[ikhan42]

Hey guys I found this site that guarantees zero backlash rack and pinion system anyone have any experience with this or know anyone who has used this in a system am a little skeptical that there will be zero backlash.

thanks
ikhan42

[ger21]

Can you post a link to the site you're talking about?

[ikhan42]

Sorry thought I had pasted the link here it is

http://www.nexeneurope.com/en/model/rps-classic.php

ikhan42

Can you post a link to the site you're talking about?

[ger21]

Those cost about 10 times more than regular rack and pinion, which is probably why I haven't seen anyone using them.

[svenakela]

...at a speed 10 times higher than regular rack and pinion.

[mike_Kilroy]

I'm more than skeptical. as an AIME certified motion control engineer, I cannot see any physics that matches our euclidean math that might make this design "0 backlash."

Ok, I can accept claims that life may be extended by roller bearings on the meshing 'teeth.' but there is nothing here I see that could possibly in my mind equate to "0 backlash." to get 0 backlash from a rack/pinion, you need some method to make the space between teeth and rack zero - this does not do that.

I vote bad advertising.

[ikhan42]

There are alot of good writeup's on this setup but I dont think I can justify costs and im guessing its very expensive as there are no prices on the website and the suppliers here in australia arent responding to enquiries.

Guys are the split pinions expensive and any one know where I can buy rack and split pinions in sydney australia.

I am very keen to start building the cnc as I have a bunch of working projects that I need to do at hom that I have been putting off for years and now more projects are being pushed my way as our house is getting older (so am I ) I am also wanting to design a simulator and make all the dial instruments my self with aluminium face plates and am guessing a cnc machine for cutting the dials and also etching the numbers would be a good thing for me to invest in. Hey might even help me understand gears to make the instruments.

I am sure I will have a million more questions as time goes by.

regards
ikhan42

I'm more than skeptical. as an AIME certified motion control engineer, I cannot see any physics that matches our euclidean math that might make this design "0 backlash."

Ok, I can accept claims that life may be extended by roller bearings on the meshing 'teeth.' but there is nothing here I see that could possibly in my mind equate to "0 backlash." to get 0 backlash from a rack/pinion, you need some method to make the space between teeth and rack zero - this does not do that.

I vote bad advertising.

[mike_Kilroy]

ATLANTA Ultra-High Precision Rack & Pinion Drive Systems

has a good name.

I recently helped diagnose a shaking problem on a rp dual system that used Y shaped bearings riding on top of thomson shafting. the 5000# gantry was not heavy enough to prevent it LIFTING as the clearance was to tight - causing the shaking they were trying to prevent! anyway, you need to check specs to see if a split pinion is good enough for your need. an alternative is a spring loaded dual pinion box but they start getting expensive. then you can use an antibacklash servo system like we sell with dual servo motors and dual pinions on same rack but that too is expensive.

[ikhan42]

Mike,

I had a look at the atlanta site yesterday I likes the dual pinion dual motor setup. As I mentioned its not going to be a industrial machine its going to be doing stuff like kitchen cupboard doors, shelves, the instruments for the flight sim though I am thinking on building a mini mill for circuit board and the flight sim instruments.

How much are the dual pinion systems with anti backlashing servo, everyone I as for a quote from their web site requests seem to not respond to inquiries.

Also a question cant I just make a plate with 2 pinions on it connected together with 1:1 ratio gear so both pinions rotate at the same rate? would this not fix the backlashing issue. Even better couldnt I do that with dual split pinions ?

Also the antibacklash servo you are referring to I thought its the rack and pinion that cause the backlash not the motor.

ikhan42

ATLANTA Ultra-High Precision Rack & Pinion Drive Systems

has a good name.

I recently helped diagnose a shaking problem on a rp dual system that used Y shaped bearings riding on top of thomson shafting. the 5000# gantry was not heavy enough to prevent it LIFTING as the clearance was to tight - causing the shaking they were trying to prevent! anyway, you need to check specs to see if a split pinion is good enough for your need. an alternative is a spring loaded dual pinion box but they start getting expensive. then you can use an antibacklash servo system like we sell with dual servo motors and dual pinions on same rack but that too is expensive.

[ger21]

Just about everyone here building rack and pinion machines uses a basic single pinion, spring loaded into the rack ala cncrouterparts.com
There's really no need for the greater expense of split pinions for what you'll be doing.

[ikhan42]

Ger,

Thanks for the info have had a look at the cncrouterparts.com website and they are pretty much a one stop shop for parts.

I am putting an order in for the parts I need for the table but have noticed that they have the pinion included in their rack and pinion spring loaded kits however they dont seem to have the rack. I am guessing the teeth on the rack and pinions are an international industry standard and any rack that matches the 20pitch will suffice globally is this correct?

Also is there any rule of thumb of what motor to use I am not sure wether to use the nema23 or nema34 motors i am leaning towards the larger motor but am thinking maybe for what I am using this for the motor may not be a good thing. Is there also any reason why I cant use the nema34 for the x axis and the use the nema23 for the y and z axis.

thanks
ikhan42

Just about everyone here building rack and pinion machines uses a basic single pinion, spring loaded into the rack ala cncrouterparts.com
There's really no need for the greater expense of split pinions for what you'll be doing.

[ger21]

The rack is 20° pressure angle, 20 pitch. There are different pressure angles and pitches available. Make sure you get the correct one. If you can't find them in Australia, see if Moore Gear can ship to you.

Also is there any rule of thumb of what motor to use I am not sure whether to use the nema23 or nema34 motors

The proper way to choose a motor is to calculate the required torque to accelerate the weight you have to move to a target velocity at a target acceleration rate.
Most new to CNC have no idea what they want or need.
So they just go with the Nema 23, which works fine in most lighter weight machines. If you're moving 150 lbs or less, they should be OK.

[mike_Kilroy]

Mike,
......How much are the dual pinion systems with anti backlashing servo, everyone I as for a quote from their web site requests seem to not respond to inquiries.......

Also a question cant I just make a plate with 2 pinions on it connected together with 1:1 ratio gear so both pinions rotate at the same rate? would this not fix the backlashing issue. Even better couldnt I do that with dual split pinions ?

Also the antibacklash servo you are referring to I thought its the rack and pinion that cause the backlash not the motor.
ikhan42

You didn't ask us for a quote we will quote right away. seriously, to quote requires knowing what size servos are required and how you will command them.... do you have a size in mind? if not you can give us the mechanical data you want to do and we will size it for you.

all that said, some people's dual servo antibacklash systems require 2 complete servo axes PLUS another something that ties them together. complex, and hard to setup & tune. some of our kollmorgen drives have anti-backlash firmware built in and so you just buy 2 complete servo systems. so cost is 2 servo systems. price depends on how big they are.

2nd question above is a bit confusing. if you put 2 pinions on 1 rack and do not preload them against each other they will not take out the backlash. hence split pinions that you install then twist to make the single pinion hit both sides of the rack teach. dont need 2 just one.

and lasgt paragraph above quoted: yes it is the rack/pinion that has the backlash. dual servos setup in antibacklash mode make a constant torque between the 2 pinions so they push against both sides of the rack. some systems allow the 2nd motor to cross the backlash and help accelerate the load when needed.

[Al_The_Man]

As I mentioned its not going to be a industrial machine its going to be doing stuff like kitchen cupboard doors, shelves, the instruments for the flight sim though I am thinking on building a mini mill for circuit board and the flight sim instruments.

As Gerry mentioned, what kind of precision are you looking for? That is what you need to ask yourself.
R&P can be adequate for most of the applications you indicate you want to machine.
There are suppliers that can provide precision machined rack with machined ends such as SDP Spur Gears, Helical Gears, Miter Gears, Worm Gears, Worms, Anti-backlash Gears, Anti-backlash Worms and Bevel Gears from SDP/SI
For machine design software, there is http://www.kollmorgen.com/en-us/supp.../motioneering/
If you need to use a dual servo on the long axis there are controls that will gear one servo off the other in a master slave configuration.
Al.

[ikhan42]

Mike,

You are correct i haven's asked you guys for a quote yet I had emailed companies that were listed in the cnc machining hand book and none of them replied.

I am thinking about a nema34 motor for the x axis and maybe nema23 motors for the y and z axis.

I am looking at a 5 by 4 foot machine used for wood, thin aluminium, and steel maybe down the track. I am also thinking of making a small cnc machine for doing Printed circuit boards and engraving.

The use of the machine will initially be making kitchen cup baord doors to get my wife of my back but ultimately will be used for machining flight instruments for simulators out of aluminium, steel and plastics.

I was thinking of using the driver board and break out boards either from keiling or cncrouter parts but am open to other recommendations

if you can provide pricing that would be great.

thanks
ikhan42

You didn't ask us for a quote we will quote right away. seriously, to quote requires knowing what size servos are required and how you will command them.... do you have a size in mind? if not you can give us the mechanical data you want to do and we will size it for you.

all that said, some people's dual servo antibacklash systems require 2 complete servo axes PLUS another something that ties them together. complex, and hard to setup & tune. some of our kollmorgen drives have anti-backlash firmware built in and so you just buy 2 complete servo systems. so cost is 2 servo systems. price depends on how big they are.

2nd question above is a bit confusing. if you put 2 pinions on 1 rack and do not preload them against each other they will not take out the backlash. hence split pinions that you install then twist to make the single pinion hit both sides of the rack teach. dont need 2 just one.

and lasgt paragraph above quoted: yes it is the rack/pinion that has the backlash. dual servos setup in antibacklash mode make a constant torque between the 2 pinions so they push against both sides of the rack. some systems allow the 2nd motor to cross the backlash and help accelerate the load when needed.

[mike_Kilroy]

will do. PM me with your email address please.

Al offered link to our free Kollmorgen Motioneering program which will do all the heavy lifting of equations and such - you just supply the sizes, weights, speeds you want, and it will help pick the correct size motors. If you do that and send me the file or the motors picked it would be best so the right motors are picked. I assume from the control then you would want step/dir commands to the drives. 120v? 230? 1ph or 3 phase? What's your preference?

I think from your description a dual motor antibacklash system (that doubles the servo system cost for that axis) does not sound like it makes any sense - it sounds like you should just pick a single split pinion that you can twist and lock in to take out the backlash for your needs. Keep in mind an antibacklash system is NOT a master slave system - totally different control algorithms. A master slave system will do nothing for eleminating backlash.

Al asked you for the accuracy and repeatability you are after - you should decide that up front so the hardware is picked to achieve it....

[ger21]

I am looking at a 5 by 4 foot machine used for wood, thin aluminium, and steel maybe

Cutting steel with a router is almost never an option. Cutting steel typically requires much lower spindle speeds, coolant, and far more rigidity than routers typically possess.

What kind of budget are you looking at? I'm going to guess that the Kollmorgen setup will be at least 3 times the cost of the CNC Routerparts setup that almost everyone here uses.

[ikhan42]

Mike

Thats where I am struggling, I am guessing its a better option for me to build the table first to work out weights and then work from there the motor options. I am thinking of making the gantry out of steel and having it all welded together rather then the extruded aluminium option but am not to sure if steel will make a more rigid gantry compared to the extruded aluminium or weather both options are much of a muchness. Common sense tells me steel will be better but common sense isnt engineering. So many decisions to make.

I am looking at repeatability to be fairly high and good accuracy as mentioned I am going to be doing my kitchen cabinets initially and dont wont my wife killing me by spending a machine that produces inaccuracies in the door designs.

ikhan42

will do. PM me with your email address please.

Al offered link to our free Kollmorgen Motioneering program which will do all the heavy lifting of equations and such - you just supply the sizes, weights, speeds you want, and it will help pick the correct size motors. If you do that and send me the file or the motors picked it would be best so the right motors are picked. I assume from the control then you would want step/dir commands to the drives. 120v? 230? 1ph or 3 phase? What's your preference?

I think from your description a dual motor antibacklash system (that doubles the servo system cost for that axis) does not sound like it makes any sense - it sounds like you should just pick a single split pinion that you can twist and lock in to take out the backlash for your needs. Keep in mind an antibacklash system is NOT a master slave system - totally different control algorithms. A master slave system will do nothing for eleminating backlash.

Al asked you for the accuracy and repeatability you are after - you should decide that up front so the hardware is picked to achieve it....

[ikhan42]

Ger,

I wasnt looking at putting a "router: on the cnc machine was going to use some kind of motor with speed controls that will be controlled by the cam software. From what I have read I will need something like an r8 collet to hold the bits.

Was going to ask down the track what is good to use as the machining device.

thanks
ikhan42

Cutting steel with a router is almost never an option. Cutting steel typically requires much lower spindle speeds, coolant, and far more rigidity than routers typically possess.

What kind of budget are you looking at? I'm going to guess that the Kollmorgen setup will be at least 3 times the cost of the CNC Routerparts setup that almost everyone here uses.

[ikhan42]

Ok have been looking at some of the 8020 stuff have found this as an option for the frame what do you guys think

40-8016 t slotted profile looks solid and heavier than the 3030. Also has anyone tried the Linear Motion Assembly from 8020 info available here The 80/20 Training Center - T-Slot Accessory Introduction.

regards
ikhan42

Mike

Thats where I am struggling, I am guessing its a better option for me to build the table first to work out weights and then work from there the motor options. I am thinking of making the gantry out of steel and having it all welded together rather then the extruded aluminium option but am not to sure if steel will make a more rigid gantry compared to the extruded aluminium or weather both options are much of a muchness. Common sense tells me steel will be better but common sense isnt engineering. So many decisions to make.

I am looking at repeatability to be fairly high and good accuracy as mentioned I am going to be doing my kitchen cabinets initially and dont wont my wife killing me by spending a machine that produces inaccuracies in the door designs.

ikhan42