Rack and Pinion - understanding Diametral Pitch (DP) vs. module
 

Hi everybody

I ordered OM 7.2. I checked also MM Gear Resolution table but I couldn´t understand exactely.
Do I have to use for a OM 7.2 a 36 teeth pinion or can I also use a 24.:confused:
What is the consequence?

Thx
Claudiu

Claudiu,
Are you using USA style 20 pitch or Mod 1 or 2 rack.

Pinions in either case should allow for you to use anything between 20 - 36 teeth. The MM builders typically use a 30-35 tooth for the 7.2 geared motors.
Using the geared motors your really only affecting speed of the machine. Yes, you are affecting the torque value too, but the needed torque isn't drastically effected.

My recent couple of builds use 7.2 Geared motors with 30T pinions on 20 pitch rack.

Claus, if you want max speed with slightly lower cut quality, use 36 teeth module 1. If you want slightly lower speed and better cut quality, use 24 teeth module 1. The differences are not as big as they sound.

Metric System
 

Sorry, no Pitch, metric !!!

So for the first try I´m going Metric System with 35 teeth on a 15 mm rod.
Let´s see what happens.

What about using 35 teeth for the x and y, and a 20 for the z?
Any opinions?

Thx

Module 1
 

Module 1, sorry I´m new here, so sometimes I do not understand immediately...:confused:

20 teeth, module 1, is too small for a 15mm shaft. Check the dimensions yourself. It is okay to mix the gear pinion sizes. Actually, they are not expensive, you can buy some different sizes for experimenting.

Gerald and All,
For Rack and pinion in metric system.
If I use rack at module1(15x15mm),what is the popular teeth of pinion gear?
If I use rack at module1.5(15x15mm or 17x17mm),what is the popular teeth of pinion gear?

Add Information,
I use stepping motor with gear reducer at 4:1 ratio transmission.( X and Y axis)
Driver timing pulley = 18 teeth
follower timing pulley = 72 teeth
XL belt.

Hope your help
Mongkol

If I use rack at module1(15x15mm),what is the popular teeth of pinion gear?
Somewhere between 24 and 36 teeth. 24 will be a bit smoother, 36 a bit faster in soft material. Doesn't make too much difference. Most go for the bigger & faster.

If I use rack at module1.5(15x15mm or 17x17mm),what is the popular teeth of pinion gear?
20 to 24 teeth. Not many people have used module 1.5

Gerald,
Big Thanks for the informations.

Puzzled with DP. What does it mean?
 

Dear All,
I choose the rack and pinion at module1.0 and the popular pressure angle at 20 degree. I am little puzzled with Diametral Pitch(DP). What does it mean?What is the effect if I choose the different DP at 16,20,24 or so on? Pls advise.
Pls have a look the example in attached link.
http://www.qtcgears.com/e-store/RFQ/...g_4-002_1.html
http://www.qtcgears.com/e-store/RFQ/...g_4-005_1.html

Mongkol

See: http://www.sdp-si.com/D190/HTML/D190T109.htm

Diametral Pitch = The number of teeth of a gear per inch of its pitch diameter (teeth per diameter)

Module = amount of pitch diameter per tooth, in millimeters (diameter per teeth)

Gerald,
It helps me go to the right direction. Thanks for the information.

Ton:)

having a hard time understanding MOD
 

Was a separate thread, now moved in here . . .

Hi all,
What is the difference between mod 1 and mod 6 ( do mod 1 have a smaller and finer gear than mod 2)? the only spec I got is mod 1 = 15x15 and mod 2 = 60x60 it doesn't make any sense for me.

Yes, mod 1 is finer then mod 2, & there are mod 0.5 as well. bigger the number larger the gear pitch. wiki spur gear will go a long way.

Please read before starting a new thread! :mad:

Rack and Pinion - understanding Diametral Pitch (DP) vs. module <-----this thread

Yes I did read the posting but really having a hard time understanding.

A typical mod 1 rack is a square bar of steel 15 x 15mm. A typical mod 6 rack is a huge square bar of steel 60 x 60mm.

Does this help?

yes I know that mod 1 is 15x15 and mod 6 is 60x60 but what I didn't know is the little mountains is finer and closer together on mod 1 compare to mod 6. Thanks I will stick to mod 1.

Here is also a nice explanation on the terms : like root, pitch and outside diameter. http://shopswarf.orconhosting.net.nz/spur.html

Ries

Ries, that explanation ignores the metric world that uses the concept "module" to define the "coarseness" of the teeth.

The long rack
 

Gerald,
I have some question with the rack of module=1
Is it necessary to use the standard size of 15 x 15 mm for this?
My supplier can make it with one piece but he can not follow size 15 x 15 mm.
size 20x 20mm,Is it possible for ? Does it effect?

Mongkol

Hi Ton,
There is a overhang clearance of 20~25mm between the edge of the angle rail to the main beam depending on how accurate you construct your table & rail alignment. This is the space where your rack will mount. As long as you can fit your rack in, the width of the rack doesn't matter, I recon the motor mount can accept 20mm high rack, if it doesn't, you can always extend the slot on the motor mount.

As Ken says, 20X20 could work, but you have to proceed very carefully. Also be careful at the gantry where you are maybe using 52mm wide tubes instead of 50mm wide tubes . . . . the y-car must still fit freely over the gantry and racks.

Ken and Gerald,
Big Thanks for your guide.:)