Re: Gecko Stepper on Bridgeport

Hi Ian, welcome to the group.

I am very interisted in you current retrofit project as i am
attempting somthing similer. I have a standard bridgeport with J
head made in germany (i am in USA). Currently the machine has
metric acme lead screws and i have some M112 motors to put on it. I
also want to use the geko drives but was more interisted in the G210.

From your message i calculate you are using a 2.5 to 1 pully ratio.
I was thinking of using a 2 to 1 ratio for a trade off bettween
power, speed, and resolution.

I also see you are using a 40 volt AC transformer. This would give
you about 56VDC. You should be using a 51VAC transformer which would
give you about 72VDC. This gives you a little room for voltage
surges as the maximum voltage a G210 can handle is 80VDC. Remember
the 42 frame motors need lots of voltage. You will get more speed
from the extra voltage. If you make the change to higher voltage let
us know of the speed improvment.

Also,let us know what the real world performance is when you get the
motor connected to the table.

Wally K.

--- In CAD_CAM_EDM_DRO@egroups.com, "Ian Eagland" <ian@e...> wrote:
> Hi
>
> By way of introduction we were a volume retrofit company in the UK
in
> the recent past but we now sell PC based retrofit kits into the
> industrial market using Ahha software. We sell to other retrofit
> companies and direct to end-users. Our best selling kit is for the
> Bridgeport Series 1 BOSS machines using the original drives.
>
> We have a number of customers interested in 4th Axes so we bought
> some Gecko drives both stepper and servo. We have been contacted by
a
> number of list members who are interested in our experience with
> Gecko drives. We have finally wired a G201 stepper to a Bridgeport
> Series 1 X-axis motor.
>
> This is a UK built Series 1 Boss 6 with metric ball screws. The
> pulley ratio is such that 1 full step gives a table movement of
> 0.01mm (close to 0.0004") The Motor is a Superior Electric M112
> rather than the more common Sigma and we have always considered the
> Superior motor to be slightly more powerful (As an aside there must
> have been some supply problems into the UK when these machines were
> first built as there were 4 volume manufacturers of Stepper driven
> CNC machines in the UK: - Bridgeport, Matchmaker, Beaver and Acton
> and they all used a mixture of Sigma and Superior motors)
>
> The Transformer on the Bridgeport is too high a voltage for the
Gecko
> so we are using an off the shelf transformer giving 40 Volts AC.
The
> Drive is a standard G201 not the G201 optimised for the size 42
> motor. We originally mounted the drive on a heat sink as is
required
> for the full 7 amps but were still concerned at the temperature it
> was reaching so we finally fitted a small fan blowing through the
> sink.
>
> The smoothness of the axis compared to the original drives is
> OUTSTANDING. We have been experimenting with rapid traverse rate to
> find the stall point. We have set the acceleration at 40, 000 steps
> per second per second which is reasonable. We have found we can get
> 100% reliable operation up to 13,000 steps per second tested over a
> period of 8 hours. At 14,000 steps per second we lost the odd step
> here and there. At 15,000 steps per second we get stalling. On our
> set up 13,000 steps per second is about 30 inches a minute. With
the
> original drives we normally set the machines at 100 inches a
minute.
> We understand from Mariss that size 42 motors will run out of
torque
> as motor speed increases when driven by the G201 so we would expect
> different results on an earlier Series 1 machine with imperial
screws
> and 1:1 belt ratios. Whether this would be better or worse I would
> not like to say as although the revs are lower so is the torque
> available at the ball screw. Incidentally with UK Series 1 machines
> you can tell if they have the belt ratio by the speed control and
> brake operation. If they are air operated the machine has the
> reduction ratio giving .01mm per step. If they are manually
operated
> the steppers are 1:1 giving .001" per step. We have squeezed a
> 2:1 ratio into some of these earlier machines to give better
> resolution and torque but it does require 1 special timing pulley
> manufactured, some re machining on the X Axis nut and stripping the
> head to change the timing belt.
>
> We would have no hesitation in using these drives with 42 motors on
> 4th axes, as these typically require less power. As an axis drive
the
> slow rapid rate is frustrating if you need to jog the length of the
> table but the machining performance is fine at the feed rates I
> normally use.
>
> The Servo drive has only been connected to a motor on the bench at
> the moment using the same 40-volt transformer. It is a 42 size
Baldor
> rated at 5nm with a 1000 line encoder and the bench performance is
> VERY impressive. When we get time we will fit this to a machine and
> find out just how far we can push it.
>
> Ian Eagland
> Eagland Machine Tools Ltd