Just a suggestion - is to do a periodic check on the travel distance compared to the DRO reading.
I hope this suggestion helps to keep the ' Stupid Bunnies ' under control - they seem to run wild at this shop!
Buzz #60

[krabenaldt]

I noticed the cut quality on the diamond and circle cutouts to be pretty good as far as I could tell from the pictures. Does a chain drive eliminate some of the issues on cut quality by not introducing vibrations from what would seem to be a more rigid system of the rack and pinion? I followed alot the past discussion made regarding poor quality cuts (or chatter), geared motorheads, belt drives, etc. I always thought that vibration or resonance could have been a factor. I do not wish to start a debate all over again but curious if the "give" I saw on the videos with the chain drive softened the vibrations.

I have collected some of the steel and the laser cut parts but have not started my build yet.

Kevin

[ws customs]

I have used chain on one of my cncs and it works great with no backlash the black foot cnc s on buildyourcnc.com also use chain to great effect

[cmd1991]

WFY,
Thanks for that information. Like you said there's not a lot of load on it, but I wondered too if it will eventually loosen/stretch. I'll keep an eye on it.

krabenaldt,
This is my first cnc ever, so I'm still learning, but it seems like the tensioned chain may help with backlash. On the negative side though, occasionally the chain itself will bounce/shake at certain speeds. I haven't noticed that it drastically affects the cut quality, I would just rather not see it shake. I'm guessing if I could eliminate the direct drive by making belt transmissions, It would make the cuts even more smoother, and hopefully reduce the chain vibration.

ws customs,
buildyourcnc was part of my inspiration for this project.

[chunkychips]

Excellent build Collin.

Particularly like the colour. I might have to deviate from MM blue as well .... just let me check that User Agreement again ... :P

I have been wanting to use chain or timing belt for my MM and was wondering, are you relying on gravity and the chain tension to keep the gantry down or do you have a hidden bearing opposing (pushing up) under the x and y rails.

I was thinking that if i used a chain/timing belt i might add a bottom bearing (spring loaded?) to keep things together.

Any comments?

[servant74]

What drives going to chain over rack and pinion? Cost? If so, about what kind of difference are we talking?

I can accept 'because I want to' as a valid reason too!

[chunkychips]

For me it is primarily cost.

Rack is really expensive in Aus. about 6x more!!

Compare results from one supplier:
$320 + for a 1020mm length of Module 1 10x15mm rack here
to $70 for 2440mm of 5mm GT timing belt 15 mm wide here
to $47 for 3m of seemingly suitable chain here

Now I'm not saying these materials are mechanically equivalent (I'm not an engineer) and I'm not saying they represent the best price available. I'm just comparing prices for the three from the same supplier. The difference is massive.

I did notice another post here that seems to suggest I can get the rack a LOT cheaper in Aus (~$42/m) so I will have a look this week. If that is the case then I am happy to go with rack as it doesn't deviate from the original design.

[KenC]

AU320/m of module 1 rack! That is day light robbery!

[cmd1991]

Chunkychips: Glad you like the color! Dad was actually hoping for a little darker red, I thought a nice DARK blue would have looked nice too, but It DOES look good. There are no bearings or anything holding the gantry down, but there is a bearing on the other side of the Y car. Just like the plans call for. In all of our playing, testing, working, etc. we have not had problems with it derailing except for a couple of cases when we ran into something. I don't know about timing belt. I just figured chain would last longer.

servant74:
Part of the reason was cost, (For us it was about $275 savings) and I think there might be less backlash with tensioned chain.

[chunkychips]

Collin I have looked over you build a few times now. It continues to impress me.

I had a couple more questions I was hoping you might answer:

1. Did you use the standard motor mounts or did you make your own (they look custom)?
2. What size steel did you use in your legs and bracing?
3. I noticed that you chose not to add diagonal bracing to the legs. Has this caused any problems? Do you notice any instability or resonance especially at higher speeds? ie if you did it all again would you add bracing?

I have been wanting to make full use of the space under my table (mine will be in my garage and space is at a premium) and your design fits the bill. I have seen the other under table storage solution on the forum but yours appeals more if it works.

Thanks again

[scot]

Hi Chunkychips,
This is Scot, Collin's uncle. Collin and I worked together to build this project for their shop. It was a great experiance one thing I do is design fabricate stuff. Said that just so you know this is nothing new for me and that you might have a little more confidence in what we did.
We did use the standard mounting plates but modified them by adding a longer end so they would bolt on level. I think you can tell with that info if not ask again and i'll explain more, Oh yeh we machined a recess for the motor and moved it placement slightly.
The whole table is a redesign only because I saw too many possible problems with welding pull and I was teaching Collin how to weld and I like to make things easy on myself and others.
The box tubing for the table is 3"x8", 3"x6" would be just fine and even 3"x4" would work good, 1/4" thick.
The legs are 3"x3"x 1/4" with 3/4" leveling bolts.
We have no problem at all with table movement. All seems must be completely welded.
If for some reason you just have to have a brace you can put a short one from the upper part of of the leg to the main rail and still have storage. I was worried that welding to the main beam could cause it to bend or pull out of shape so thus the design.
The chain drive works well, I am in the process now building gear reduction boxes for the motors, Collin wants more power.
The tube main beam is the real secret to this design it has much more rigidity.
Hope this helps Nick if there is anything else we can do just ask, Thanks,
Scot

[chunkychips]

Thanks for the detailed response Scot and congrats on a great build.

That's some fat steel you're using there. Did you also use 1/4" in the Y beams
and the (2"x2"s ??) around the legs?

[scot]

Hi Nick,
We used the recommended size for the y beams we thought that weight was an issue there. After seeing Mech run I think that could be 1/8" It would stableize the downward thrust into the wood by the router. But not necessary if you have hold down bearings, which we don't. I was concerned about motor power too, turns out to be a non issue.
Had to go back and look at the scrap we used 1/8 on the 2x2 I think I would bump that up to 3/16, weight is always an advantage on machinery vibration issues and the like, 10 sheets of plywood underneith will work too.
Thanks for the good comments people look at it and say," what did you build", it looks manufactured to most people.
So thanks too, to the MechMate forum and everyone who helped we enjoyed the build.
Scot

[cmd1991]

Okay,
I have some more pictures for your viewing.

The first 2 are of our belt reduction drives.

Here is the link to the place we ordered the belts and gears from.
4 15 tooth gears
4 45 tooth gears
I ordered 5 belts so we would have an extra one.

https://sdp-si.com/eStore/

Part Number Quantity Unit Price Extension
------------------------------------------------------------------------
A 6A 3-15DF03716 4 $10.49/Each $41.96
A 6A 3-45NF03716 4 $17.42/Each $69.68
A 6R 3-054037 5 $5.60/Each $28.00
------------------------------------------------------------------------

Subtotal: $139.64
Shipping: *
Handling: $3.95
Sales Tax ( NY State Only ): $0.00

The plates are 1/2" aluminum, and we ordered the bearings from vxb.com
Scot did all the machining on them.

Now we have much more torque, and don't have to worry about skipped steps.

Now, I am currently working on meeting the electrical requirements for our 15hp vacuum, as well as a 3hp perske spindle. We puchased these from a gentleman on the shopbot forum.

The last photo is of the acrylic door panel I made for the control box.

[cmd1991]

Here are some more pictures of some of the stuff we've made.

We cut 9 of the black corner tops
21 sets of the straight cubicle and filing cabinet tops
3 conference room tops
4 table tops and an island in the breakroom
3 smaller tops for the 2nd level breakroom
The last picture is of a wall in the front entrance area.
That's a prototype of this business' logo in the center.
We cut out the top for the reception desk also, but I don't have a good picture of that yet.

We've used the mechmate on several other jobs also, but this is the biggest one we've used it on so far!

[MetalHead]

Wow !! Nice work !!!

[domino11]

Nice!

[belmekki]

Hi there,
excellent job Collin. I have liked your design on the chain drive. I myself interested in it because, as you pointed it , of cost. Rack and pinion are out of price here in Oran where I live. I gathered everything on the mechmate cut pieces and made it as one here in the forum did it before '' the bolted version''. I have got one question:
What are the specs the sprocket tooth and the chain ?
thanks in advance and congratulations
BRAVO

[cmd1991]

Originally Posted by belmekki

Hi there,
excellent job Collin. I have liked your design on the chain drive. I myself interested in it because, as you pointed it , of cost. Rack and pinion are out of price here in Oran where I live. I gathered everything on the mechmate cut pieces and made it as one here in the forum did it before '' the bolted version''. I have got one question:
What are the specs the sprocket tooth and the chain ?
thanks in advance and congratulations
BRAVO

Hello,
The chain is #35 chain.

The sprocket on the stepper motor is 10tooth with a 1/2" bore.

The idlers are 18tooth with a 1/2" bore as well.

I also bought 4 boxes of 10' lengths of chain.

I ordered the sprockets and the chain from surpluscenter.com

Total was $106

[cmd1991]

Here is a picture of the finished "JH" logo. We painted it with a high gloss oil based paint.

The second picture is of a curved piece of crown mould.
The customer (fellow cabinet maker) made a curved cabinet, then brought us a block of maple with the same radius as the cabinet. I drew the 3d model in sketchup (free edition) then exported the .stl, and did the cam process with freemill (also freeware). I was not expecting to do this with free software.

We ended up needing to buy a extra long 1/2" straight flute bit due to the height of the mould. I used a .060" stepover. It did need some sanding
It wasn't perfect, but the customer needed it pronto, and we decided we would do it for the sake of education

Not bad for the first 3d project.

[hennie]

You have my attention!

[jhiggins7]

Nice work, Colin. Thanks for sharing.

[domino11]

Wow, impressive. Did you scan the profile of the existing molding for doing the 3d model? Interested in the process.

[belmekki]

Very nice job Colin! thank you for the chain and sprockets characteristics. Are these with the pinion reduction you have talked about or is it a standalone transmission setting. Thanks again

[cmd1991]

Originally Posted by belmekki

Very nice job Colin! thank you for the chain and sprockets characteristics. Are these with the pinion reduction you have talked about or is it a standalone transmission setting. Thanks again

The last specs are for the chain sprockets only. The belt transmission parts are in post #75.

@ Domino11
That was the trickiest/hardest part of the whole job! I DID trace it on paper then scanned it in, then scaled it to the right dimensions, and imported it to sketchup. However, I still needed to trace that scanned picture with the pencil tool in sketchup. That was trickier than anticipated. The process could be improved somehow.?!? It turned out fairly accurate. The profile wasn't perfect, but that's what practice is for right?

[cmd1991]

Well folks, The time has come.... As much as I hate to do this....As long as I have put this off....It doesn't change the facts. I've decided to fit her with the rack and pinion according to the original design. I wanted the chain to work. I really did! But, There were some things I didn't like that I decided were not worth "playing with" in a production shop. While I think it would work, and be a low cost solution for a hobby user, etc. I was having problems with the chain stretching and binding up the steppers. The cost was not significant enough to prevent us from just doing it like everybody else. I ordered all the parts and had it working again with just under 2 days of down time. Side bonus was that I got a welder out of the deal.

We also got the vacuum all hooked up. I divided the table up into 6 zones. Let me tell you. "That table works nice!"

The spindle is also hooked up. Did I mention I've been learning about 3 phase electricity lately?

I Built my own Rotary phase converter for the 15hp vacuum. Fun
I might post pictures of that later on.

I also attached a picture of one of 25 entertainment center that we just finished. We used it to cut the top and bottom, the shelf in the middle, and the bendable plywood for the face.

The rocking chair is a project I'm taking on for an amish friend.


P.S. I'm sure some of you could have told me the chain wasn't the best idea.
Please, let me know what you were thinking. I won't be offended.

[Kobus_Joubert]

Looking good Colin.. Glad you are honest about the chain thing....and are happy with the original design. In my 3 years I have see a lot of people with some bright ideas. Some locals that I assisted also tried some modifications.... some of them are still not finished after 2 years of building. I have always said to them to keep to the original design as it worked out well for me.
I will say nothing about your chain attempt....too afraid of venom spitting okes on the other side of the world.. you know what I mean...

[sailfl]

Collin,

You gave it a shot and it didn't work the way you wanted it to work. It is better to try than to wonder if it would have work. Thanks for sharing you experiment.

We all learn from others.

[bradm]

Colin, I don't think you're going to get any "I told you so" responses; many of us were pulling for it to work, and we appreciate the feedback on the results. "Failed" experiments are often more educational than "successful" ones.

With the understanding that you've moved on for good reasons (like running a business), I'd like to know if you feel that some kind of dynamic chain tensioner such as a spring or large weight could work, or if other issues render this approach dead.