PRT Alpha W/Direct Drive Motors

[CNYDWW]

Hey Guys,

Now that i finally have the PRT FrankenBot Standard that work bought off of me up and running. They're noticing how beat up the PRT Alpha is along with how rough it runs. I'm going to pitch an upgrade. First thing, retro Z axis, new pinon gears all the way around along with a general tune up. Last thing i'd like to pitch the powers that be are these.

http://www.automationtechnologiesinc.com/products-page/cnc-gear-box/51-planetary-gearbox-for-automation-systems-4-thousand-rpm

The direct drive on the alpha i think is it's downfall. I'm going to talk to tech support when i get the chance to see if there's a better pinion gearing that will work with the 5:1 Ratio on these.

Any thoughts?

Regards
Randy

[danhamm]

Randy, I bought these and tried them out, they have between 8 thou and 14 thou end play using a 30 tooth gear, other than that they are good.
I couldnt hack the end play ...I think they are the same motors Keling sells..



No.:Product NameMK P/NQty (set)Unit Price (USD/set)Amount (USD)1Stepper Motor34HS9801-G54151.00604.002Stepper Driver2LA860470.00280.003Express Freight Charges　110.004PayPal Surcharges (5%)　49.70　　　　　　Total amount: USD1043.70
This is for 4 motors and drivers.

[gerryv]

Hey Dan, I was looking at these for use on a CNC sanding bed. Can you un-thicken me a bit on how endplay was an issue. Just can't get the ol' visualization lobe fired up lately. Hey Dan, I was looking at these for use on a CNC sanding bed. Can you un-thicken me a bit on how endplay was an issue. Just can't get the ol' visualization lobe fired up lately. I don't think the question is a deflection from Randy's question as the machine would be very similar but ignore if you think it is.

[Brady Watson]

Randy,
Direct drive Alphas absolutely EAT pinion gears - so replace them and then see what happens. Since they are only 20T, there are only like 1 or 2 teeth engaged in the rack at any one time, and that means that all the force of cutting is being applied to those little teeth - so they wear quickly.

Also, since this is a PRT, take a file and clean up the bottom edges of the rail 'pyramid' profile. Since these rails are so soft, the wheels roll forge them and the steel sorta smears down to the bottom edge. It is best done by hand with a bastard file on an angle (it'll tell you what angle it wants to be) and it really doesn't take long. No power tools or you'll get into trouble...Then steel wool (coarse) over the stuff you cleaned up and feel for any bumps with your fingers - be careful of the splinters! Oil a rag an run it over the rails. Clean weekly or as needed with a brown scotch pad to keep them clean.

You'll be really surprised at how much better the tool will run with just these 2 things. While you're there, inspect the t-rail. Clean up as necessary and adjust v-rollers accordingly. If you don't have 8 v-rollers on the Z tower, add 4 more.

-B

[danhamm]

Gerald, end play means when the motor and gear is engaged tightly in the rack you can move the gantry or z-axis to and fro a given distance.
where it shows up the most is in small circles they are egg shaped in either the x or y, the most extreme test is cutting hard material such as aluminum, 10 thou. slop is a bit breaker.
But, depending on what you do with your machine, and how stiff and heavy it is you may never notice the end play, there are a lot of folks running pk296a2a 7.2 and 3.1 motors and swear they have none. I bought 4 of them brand new and every one of them had slop.

[CNYDWW]

Randy,
Direct drive Alphas absolutely EAT pinion gears - so replace them and then see what happens. Since they are only 20T, there are only like 1 or 2 teeth engaged in the rack at any one time, and that means that all the force of cutting is being applied to those little teeth - so they wear quickly.

Also, since this is a PRT, take a file and clean up the bottom edges of the rail 'pyramid' profile. Since these rails are so soft, the wheels roll forge them and the steel sorta smears down to the bottom edge. It is best done by hand with a bastard file on an angle (it'll tell you what angle it wants to be) and it really doesn't take long. No power tools or you'll get into trouble...Then steel wool (coarse) over the stuff you cleaned up and feel for any bumps with your fingers - be careful of the splinters! Oil a rag an run it over the rails. Clean weekly or as needed with a brown scotch pad to keep them clean.

You'll be really surprised at how much better the tool will run with just these 2 things. While you're there, inspect the t-rail. Clean up as necessary and adjust v-rollers accordingly. If you don't have 8 v-rollers on the Z tower, add 4 more.

-B

Thanks Brady,

I've already dressed the rails etc. That was one of the first things I did. There are only 4 V rollers on the z axis of both machines. Most of the deflection is happening in the x direction and is minimal in the Y. My older standard has less then the alpha. I also learned that they had someone operating the alpha cutting 1/4" per pass at 5IPS with a 1 1/4" surfacing bit. This was before my time. Personally, i would never go more then a 1/16" per pass. Finish is so much nice.

Thanks and Regards

Randy