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IndustryArena Forum > MetalWorking Machines > Benchtop Machines > G0704 Linear Rail Conversion
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  1. #1
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    G0704 Linear Rail Conversion

    Hey guys and gals.
    It's been a LONG time since I've posted any projects on here, mainly due to business being so good the past few years I really just haven't had time. However I have one that I thought I'd share. A little back story is necessary.

    We purchased a Precision Matthews PM25MV back when the G0704 was first released from Grizzly. I don't have an exact date but I believe it was somewhere around 4-5yrs ago. We converted it to CNC with a full enclosure for flood coolant. It has a 2hp 56C three phase motor aboard, powered by an Automation Direct GS3 vector drive. And the list goes on. The mill rips pretty good for it's size. If you have one of our belt drive kits, you know the quality it's capable of.

    I've run this mill pretty much every day for the past 4 years making all of our production stuff as well as the job shop stuff that comes thru from time to time. The mills gibs were not great from the get go. The Z has always been a little tight towards the top of the column, which I've seen numerous others have similar issues. The X has a little slop in it where I can't adjust it tight enough without inducing an unacceptable amount of backlash. The Y has always been very good though.

    Last week things went south. I was running the machine as I normally do any other day, doing some 3D machining. When the Z went to go in the positive direction, the motor stalled, and being a stepper driven motor the control has no idea. That was followed by an X move with the cutter buried deep in the part. I think we all know what happens next..... Crash. After this I could not move the Z up or down more than about an inch without stalling the stepper. Obviously something major went wrong. After further investigation and removing the way cover, I noticed the gib strip was hanging half way out the bottom of the vertical slide! The retaining screw had dropped out and when the head went to go up the gib strip stayed put and tightened its self VERY tight.

    I removed everything for further inspection to be sure nothing else was damaged. I took the ballscrew assembly out and mounted it in the lathe to check for straightness. Well guess what......bent. At this point I was debating if I wanted to fix the machine or just buy something bigger better stronger. i.e. Tormach, Novakon etc... After sleeping on it, I decided to just make the repair. My solution is obviously a new ball screw, but what about the ways? Not so easily replaced. I've worked a lot with Hiwin linear rails and they are amazingly smooth and rigid. This was my solution for the ways.

    With that being said I fired up Solidworks and started designing the necessary mods to mount 15mm Hiwin linear rails on my column. The main limiting factor was that I wanted to retain the same mounting height as the dovetails so that nothing else needed modified. With some pocketing of the vertical slide and a small recess on the column, it was easily achieved.

    With the so so dovetail ways, and the amount of weight I was moving with the heavy 56c motor, I couldn't achieve any faster than 90ipm on the Z. Keep in mind my machine is not direct drive on the Z, as it has a 2:1 timing pulley reduction. The motor is the very common 570oz stepper. The machine was very reliable at this speed, but very slow. I figured with having to disassemble EVERYTHING I would change the Z to direct drive. With this and the combination of the ultra smooth linear rails, I hope to up this rapid speed drastically. I got the all the machining on the column done, and will have the vertical slide done in the next day or so.

    I think that about covers it for the initial post. Onto the pictures. The very first picture is the mill shortly after I had it up and running. The following picture was from a couple days ago. This machine has made A LOT of chips over the past few years.
    www.benchtopprecision.com
    | BF20/G0704 Belt Drive Kits | X2 Mini-Mill Belt Drive Kits |

  2. #2
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    Re: G0704 Linear Rail Conversion

    I am watching! Cant wait to see it operational.
    A lazy man does it twice.

  3. #3
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    Re: G0704 Linear Rail Conversion

    The rails should be here this week hopefully. Ballscrew is due to arrive tomorrow. Stay tuned!
    www.benchtopprecision.com
    | BF20/G0704 Belt Drive Kits | X2 Mini-Mill Belt Drive Kits |

  4. #4
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    Re: G0704 Linear Rail Conversion

    BTP;
    Can you give a bit more detail on how you prepared the column and Z axis slide to accept the hiwin linear rails. I have a RF-45 sitting in the shop that I worked on for years trying to get the Z axis under control. I have since purchased a Torus Pro, thus the 45 just sits. However, that said, I want to rip it apart, do it right this time, install rails and good ball screws and see what results.
    Good luck on your conversion and thanks in advance for the info.
    Bill
    billyjack
    Helicopter def. = Bunch of spare parts flying in close formation! USAF 1974 ;>)

  5. #5
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    Re: G0704 Linear Rail Conversion

    Beautiful. I have no idea but I have this feeling it'll slide smooth like butter. I'm watching. Good luck.

  6. #6
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    Re: G0704 Linear Rail Conversion

    very interested in seeing this.

  7. #7
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    Re: G0704 Linear Rail Conversion

    Quote Originally Posted by bill south View Post
    BTP;
    Can you give a bit more detail on how you prepared the column and Z axis slide to accept the hiwin linear rails. I have a RF-45 sitting in the shop that I worked on for years trying to get the Z axis under control. I have since purchased a Torus Pro, thus the 45 just sits. However, that said, I want to rip it apart, do it right this time, install rails and good ball screws and see what results.
    Good luck on your conversion and thanks in advance for the info.
    Bill
    Basically all you need to do the column is create two parallel lips that each rail can sit against to assure they are parallel to one another, and then add the tapped holes. Hiwin has a great manual for mounting styles, as there are a few different ways you can do it. These 15mm rails are a bit small for a RF45. I'd step up to a 20mm or 25mm. I purchased my rails from Automation4less.com. Great service and quick shipping.
    www.benchtopprecision.com
    | BF20/G0704 Belt Drive Kits | X2 Mini-Mill Belt Drive Kits |

  8. #8
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    Re: G0704 Linear Rail Conversion

    Small update. The new ball screw has arrived and the linear rails as well. Some pictures for your viewing pleasure and a video showing how SMOOTH linear rails are. I machined the four pockets on the vertical slide, but forgot to cut the clearance for the old dovetails to clear the linear rail. :tired: So tomorrow I will put it back up and remove the necessary material.

    www.benchtopprecision.com
    | BF20/G0704 Belt Drive Kits | X2 Mini-Mill Belt Drive Kits |

  9. #9
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    Re: G0704 Linear Rail Conversion

    I like it, but don't you think this will be a less rigid setup?

  10. #10
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    Re: G0704 Linear Rail Conversion

    Quote Originally Posted by oxi View Post
    I like it, but don't you think this will be a less rigid setup?
    I sort of agree - that is a massive slot to carve out that surely will affect column twisting?

  11. #11
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    Re: G0704 Linear Rail Conversion

    What slot? I simply machined off the dovetails. The slot in the center is the one from the factory. Don't be fooled by how smooth the linear rails are. They are VERY rigid. I've used many linear rails in different machine tool applications and they've been nothing but an improvement. I have full confidence this will be a positive upgrade.
    www.benchtopprecision.com
    | BF20/G0704 Belt Drive Kits | X2 Mini-Mill Belt Drive Kits |

  12. #12
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    Re: G0704 Linear Rail Conversion

    I've been toying with this idea for my Taig mill as well. Looks like you're making good progress.

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