SFA

Blick Leatherhead Report

I had an opportunity to test the Blick Leatherhead and I am very impressed. I have wanted such a product since I got into the CNC stone game in 2000. The ingenious design provided options to use 4” and 5” snail lock brushes and Frankfurt style brushes. I am told that the system can now also use 6” snail lock brushes as well. Being an educator I was a little disappointed at just how easy it was to use because there is no education required – only fine tuning I suspect.

We spent a little time getting the tool and kits information sorted out for each of our applications so the operator could load a tool that is completely set and ready to work with one click for each style of application. With no intention of doing it that way we ended up using a feedrate of 100 ipm and RPM’s of 1500 for each single test we made simply because it worked so well that we did not feel a need to try anything else for our initial test.

We started with 4” brushes for applying leather finish and performed our tests with a white marble and then black granite using a zig-zag pattern. Both colors came to a nice leather finish quickly. We moved on to Frankfurt style pads and went after honed and then polished surfaces again on white marble and a strong hard black granite using a looping pattern.

I performed this test with a hard working young man who has many years of experience and is highly skilled in doing every possible type of hand fabrication technique. As I prepared to go he and his colleagues were standing around the table with the parts we finished, all had big smiles on their faces. As I left he came to me and stated that I would just never know how much this will do for the shop work load and what a great thing this really is. He was very happy! I guess there is not much left to say about that…

I am confident there must be some feeds and speeds that could improve our applications. As always time was limited. With this opening test I am left confident this product is an asset to the CNC stone machining business.

Jerry Kidd

Hello Jerry,

Thank you for your report. I for one have been struggling with leathering on the cnc since I could never bring the processing time to a reasonable length. Let's take a common example that comes up in our shop: 1 slab of Leathered Black Pearl granite.

Machine setup:
5 min measure slab
5 min cnc programming
5 min vacuum cup setup
5 min slab loading on cnc

Pos 1 - 120 grit metal segmented diamond to remove existing polish:
10 min tool setup - make sure tool removes polish
40 min cycle time

Pos 2 - 36 grit diamond brush
5 min tool setup
40 min cycle time

Pos 3 - 120 grit diamond brush
5 min tool setup
40 min cycle time

Pos 4 - 320 grit diamond brush
5 min tool setup
40 min cycle time

Pos 5 - 240 grit silicone carbide brush
5 min tool setup
40 min cycle time

5 min slab unloading + cleanup

Total slab processing time: 4 hr 15 min

I would love to hear your thoughts on your process if it is significantly quicker.
Of course leathering marble could be a 1 pass process but we don't do much of leathered marble.

Not sure a cnc router brushing head can operate all brushes as effectively as a dedicated machine. But then again, at least it is possible to brush on a cnc . My bed polisher can not do edges no matter how much time is dedicated to the chore.

If a cnc can brush as effectively, then I would look at a different sequence and brick/brush schedule. You should be able to achieve suitable results in 3 or 4 cycles.

What exact brushes are you using?

flav wrote:Hello Jerry,

Thank you for your report. I for one have been struggling with leathering on the cnc since I could never bring the processing time to a reasonable length. Let's take a common example that comes up in our shop: 1 slab of Leathered Black Pearl granite.

Machine setup:
5 min measure slab
5 min cnc programming
5 min vacuum cup setup
5 min slab loading on cnc

Pos 1 - 120 grit metal segmented diamond to remove existing polish:
10 min tool setup - make sure tool removes polish
40 min cycle time

Pos 2 - 36 grit diamond brush
5 min tool setup
40 min cycle time

Pos 3 - 120 grit diamond brush
5 min tool setup
40 min cycle time

Pos 4 - 320 grit diamond brush
5 min tool setup
40 min cycle time

Pos 5 - 240 grit silicone carbide brush
5 min tool setup
40 min cycle time

5 min slab unloading + cleanup

Total slab processing time: 4 hr 15 min

I would love to hear your thoughts on your process if it is significantly quicker.
Of course leathering marble could be a 1 pass process but we don't do much of leathered marble.

jeez, it takes us less time with a floor machine.

what feed and speed are you running the heads? Also are you running a single 5" head or the triple?

Dan R. wrote:What exact brushes are you using?

Abressa 10" satinex diamond brushes

Can you tell me how long it takes you to do a full slab leathered on your bed polisher?

About 10-15 minutes per cycle. Depending on color and recipe, total time is about 45 minutes. We use 5 Frickert bricks per grit on a COMES head. The head rotates @ 380. The COMES head functions with a sweeping motion on the heads. It really makes a difference on the aggression, thus the finish and time required.

On our Northwood with the slab texturing software we seem to average about 2 hours a slab on most granite we have tried. We have some silver travertine to do this week and some black pearl so I will have the guys check the times. We have been very pleased with the results so far.

I am sorry I have not been able to get on the site and address some of the comments until now. My first thought is that I am somewhat surprised how this turned into a Leatherhead versus a dedicated bed polisher thread. I had thought of this tool as something for the little shops who cannot afford or simply do not have a bed polisher. Thanks for broadening my horizons… I think it cool that something else productive has happened from this posting.
I unfortunately will most likely never have the opportunity to do all the testing that will be needed to answer most of your questions. I will try to address some of the things but what I would say to all of you is that it will be you guys who perfect how to use this tool.
Since this test the young man who I worked with has decided that for leather it is best to use a circular polishing pattern instead of a linear zig-zag pattern. He found if he made his leathering effect with a traditional zig-zag pattern it looked and felt great but later when he walked up to the table and the stone was completely dry he felt he could see that pattern. After changing to the circular pattern he feels confident that he is no longer getting that undesired visual effect. He also is often in a situation where he must plane down the surface with as stubbing/calibration wheel before leathering. These tools leave lines that unless they are addressed will show up in the leathering effect also. He has modified his leathering brush system by switching out the first two positions will metal tools that are removing those lines and then he continues with the brushes.
I think the speeds and feeds are very important but what I am not hearing about from any of you is just how much do you press the tool into the stone. It will be the combination of these three variables that will lead to your ultimate success. In our case we were able to take the amount of pressing to a very controlled level because the machine we tested on was one of my Omag machines and it has a Renishaw probe on it that is mounted in a way that leaves it accessible to use on the Leatherhead. It worked even with the brushes because the bristles are so densely populated. I think from what I am hearing that most people are pushing too much, we pressed into the stone somewhere around .015 to .020 inch. I am not saying that is the right amount it is simply where we started.
I think that is the basics of what I can pass on. I have not addressed what brand of tools we used and I am not going to since I am tied to a manufacturer, I believe just as with everything else that some tools are going to work better than others so you guys need to share that with each other. Do what this website was made for and help each other out by posting what is working for you with what tools so you all can benefit. This tool is clearly a wonderful CNC asset, work together and tune it out so all of you can benefit from it.
Jerry Kidd

Dan who is experienced in brushing due to having a bed polisher just gave some suggestions and answered Flavs question, it certainly wasn't "bedpolisher versus leatherhead".
Thank you Jerry for making this thread.

Jerry, good to see you you here!

I did not try to make it an adversarial thread, just explained where I was coming from. A bit of background to establish a level of knowledge, as it were.

The name brand of the tooling is less important than the composition of the tooling.

I think your advice is spot on concerning pressure. Very little is required, so that the brush heads can sweep. With your test subject, I suspect that the stubbing wheel as the cause for the linear marks. Especially since the Blick head, itself, is rotatory. This rotational pattern may well be the reason for the long(ish) run times. A diamond filament wire brush would, most likely, solve this issue for him.

Brushing on a cnc is a option. The option is both expensive and cheap and the same time, depending on the urgency of the project, schedule of the machine and many other factors. As always, it is far better to have more choices than less. The Blick Leather head is certainly a game changer choice for those who need some leathering without the added expense of a dedicated machine.

Are there any among us that can comment on optimal rpm for leathering on the cnc? We have an omlat electrospindle on our cnc and I an not sure if it has the required torque to leather at 400 rpm. But I could be wrong since I am guilty of being 'one of those guys that applies too much pressure'. Need to do more testing and report back.

Dan, since you seem to be the elected expert on the subject, can we pick your brain a little more on the pattern you run on leathering slabs? (1 pass perimeter + zig zag interior? Or all spiralling motion?).

I can not comment on spindle torque of cnc.

As far as being an expert, hardly. Thanks for the kind words. I started with no knowledge and many shared with me. I learned some things the by trial and error. I am more than happy to pass on what I have learned.

No problem with general leathering techniques.

We use Tenax brushes. They are very proactive in developing products and offer products for granite, marble and ES.

One cycle:
1. Perimeter pass: this does one lap around the perimeter
2. Straight line pattern in the X axis (north/south) with a 4" overlap per pass.
3. Straight line pattern in the Y axis (east/west) with a 4" overlap per pass.
4. Zig zag pattern along the X axis with a 16" Y axis variance and a 4"overlap.

On lighter colored stone we can sometimes skip step 2 or 3.


Some free eduction from our experiences.
1. Brushing the front is far better than brushing the back. Breaking the polish is far easier than grinding out saw marks.
2. The wire brushes from Tenax work wonders on breaking the polish for brushing slabs.
3. Record your recipes and have finish consistency in the future, especially for repeat accounts (builders, K&B dealers)

Wow! I am not sure if it is what I said technically or if it is just Dan has a lot of supporters eager to defend him but if you consider that I did not say anything like I am reading there is something wrong here. I was sincere. I am sorry that there is so much negative response to people bring up other stuff. My personal opinion is that it is pretty much always good. This case is an excellent example of something else good happening, a man who could use a better tool found one.

To quote the movie – “Take a Valium for Christ’s sake.”

This forum is for people to learn from each other right?
Jerry Kidd

Oh for the rpm I would be concerned about that low for that type of spindle. We ran at 1500 rpm and it worked well for us.

Jerry Kidd

Jerry, I never took any offense and never thought that anything was negative in this thread. The net has a way of loosing subtle content as result of poor syntax skills.

It would interesting to explore the relationship between rpm and pressure. The pressure should always be just enough to permit full contact between the brick and the piece, with little to no bristle deflection. With excess bristle deflection, the finish will not have a suitable texture and will be honed.

Jerry, I wasn't defending anybody I am just happy to hear everybody's point of view and personal experiences with brushing.
How much do you think the feedrate can be increased? it appears to me feedrate is the main reason for the time difference in processing a slab with a Blick Leatherhead and the dedicated slab polishing machine.

I don't think anyone was intending to offend anyone. I didn't feel offended?

Dan, I'm running some numbers on your cycle on leathering a 10 ft by 6 ft slab:
1 cycle -> roughly 332 ln ft
15 min cycle time gives us 265 ipm feed rate
That is fast, but not ridiculously fast compared to the number of passes in a cycle

What I am trying to achieve here is to bring my cycle time from 40 min down to 15 min (or 10 min ).
If I've been doing it all wrong up till now (applying too much pressure) then maybe I can more than double my feed rate.

The pressure should be just the brushes touching the stone. The sweeping motion is what makes them work, not pushing hard on them, only the contact. Your head is a 10" head. My is about 20" with slots for 5 frickert bricks (brushes. So, the sirio is covering a lot of area in one pass. Do not compare your spindle to a 29 hp dedicated vertical shaft motor that is specifically designed for this task.

Find a solution that yields a good finish. Charge accordingly. Fine tune it as you go forward. Mess with speed rate, various brushes, etc.

It still amazes me how I can be wrong on so many things

Ken,
The important thing is to keep trying.

Regarding how much faster the feedrate could be - I would like to test that area because watching it I was guessing that the feedrate could possibly double. But fact is I do not know yet. We all need time to do more testing but we can help each other with posting what we find to reduce the amount of time we need to do this right.

Jerry Kidd

Thanks Dan for your comments on the pressure and how the brush should be just touching. The people that I am running into are trying to press too hard. Next time I get to test the tool I will double my feedrate.

the only thing im trying to figute out is why there are trail marks??? I would think it is a pressure issue because it wouldnt matter if its a straight line or circles there is still a pattern.

as far as speeds go or table times if your just "tickling" for pressure you would think it can be done ALOT faster. Its very difficult for us to come up with answers to this along with running finished parts.

Who else is running a blick head on there CNC and what size are you running the 5" single or 10" triple??

I think Dans machine wont be much help since his is made for this process although I greatly appreciate his input.

I spoke with a couple people at the show that use various methods other than a Sirio for leathering. It seems that longer run times are the norm, even using the same brushes. The difference, imo, must be the sweeping motion of the COMES head. This appears to be the most significant difference.

The torque a cnc spindle is limited to may be a factor for pressure and possibly rotating a large head. Could feed rate be cranked up with a smaller (more easily balanced) head?

Is there a significant difference in the available torque between the various style of spindles? ie: EDS, electro spindle, etc?

Would it be possible to mount a COMES head on a cnc? They are pretty large and heavy, compared to the Blick set up. Perhaps, a smaller COMES head could be a solution. Or maybe, longer run times are the reality with a secondary use tool (Blick Leather Head) on a machine (cnc) specifically designed for a different use.

My experience my not be directly applicable to a Blick head, but the brushing info should be interpretable for any brushing application.