Check out Redex’s own David Regiec being interviewed by Power Transmission Engineering Managing Editor Randy Stott. These two discuss the rigidity and precision requirements of a machine tool gearbox as part of the Revolutions Series on Power Transmission Engineering TV (https://www.powertransmission.com/tv/).
Randy Stott: Welcome to Revolutions, the show where we talk about power transmission and motion control. I’m your host, Randy Stott, and I’m here with Dave Regiec, from Redex. Thanks, Dave, for joining us.
Dave Regiec:[00:00:26] Thanks for having me.
Randy Stott: [00:00:28] We’re here at IMTS 2018 and I understand that Redex has a number of gearbox models that are specifically designed for machine tools. Can you tell me a little bit about them?
Dave: [00:00:38] That’s correct. Yes, our whole goal was to design a range of products that have the stiffness and smooth running requirements that machine tools ask for-
Randy: [00:00:52] Mhm (affirmative)
Dave: [00:00:53] -So we’ve developed several patents to that end. We actually integrate the output pinion onto the gearbox, what that does is it allows us to have the smallest shaft possible, while at the same time ensuring torsional stiffness. Then we can put a big bearing over the top of it and ensure radial stiffness, and this is really what machine tool manufacturers need: a very stiff, rigid solution that can position within thousandths or even tens of thousandths of an inch.
Randy: [00:01:24] Okay. Are there any other features of the gearbox that add to the stiffness and the ability of it to maintain that?
Dave: [00:01:31] Well, yeah, of course. It’s a planetary gear train, so inherently it is torsionally stiff. We’ve been making- Andantex is part of a Redex group, Redex is a french company that’s been making planetary gear boxes for almost 70 years. Hardened and ground gears, high performance, so we have all the knowledge to be able to do this.
Randy: [00:01:57] I know that part of the equation for machine tool users is probably precision. Is there anything that you can tell me about the precision of the gear boxes?
Dave: [00:02:05] Well, yeah, the precision comes from not just the gearing, which we already hardened and ground, and as I explained we have 70 years of experience with that, but it’s every part in the housing, because every part can add to error. So we have every part 100 percent inspected, and we have machinery now that lets us make parts within microns.
Randy: [00:02:29] Mhm. Do you do anything special to control backlash?
Dave: [00:02:34] The backlash in the gearbox itself is controlled by the quality of the parts, but we provide two gearboxes together in what we call twin drive or dual drive arrangements. The dual drive is a mechanical preload, so you can use one motor, and you can mechanically preload the whole system so it has zero backlash. Twin drive uses two motors, and in that case the drive controls the backlash. One is driving, and one is braking, so you can have zero backlash over the whole range.
Randy: [00:03:12] Okay, can you give me some idea of what sizes and ranges and torques and speeds that we’re talking about?
Dave: [00:03:18] Okay, so we go from size zero to size six. Size zero is about 200 newton meters, size six is 15,000 newton meters. So we really have the largest Servo quality gearbox on the market, and that’s really where we do shine, in the bigger sizes.
Randy:[00:03:46] And what sort of applications would those be for? Especially the bigger ones.
Dave:[00:03:50] The bigger ones, what we’ve done, of course, are really large milling machines for making huge parts. We also use them on fiber placement machines, for example, one of them makes the fuselage of a 787. So the machine is huge, it has to move at a very high speed, 50 meters per minute, and we’re moving 180 tons, so that’s what it’s for.
Randy: [00:04:19] Aside from the gearboxes, do you also provide other parts of the system?
Dave: [00:04:24] Well, yeah, we provide a complete system. We start with a gearbox, the gearbox as I had mentioned has an integral output pinion, but we also have a whole family of racks and pinions. The racks are a similar quality, so we can provide the rack, the pinion, the gearbox, and an automatic lubrication system to lubricate the whole thing. Of course we’re a mechanical company but we provide everything from the driven part to the motor.
Randy: [00:04:52] Very good. Is there anything else that you’d like to share about what Redex is doing here at the show?
Dave: [00:05:00] The other thing I’d just like to say is, in addition to the axis drives, we move axis, we also have two speed spindle drive systems. So, we like to call ourselves the machine drives company, because we can move your axis, and we can give you high torque at your spindle. We have the engineering behind it, we’re able to select the units, advise you on how to install them, and even assist in the installation.
Randy: [00:05:27] Very good. Dave, I’d like to thank you for joining me today.
Dave: [00:05:29] Oh, hey, thanks for your time.