[Christine88]

Hello all

Well recently I purchased one of those Inventables CNC mill kits which are basically great little machines for hobby stuff but I want to upgrade it for more accuracy. Basically the main problems I have found with the basic kit is squareness of the XYZ makerslide rails. The ends are not square and they have a slight amount of twist. Anyway I want to replace the makerslide extrusion XYZ rails with similar components that are more accurate and have no twist or other anomaly that effect accuracy. Can someone here recomend anything? I'd be interested in hearing from some of you guys who have been down this road and perhaps ran into the same issues. Please advise.

Christine

[123CNC]

If hobby level, recommend eBay for used linear guides such as THK, NSK, IKO, Hiwin, Rexroth and others. Don't count on any direct drop-in replacement, more like building a new machine using what you can from the old.

Depending on materials you are cutting and the accuracy you are hoping for, you may need to look at rigidity as well. Then look at the spindle, tool holders, etc. Not knowing exactly what Inventables Kit you are dealing with, your components for linear drive may need to change as well, e.g. does your mill currently use precision ground ballscrews, rolled ballscrews, rack and pinion, or belt drive.

But if it is all in the name of fun, incremental improvements and learning are a great way to go.

[Christine88]

If hobby level, recommend eBay for used linear guides such as THK, NSK, IKO, Hiwin, Rexroth and others. Don't count on any direct drop-in replacement, more like building a new machine using what you can from the old.

Depending on materials you are cutting and the accuracy you are hoping for, you may need to look at rigidity as well. Then look at the spindle, tool holders, etc. Not knowing exactly what Inventables Kit you are dealing with, your components for linear drive may need to change as well, e.g. does your mill currently use precision ground ballscrews, rolled ballscrews, rack and pinion, or belt drive.

But if it is all in the name of fun, incremental improvements and learning are a great way to go.

Thank you for replying. No there is nothing precision ground at all. It uses delrin v-wheels that ride on like shaped rails that are an integral part of the makerslide aluminum extrusion.

[123CNC]

Clarification, yes I understood the use of the 'Maker Slides,' the question was how do you move the carriages along the slide? How is linear motion produced along the rail? For example, common among 3D printers a stepper motor with a timing pulley rotates and moves a timing belt which translates the rotary motion to linear motion, pulling the carriage along the linear slide or guide. In larger CNC mills, it would be common to find steppers or servos directly or via gear reduction (gears or timing pulleys) driving a ballscrew and ball nut combination. The ballscrew precision grades can of course vary ($) with better precision in the 'precision ground' category than obtained in 'rolled' ballscrews, verses acme screws and 'backlash' nuts.

Just trying to add a little grander picture of information in your pursuit of accuracy and precision. Don't want you to be overly disappointed if 'new' precision rails alone don't meet your goal, especially given the cost and efforts.

Perhaps posting a picture of your 'Inventables Kit CNC mill' will aid others in contributing comments or suggestions in best bang for the buck alterations. Ultimately your goals for the machine will define what is the best path forward, or an entirely new path in a different direction. Rails alone may get you where you want to be, or maybe even other easier alterations. If you can share any details on what you are trying to cut or produce and what sort of tolerances and repeatability you would like or 'need' to achieve.

It is difficult to give directions to an unknown destination. But if it is all about the journey not the destination that's great too, experiment and discover.

[Christine88]

Clarification, yes I understood the use of the 'Maker Slides,' the question was how do you move the carriages along the slide? How is linear motion produced along the rail? For example, common among 3D printers a stepper motor with a timing pulley rotates and moves a timing belt which translates the rotary motion to linear motion, pulling the carriage along the linear slide or guide. In larger CNC mills, it would be common to find steppers or servos directly or via gear reduction (gears or timing pulleys) driving a ballscrew and ball nut combination. The ballscrew precision grades can of course vary ($) with better precision in the 'precision ground' category than obtained in 'rolled' ballscrews, verses acme screws and 'backlash' nuts.

Just trying to add a little grander picture of information in your pursuit of accuracy and precision. Don't want you to be overly disappointed if 'new' precision rails alone don't meet your goal, especially given the cost and efforts.

Perhaps posting a picture of your 'Inventables Kit CNC mill' will aid others in contributing comments or suggestions in best bang for the buck alterations. Ultimately your goals for the machine will define what is the best path forward, or an entirely new path in a different direction. Rails alone may get you where you want to be, or maybe even other easier alterations. If you can share any details on what you are trying to cut or produce and what sort of tolerances and repeatability you would like or 'need' to achieve.

It is difficult to give directions to an unknown destination. But if it is all about the journey not the destination that's great too, experiment and discover.

I'll try to post a pic here but basically it uses XYZ stepper motors and a TinyG controller board. It also uses a timing belt configuration to drive the axis.

[Christine88]

Just want to add that I'll mostly be doing wood engravings using Artcam. I'd like to get an accuracy of about +- .001" ideally but would settle for +- .005".

[RCaffin]

Ah, Jack up the Z-axis motor and replace everything under it.
Can't make a silk purse out of a sow's ear.
Translation: the basic hardware is just not up to anything better than what you have.

Cheers
Roger

[aarggh]

Christine, the first obvious problem you have is the use of the Dremel, they're a fine tool for general polishing, grinding, engraving, etc, but pretty much worthless for any worthwhile degree of CNC machining. They're too low power, and the runout is abysmal, you will never get a decent tight tolerance with a Dremel.

This seller supplies a really dirt cheap but beautifully made spindle (as well as a fantastic little machine called the Sable-2015) that with a little modification to your Z plate that will be far more appropriate for machining:

ER11 Spindle for Sable 2015 SPD ER11 ENGRAVER Mill PCB's Engraving | eBay

So far as the machine goes, it's not a terrible design at all, all machines suit a purpose and price range, but you will have some work ahead of you to stiffen, and make the machine more robust. For example some really easy things to improve the design without too much cost, or effort, would be to add right angle support brackets to the thin plates that bolt the Y axis to the extrusions under the MDF spoilboard. And also along the top and ends of the X axis to make the gantry sides a lot more rigid. Just replacing the Dremel alone will vastly improve the quality of the finished work.

It's all very doable, you just need to look at all the points that can possible flex under load, and brace, support, or fix them (usually at a right angle) in a way that minimises this as much as possible, but I wouldn't go the route of wholesale replacing of components, I think you'll more than likely end up having expended vast amounts of money, while having a machine in various states of disrepair and thus unusable. I'd recommend beef it up as much and as simply as you can, if it still doesn't cut if for you, (pun intended!), then look at another more suitable machine and relegate this as a dedicated engraving machine, which I'm sure it would be perfectly fine for.

cheers, Ian

[Christine88]

Christine, the first obvious problem you have is the use of the Dremel, they're a fine tool for general polishing, grinding, engraving, etc, but pretty much worthless for any worthwhile degree of CNC machining. They're too low power, and the runout is abysmal, you will never get a decent tight tolerance with a Dremel.

This seller supplies a really dirt cheap but beautifully made spindle (as well as a fantastic little machine called the Sable-2015) that with a little modification to your Z plate that will be far more appropriate for machining:

ER11 Spindle for Sable 2015 SPD ER11 ENGRAVER Mill PCB's Engraving | eBay

So far as the machine goes, it's not a terrible design at all, all machines suit a purpose and price range, but you will have some work ahead of you to stiffen, and make the machine more robust. For example some really easy things to improve the design without too much cost, or effort, would be to add right angle support brackets to the thin plates that bolt the Y axis to the extrusions under the MDF spoilboard. And also along the top and ends of the X axis to make the gantry sides a lot more rigid. Just replacing the Dremel alone will vastly improve the quality of the finished work.

It's all very doable, you just need to look at all the points that can possible flex under load, and brace, support, or fix them (usually at a right angle) in a way that minimises this as much as possible, but I wouldn't go the route of wholesale replacing of components, I think you'll more than likely end up having expended vast amounts of money, while having a machine in various states of disrepair and thus unusable. I'd recommend beef it up as much and as simply as you can, if it still doesn't cut if for you, (pun intended!), then look at another more suitable machine and relegate this as a dedicated engraving machine, which I'm sure it would be perfectly fine for.

cheers, Ian

Yeah I'm looking at some other machine options rather than just waist time and money. I did purchase the quiet cut spindle upgrade which is a lot better.

[123CNC]

Christine,

The dominos start to fall once you start increasing the load or cutting forces on the tool or cutting bit. As others have mentioned, if you use your machine for very very light cuts, such as engraving (or 3D printing, no appreciable load) you could probably get away with some minor adjustments like stiffening your slides and the joints or interconnections and get some improvement.

But if you plan on 3D carving say with any bits greater than 1/8" diameter and want to obtain 0.005" or 0.001" accuracy, I'm afraid your destiny as you have surmised is likely on a different path.

[Christine88]

Christine,

The dominos start to fall once you start increasing the load or cutting forces on the tool or cutting bit. As others have mentioned, if you use your machine for very very light cuts, such as engraving (or 3D printing, no appreciable load) you could probably get away with some minor adjustments like stiffening your slides and the joints or interconnections and get some improvement.

But if you plan on 3D carving say with any bits greater than 1/8" diameter and want to obtain 0.005" or 0.001" accuracy, I'm afraid your destiny as you have surmised is likely on a different path.

Wood engraving is what I planned on and also laser engraving. I have a laser and Artcam so mostly art type stuff. I doubt any metal cutting.

[123CNC]

Christine,Disclaimer, no affiliation nor customer, but you may want to check-out Andrew Werby's site ([url=http://www.computersculpture.com]). He posts here on the zone as awerby, and if I recall based out of Oakland CA, which is at least locally well known for its artsy industrial/arts community in West Oakland. He is obviously passionate about artistic use of technology, as well the technology itself. In particular he and his associates have done an excellent job on his Links page with lots and lots of good sites to go to for pursuing all realms of the process and technology. Very educational, and of course some commercial push as well. But still lots of good information to aid you in making a 'better' informed decision in your pursuit.

[123CNC]

Of course, CNCZone, which you have already found, is also a great place to do some re-Search (emphasis on site search function).