First time build - Steel Frame CNC Router

Hi Everyone,

As this is my first post here, let me start by saying that I have never built a CNC machine before and other than a general college course on CNC/machining and reading this forum/CNCZone, I have had very little experience with either CNC or machining so hope you guys can keep me right :encouragement:

Following the advice given to others on here, I started reading through the build logs section of this forum and found a few designs I liked and also many handy tips that should help me along the way. I think I am now at the stage where I can start this build log to develop the design and hopefully soon start building! Please see following summary of the design:

Requirements -

• Machine profiles out of Wood/MDF
• Aluminium work ranging from machining profiles from plate and also machining blocks for which typical maximum total cutting depths are around 30mm
• Able to do some detailed work with both wood and aluminium like the Aztec calendar posted here

I understand that one machine cant suit all materials/requirements and so I will be more than happy if the machine is slow at cutting wood but is also strong/stiff enough to machine aluminium.

Design -
The attached is what I drew up based on what has been designed and seemed to work for others on this forum.

Attachment 17106Attachment 17103Attachment 17104Attachment 17101Attachment 17105Attachment 17102

• Cutting Area approx 750 x 400 x 100
• 2.2kW Chinese Water cooled spindle
• Rails are HGR20 on all axis (dimensions: 1000mm/600mm/300mm ) with wider type carriages on the X axis only
• Ball screws are 1050mm 1610 (double) on X Axis, 650mm 1610 (single) on Y Axis and 250mm 1605 (single) on Z Axis
• Motors are 3x NEMA 23 3.1Nm. One motor has been used with a belt drive for the double screws on the X Axis. This is mainly because I will be using LinuxCNC and have heard it doesn't support slaved motors.
• Frame is from 50 x 50 steel box section with larger sections being 100 x 50 (3 or 4mm thick). Side plates on the gantry are 10mm thick steel and all other plates including Z-Axis assembly and X-axis support bearing support plates are 20mm thick aluminium.

Some initial Questions -
1. Am I heading in the right direction with this setup or does it make more sense to look at something different?
2. Will 4x M8 bolts supported by the aluminium blocks tapped 15mm on each side of the gantry be enough to support the full gantry? Would it be better to make the supports from steel and weld the gantry box section to this with holes in the box section to get access to the carriage bolts?
3. What is the recommended thickness for the gantry box section? I will be using 3 of 4mm for the frame.
4. I have seen mention of Bearing spacing/aspect ratio on the forum so from the model, measurements taken between the inside of rail blocks and inside of rails are as follows:
X Axis - 42.74mm between blocks, 680mm between rails
Y Axis (Gantry) - 40.50mm between blocks, 150mm between rails
Z Axis - 30mm between blocks, 130mm between rails
Will this be OK or is adjustment of these dimensions required?
5. Is compressed air a requirement for when machining Ali? If so, I will need to build a compressor into my budget.

I haven't ordered anything yet as this is my first build and know for sure that I have cocked up on something somewhere! So I look forward to all the comments/guidance you guys can provide.

Erm i think you should look at your Frame section size in the model because it looks too large to be 50mm and out of proportion. This can affect how things fit so worth putting write now.

As for the rest then it's mostly there with just a few exceptions.
You need ends on Gantry to help stiffen the gantry up.
Brace the ballnut Drop bracket on the Gantry ballscrew and try to keep the Drop brackets on the Slaved axis to shortest possible length.
Put some short legs on it or adjustable feet it will make setup easier.

1 x 3Nm motor driving two screws with belts will struggle so I'd think about using larger motor. 6nm would be better but unfortunatly this means nema 34 and plenty of volts. Idealy Mains voltage drives.
Or other option is to use higher pitch 20mm and gear it 2:1. This will double your torque and lower the actual ballscrew speed so reducing chance of whip and resonance but will give roughly the same speed as 10mm pitch.

Material thickness then 4 mm for steel box and if Gantry is Ali then thick has possible idealy 10mm.

Yes Air is required for cutting ali properly mainly to clear chips and stop re-cutting.

Hi Examorph and welcome to the forum. Its nice to see that you have done a lot of research into this and I think you will do well.
I would not buy any electronics etc until you are well on the way with the build as no doubt things will change with time. I notice you are going with Liniuxcnc you are correct that it is not easy to slave with it although some have done it with extra electronics (but not for the feint hearted). Will you be going down the Mesa route ie 5i25 and 7i76 cards.
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Good luck with the build and has been said all questions are good even the dumb one's as they will save you a lot of time and money.

The Y axis front plate looks like it is a long way from the front of the gantry, perhaps 20mm or so? This reduces the stiffness for no real reason. I would aim for a gap of 5mm or so depending on how accurate you think you can make everything / flatness of gantry section.

Also the X axis connection down to the ballnut looks a bit less stiff than it could be. Can it be optimised a bit more? Maybe raising the ballscrews a bit in Z and mounting the ballnut to the [I]underside of the X axis bearing plate (bolting in the Z direction instead of Y direction). I think I would use another spacer / packer piece under the bearing plate to avoid raising the ballnut too much and creating a problem attaching the bearings and steppers into the frame at each end. You may even be able to mount the ballscrews closer to the sides of the frame (in Y) which all helps.

Thanks everyone for the comments, please see below revised design showing modifications are per your suggestions (I think :nevreness:).

Attachment 17114Attachment 17115Attachment 17116

Still need to figure out some of the finer details for fittings, positions, etc but think it will be OK for initial review.

JAZZCNC - I checked and checked again and its definitely 50x50mm box section drawn in SolidWorks all to scale (although spindle might be out as this was a copy/paste job :whistle:). Might look off because of the machine being quite small compared to others (750 x 400 x 100 cutting area).
The ends on the gantry are welded and don't go all the way as I wasn't too sure how else to get access to the bolts. Gantry is all steel, would 4mm box section for this be OK also?
To confirm, as the size of the machine is fairly small, would it still need the 20mm pitch screws or larger motor for the X-Axis or can it do without? If needed, are they 2020 ball screws?

Clive S - Sorry I have never heard of the mesa route before and still after reading up on it I have no clue :hopelessness: does the 7i76 replace the BoB and 5i25 act as some sort of motion controller?

RouterCNC - Simplest way I could think of pulling up the X Axis screws was just to stick it onto some box section and weld wherever it needed to be as well as using a 5mm aluminium spacer to help align things as suggested, will this do the job?

Thanks again for the comments and guidance guys.

Quote:

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Clive S - Sorry I have never heard of the mesa route before and still after reading up on it I have no clue :hopelessness: does the 7i76 replace the BoB and 5i25 act as some sort of motion controller?

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Ok This is the forum for Linuxcnc stuff. https://forum.linuxcnc.org/forum/index and this post will give you an idea https://forum.linuxcnc.org/forum/27-...d?limitstart=0.
This is where you can get them in Europe http://eusurplus.com/index.php?route...tegory&path=63.
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Basically the 5i25 is the card that goes into a pci slot in the PC (Linuxcnc is a real-time op system and does the motion controller stuff) and the 7i76 is the BOB for all the input/outputs etc.

Thanks for explaining this to me Clive. Reason for LinuxCNC was really just because it was free, but after looking at the boards it may end up being cheaper and easier just buying a Mach 3 License and one of these boards.

I updated the design slightly to raise the Y Axis ball screw by sitting it on some box section, similar to the X Axis (not sure if it would be stiffer buying wider box section and turning it 90 degrees or maybe also taller and having it sit at the base of the 'L' ?). Another reason for doing this was that I found on kincreaky's build log that Chai could supply these so I added them to all 3 axis and will get them with the rails/screws as it will save shipping.

Attachment 17152Attachment 17153Attachment 17154

This also gives me enough space to go with a belt to drive the gantry screw which might be better?
I remember reading somewhere that 25mm end machining is recommended when using pulleys, will this be enough in my case or do I need more?

The X axis bearing connection looks better now. For info you can buy ballnut mounts off e-bay which are longer than the one you have drawn so give a bigger footprint and are stiffer. They are connected by 4 bolts, not 2 which is better.
http://www.ebay.co.uk/itm/Ball-Nut-M...QAAOSwHnFVjdoi


On the Y axis the 2 ways of mounting the ballscrews you have drawn are probably similar in stiffness so go for what seems most practical to make - but how will you mount that box section end-on? You mention turning it around which would be better.

Quote:

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Originally Posted by routercnc

but how will you mount that box section end-on?

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I was planning on welding it direct to the gantry box section as its all going to be out of steel, would this be ok?

Quote:

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Originally Posted by routercnc

You mention turning it around which would be better.

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Ok thanks, will turn the ball screw supports on the Y Axis around and use 70 x 50 box section to leave some clearance on each side.

Examorth The board that you linked is the pmdx Is an excellent BOB but for the best results it will need a motion controller like say the Ethernet smooth stepper as the PP on pc's these day are flaky to say the least. There will be more support on this forum with Mach3. Good luck with the build.

Quote:

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Originally Posted by examorph

Thanks for explaining this to me Clive. Reason for LinuxCNC was really just because it was free, but after looking at the boards it may end up being cheaper and easier just buying a Mach 3 License and one of these boards.

I updated the design slightly to raise the Y Axis ball screw by sitting it on some box section, similar to the X Axis (not sure if it would be stiffer buying wider box section and turning it 90 degrees or maybe also taller and having it sit at the base of the 'L' ?). Another reason for doing this was that I found on kincreaky's build log that Chai could supply these so I added them to all 3 axis and will get them with the rails/screws as it will save shipping.

Attachment 17152Attachment 17153Attachment 17154

This also gives me enough space to go with a belt to drive the gantry screw which might be better?
I remember reading somewhere that 25mm end machining is recommended when using pulleys, will this be enough in my case or do I need more?

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Not that it matters too much, but you have the rail carriage flipped upside down from, on the left hand side as seen in the second photo

[QUOTE=examorph;75595]I was planning on welding it direct to the gantry box section as its all going to be out of steel, would this be ok?

Sorry, missed that it was a steel gantry. Then end-on as originally drawn in post#7 would be slightly stiffer. Go easy on the welding to minimise the gantry warping.

CannonGuy - Thanks for spotting the upside down rails on the one side, it was me being lazy and mirroring everything along the mid plane!! Will probably leave it as a mirror as the feature tree on the SW assembly is already starting to get crowded.

routercnc - Thanks for confirming. I read on a few build logs that people have been keeping the temp below 60C to reduce warping, so will probably stick to this. I have a stick welder but can get a mig arranged if you guys recommend it?

Speaking of welding, do you guys recommend the epoxy leveling route on the x axis for a build this size? With the Y and Z axis do you normally not do this?

In principle epoxy levelling is worth-while on both the X (longest) and Y (across gantry) axes otherwise you are only getting some of the advantages.

In your case the Y axis will be difficult unless perhaps you epoxy the top rail, then when dry and the rail is fixed turn it upside down and use a DTI to dial in the other rail whilst it has a fast setting compound under it? I've not used them myself but I think Dean has talked about some kind of putty instead of shimming?

For the Z axis epoxy is not required as you would ideally use Aluminium EcoCast plate which should be pretty flat to start with. Alternatively you can use standard aluminium plate and skim it flat on a milling machine as the part is quite small.

With the welding MIG is nicer to use, but should be OK with stick/ARC for what you are doing.

I see a few things I'd look at. (I realise now why it looks strange.? You have drawn box section with square edges and normally they are radiused which makes the tubes look larger.1)

Gantry mounting is weak point. No end support will let it resonate with only lower bolts supporting the upper rectangle. You are using only fraction of the plate to sit it on and with only 4 bolts inline. You would be better extending gantry width to cover the whole bearing plate width and have square 4 bolt pattern.

Has I mentioned in reply to your PM I'd look at ways to protect the ballscrews from debris. The screws are a little high and funerable. I'd be looking to add gantry sides which drop down the sides to allow screws to be lower and drop on the inside of the screw so covers can be added without interference from bearing plates. The gantry side also strengthens the gantry.

Regards welding then you have a lot of tubes all intersecting at the same points which means a lot of heat will be generated there. Idealy you should try to offset any tubes so the don't all meet at the same points. This will reduce warping and stress.
You also have tubes you don't need the Centre vertical ones for instance. The diagonal ones are enough and it's less welding, less heat and distortion. (see pic)

Mig welder is far better than Arc when comes to heat so if you have access to one I'd use it.

I'd also extend the Top rail 100mm past the end this will allow spindle to pass end giving more flexabilty to machine.

Regards PMDX then you want 126 BOB not 122 it's far better. If you go with Belts then buy Cslabs IP-M.
Attachment 17158

routercnc - Thanks, will go down the epoxy route on the X and EcoCast plate on the Z.

JAZZCNC - Thanks for spending the time making the changes to the model to show me, this is much appreciated!
Any chance you could send me the SW files for this please or let me know what size rad it is and I will draw it up? Also, just to confirm as I haven't done much machining so not sure, what flexibility does the spindle overhanging extra 100mm give you? Is it normal to machine stuff which sits off the end of the table?
I will get a Mig welder arranged as suggested and also have a play about with the gantry sides and see if I can setup what you've recommended, should have some images up for comment soon.

Quote:

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Originally Posted by examorph

JAZZCNC - Thanks for spending the time making the changes to the model to show me, this is much appreciated!
Any chance you could send me the SW files for this please or let me know what size rad it is and I will draw it up?

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I liked the Bloody Hell version better. . .Lol

The changes to the model took 5mins. You need to learn how to use Weldments and structural members then frame design is simple, quick and accurate.
I'll send the model back to you with a few more changes and suggestions based on what you've drawn already. I haven't changed what you did at all just added a new configuration with my frame etc so you can flick back n forth and see the diffference.

You'll also see how I made the frame.!!

The extra 100mm doesn't affect the machine stiffness but does make it more versatile. Ie cutting dove tails on draw ends, cutting locks or hindges into doors. Machining over height parts that won't fit under gantry or using extra long reach tools. It also allows an easy way for a 4th axis without affecting the cutting area or having to fit or remove everytime use machine.

Quote:

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Originally Posted by JAZZCNC

I liked the Bloody Hell version better. . .Lol

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Haha, well in that case then, Bloody Hell Dean! Cheers for all the help!
Got a habit of going back over emails and making them more formal at work, think I carried that through here too :witless:

Looking forward to seeing how you done the models and checking out Weldments and structural members on youtube now.

I made a few changes to the gantry sides as suggested:
Attachment 17174Attachment 17173Attachment 17175Attachment 17176Attachment 17177
Side plate is 10mm thick steel welded to gantry box section. Clearance between the frame and gantry sides is 10mm, so need to be sure that bolts which go into the ball nut bracket are only M5 so that the head doesn't stick out too far.

Images of X Axis carriage support plate also attached, thought it might be easier for access if I followed other designs on this forum and had bolts running into the side. If you think the 4 bolt square pattern on top face would be better, I could probably cut a slot in the gantry base 'L' to get access to them and have it that way instead?
If holes seem to close on the support plate, would it be worth going with the smaller width type carriages (without the flange) on the X also?

One thing I haven't really thought out yet for the frame is the bed. Will look back through some build logs and see how others have been doing it and get something up for comment soon.

Some things I am struggling with and hope you guys can help me with please:
1. Does using wider/flange type carriages on the X Axis have any benefit over the smaller width type carriages or am I OK going with the smaller ones?
2. Are there any cost effective ways of setting up a decent bed? I am seeing tool steel and aluminium beds on other build logs which I read can be >£300 :nightmare:

#1 They give a little more support but it's not a game changer and using the narrow type is ok if you have them or can't fit the wide ones in. If no obsticles then I'd always use the wide if possible, the price difference is nothing.

#2 Depends what your doing but Don't waste your money on Aluminium bed if your mostly cutting woods because most of the time you'll have spoil board on top. For the main base a good grade ply wood sealed is fine. Then put spoil board on top of this and surface that.
If you need the flatness of Tooling plate or surfaced aluminium bed and plan on using coolant all the time then you'll need something that's stable so spend the money but IME most the time you'll have spoil board on top. And probably screwing into it.?
Most common question I'm asked is "What do I use for work holding" the answer is "Anything that Works".!! . . . I'll Clamp, screw, bolt , stick or suck and often some combination of few of them just to get a job done. Thou by far the most common is screwing down into spoil board.!

You can check out my thread I am almost finished with my machine.
It is 90% steel

http://www.mycncuk.com/threads/5237-...LD-please-help

Dean - Thanks for clearing things up for me, I will be doing some aluminium work on it but was going to go down the route of using a mist rather than flood cooling, will this still be OK with the ply wood sealed base and spoil board setup? Also, probably a silly question but what are the typical depths for the ply wood base and spoil board? Just checking as I want to make sure I leave enough space bellow the spindle.

DigiSoft - Thanks for the link, I remember seeing it previously. Really nice buildd!

Provided you seal very well then yes with Low qty mist then yes Ply will be fine. Problem then comes from your Spoil board. Even Low volume Mist still creates mositure which gets into spoil board which isn't sealed. Often MDF is used for spoil board because it's cheap.

Really if your planning on using any wet kind lube often, even with air, then you'll want something that's resonably stable.

Depths are usually a multiple of sheet sizes so 18 or 25mm etc.

I had a resin impregnated board on the floor of my trailer. It seemed indestructible. I was wondering if that would make a good base as it is waterproof.

Going back to your sketch in post#19, I would extend the side pieces forward so it matches up along the whole side of the X bearing plate. You can then pickup another bolting point on the front X bearing between the 4off vertical bolts for the X bearing.

This side piece extension would be triangular in shape and fill in from the top of the gantry down to the end of the X bearing plate.

It would then (optionally) be triangular back out to the ballnut mounting point, or just go straight back.

This would provide much more support for the gantry onto the bearings for not much effort (apart from a bit more material).

Dean - Cheers for the advise. I swapped over the carriages for the narrower ones on the x axis and drew up the frame as per the setup you recommended using 4mm external rads on the section. Only thing I added was the box section running along the back (between the two x rail support sections) to let me mount a bearing for the belt onto (same as yours on post #7 here).

Routercnc - Thanks for the great idea, I updated the design with the following adjustments:

• Extending the plate 20mm short of the full bearing plate to keep standard sizes (200mm width x 300 height)
• Instead of being triangular back to the ball mount, I made rectangular cutouts on each side as any other way caused it to clash with the aluminium x axis ball-screw bearing supports and as a result, reduce working area.

I am going to try get access to a mill for this, but if all else fails are there any other options for cutting the steel plates?

Attachment 17424Attachment 17426Attachment 17425Attachment 17427
Gantry weight (just side plates and box section) is coming out at roughly 17.5kg @3mm wall thickness. When put together with Z axis, spindle and motors, will this handle OK with the one 3.1Nm motor on the x Axis?

Also, I checked the z extension using the 25mm tall bed/spoil board and the below image shows the spindle end going slightly into the bed at full extension. Would it be worth changing the 100 x 50 box section under the x axis rails to 120 x 50 or maybe higher?

Attachment 17428

Quote:

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Originally Posted by examorph

I am going to try get access to a mill for this, but if all else fails are there any other options for cutting the steel plates?

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Yes easy done without Mill. Print templates stick on steel with spray mount then get some 1mm Cutting discs for grinder which will slice thru that plate like Hot knife thru butter. Follow the lines and away you go will take about 20min per side.

Quote:

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Originally Posted by examorph

Gantry weight (just side plates and box section) is coming out at roughly 17.5kg @3mm wall thickness. When put together with Z axis, spindle and motors, will this handle OK with the one 3.1Nm motor on the x Axis?

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No you'll need either a ratio to increase torque or larger motor. I'd suggest 6.1Nm Nema 34 for X axis and run the whole machine with 65-70V.
Now here's the beauty of this system if you have one already and want to try using Nema 23 3.1nm motor then it's not going to cost you a fortune if doesn't work.
Use nema 23 motor with 1.5:1 Ratio (if using 10mm pitch screws) to increase torque and if it doesn't work then just replace motor with 34 and bore the pulleys to fit new shaft size which will be same or larger than 23. Depending on how you make the motor mount then you may need to alter or change this also.
68Vdc is at the bottom end you'd run nema34 motor and top end for nema 23 so will still give you decent performance so very little risk or cost involved.

Quote:

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Originally Posted by examorph

Also, I checked the z extension using the 25mm tall bed/spoil board and the below image shows the spindle end going slightly into the bed at full extension. Would it be worth changing the 100 x 50 box section under the x axis rails to 120 x 50 or maybe higher?

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How deep.? But in any case I'd lift the Spindle mount up slightly because it's a little low, You only need the Spindle Collet nut sticking slightly below the bottom plate. The slightly higher spindle mount doesn't hurt stabilty and offers some flexabilty if you need to slide the spindle up or down. Which you some times may want to do if using tall material.
I wouldn't sacrifice Strength having too large an extension or hieght for the few times you'll probably need full extension.

Dean - Cheers again for the help, good to know I can cut thru 10mm steel plate simply with an angle grinder! I haven't ordered anything yet so good spot on the motor, will get in the 6.1Nm to be on the safe side. Do you have any recommended suppliers as I dont think CNC4You do this and also, will it work fine with AM882 Drives?
I lifted up the spindle slightly but think this, like many other things might have to be one which gets put right during the build.
Attachment 17430
Do you think I am in a position now where I can start getting some of the linear motion stuff in from Fred Lee and start looking at local suppliers for the frame materials? If so, could you please cast your eye over the below list to make sure I haven't cocked anything up?

Linear Rail -
2 x Hiwin HGR20- 300mm linear rail
2 x Hiwin HGR20- 600mm linear rail
2 x Hiwin HGR20- 1000mm linear rail
12 x HGH20CAZ0C Hiwin block

Ballscrew -
1 x SFU / RM 1605-L250mm Overall length- C7 ballscrew with a ballnut with end machined and increase dimension F on end machining to 25mm for pulley
1 x SFU / RM 1610-L650mm Overall length- C7 ballscrew with a ballnut with end machined and increase dimension F on end machining to 25mm for pulley
2 x SFU / RM 1610-L1050mm Overall length- C7 ballscrew with a ballnut with end machined and increase dimension F on end machining to 25mm for pulley
4 x BK / BF 12 support for ballscrew


Some things I am not too sure about are if the reference is right for the narrower carriages, if the Z0 pre-load is what is normally gone for and also if the end machining info is right?

Hi, a bit of advice.

I see sth strange in this machine. May be i am wrong, but before buying and spending and cutting material, better do a continuity check. Element by element the way you will mount it together and check if thats possible and the difficulties.
I do that with whatever i build and in spite of that some times is difficult in real life to mount things together, there was an element in my first machine that cleared mere 1-2mm or it would not enter. Even that i have checked that 10 times .So dont use just copy paste, Hi but move the elements as they will be moved in real life.

My rule of a thumb is to leave clearance holes at least 1.5mm bigger in diameter, better 2mm. Cause the paint, the welding, etc... And when you weld, aim at precision, dont be in a rush. I have welded 1 meter machine under 1mm precision and 3 meter machine around 1mm. Its not a joke. And it was one of the first thing i welded. By the way 250A mig is best for home fabrication and costs about 350euro on ebay. Later when you can could change gun and cable with a brand one. Thats what i did.

Buy more material and use extra cut to size pieces as hard stops so you could achieve precision mounting. later you would use them for sth. And steel is cheap.

You need light preload, not 0 preload for the bearing blocks. Wider block serve nothing more than easier to mount usually for the gantry legs. On Z almost always the normal blocks are a must. Make sure you buy the long carriages.

Hi Boyan, thanks for the advise. I looked at the design again and the main areas I think may cause me some headache are lining up the x axis bearing supports with the gantry sides (as clearances are small) so guess there will be a lot of back and forth with the hand file for this, and another area was the ball screw bearing support depths on the x axis being difficult to line up without a mill, so I reduced these in width and made them into spacers with thru holes instead (nut/bolt onto box section), allowing me to again skim them down easily with a file if required.

Also, I noticed that I could extend the rails on the x axis all the way along the box section and reduce the length of box section to better utilize the full length of the ball screw, so the X axis rail is now 1050mm. Front hard stop was easily added with a bit of 50 x 50 box section but for the back, I used 10mm plate as anything over the back face would get in the way of the belt. Not sure if this will be enough?
Attachment 17469Attachment 17468Attachment 17470
For the carriages, should it be 'ZA' pre-load? Also how do you define the longer carriages in the part reference and what is the length of these so I can double check the models please?

Yes, ZA preload. BST Automation aliexpress, Fred if you have not figured the provider. You could use my name as reference and he will give you the right prices. Most of the people here buy the stuff from him. Alsmost always he has the best price and most importantly packs very well and stands behind if there is an error or fault

Hard stops also could be 4 big bolts or small plates welded at the sides that the plate that attaches to the ball screw hits them at end of travel. Your looks ok, just dont like the plates at the back of table, better as in front- box section.

The main mission of the hard stops /according to me/ apart of stopping the machine travel, is to stop it at that moment say just 2cm before ballnut travel ends. They must be nearly as possible square as i mount there the limit switches and they are my reference of squareness. So i use straight edge and make them truly square and weld them at the end when gantry is mounted and squared. If you understand what i mean

So i see the real beauty when the machine frame length or say distance between hard stops at the end of frame is = (desired travel) + 2cm
where travel = ball screw length - length of the gantry legs) + 2cm

So i know i have not wasted spinning mass that does nothing

Boyan - Thanks for the advise, I will look into the distance and confirm the 2cm as per your comments.

Are there any advantages to using the longer type carriages? Models are based on the shorter ones 'CA', and using the longer 'HA' type carriages will further reduce the cutting area.

Quote:

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Originally Posted by examorph

Boyan - Thanks for the advise, I will look into the distance and confirm the 2cm as per your comments.

Are there any advantages to using the longer type carriages? Models are based on the shorter ones 'CA', and using the longer 'HA' type carriages will further reduce the cutting area.

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Depends on what you want to cut. as they are very similarly priced and i wanted to cut aluminum i like the long ones. But i like also to overbuild a bit :-) . For wood i dont think it matters anyway

I also want to be cutting aluminium, so updated the models with the longer carriages (CAD models from here) and replaced the rear hard stops with large bolts (will use a steel plate spacer on the inside of the box section to support these). One thing I cant figure out is if I was unlucky enough to hit the hard stops, would it not end up distorting the frame and cause more problems?

Anyways, the larger carriages didn't make that big of a difference to the work area and seemed to fit OK with the existing setup (slight overhang though) so all in all, seems to have worked out ok.
Attachment 17484Attachment 17485Attachment 17486Attachment 17487Attachment 17488
I have shown carriage spacing for each axis. Can I reduce or need to increase it anywhere?

Do you guys thinks i'm now OK ordering in the linear components? If so, hoping you could help me with a few things:

Linear Rail -
2 x Hiwin HGR20- 300mm linear rail
2 x Hiwin HGR20- 600mm linear rail
2 x Hiwin HGR20- 1050mm linear rail
12 x HGH20HA ZA Hiwin block
Do you normally tend to specify the accuracy and dust protection indexes as part of the carriage/rail refereces when ordering from Fred Lee?

Ballscrew -
1 x SFU / RM 1605-L250mm Overall length- C7 ballscrew with a ballnut with end machined and increase dimension F on end machining to 30mm for pulley
1 x SFU / RM 1610-L650mm Overall length- C7 ballscrew with a ballnut with end machined and increase dimension F on end machining to 30mm for pulley
2 x SFU / RM 1610-L1050mm Overall length- C7 ballscrew with a ballnut with end machined and increase dimension F on end machining to 30mm for pulley
4 x BK / BF 12 support for ballscrew

If you spot anything out, please let me know.

Personally I would specify the F length to be 30mm ( you can always cut it shorter)

examorph I forgot be very clear when you order the screws that that you quote the total length of the screw including the F length. ie. 1605-L250mm including F=30mm length .

If you decide on the extra 5 mm don't forget to change your sizes

Clive - Thanks for the advice and the heads up. I have updated the original post (#36) to show the 30mm length, will just send a copy of this to Fred Lee when ordering. One thing I am not too sure about is, do they cut this from longer material stock and give you an "extra" Xmm on top of the standard amount or do they just machine back the 30mm and as a result, reduce the original screw length?

Also, any advise on if you normally specify the accuracy and dust protection after the carriage ref ie, HGH20HA ZA C SS ?

Quote:

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Originally Posted by examorph

Clive - Thanks for the advice and the heads up. I have updated the original post (#36) to show the 30mm length, will just send a copy of this to Fred Lee when ordering. One thing I am not too sure about is, do they cut this from longer material stock and give you an "extra" Xmm on top of the standard amount or do they just machine back the 30mm and as a result, reduce the original screw length?

Also, any advise on if you normally specify the accuracy and dust protection after the carriage ref ie, HGH20HA ZA C SS ?

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I don't think you are understanding this. I see that you have altered the F length to 30mm but you have not altered the overall length.

The overall length = the end for the BF bearing then the screw part then the BK bearing including the threads and the F length So L = the total length .


Ask Fred for the quotation and he will get back to you very quickly usually within about 36 hours.

Edit I think you did alter the length but check